What is the first part of an IP address?
IP address
An IP address serves two principal functions. It identifies the host, or more specifically its network interface, and it provides the location of the host in the network, and thus the capability of establishing a path to that host. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there."
The header of each IP packet contains the IP address of the sending host, and that of the destination host.
IPv6 address
Such an address is generated using two hash functions that take several inputs.
The first uses a public key and a random modifier; the latter being incremented repeatedly until a specific amount of zero bits of the resulting hash is acquired.
The second hash function takes the network prefix and the previous hash value.
The least significant 64 bits of the second hash result is appended to the 64-bit network prefix to form a 128-bit address.
I-number
The i-number form of an XRI is designed to serve as an address that does not need to change no matter how often the location of a resource on (or off) the Internet changes. XRIs accomplish this by adding a third layer of abstract addressing over the existing layers: IP numbering (first layer) and DNS naming (second layer). The notion of a third layer for persistent addressing is not new — Uniform Resource Names (URNs) and other persistent identifier architectures have been developed for this purposes. However the XRI layer is the first architecture that combines a uniform syntax and resolution protocol for both persistent and reassignable identifiers.
IP postcode area
The approximate coverage of the postcode districts:
! IP1
! IP2
! IP3
! IP4
! IP5
! IP6
! IP7
! IP8
! IP9
! IP10
! IP11
! IP12
! IP13
! IP14
! IP15
! IP16
! IP17
! IP18
! IP19
! IP20
! IP21
! IP22
! IP23
! IP24
! IP25
! IP26
! IP27
! IP28
! IP29
! IP30
! IP31
! IP32
! IP33
! IP98
Subnetwork
The result of the bitwise AND operation of IP address and the subnet mask is the network prefix . The host part, which is , is derived by the bitwise AND operation of the address and the one's complement of the subnet mask.
Private IP
PIP in telecommunications and datacommunications stands for Private Internet Protocol or Private IP. PIP refers to connectivity into a private extranet network which by its design emulates the functioning of the Internet. Specifically, the Internet uses a routing protocol called border gateway protocol (BGP), as do most multiprotocol label switching (MPLS) networks. With this design, there is an ambiguity to the route that a packet can take while traversing the network. Wherein the Internet is a public offering, MPLS PIP networks are private. This lends a known, often used, and comfortable network design model for private implementation.
IP address
Commonly, the NAT device maps TCP or UDP port numbers on the side of the larger, public network to individual private addresses on the masqueraded network.
IPv6 address
An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets, a group sometimes also called a hextet). The groups are separated by colons (:). An example of an IPv6 address is:
The hexadecimal digits are case-insensitive, but IETF recommendations suggest the use of lower case letters.
The full representation of eight 4-digit groups may be simplified by several techniques, eliminating parts of the representation.
Octet (computing)
An IPv6 address consists of sixteen octets, shown using hexadecimal representation (two digits per octet) and using a colon character (:) after each pair of octets (16 bits also known as hextet) for readability, like this FE80:0000:0000:0000:0123:4567:89AB:CDEF. If two or more consecutive octets equal zero they may be replaced by two following colon characters (::) but this can be used only once in a given IPv6 address to avoid ambiguity. The previously given IPv6 address can thus also be written as FE80::0123:4567:89AB:CDEF. In addition leading zeroes may also be omitted as they are not significant bits in the address. Applying this to the previous example mentioned will result in an IPv6 address of FE80::123:4567:89AB:CDEF.
IP address
Multiple client devices can appear to share an IP address, either because they are part of a shared hosting web server environment or because an IPv4 network address translator (NAT) or proxy server acts as an intermediary agent on behalf of the client, in which case the real originating IP address might be masked from the server receiving a request. A common practice is to have a NAT mask a large number of devices in a private network. Only the "outside" interface(s) of the NAT needs to have an Internet-routable address.
Provider-independent address space
A provider-independent address space (PI) is a block of IP addresses assigned by a regional Internet registry (RIR) directly to an end-user organization. The user must contract with an Internet service provider (or otherwise also known as a Local Internet Registry (LIR)) to obtain routing of the address block within the Internet.
IP fragmentation
IP fragmentation is an Internet Protocol (IP) process that breaks packets into smaller pieces (fragments), so that the resulting pieces can pass through a link with a smaller maximum transmission unit (MTU) than the original packet size. The fragments are reassembled by the receiving host.
Martian packet
A Martian packet is an IP packet seen on the public internet that contains a source or destination address that is reserved for special-use by Internet Assigned Numbers Authority (IANA). On the public Internet, such a packet’s source address is either spoofed, and it cannot actually originate as claimed, or the packet cannot be delivered.
IP address
A "sticky dynamic IP address" is an informal term used by cable and DSL Internet access subscribers to describe a dynamically assigned IP address which seldom changes. The addresses are usually assigned with DHCP. Since the modems are usually powered on for extended periods of time, the address leases are usually set to long periods and simply renewed. If a modem is turned off and powered up again before the next expiration of the address lease, it often receives the same IP address.
IP address
An IPv4 address has a size of 32 bits, which limits the address space to (2) addresses. Of this number, some addresses are reserved for special purposes such as private networks (~18 million addresses) and multicast addressing (~270 million addresses).
Care-of address
Used in Internet routing, a care-of address (usually referred to as "CoA") is a temporary IP address for a mobile device. This allows a home