text:
/*
 *  This file was autogenerated by the GPUdb schema processor.
 *
 *  DO NOT EDIT DIRECTLY.
 */
package com.gpudb.protocol;

import java.util.LinkedHashMap;
import java.util.Map;
import org.apache.avro.Schema;
import org.apache.avro.SchemaBuilder;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.IndexedRecord;

/**
 * A set of results returned by {@link
 * com.gpudb.GPUdb#grantRole(GrantRoleRequest)}.
 */
public class GrantRoleResponse implements IndexedRecord {
    private static final Schema schema$ = SchemaBuilder
            .record("GrantRoleResponse")
            .namespace("com.gpudb")
            .fields()
                .name("role").type().stringType().noDefault()
                .name("member").type().stringType().noDefault()
                .name("info").type().map().values().stringType().noDefault()
            .endRecord();

    /**
     * This method supports the Avro framework and is not intended to be called
     * directly by the user.
     *
     * @return  the schema for the class.
     *
     */
    public static Schema getClassSchema() {
        return schema$;
    }

    private String role;
    private String member;
    private Map<String, String> info;

    /**
     * Constructs a GrantRoleResponse object with default parameters.
     */
    public GrantRoleResponse() {
    }

    /**
     *
     * @return Value of {@code role}.
     *
     */
    public String getRole() {
        return role;
    }

    /**
     *
     * @param role  Value of {@code role}.
     *
     * @return {@code this} to mimic the builder pattern.
     *
     */
    public GrantRoleResponse setRole(String role) {
        this.role = (role == null) ? "" : role;
        return this;
    }

    /**
     *
     * @return Value of {@code member}.
     *
     */
    public String getMember() {
        return member;
    }

    /**
     *
     * @param member  Value of {@code member}.
     *
     * @return {@code this} to mimic the builder pattern.
     *
     */
    public GrantRoleResponse setMember(String member) {
        this.member = (member == null) ? "" : member;
        return this;
    }

    /**
     *
     * @return Additional information.
     *
     */
    public Map<String, String> getInfo() {
        return info;
    }

    /**
     *
     * @param info  Additional information.
     *
     * @return {@code this} to mimic the builder pattern.
     *
     */
    public GrantRoleResponse setInfo(Map<String, String> info) {
        this.info = (info == null) ? new LinkedHashMap<String, String>() : info;
        return this;
    }

    /**
     * This method supports the Avro framework and is not intended to be called
     * directly by the user.
     *
     * @return the schema object describing this class.
     *
     */
    @Override
    public Schema getSchema() {
        return schema$;
    }

    /**
     * This method supports the Avro framework and is not intended to be called
     * directly by the user.
     *
     * @param index  the position of the field to get
     *
     * @return value of the field with the given index.
     *
     * @throws IndexOutOfBoundsException
     *
     */
    @Override
    public Object get(int index) {
        switch (index) {
            case 0:
                return this.role;

            case 1:
                return this.member;

            case 2:
                return this.info;

            default:
                throw new IndexOutOfBoundsException("Invalid index specified.");
        }
    }

    /**
     * This method supports the Avro framework and is not intended to be called
     * directly by the user.
     *
     * @param index  the position of the field to set
     * @param value  the value to set
     *
     * @throws IndexOutOfBoundsException
     *
     */
    @Override
    @SuppressWarnings("unchecked")
    public void put(int index, Object value) {
        switch (index) {
            case 0:
                this.role = (String)value;
                break;

            case 1:
                this.member = (String)value;
                break;

            case 2:
                this.info = (Map<String, String>)value;
                break;

            default:
                throw new IndexOutOfBoundsException("Invalid index specified.");
        }
    }

    @Override
    public boolean equals(Object obj) {
        if( obj == this ) {
            return true;
        }

        if( (obj == null) || (obj.getClass() != this.getClass()) ) {
            return false;
        }

        GrantRoleResponse that = (GrantRoleResponse)obj;

        return ( this.role.equals( that.role )
                 && this.member.equals( that.member )
                 && this.info.equals( that.info ) );
    }

    @Override
    public String toString() {
        GenericData gd = GenericData.get();
        StringBuilder builder = new StringBuilder();
        builder.append( "{" );
        builder.append( gd.toString( "role" ) );
        builder.append( ": " );
        builder.append( gd.toString( this.role ) );
        builder.append( ", " );
        builder.append( gd.toString( "member" ) );
        builder.append( ": " );
        builder.append( gd.toString( this.member ) );
        builder.append( ", " );
        builder.append( gd.toString( "info" ) );
        builder.append( ": " );
        builder.append( gd.toString( this.info ) );
        builder.append( "}" );

        return builder.toString();
    }

    @Override
    public int hashCode() {
        int hashCode = 1;
        hashCode = (31 * hashCode) + this.role.hashCode();
        hashCode = (31 * hashCode) + this.member.hashCode();
        hashCode = (31 * hashCode) + this.info.hashCode();
        return hashCode;
    }

}


Genting hotel is the designer adopts the design style of jan Europe, combines the concept of "elegance, nature", the hotel whole space is delicate but not lose luxuriant, exalted and not show grandiose. Hotel space club, mainly including the lobby, restaurants, wine cellar, conference hall, KTV rooms, space curve, the details of the best, make the person feel the beauty of the romantic European culture. This style from the whole to the local, from the space to the interior furnishing, elaborately carved, gives a meticulous impression. Retained material qualitative, colorific roughly feel on one hand, can grasp the European tradition of history and profound cultural background, and abandoned the overly complex texture and decorative, simplify the line.


text:
Service to the Nation
President John F. Kennedy motorcade, Dallas, Texas, Friday, November 22, 1963. Also in the presidential limousine are Jackie Kennedy, Texas Governor John Connally and his wife, Nellie.
Friday, November 22, 2019. Yesterday was warmer in New York with lots of sunshine and temps in the low 50s at the house of this writing (9:45 pm).
Jack Kennedy. He was murdered on this day, 11/22, 56 years ago in Dallas. Everything changed instantly after that, as it did in this young man's ill-fated life (he was 46). The following three days America watched (then black and white) television. Stunned. We watched and watched. There was a sense among many of us (and the opposite among many others) of witnessing a personal tragedy. His presence represented hope to many, and not accidentally. He was brilliant as well as charming, as well as rich. An ideal if there ever was one for the American male in that age.
His polls weren't so high at the time of his trip to Dallas, and it was only a month away from the '64 election year. The press by then had got beyond the first days of his exciting and glamorous Presidency when Jack and Jackie had ushered in a New Generation of Americans. They personified the changes that came with the first half of the 20th century. They were younger than what we were used to as a President and First Lady. On a cover of Esquire — then a hot, must-read magazine, they were referred to as our first President and First Lady "who look like movie star." As, indeed, they did.
The President of the United States, John F. Kennedy, at Bailey's Beach, Newport, 1962.
To a whole (younger) generation, they were relatable. And in a good way. Handsome, beautiful, smart, kind; an ideal before our eyes. (And rich too; i.e. the lottery). By late November, two years into his Presidency, however, the trip to Dallas was a potential solution or demonstration for improving his ratings.
This was an era of an enormous even raucous change. The "liberation" movements were growing, and the old ways were going to be replaced whether we liked it or not. The Women's Liberation, the Gay Liberation, the Civil Rights Movement, all got started quite naturally with that man and his wife in the White House.
The Second World War had ended in victory, the new liberation movements were simply reflecting the evolution of the beast (us). And Jack Kennedy, a very rich man's son, an Irish-Catholic, a witty, even self-effacing man in public press conferences, good looking, naturally curious, seriously smart, he represented that victory for many who voted for him as President.
That's how it looked up until the months before November 22, 1963. The romance of newness of the First Family had passed and troubles were brewing, like Vietnam. We knew nothing about his sex life although there were always stories of his "fervor" but they were bits of amusement. I was told once by a close associate of the President (long after his death) that the inside name for him among friends was "Jack the Zipper."
They had a good laugh over it. Everybody did. Or, almost everybody. Privately that would have amused him too. There were always rumors about his "affairs" but they were the stuff of gossip that titillated, and ultimately awed and amused a good many of us. He was our Man.
If you ever get a chance to see him in a press conference (YouTube) and you've never seen him live, treat yourself to his presence. Yes he was a professional with his persona, and witty and clever with words. But in watching you see that he's one of us, ideally speaking, a man of a life that was always complex, even psychologically stressful for the child. It was one of material abundance and an often physically absent father and mother.
The father was absent physically much of the time when the children were growing up, but he kept in constant close communication by mail or phone with each of his children. He was always parenting. From that came the light of a man whose presence — with his movie star looking wife Jacqueline — directed the younger generation of American people to look forward, to look up, and work to make the best of it for not only yourself but for your neighbors.
Then they shot him. They had their reasons. I'll never know what they were I'm not referring to Lee Harvey Oswald who, as he was being escorted from his holding jail and exiting the police station and shouting "I've been framed! I've been framed!" — a man named Jack Ruby suddenly ran out of the crowd, and pointing a gun, shot and killed Oswald — before the shocked eyes of the nation in mourning.
The world that came in with this intelligent young man and his wife is still with us, nevertheless.
Speaking of Service to the Nation. In celebration of its 100th anniversary, Leanne Caret, President & CEO, Boeing Defense Space & Security was honored at the Soldiers', Sailors', Marines', Coast Guard & Airmen's Club with the "Service to the Nation Award." Leanne Caret was joined by guest Speakers Colonel Jack H. Jacobs, USA (Ret) Congressional Medal of Honor Recipient and Tony Lo Bianco.
Among those attending included Margo and John Catsimatidis, Julia Irene Kauffman, Dr. Gregory and Mrs. Margaret Hedberg and Mrs. Ryland E. D. Chase. Proceeds from the evening went to benefit SSMAC, a non-profit organization that for one hundred years has provided warm, friendly and safe accommodations for more than five million men and women in the Armed Forces as well as those of our allies.
Leanne Caret and friends.
Major General Michael Boyd, Marianne Minish, Charlotte Minnich, and William Minnish.
The Junior Committee.
The Cathers family.
Kathy Trenholm and Shelby Willcox.
Colonel Jack H. Jacobs.
L. to r.: Becky Chase Hughes and Alison Chase; Marvin Scott, Leanne Caret, and Ray Johns.
NYPD Pipes and Drums of The Emerald Society.
Color Guard.
USO Show Troupe.
Bill McShane.
The Hedberg table.
John Catsimatidis, Hazel Cathers, Margo Catsimatidis, and Marvin Scott.
Nancy McLoughlin's table.
Tribute to Ivan Obolensky.
L. to r.: Robert and Susan Frederick; Ashley K. Hildebrand and Gregory Hildebrand.
In the case you (hope you didn't) missed it department. On Thursday, October 31, 2019, The Society of Memorial Sloan Kettering (MSK) hosted its 4th Annual Opening Night of TEFAF New York Fall at the Park Avenue Armory. The Opening Night of TEFAF New York Fall was generously underwritten by Fiona & Stanley Druckenmiller and sponsored by Etro.
The Opening Night offered The Society's members and New York's most notable collectors, philanthropists and leaders in fashion and design an exclusive preview of the fair's sensational, museum-quality pieces before opening to the public the next day. TEFAF New York Fall, which focuses on decorative art and jewelry from antiquity through the early 20th century, is recognized for championing the finest art dealers and experts from around the world, as well as providing the highest quality art fair experience.
George Farias, Jennifer James, Libby Fitzgerald, Alex Papachristidis, Betsy Pitts, Nanne Dekking, Kate Allen, Lisa McCarthy, Patrick van Maris, and Nina Carbone.
Jennifer James, Betsy Pitts, Kate Allen, Marco Felci, Libby Fitzgerald, Lisa McCarthy, and Nina Carbone.
L. to r.: Martha Stewart; Aerin Lauder; Audrey Gruss.
George Farias, Nanne Dekking, Kate Allen, Patrick van Maris, and Alex Papachristidis.
L. to r.: Rena Kirdar Sindi and Alex Papachristidis; Kate Richards and Rocky Ommen.
L. to r.: Andrew and Kate Davis; Kate Allen, Claudia Overstrom, and Betsy Pitts.
Caroline and Tom Dean.
More goodies gone by. Hundreds of guests gathered at the Guggenheim Museum to celebrate the debut of Gwathmey Siegel Kaufman 50+, a monograph published by Rizzoli, written by authors Bob Siegel and Gene Kaufman.
Known for an architecture of distinctive modernism that is well crafted, refined, and often luxurious, Gwathmey Siegel Kaufman has been the "go-to" firm for decades for some of the nation's, and ever more so the world's, most discerning clientele. This landmark volume is a comprehensive look at the legendary firm and a celebration of its more than 50 years in existence as an architectural tastemaker.
Gwathmey Siegel Kaufman 50+ illustrates new and rarely seen photos and drawings for the firm's most iconic projects.
Book authors Bob Siegel and Gene Kaufman pose with the book, published by Rizzoli and now on sale.
Joe Moinian, Bob Siegel. and Alan Miller.
Sam Chang, Bob Seigel, and Gene Kaufman.
Gene Kaufman and Pianist Terry Eder.
Bob Siegel, Hazel Siegel, Terry Eder, and Gene Kaufman.
Gene Kaufman, in between Gene Lee (L) and Graham Gillespe (R), signs a copy of Gwathmey Siegel Kaufman 50+
Photographs by Angela Pham & Mike Vitelli/BFA.com (TEFAF); Annie Watt (SSMCA); Marc Basch & Fred Aquilino (Gwathmey)
Party PicturesNov 24
The American Friends of Blérancourt's Annual Gala, honoring Hélène David-Weill; The Royal Oak Foundation's annual benefit honoring the Duke of Devonshire; CeCe and Lee Black hosted a cocktails party for newlyweds Liz McDermott and Ben Barnes.
NEXT POST For the Sake of us all

redpajama_set_name: RedPajamaCommonCrawl


The ongoing strike of the Academic Staff Union of Universities, ASUU took a different turn on Saturday at the Dutse-Alhaji area of Abuja when a female student of the University of Abuja made to hang herself in protest of the nearly four months old strike.
The female student identified as Jane Okoro had already hanged herself, but fell off the ceiling while struggling, apparently because the rope she used was not strong enough.
Jane had sent her two younger brothers on an errand, just a way of sending them out of the house to be able to carry out the abominable act, but one of the brothers returned after 15 minutes and saw her on the floor with a rope tied round her neck while another rope dangled from the ceiling fan. The 15 year old boy raised the alarm, thinking that his sister was dead, attracting neighbours and other onlookers into their compound. However, it was discovered by those who got there first, that Jane was alive as it was only a suicide attempt.
Meanwhile, the mother who returned from the market immediately after the news got to her had told our correspondent in tears that, her daughter must have attempted to commit suicide because of the ongoing ASUU strike. She said, I will ask her questions on why she wanted to do this to us. She has been complaining to me about this ASUU strike. She said, at her age, she should have been done with school, and begin to take care of the children and I. Her father is late. I know that only this week, she had complained to me up to 6 times on how frustrating this strike has been. I know other things may have contributed, but ASUU strike may have contributed the most; but for whatever reason, it was devilish for my daughter to have attempted suicide." She said.
Attempt to speak with Jane failed as she could not respond to questions from our correspondent. The only statement she muttered was " It was a better option".
However, a female friend of Jane who had pleaded not to be mentioned showed her recent conversation with Jane on her Blackberry. She said " my last chat with her was on this very ASUU strike. See what she posted, " I tire for these ASUU peopleoooo" She showed our correspondent the chat.
WHAT AN IGNORANCE? FOR SOMEONE 2 COMIT SUICIDE BCOS OF ASUU STRIKE. MAYBE NA HELL SHE LK PASS D STRIKE. D FOOD U ARE TIRED 2 EAT IS WHAT ANOTHER BEING IS PRAYING HARD 2 GET 4 CONSUMPTION. DIS IS A FOOD 4 THOUGHT.


text:
Gibberula simplex is a species of sea snail, a marine gastropod mollusk, in the family Cystiscidae.

References

simplex
Gastropods described in 1957

redpajama_set_name: RedPajamaWikipedia


text:
Surpassing Expectations
The Digital Transition
WE FM 99.9 | The Clean, Fresh Sound
UK downgrades terror threat advisory for Trinidad and Tobago
WeFM
A terror threat advisory issued for Trinidad and Tobago by the United Kingdom, has been downgraded.
In a press release on Thursday, the Ministry of National Security said the UK informed National Security Minister Stuart Young that the downgrade was a direct result of the hard work done in the area of countering terrorism.
The UK also noted that most tourist visits have been trouble-free in the recent past and attributed the development to sustained collaboration with the Government.
The previous advisory stated that terror attacks were "very likely" to occur in the twin island republic.
However, the UK Government's website now states that terrorists are 'likely' to try to carry out attacks in Trinidad & Tobago.
It also said that while there have been "no recent attacks in Trinidad and Tobago, more than 100 Trinidad and Tobago nationals have travelled to Syria and Iraq."
In November 2017, the Government signed a Memorandum of Understanding on security cooperation with the United Kingdom which included strengthening bilateral efforts on countering terrorism in all its forms.
The Ministry of National Security said the latest development is a"welcomed endorsement by the United Kingdom," and the government looks forward to a continued bilateral relationship towards the safety and security of citizens.
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I agree, augmented reality often just seems to be 'cool' rather than actually good enough to be useful. I've never seen a use for it that's actually better than the alternative more traditional interfaces.
I just don't quite see that waving my phone around is a step forward even if it uses image recgonition and AR overlays. AR is a good bang for the buck as its quite easy to develop and has a high wow factor. It just seems a bit lost in the everyday environment above and beyond the odd application such as hertiage.
The way AR is presented here is not only NOT a step forward, it's a step backward actually. It just adds more complexity to simple processes (such as checking weather or bus timetables) for the sake of coolness. But coolness is always subject to fast inflation. Evantually people will search for things that are more efficient. Why to grab your phone and aim at buses if you can just have a look at the electronic sign next to the bus stop?
It might end up as a cool gadget for car dealers or something but can't see a reason why people would use it for the very same information they can get through faster and lighter AR-free iphone apps.
Consider AR applications aside from a smart phone. What about military environments with AR embedded in a helmet that soldiers wear on an every day basis? This is more than a high wow factor, it would reduce casualties in the field.


It's the last day of November. Thanksgiving is behind us. December is tomorrow. Looking ahead to a White Christmas begins.
November is typically the wettest and windiest month as the Pacific Storm Track seasonally realigns itself. We've been touched by the Pineapple Express, but just barely. A few days of wind and rain reinforced the region's reputation, but only enough to bring the year up to normal. There weren't even many power outages. Stacks of candles and batteries are sitting idle, waiting for a reason to be.
We've also missed out on cold. A few days of frost closed the gardening season for many plants. But, instead of our typical dusting that adds up to almost an inch (an inch!) of snow in the month, we've had nothing. A couple of hours away, there's enough to open ski areas, and begin replenishing the mainland's water supply. But here on the island, nothing.
Weather is unpredictable, and even more unpredictable along the Pacific Coast. Inland forecasts benefit from a dense network of weather stations, largely defined by towns and cities. There aren't many towns or cities in the ocean. Weather hits the Olympic Mountains and redefines itself north, east, and south of the barrier.
Blame or thank the warm water. Puget Sound and the Salish Sea aren't considered warm by swimmers, but the waters are warmer than freezing. Elevation and distance from the water make it easier for snow to survive, hence the mountains are white while the island is merely wet.
December is our snowiest month. Our average of 1.7 inches wouldn't delay schools in much of the country, it tends to come in either very light or reasonably heavy amounts.
Now is the time get up the lights, the wreathes, and the ornaments regardless of the weather. A bit of frost is a cultural reminder, and the bonus will be if enough snow covers to create natural landscapes for cards.
In the meantime, we get to enjoy driving without waiting for snow plows, or having to shovel sidewalks; but still get to find the snow if we really want to. And, if it does snow more than a couple of inches here, well, be ready to stay home, light those candles, and dive into a book.
This entry was tagged Christmas, climate, Pineapple Express, snow, weather, Whidbey Island. Bookmark the permalink.


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A tax firm gave inaccurate advice to a small business, which resulted in IRS fines and an audit exposure.
A clothing manufacturer inadvertently sewed incorrect care labels onto their garments and clothes shrank. The retail store chain selling the product sued them for numerous customer complaints and diminished sales.
A plumbing repair leaked and flooded the entire office.
Disgruntled investors were dismayed at their monthly investment returns.


text:
List of Names of Children Who Attended and Died at Canadian Residential Schools is Unveiled
2800 have been named while 1600 remain unnamed
By Lisa Morgan Uncategorized 30.09.2019
Today, the National Centre for Truth and Reconciliation revealed the names of 2,800 children who died in residential schools. The ceremony was held at the Canadian Museum of History in Gatineau, Que.
Idil Mussa, who works for the CBC, shared a video of the unveiling on her twitter.
I'm at a ceremony this morning where the names of children who attended & died at Canadian residential schools is being unveiled on a 50-metre long ceremonial cloth. #OrangeShirtDay2019 pic.twitter.com/OpNQs9BxHc
— Idil Mussa 🇨🇦 (@idilmussa) September 30, 2019
When I watch this 50-metre-long cloth go by with the names of 2,800 children dead, I get angry that so many lives were lost, that the cultural genocide almost succeeded. A total of 150,000 Indigenous children are thought to have spent at least some time in a residential school and the most accurate number of children identified by name and unnamed death records is 4,200.
The names on the list were carefully researched and confirmed and there are another 1,600 who died, but remain unnamed. Ry Moran, director of the National Centre for Truth and Reconciliation says "Even our recent research efforts have uncovered another 400 students. We know there's many more students to be found."
What ages are the children on this list? "Infants, three-year-olds, four-year-olds all the way up through their teenage years. We've got some students on this list that are named as 'babies'", says Moran
The names are available in a book.
Here is the book. pic.twitter.com/tOspiiHfgX
Information on Orange Shirt Day
Image: Idil Mussa/Twitter
Tags: canada, First Nations, OrangeShirtDay, Truth and Reconciliation
"Peace By Chocolate" CEO Becomes a Canadian Citizen
"Canada Strong" Fundraiser for Airplane Crash Victims
Who Should Be on Our $5 Bill?


Mattia Perin was not expecting to play alongside Cristiano Ronaldo when he joined Juventus, but he is excited to do so.
Juve paid Genoa an initial €12 million (£10.6m/$14m) to sign the goalkeeper after Gianluigi Buffon confirmed his 17-year stay at Turin would end after the 2017-18 season.
On Tuesday the Bianconeri announced they had shelled out €100m (£88m/$117m) more than the fee for Perin to snare five-time Ballon d'Or winner Ronaldo from Real Madrid.


text:
Internet-Draft SCION I-D August 2022
de Kater, et al. Expires 27 February 2023 [Page]
PANRG
draft-dekater-panrg-scion-overview-02
C. de Kater
ETH Zuerich
N. Rustignoli
A. Perrig
SCION Overview
The Internet has been successful beyond even the most optimistic expectations and is intertwined with many aspects of our society. But although the world-wide communication system guarantees global reachability, the Internet has not primarily been built with security and high availability in mind. The next-generation inter-network architecture SCION (Scalability, Control, and Isolation On Next-generation networks) aims to address these issues. SCION was explicitly designed from the outset to offer security and availability by default. The architecture provides route control, failure isolation, and trust information for end-to-end communication. It also enables multi-path routing between hosts.¶
This document discusses the motivations behind the SCION architecture and gives a high-level overview of its fundamental components, including its authentication model and the setup of the control- and data plane. A more detailed analysis of relationships and dependencies between components is available in [I-D.rustignoli-scion-components]. As SCION is already in production use today, the document concludes with an overview of SCION deployments.¶
About This Document
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://scionassociation.github.io/scion-overview_I-D/draft-dekater-panrg-scion-overview.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-dekater-panrg-scion-overview/.¶
Discussion of this document takes place on the WG Working Group mailing list (mailto:panrg@irtf.org), which is archived at https://datatracker.ietf.org/rg/panrg. Subscribe at https://www.ietf.org/mailman/listinfo/panrg/.¶
Source for this draft and an issue tracker can be found at https://github.com/scionassociation/scion-overview_I-D.¶
This Internet-Draft will expire on 27 February 2023.¶
This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document.¶
1.1. Why SCION - Motivation
1.1.1. Scope of SCION
1.1.2. Practical Considerations Based on Related RFCs
1.1.3. Why Now?
1.2. SCION Overview
1.2.1. Network Architecture and Naming
1.2.2. Routing
1.2.3. Infrastructure Components
1.2.4. Formal Verification
1.3. Conventions and Definitions
2. Key Concepts
2.1. Authentication
2.1.1. The Control-Plane PKI (CP-PKI)
2.1.2. TRC Update and Verification
2.1.3. Dissemination of TRC Updates
2.1.4. Grace Period
2.1.5. Revocation and Recovery from a Catastrophic Event
2.2. SCION Control Plane
2.2.1. Path Exploration
2.2.2. Path Registration
2.2.3. Path Lookup
2.2.4. Link Failures
2.3. SCION Data Plane
2.3.1. Path Construction via Segment Combination
2.3.2. Path Authorization
2.3.3. Forwarding
2.3.4. Intra-AS Communication
3. Deployment
3.1. Autonomous System Deployment
3.2. Internet Exchange Points
3.3. End Hosts and Incremental Deployability
3.3.1. Native End Hosts
3.3.2. SCION to IP Gateway (SIG)
3.4. Deployment Experiences
The Introduction section explores the motivation to develop SCION, followed by a short description of SCION's main elements. The sections after the Introduction provide further insight into SCION's key concepts and deployment scenarios. The document concludes with some concrete case studies where SCION has been successfully deployed in production.¶
Since its inception, the Internet has continued to expand, encompassing new uses over time. The continuous expansion has brought many issues to light, including a lack of control, limitations in scalability, performance and security, occurrences of severe outages, weak fault isolation, and energy consumption. With the core focus on functionality and operation, the current Internet offers little protection against attacks such as spoofing, IP-address hijacking, denial-of-service, and combinations of these. For more background information, see [SCHUCHARD2011], [LABOVITZ2000], [GRIFFIN1999], [SAHOO2009], and [RFC4264].¶
There have been numerous initiatives to address the above issues. Although these initiatives have brought many improvements, concerns regarding security and scalability still remain. For more details, see, e.g., [RFC4033], [RFC6480], [RFC8205], and [RFC8446], as well as [LYCHEV2013], [LI2014], [COOPER2013], [ROTHENBERGER2017], [MORILLO2021], and [KING2022].¶
As a consequence, today's Internet fails to fulfil many users' requirements. This especially pertains to the demands of enterprises globally exchanging sensitive information, such as financial institutions, healthcare providers, universities, multinationals, governments, critical and transportation infrastructure operators. These users require the Internet to be highly available at all times. They expect reliable operation of the global network also in case of failures. They need availability guarantees across multiple routing domains, even in the presence of attacks. They further want to rely on an Internet that can be multilaterally governed and is free from global kill-switches.¶
SCION has been developed in order to meet the above-mentioned requirements. SCION aims to reach the following goals:¶
Provide high-availability architecture (also in the presence of adversaries)¶
Provide fast failover in the case of inter-domain link or router failures¶
Prevent from IP-address hijacking, DoS, and other attacks¶
Enable path transparency as well as application-specific path optimizations¶
Improve the inter-domain control plane's scalability¶
Prepare the Internet for tomorrow's applications, such as virtual reality, Internet of Things (IoT), and all other applications requiring high-performance connectivity.¶
The above section describes SCION's aspiration to improve inter-AS routing and to focus on providing end-to-end connectivity. However, SCION does not solve intra-AS routing issues, nor does it provide end-to-end payload encryption, and identity authentication. These topics, which are equally important for the Internet to perform well, lie outside the scope of SCION.¶
The SCION inter-domain routing concept has initially been developed by researchers of the ETH Zuerich [PERRIG2017], and could in the meantime also gain attention and recognition in the international academic world. However, for an IT architecture to be successful, it must work well in practice, too. This section pays attention to the implementation considerations of a conceptual framework such as SCION in real life, on the basis of some RFCs exploring this topic. It also verifies in how far SCION meets the requirements mentioned and questions raised in these RFCs.¶
1.1.2.1. Avoiding Pitfalls
[RFC9049] describes why previous proposals to tackle some of the Internet's fundamental issues did not manage to succeed. SCION seems to avoid the pitfalls mentioned in that document. For example, SCION does not have to be adopted by the entire Internet to be effective: The routing architecture provides benefits already to early adapters. Even if only a small part of the global network works with SCION, adapters will still take advantage of using the SCION routing technology. Moreover, not only users of SCION benefit from it, also ISPs and operators benefit from deploying SCION: early deployments showed that providers can charge the use of SCION as premium connectivity, with users who are willing to pay for it. Furthermore, SCION can be installed on top of and function alongside the existing routing infrastructure and protocols--there is no need for high-impact changes in an operational network.¶
Another RFC that must be mentioned in this context is [RFC5218], "What Makes for a Successful Protocol?". SCION seems to fulfil most factors that contribute to the success of a protocol, as described in section 2.1 of the RFC. This includes such factors as offering a positive net value (i.e., the benefits of deploying SCION outweigh the costs), incremental deployability, and open source code availability. More importantly, SCION averts the failure criteria mentioned in section 1.4 of the RFC: SCION is already deployed and in use by many actors of the Swiss financial and academic ecosystems, and allows for multiple implementations, both open and closed source. As existing SCION implementations are easily portable, adoption in mainstream platforms is also possible.¶
1.1.2.2. Answering Questions
SCION can be considered a path-aware internetworking architecture, as described in [RFC9217]. This RFC poses (open) questions that must be answered in order to realize such a path-aware networking system. It was originally written to frame discussions in the Path Aware Networking Research Group (PANRG), and has been published to snapshot current thinking in this space.¶
SCION intends to answer the questions raised in this RFC. This especially pertains to the second, third, seventh, and eighth question:¶
How do endpoints and applications get access to accurate, useful, and trustworthy path properties?¶
How can endpoints select paths to use for traffic in a way that can be trusted by the network, the endpoints, and the applications using them?¶
How can a path-aware network in a path-aware internetwork be effectively operated, given control inputs from network administrators, application designers, and end users?¶
How can the incentives of network operators and end users be aligned to realize the vision of path-aware networking, and how can the transition from current ("path-oblivious") to path-aware networking be managed?¶
SCION's answers to these questions can be found in Key Concepts (Section 2) and Deployments (Section 3.4), respectively.¶
The emergence of multiple SCION implementations and early deployments highlights the need for standardization. The time seems therefore ripe to take SCION to the IETF, also in order to contribute to the important discussion regarding path-aware networking.¶
SCION has been designed to address the fundamental issues of today's Internet depicted in Why SCION - Motivation (Section 1.1). The following section gives a high-level overview of SCION's main elements, providing a basic understanding of this next-generation inter-network architecture.¶
SCION's main goal is to offer highly available and efficient inter-domain packet delivery--even in the presence of actively malicious entities. To achieve scalability and sovereignty, SCION organizes existing ASes into groups of independent routing planes, called Isolation Domains (ISD). An AS can be a member of multiple ISDs. All ASes in an ISD agree on a set of trust roots, called the Trust Root Configuration (TRC). The ISD is governed by a set of core ASes, which provide connectivity to other ISDs and manage the trust roots. Typically, a few distinguished ASes within an ISD form the ISD's core.¶
Isolation domains serve the following purposes:¶
They allow SCION to support trust heterogeneity, as each ISD can independently define its roots of trust;¶
They provide transparency for trust relationships;¶
They isolate the routing process within an ISD from external influences such as attacks and misconfigurations; and¶
They improve the scalability of the routing protocol by separating it into a process within and one between ISDs.¶
ISDs provide natural isolation of routing failures and misconfigurations, provide meaningful and enforceable trust, enable endpoints to optionally restrict traffic forwarding to trusted parts of the Internet infrastructure only, and enable scalable routing updates with high path-freshness.¶
1.2.1.1. Links
There are three types of links in SCION: core links, parent-child links, and peering links.¶
A core link can only exist between two core ASes.¶
A parent-child link requires that at least one of the two connected ASes is a non-core AS. ASes with a parent-child link usually belong to the same entity or have a provider-customer relationship.¶
A peering link also includes at least one non-core AS.¶
See Figure 1 for a high-level overview of the SCION network structure.¶
:                               :
:      [TRC]                      :
:          (::::::::::::::)         :      ......................
:        (::::: ISD core :::::)       :    :                      :
:    (:: +---+ ::::::::: +---+ ::)    :   :    [TRC]               :
: (::::: |CAS|===+---+ : |CAS| :::::) :  :        (: ISD core :)    :
:    (:: +---+ : |CAS|===+---+====)===:==:=====(=+---+ :: +---+ :)  :
:       /(:::::: +---+ ::::::) \      :  :    (: |CAS| == |CAS| :)  :
:      /  (::::::: | :::::::)   \     :  :     ( +---+ :: +---+ )   :
:     /            |             o    :  :       /(::::::::::::)    :
:    o             |           +---+  :  :      /         \         :
:  +---+           |          /|ASb|  :  :     /           \        :
:  |ASa|           |         / +---+  :  :    o             o       :
:  +---+           |        /    |    :  :  +---+          +---+    :
:    |             |       /     |    :  :  |ASx| ---------|ASy|    :
:    |             |      /      o    :  :  +---+          +---+    :
:    o             o     /     +---+  :  :    |                     :
:  +---+         +---+  /      |ASe|  :  :    o                     :
:  |ASc|---------|ASd| o       +---+ -:--:--+---+                   :
:  +---+         +---+                :  :  |ASz|      ISD 2        :
:                                   :    : +---+                  :
:            ISD 1                :      ........................
Parent AS - child AS: o
Peering link: ----
Core link: ===
Core AS: CAS
Figure 1: SCION network structure
SCION operates on two routing levels: intra-ISD and inter-ISD. Both levels use path-segment construction beacons (PCBs) to explore network paths. A PCB is initiated by a core AS and then disseminated either within an ISD (to explore intra-ISD paths) or among core ASes (to explore core paths across different ISDs). The PCBs accumulate cryptographically protected path and forwarding information on AS-level, and store this information in the form of hop fields (HFs). End hosts use information from these hop fields to create end-to-end forwarding paths for data packets, who carry this information in their packet headers. This concept is called packet-carried forwarding state (PCFS). The concept also supports multi-path communication among end hosts.¶
The process of creating an end-to-end forwarding path consists of the following steps:¶
First, an AS discovers paths to other ASes, during the path exploration (or beaconing) phase.¶
The AS then selects a few PCBs according to defined policies, transforms the selected PCBs into path segments, and registers these segments with its path infrastructure, thus making them available to other ASes. This happens during the path registration phase.¶
During the path resolution phase, the actual creation of an end-to-end forwarding path to the destination takes place. For this, an end host performs (a) a path lookup step, to obtain path segments, and (b) a path combination step, to combine the forwarding path from the segments.¶
Figure 2 below shows the SCION routing process in a nutshell.¶
+------------------+             +------------------+
| Path Exploration |             |                  |
|   (Beaconing)    |------------>|Path Registration |
|                  |             |                  |
+------------------+             +--------+---------+
+-----------------+
+------------------v-----------------------+
|            Path Resolution               |
|+--------------+     +-------------------+|
|| Path Lookup  |---->| Path Combination  ||
+------------------------------------------+
Figure 2: SCION routing in a nutshell
1.2.2.1. ISD and AS numbering
SCION decouples end-host addressing from inter-domain routing. Routing is based on the <ISD, AS> tuple, agnostic of end-host addressing. Existing AS numbers are inherited from the current Internet, but a 48-bit namespace allows for additional SCION AS numbers beyond the 32-bit space in use today. The end host local address is not used for inter-domain routing or forwarding, does not need to be globally unique, and can thus be an IPv4, IPv6, or MAC address, for example. A SCION address is therefore composed of the <ISD, AS, local address> 3-tuple.¶
The beacon service, the path service, and the certificate service are the main control-plane infrastructure components within a SCION AS. Each service can be deployed redundantly, depending on the AS's size and type. Existing Internal routers are used to forward packets inside the AS, while SCION border routers provide interconnectivity between ASes.¶
The beacon service discovers path information. It is responsible for generating, receiving, and propagating PCBs. Periodically, the beacon service generates a set of PCBs, which are forwarded to its child ASes or neighboring core ASes. The PCBs are flooded over policy-compliant paths to discover multiple paths between any pair of core ASes.¶
The path service stores mappings from AS identifiers to sets of announced path segments. The path service is organized as a hierarchical caching system similar to that of DNS. Through the beacon service, ASes select the set of path segments through which they want to be reached, and they register them to the path service in the ISD core.¶
The certificate service keeps cached copies of certificates and manages keys and certificates for securing inter-AS communication. The certificate service is queried by the beacon service when validating the authenticity of PCBs (i.e., when the beacon service lacks a certificate).¶
Border routers are deployed at the edge of SCION ASes. The main task of border routers is to forward packets to a neighbor border router or to the destination host within the AS. While SCION takes care of inter-domain routing, it relies on existing routing protocols (e.g., IS-IS, OSPF, SR) and communication fabric (e.g., IP, MPLS) for intra-domain forwarding. Internal routers, therefore, do not need to be changed to support SCION.¶
An additional feature of SCION is its formal verification. The SCION network system consists of a variety of components such as routers, servers, and edge devices. Such a complex system eludes the mental capacities of human beings for considering all possible states and interactions. That is why SCION includes a formal verification framework developed by the Department of Computer Science of the ETH Zurich [KLENZE2021]. This guarantees that packet forwarding as well as SCION's authentication mechanisms and implementations are correct and consistent.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
This section explains the SCION key concepts, including authentication, control- and data plane.¶
SCION's control plane relies on a public-key infrastructure called the control-plane PKI (CP-PKI), which is organized on ISD-level. Each ISD can independently build its own roots of trust, defined in a file called trust root configuration (TRC).¶
Note: This section describes the SCION authentication concept on a very high level. A much more detailed description of SCION's authentication is available in [I-D.dekater-scion-pki].¶
Trust within each isolation domain is anchored in the trust root configuration (TRC) file. Each TRC contains a collection of signed root certificates, which are used to sign CA certificates, which are in turn used to sign AS certificates. The TRC also includes ISD-policies that specify, for example, the TRC's usage, validity, and future updates. A TRC is a fundamental component of an CP-PKI.¶
The initial TRC in an ISD is called the base TRC. This base TRC constitutes the ISD's trust anchor. It is signed during a signing ceremony and then distributed throughout the ISD. All entities within the ISD obtain the initial TRC with an offline mechanism such as a USB flash drive provided by a trusted AS, like the relevant ISP, or with an online mechanism that relies on a trust-on-first-use (TOFU) approach. However, all updates to the base TRCs are performed in a straightforward process that does not require any manual or out-of-band action (such as a software update), see TRC Update and Verification (Section 2.1.2).¶
Figure 3 shows the TRC trust chain and associated certificates. TRC 1 is the base TRC, and TRC 2 and 3 constitute updates to this base TRC. TRC 2 must be verified using the voting certificates in TRC 1. Control-plane (CP) root certificates are used to verify other CP certificates (which are in turn used to verify path-segment construction beacons PCBs).¶
Each SCION AS must hold a private key (to sign PCBs) and a certificate attesting that it is the rightful owner of the corresponding public key. One of the main roles of the TRC is thus enabling the verification of AS certificates and PCBs.¶
TRC 2
+--------------------------------------+
|+------------------------------------+|
||- Version       - Core ASes         ||
+--------+     ||- ID            - Description       ||    +--------+
| TRC 1  |     ||- Validity      - No Trust Reset    ||    | TRC 3  |
| (Base  |---->||- Grace Period  - Voting Quorum     ||--->|        |
|  TRC)  |     ||- ...                               ||    |        |
+--------+     |+------------------------------------+|    +--------+
|+----------------+  +----------------+|
|| Regular Voting |  |Sensitive Voting||
||  Certificate   |  |  Certificate   ||
||     Votes      |  |   Signatures   ||
||        CP Root Certificates        ||
|+----------+-------------+-----------+|
|           |             |            |
+-----------+-------------+------------+
|             |
v             v
+-----------+         +-----------+
|   CP CA   |         |   CP CA   |
|Certificate|         |Certificate|
+-+-------+-+         +-----+-----+
|       |                 |
v       v                 v
+-----------+ +-----------+      +-----------+
|   CP AS   | |   CP AS   |      |   CP AS   |
|Certificate| |Certificate|      |Certificate|
Figure 3: TRC contents and trust chain
With a base TRC as trust anchor, TRCs can be updated in a verifiable manner. There are two kinds of TRC updates: regular and sensitive updates. A regular TRC update happens when the TRC's validity period expires. This period is defined by the validity parameter in the TRC. The default is one year. A TRC update is sensitive if and only if critical sections of the TRC are affected (for example, if the set of core ASes is modified). For both regular and sensitive TRC updates, a number of votes (in the form of signatures) must be cast to approve the update. This number of votes is dictated by the voting quorum and set in each TRC with the voting quorum parameter.¶
Information about a TRC update is disseminated via the SCION's beaconing process, through the path-segment constructions beacons. Each PCB contains the version number of the currently active TRC. If an AS receives a PCB with a TRC version number higher than the locally stored TRC, it requests the PCB-sending AS for the new TRC. The new TRC is verified on the basis of the current one, and is accepted if it contains at least the required quorum of correct signatures by trust roots defined in the current TRC. This simple dissemination mechanism has two advantages: It is very efficient (as fresh PCBs rapidly reach all ASes), and it avoids circular dependencies with regard to the verification of PCBs and the beaconing process itself (as no server needs to be contacted over unknown paths in order to fetch the updated TRC).¶
At most two TRCs per ISD can be active at the same time. The TRC parameter grace period indicates for how long the currently active TRC can still be active after a new TRC is disseminated. This so-called grace period starts at the beginning of the validity period of the new TRC. An older TRC can only be active until either (1) the grace period has passed, or (2) yet a newer TRC is announced. AS certificates are validated by following the chain of trust up to an active TRC.¶
The TRC dissemination mechanism also enables rapid revocation of trust roots. When a trust root is compromised, the other trust roots can remove it from the TRC and disseminate a new TRC alongside a PCB with a new version number.¶
In case of a catastrophic event--such as several private root keys being disclosed due to a critical vulnerability in a cryptographic library--SCION is equipped with a recovery procedure called trust reset. This procedure consists of creating a new TRC with fresh, trustworthy keys (and potentially new algorithms), and redistributing this TRC out-of-band. A trust reset effectively establishes a new base TRC for the ISD. It is possible for ISDs to disable trust resets by setting the no trust reset Boolean parameter to "true" in their TRC, with the effect that the entire ISD would have to be abandoned in the event of such a catastrophic compromise (this abandonment would also have to be announced out-of-band).¶
The partition of the SCION network into ISDs guarantees that no single entity can take down the entire network. Even if several entities formed a coalition to carry out an attack, the effects of that attack would be limited to one or a few ISDs.¶
The SCION control plane is responsible for discovering path segments and making them available to end hosts. This process includes path exploration, registration, and lookup; it involves the path service, beacon service, and certificate service, both in core ASes and non-core ASes.¶
Note: This section describes the SCION control plane on a very high level. A much more detailed description of SCION's control plane will follow in a separate internet draft.¶
In SCION, the path segment construction process is referred to as beaconing. The beacon service of each AS is responsible for the beaconing process. The beacon service generates, receives, and propagates the path-segment construction beacons (PCBs) on a regular basis, to iteratively construct path segments.¶
There are three types of path segments (note that all path segments can be used to send data traffic in both directions):¶
A path segment from a non-core AS to a core AS is an up-path segment.¶
A path segment from a core AS to a non-core AS is a down-path segment.¶
A path segment between core ASes is a core-path segment.¶
All path segments are invertible: A core-path segment can be used bidirectional, and an up-path segment can be converted into a down-path segment, or vice versa, depending on the direction of the end-to-end path.¶
Path segment construction is conducted hierarchically on two levels:¶
Core beaconing is the process of constructing path segments between core ASes. During core beaconing, the beacon service of a core AS either initiates PCBs or propagates PCBs received from neighboring core ASes to all other neighboring core ASes. Core beaconing in SCION is similar to BGP's route-advertising process, although in SCION the process is periodic and PCBs are flooded over policy-compliant paths to discover multiple paths between any pair of core ASes.¶
Intra-ISD beaconing creates path segments from core ASes to non-core ASes. For this, the beacon service of a core AS creates PCBs and sends them to the non-core child ASes (typically customer ASes). The beacon service of a non-core child AS receives these PCBs and forwards them to its child ASes, and so on. This procedure continues until the PCB reaches an AS without any customer (leaf AS). As a result, all ASes receive path segments to reach the core ASes of their ISD.¶
On its way down, a PCB accumulates cryptographically protected path- and forwarding information per traversed AS. At every AS, metadata as well as information about the AS's ingress and egress interfaces (i.e., link identifiers) is added to the PCB. The ingress and egress interface IDs identify connections to neighboring ASes. These IDs only need to be unique within each AS. Therefore, they can be chosen and encoded by each AS independently and without any need for coordination.¶
SCION also supports shortcuts and peering links. In a shortcut, a path only contains an up-path and a down-path segment, which can cross over at a non-core AS that is common to both paths. Peering links can be added to up- or down-path segments, resulting in an operation similar to today's Internet.¶
To reduce beaconing overhead and prevent possible forwarding loops, PCBs do not traverse peering links. Instead, peering links are announced along with a regular path in a PCB. If the path segments of both ASes at the end of a peering link contain this peering link, then it is possible to use the peering link to shortcut the end-to-end path (i.e., without going through the core). SCION also supports peering links that cross ISD boundaries, according to SCION's path transparency property.¶
Figure 4 shows how intra-ISD PCB propagation works, from the ISD's core AS down to child ASes. For the sake of illustration, the interfaces of each AS are numbered with integer values. In practice, each AS can choose any encoding for its interfaces; in fact, only the AS itself needs to understand its encoding. Here, AS F receives two different PCBs via two different links from core AS X. Moreover, AS F uses two different links to send two different PCBs to AS G, each containing the respective egress interfaces. AS G extends the two PCBs and forwards both of them over a single link to a child AS.¶
.-----.
; Core  :
+-----+  : AS X  ;
|PCB  |   \ 2 1 / +-----+
|Core |    `+-+'  |pcb  |
|Out:2|     | |   |core |
+--+--+   +-+ |   |out:1|
|      |   |   +--+--+
v      |   |      |
.-+---+.     v
.---.       /  2   3 \             .---.
(  J  )- - -; 1      4 :- - - - - -(  H  )
`---'      :   AS F   ;            `---'
+--\7       /
+----------+ +----------+ <-+     6  5
|PCB       | |pcb       |        `+--+'
|Core      | |core      |         |  |
|Out:2     | |out:1     |         |  |
|----------| |----------|         |  |
|AS F      | |as f      |         |  |
|In:2 Out:7| |in:3 out:7|         |  |
|Peer J:1  | |peer j:1  |         |  | +----------+ +----------+
|Peer H:4  | |peer h:4  |         |  | |PCB       | |pcb       |
|          | |          |         |  | |Core      | |core      |
+--+-------+ +--+-------+         |  | |Out:2     | |out:1     |
|            |                 |  | |----------| |----------|
<+           <+                 |  | |AS F      | |as f      |
|  | |In:2 Out:5| |in:3 out:5|
+----------+ +----------+|  | |Peer J:1  | |peer j:1  |
|PCB       | |pcb       ||  | |Peer H:4  | |peer h:4  |
|Core      | |core      ||  | |          | |          |
|Out:2     | |out:1     ||  | +----+-----+ +----+-----+
|----------| |----------||  |      |            |
|AS F      | |as f      ||  |      v            v
|In:2 Out:6| |in:3 out:6||  |
|Peer J:1  | |peer j:1  ||  |
|Peer H:4  | |peer h:4  ||  |
|          | |          ||  |
+----+-----+ +----+-----+|  |
|            |     .+--+-.
v            v   ,' 5  1  `.
;           :
:   AS G    ;
\         /
+---` 4  3 ,'
<-+     `--+'
|  +----------+ +----------+
|  |PCB       | |pcb       |
|  |Core      | |core      |
|  |Out:2     | |out:1     |
+----------+ +----------+ |  |----------| |----------|
|PCB       | |pcb       | |  |AS F      | |as f      |
|Core      | |core      | |  |In:2 Out:5| |in:3 out:5|
|Out:2     | |out:1     | |  |Peer J:1  | |peer j:1  |
|----------| |----------| |  |Peer H:4  | |peer h:4  |
|AS F      | |as f      | |  |----------| |----------|
|In:2 Out:6| |in:3 out:6| |  |AS G      | |as g      |
|Peer J:1  | |peer j:1  | |  |In:1 Out:3| |in:1 out:3|
|Peer H:4  | |peer h:4  | |  |          | |          |
|----------| |----------| |  +----+-----+ +----+-----+
|AS G      | |as g      | |       |            |
|In:5 Out:3| |in:5 out:3| v       v            v
|          | |          |
+----+-----+ +----+-----+
|            |
v            v
Figure 4: Intra-ISD PCB propagation from the ISD core down to child ASes
2.2.1.1. Security
Each PCB contains signatures of all on-path ASes. Every time a beacon service receives a PCB, it validates the PCB's authenticity. During this process, the beacon service can query the certificate service, for example, when it lacks an intermediate certificate.¶
2.2.1.2. Policies
Each AS can independently set policies dictating which PCBs are sent in which time intervals, and to which neighbors. In particular, PCBs do not need to be propagated immediately upon arrival. However, during bootstrapping and if the AS obtains a PCB containing a previously unknown path, the AS should forward the PCB immediately, to ensure quick connectivity establishment.¶
Both the beacon service and the path service are involved in the path registration process. A non-core AS typically receives several PCBs representing several path segments to various core ASes. Out of these PCBs, the non-core AS must select those down-path segments through which it wants to be reached. It is the task of the AS's beacon service to make this selection, according to the criteria described in Path-Segment Selection (Section 2.2.2.1). The beacon service then registers these path segments both at the local path service and at the path service of all core ASes. When links fail, segments expire, or better segments become available, the beacon service updates the down-path segments registered for its AS.¶
As a result, a core AS's path service contains all intra-ISD path segments registered by the leaf ASes of its ISD. In addition, a core AS path service also stores the preferred core-path segments to other core ASes.¶
2.2.2.1. Path-Segment Selection
Among the received PCBs, the beacon service of an AS must choose (1) a set of PCBs to propagate further, and (2) a set of path segments to register. The selection of these PCBs and path segments is based on a path quality metric. This metric aims at identifying consistent, diverse, efficient, and policy-compliant paths:¶
Consistency implies that at least one property along the path is uniform, such as an AS capability (e.g., high bandwidth).¶
Diversity means that the set of paths announced over time are as path-disjoint as possible, in order to provide high-quality multipath options.¶
Efficiency refers to the length, bandwidth, latency, utilization, and availability of a path, where more efficient paths are naturally preferred.¶
Policy compliance implies that the path adheres to the AS's routing policy.¶
Based on past PCBs, the AS beacon service assigns scores to the current set of candidate path segments, and sends the best segments in the next beaconing interval.¶
Core beaconing operates similarly to intra-ISD beaconing, except that core PCBs only traverse core ASes. The same path selection metrics apply, where a core AS attempts to forward the set of most desirable paths to its neighbors.¶
An end host (source) who wants to start communication with another host (destination), requires up to three path segments: An up-path segment to reach the ISD core, a core-path segment to reach the destination ISD, and a down-path segment to reach the destination AS. The source host queries the path service in its AS for such segments. The path service has up-path segments stored in its database and furthermore checks if it has appropriate core- and down-path segments in its cache; in this case it returns them immediately.¶
If not, the path service in the source AS queries core path services (using locally stored up-path segments) in the source ISD for core-path segments to the destination ISD. Then, it combines up-path segments with the newly retrieved core-path segments, and queries core path services in the remote ISD to fetch remote down-path segments. To improve overall efficiency, the local path service caches the returned path segments and uses parallelism when requesting path segments from core path services. Finally, the local path service returns all path segments to the source host.¶
This recursive lookup significantly simplifies the process for end hosts (which only have to send a single query, similar to stub DNS resolvers). The caching strategy ensures that path lookups are fast for frequently used destinations (similar to caching in recursive DNS resolvers).¶
Unlike in the current Internet, link failures are not automatically resolved by the network, but require active handling by end hosts. Since SCION forwarding paths are static, they break when one of the links fails. Link failures are handled by a two-pronged approach that typically masks link failures without any outage to the application and rapidly re-establishes fresh working paths:¶
The SCION Control Message Protocol (SCMP) (the SCION equivalent of ICMP) is used for signaling connectivity problems. Instead of relying on application- or transport-layer timeouts, end hosts get immediate feedback from the network if a path stops working, and can quickly switch to an alternative path.¶
SCION end hosts are encouraged to use multipath communication by default, thus masking a link failure with another working path. As multipath communication can increase availability (even in environments with very limited path choices), SCION beacon services attempt to create disjoint paths, SCION path services attempt to select and announce disjoint paths, and end hosts compose path segments to achieve maximum resilience to path failure. Consequently, most link failures in SCION remain unnoticed by the application, unlike the frequent (albeit mostly brief) outages in the current Internet. See also [ANDERSEN2001], [KATZ2012], [KUSHMAN2007], and [HITZ2021].¶
While the control plane is responsible for providing end-to-end paths, the data plane ensures that packets are forwarded on the selected path. SCION border routers forward packets to the next AS based on the AS-level path in the packet header (which is extended with ingress and egress interface identifiers for each AS), without inspecting the destination address and also without consulting an inter-domain forwarding table. Only the border router at the destination AS needs to inspect the destination address to forward it to the appropriate local end host.¶
Because SCION splits the information about the locator (the path towards the destination AS) and the identifier (the destination address), the identifier can have any format that the destination AS can interpret--only the destination needs to consider that local identifier (see also [RFC6830]). In other words, an AS can select an arbitrary addressing format for its hosts, e.g., a 4-byte IPv4, 6-byte media access control (MAC) address, 16-byte IPv6, or any other up to 16-byte addressing scheme. A valuable consequence is that hosts with different address types can directly communicate.¶
The next two sections describe how an end host combines path segments into an end-to-end forwarding path, and how border routers forward packets efficiently.¶
Note: This section describes the SCION data plane on a very high level. A much more detailed description of SCION's data plane will follow in a separate internet draft.¶
Through the path lookup, the end host obtains path segments that must be combined into an end-to-end path. A valid SCION forwarding path can be created by combining up to three path segments, in the following ways:¶
Immediate combination of path segments: The last AS on the up-path segment is also the first AS on the down-path segment. In this case, the simple combination of an up-path segment and a down-path segment creates a valid forwarding path.¶
AS shortcut: The up-path segment and down-path segment intersect at a non-core AS. In this case, a shorter forwarding path can be created by removing the extraneous part of the path.¶
Peering shortcut: A peering link exists between the two segments, so a shortcut via the peering link is possible. As in the AS shortcut case, the extraneous path segment is cut off. The peering link could be traversing to a different ISD.¶
Combination with a core-path segment: The last AS on the up-path segment is different from the first AS on the down-path segment. This case requires an additional core-path segment to connect the up- and down-path segment. If the communication remains within the same ISD, a local ISD core-path segment is needed; otherwise, an inter-ISD core-path segment is required.¶
On-path: The destination AS is part of the up-path segment or the source AS is part of the down-path segment; in this case, a single up- or down-path segment, respectively, is sufficient to create a forwarding path.¶
Once a forwarding path is chosen, it is encoded in the SCION packet header. This makes inter-domain routing tables unnecessary for border routers: Both the ingress and the egress interface of each AS on the path are encoded as packet-carried forwarding state (PCFS) in the packet header. The destination can respond to the source by reversing the end-to-end path from the packet header, or it can perform its own path lookup and combination.¶
The SCION packet header contains of a sequence of hop fields (HFs), one HF for each AS that is traversed on the end-to-end path. Each hop field contains the encoded numbers of the ingress and egress links, and thus defines which interfaces may be used to enter and leave an AS. In addition to the hop fields, each path segment contains an info field (INF) with basic information about the segment. A host can create an end-to-end forwarding path by extracting info fields and hop fields from path segments, as depicted in Figure 5. The additional meta header (META) contains pointers to the currently active INF and HF.¶
up-path segment        core-path segment        down-path segment
+-------+              +-------+                +-------+
|+-----+|              |+-----+|                |+-----+|
|+ INF ||----------+   |+ INF ||---+            |+ INF ||-+
|+-----+|          |   |+-----+|   |            |+-----+| |
|| hf  ||--------+ |   || hf  ||---+--+         || hf  ||-+--+
|+-----+|        | |   |+-----+|   |  |         |+-----+| |  |
|| hf  ||-----+  | |   || hf  ||---+--+--+      || hf  ||-+--+--+
|+-----+|     |  | |   |+-----+|   |  |  |      |+-----+| |  |  |
|+-----+|     |  | |   +-------+   |  |  |      +-------+ |  |  |
|| hf  ||--+  |  | |               |  |  |                |  |  |
|+-----+|  |  |  | |   +--------+  |  |  |                |  |  |
+-------+  |  |  | |   |++-----+|  |  |  |                |  |  |
|  |  | |   |++ Meta||  |  |  |                |  |  |
|  |  | |   |++-----+|  |  |  |                |  |  |
|  |  | |   |+-----+ |  |  |  |                |  |  |
|  |  | +-->|+ INF | |  |  |  |                |  |  |
|  |  |     |+-----+ |  |  |  |                |  |  |
|  |  |     |+ INF | |<-+  |  |                |  |  |
|  |  |     |+-----+ |     |  |                |  |  |
|  |  |     |+ INF | |<----+--+----------------+  |  |
|  |  |     |+-----+ |     |  |                   |  |
|  |  +---->|| hf  | |     |  |                   |  |
|  |        |+-----+ |     |  |                   |  |
|  +------->|| hf  | |     |  |                   |  |
|           |+-----+ |     |  |                   |  |
+---------->|| hf  | |     |  |                   |  |
|+-----+ |     |  |                   |  |
|| hf  | |<----+  |                   |  |
|+-----+ |        |                   |  |
|| hf  | |<-------+                   |  |
|+-----+ |                            |  |
|| hf  | |<---------------------------+  |
|+-----+ |                               |
|| hf  | |<------------------------------+
|+-----+ |
+--------+
forwarding path
Figure 5: Combining three path segments into a forwarding path
It is crucial for the data plane that end hosts only use paths constructed and authorized by ASes in the control plane. In particular, end hosts should not be able to craft HFs themselves, modify HFs in authorized path segments, or combine HFs of different path segments (path splicing). This property is called path authorization (see [KLENZE2021] and [LEGNER2020]).¶
SCION achieves path authorization by creating message-authentication codes (MACs) during the beaconing process. Each AS calculates these MACs using a local secret key (that is only shared between SCION infrastructure elements within the AS) and chains them to the previous HFs. The MACs are then included in the forwarding path as part of the respective HFs.¶
Routers can efficiently forward packets in the SCION architecture. In particular, the absence of inter-domain routing tables and of complex longest-IP-prefix matching performed by current routers enables the construction of more efficient routers.¶
During packet forwarding, a SCION border router at the ingress point of the AS verifies that:¶
the packet entered through the correct ingress interface corresponding to the information in the HF,¶
the HF is still valid, and¶
the MAC in the HF is correct.¶
If the packet has not yet reached the destination AS, the egress interface number in the HF of the non-destination AS refers to the egress SCION border router of this AS. In this case, the packet can be sent from the ingress SCION border router to the egress SCION border router via native intra-domain forwarding (e.g., IP or MPLS). In case the packet has arrived at the destination AS, the destination AS's border router inspects the destination address and sends the packet to the corresponding host.¶
SCION routers use IP to communicate within an AS, therefore they rely on existing intra-domain routing protocols, such as Multiprotocol Label Switching (MPLS) or others.¶
Adoption of a next-generation architecture is a challenging task, as it needs to be integrated with, and operate alongside existing infrastructure. SCION is designed to coexist with existing intra-domain routing infrastructure, and comprises coexistence and transition mechanisms that facilitate adoption, in accordance to principles defined in [RFC8170]. The following section discusses practical considerations for deploying SCION and briefly touches on some of the transition mechanisms, with focus on:¶
Autonomous Systems (Section 3.1),¶
Internet Exchange Points (Section 3.2), and¶
end hosts (Section 3.3), covering both native SCION hosts and SCION to IP encapsulation.¶
We then describe some of the early adopters deployment experiences. A more detailed adoption plan is to be outlined in dedicated documents.¶
A SCION AS needs to deploy the SCION infrastructure components (Section 1.2.3) and border routers. Within an AS, SCION is often deployed as an IP overlay on top of the existing network. This way SCION allows to reuse the existing intra-domain network and equipment (e.g., IP, MPLS). Customer-side SCION border routers directly connect to the provider-side border routers using last-mile connections. The SCION design assumes that AS's internal entities are considered to be trustworthy, therefore the IP overlay or the first-hop routing does not compromise or degrade any security properties SCION delivers. When it comes to inter-domain communication, an overlay deployment on top of today's Internet is not desirable, as SCION would inherit issues from its weak underlay. Thus, inter-AS SCION links are usually deployed in parallel to existing links, in order to preserve its security properties. That is, two SCION border routers from neighbour ASes are directly connected via a layer-2 cross-connection at a common point-of-presence.¶
All SCION AS components can be deployed on standard x86 commercial off-the-shelf servers or virtual machines. In fact, SCION border routers do not rely on forwarding tables, therefore they do not require specialized hardware. Practice shows that off-the-shelf hardware can handle up to 100 Gbps links, while a prototype P4 implementation [DERUITER2021] showed that it is possible to forward SCION traffic even at terabit speeds.¶
Overall, an AS can be connected to SCION without high-impact changes to its network. In addition, use of commodity hardware for both control and data-plane components reduces initial deployment costs.¶
Internet Exchange Points (IXP) play as important a role for SCION as they do in today's Internet. SCION can be deployed at existing IXPs following a "big switch" model, where the IXP provides a large L2 switch between multiple SCION ASes. SCION has been deployed following this model at the Swiss Internet Exchange (SwissIX), currently interconnecting major SCION Swiss ISPs and enterprises through bi-lateral peering over dedicated SCION ports.¶
Additionally, thanks to its path-awareness, SCION offers the option of an enhanced deployment model, i.e., to expose the internal topology of an IXP within the SCION control plane. This enables IXP customers to use SCION's multipath and fast failover capabilities to leverage the IXP's internal links (including backup links) and to select paths depending on the application's needs. IXPs have therefore an incentive to expose their rich internal connectivity, as the benefits from SCION's multipath capabilities would increase their value for customers and provide them with a competitive advantage.¶
End users can leverage SCION in two different ways: (1) using SCION-aware applications on a SCION native end host (Section 3.3.1), or (2) using transparent IP-to-SCION conversion (Section 3.3.2). The benefit of using SCION natively is that the full range of advantages becomes available to applications, at the cost of installing the SCION endpoint stack and making the application SCION-aware. In early deployments, the second approach is often preferred, so that no changes are needed within applications or end hosts.¶
A SCION native end host's stack consists of a dispatcher, which handles all incoming and outgoing SCION packets, and of a SCION daemon, which handles control-plane messages. The latter fetches paths to remote ASes and provides an API for applications and libraries to interact with the SCION control plane (i.e., for path lookup, SCION extensions). The current SCION implementation uses an UDP/IP underlay for communication between end hosts and SCION routers. This allows reuse of existing intra-domain networking infrastructure. SCION end hosts can optionally use automated bootstrapping mechanisms to retrieve configuration from the network and establish SCION connectivity. This way, clients require no pre-existing network-specific configurations.¶
A SCION-IP-Gateway (SIG) encapsulates regular IP packets into SCION packets with a corresponding SIG at the destination that performs the decapsulation. A SIG can be deployed close to the end user (i.e., at branches of an enterprise, on a CPE), or within an ISP's network. In the latter case, the SIG is called carrier-grade SIG, as it serves multiple customers within the AS where it is deployed. This approach has the advantage that it does not require any changes at the customer's premises. In order to allow incremental deployability and to ease transition from legacy IP-based Internet to SCION, SIGs can be augmented with mechanisms allowing them to coordinate and automatically exchange IP prefix information. A more detailed description of the SIG and its coordination mechanisms is to be presented in dedicated documents.¶
SCION has been deployed in production by multiple entities, growing its acceptance among industry. While early deployments started on academic and research networks, SCION has expanded to serve the financial industry, government, and it is being evaluated for the healthcare sector.¶
In 2017, SCION was evaluated for production use by a central bank, with the goal of modernising the network interconnecting banks and their branches. SCION was chosen, as it allows moving away from a dedicated private network to a reliable Internet-based solution. SCION connectivity was later extended to support system-critical applications, like the national real-time gross settlement (RTGS) system, connecting all country's banks to exchange real-time payment information. The network, called Secure Swiss Finance Network or SSFN, is implemented as a SCION ISD, where a federation of three ISPs forms the ISD core. Financial institutions are themselves SCION ASes and directly connect to one or more of the core ASes. Institutions deploy SCION-IP gateways (SIGs), transparently enabling their traditional IP-based applications to use the SCION network. The concept of the SCION ISD also provides a mechanism to implement strict governance and access control (through the issuance of AS certificates).¶
Besides the SSFN, SCION connectivity has also been adopted by government entities for their international communications. In addition, Swiss higher education institutions are connected thanks to the SCI-ED network.¶
In addition to productive deployments, SCION also comprises a global SCION research testbed called SCIONLab. It is composed of dozens of globally distributed infrastructure ASes, mostly run by academic institutions. The testbed is open to any user who can easily set up their own AS with the aid of a web-based UI, connect to the network, and run experiments. The setup has been the earliest global deployment of SCION and it has been supporting research and development of path-aware networking and SCION.¶
Currently, this document has no request for action to IANA. However, when full specification of SCION is available, requests for IANA actions are expected regarding the registration of optional packet header fields as well as the coordination of SCION ISD and AS number assignments.¶
SCION has been designed from the outset to offer security by default, and thus there are manifold security considerations. As a matter of fact, SCION's protocol design has been formally verified and the open source router implementation is undergoing formal verification (see also [KLENZE2021]). Describing all security considerations here, therefore, would go beyond the scope of this document. A separate document including all security implications and considerations will follow later.¶
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Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017 , <https://www.rfc-editor.org/rfc/rfc8174>.
[ANDERSEN2001]
Andersen, D., Balakrishnan, H., Kaashoek, F., and R. Morris, "Resilient overlay networks", Proceedings of the eighteenth ACM symposium on Operating systems principles, DOI 10.1145/502034.502048, October 2001 , <https://doi.org/10.1145/502034.502048>.
[CHUAT22]
Chuat, L., Legner, M., Basin, D., Hausheer, D., Hitz, S., Mueller, P., and A. Perrig, "The Complete Guide to SCION", ISBN 978-3-031-05287-3, 2022 , <https://doi.org/10.1007/978-3-031-05288-0>.
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[DERUITER2021]
de Ruiter, J. and C. Schutijser, "Next-generation internet at terabit speed: SCION in P4", Proceedings of the 17th International Conference on emerging Networking EXperiments and Technologies, DOI 10.1145/3485983.3494839, December 2021 , <https://doi.org/10.1145/3485983.3494839>.
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Hitz, S., "Demonstrating the reliability and resilience of Secure Swiss Finance Network", 2021 , <https://perma.cc/4H3Q-WZNG>.
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de Kater, C. and N. Rustignoli, "SCION Overview", 2022 , <https://datatracker.ietf.org/doc/draft-dekater-scion-pki/>.
[I-D.rustignoli-scion-components]
de Kater, C. and N. Rustignoli, "SCION Components Analysis", 2022 , <https://datatracker.ietf.org/doc/draft-rustignoli-panrg-scion-components/>.
[KATZ2012]
Katz-Bassett, E., Scott, C., Choffnes, D., Cunha, Í., Valancius, V., Feamster, N., Madhyastha, H., Anderson, T., and A. Krishnamurthy, "LIFEGUARD: practical repair of persistent route failures", ACM SIGCOMM Computer Communication Review vol. 42, no. 4, pp. 395-406, DOI 10.1145/2377677.2377756, September 2012 , <https://doi.org/10.1145/2377677.2377756>.
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King, D., Farrel, A., and C. Jacquenet, "Challenges for the Internet Routing Systems Introduced by Semantic Routing", 2022 , <https://datatracker.ietf.org/doc/draft-king-irtf-challenges-in-routing/>.
[KLENZE2021]
Klenze, T., Sprenger, C., and D. Basin, "Formal Verification of Secure Forwarding Protocols", 2021 IEEE 34th Computer Security Foundations Symposium (CSF), DOI 10.1109/csf51468.2021.00018, June 2021 , <https://doi.org/10.1109/csf51468.2021.00018>.
[KUSHMAN2007]
Kushman, N., Kandula, S., and D. Katabi, "Can you hear me now?!: it must be BGP", ACM SIGCOMM Computer Communication Review vol. 37, no. 2, pp. 75-84, DOI 10.1145/1232919.1232927, March 2007 , <https://doi.org/10.1145/1232919.1232927>.
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Labovitz, C., Ahuja, A., Bose, A., and F. Jahanian, "Delayed Internet routing convergence", Proceedings of the conference on Applications, Technologies, Architectures, and Protocols for Computer Communication - SIGCOMM '00, DOI 10.1145/347059.347428, 2000 , <https://doi.org/10.1145/347059.347428>.
[LEGNER2020]
Legner, M., Klenze, T., Wyss, M., Sprenger, C., and A. Perrig, "EPIC: Every Packet Is Checked in the Data Plane of a Path-Aware Internet", 2020 , <https://www.usenix.org/conference/usenixsecurity20/presentation/legner>.
[LI2014]
Li, Q., Hu, Y., and X. Zhang, "Even Rockets Cannot Make Pigs Fly Sustainably: Can BGP be Secured with BGPsec?", Proceedings 2014 Workshop on Security of Emerging Networking Technologies, DOI 10.14722/sent.2014.23001, 2014 , <https://doi.org/10.14722/sent.2014.23001>.
[LYCHEV2013]
Lychev, R., Goldberg, S., and M. Schapira, "BGP security in partial deployment: is the juice worth the squeeze?", ACM SIGCOMM Computer Communication Review vol. 43, no. 4, pp. 171-182, DOI 10.1145/2534169.2486010, September 2013 , <https://doi.org/10.1145/2534169.2486010>.
[MORILLO2021]
Morillo, R., Furuness, J., Morris, C., Breslin, J., Herzberg, A., and B. Wang, "ROV++: Improved Deployable Defense against BGP Hijacking", Proceedings 2021 Network and Distributed System Security Symposium, DOI 10.14722/ndss.2021.24438, 2021 , <https://doi.org/10.14722/ndss.2021.24438>.
[PERRIG2017]
Perrig, A., Szalachowski, P., Reischuk, R., and L. Chuat, "SCION: A Secure Internet Architecture", ISBN 978-3-319-67079-9, 2017 , <https://doi.org/10.1007/978-3-319-67080-5>.
Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, DOI 10.17487/RFC4033, March 2005 , <https://www.rfc-editor.org/rfc/rfc4033>.
Griffin, T. and G. Huston, "BGP Wedgies", RFC 4264, DOI 10.17487/RFC4264, November 2005 , <https://www.rfc-editor.org/rfc/rfc4264>.
Thaler, D. and B. Aboba, "What Makes for a Successful Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008 , <https://www.rfc-editor.org/rfc/rfc5218>.
Lepinski, M. and S. Kent, "An Infrastructure to Support Secure Internet Routing", RFC 6480, DOI 10.17487/RFC6480, February 2012 , <https://www.rfc-editor.org/rfc/rfc6480>.
Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The Locator/ID Separation Protocol (LISP)", RFC 6830, DOI 10.17487/RFC6830, January 2013 , <https://www.rfc-editor.org/rfc/rfc6830>.
Thaler, D., Ed., "Planning for Protocol Adoption and Subsequent Transitions", RFC 8170, DOI 10.17487/RFC8170, May 2017 , <https://www.rfc-editor.org/rfc/rfc8170>.
Lepinski, M., Ed. and K. Sriram, Ed., "BGPsec Protocol Specification", RFC 8205, DOI 10.17487/RFC8205, September 2017 , <https://www.rfc-editor.org/rfc/rfc8205>.
Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018 , <https://www.rfc-editor.org/rfc/rfc8446>.
Dawkins, S., Ed., "Path Aware Networking: Obstacles to Deployment (A Bestiary of Roads Not Taken)", RFC 9049, DOI 10.17487/RFC9049, June 2021 , <https://www.rfc-editor.org/rfc/rfc9049>.
Trammell, B., "Current Open Questions in Path-Aware Networking", RFC 9217, DOI 10.17487/RFC9217, March 2022 , <https://www.rfc-editor.org/rfc/rfc9217>.
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Schuchard, M., Mohaisen, A., Foo Kune, D., Hopper, N., Kim, Y., and E. Vasserman, "Losing control of the internet: using the data plane to attack the control plane", Proceedings of the 17th ACM conference on Computer and communications security - CCS '10, DOI 10.1145/1866307.1866411, 2010 , <https://doi.org/10.1145/1866307.1866411>.
Many thanks go to Cyrill Kraehenbuehl and Juan A. Garcia-Pardo for reviewing this document. We are also indebted to Laurent Chuat, Markus Legner, David Basin, David Hausheer, Samuel Hitz, and Peter Mueller, for writing the book "The Complete Guide to SCION" (see [CHUAT22]), which provides the background information needed to write this informational draft.¶
Corine de Kater
Email: corine.dekatermuehlhaeuser@inf.ethz.ch
Nicola Rustignoli
Email: nicola.rustignoli@inf.ethz.ch
Adrian Perrig
Email: adrian.perrig@inf.ethz.ch


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Capturing the essence of design in built landscapes.
This diamond-in-the-rough revealed its true heritage with some historical digging. It came to light that the original architect was Lutah Riggs. The landscape design process was greatly informed by her original architectural forms and lines, and was modernized in a way that pays homage to the past while integrating contemporary approaches to water conservation, material selection, and current trends in outdoor living. The entire property was renovated including new pool, walls, fences, pathways, patios, planting, lighting, and irrigation.
Set at the base of the Santa Barbara back country, a dated ranch style home underwent a full remodel and transformed into a modest farmhouse that lives large, both inside and out. The full landscape renovation created funtional spaces, outdoor rooms, hidden treasures for children, all the while reinforcing the tasteful simplicity of the architecture and leaning on the borrowed landscape for context.
Re-designed landscape of George Washington Smith's original artist studio.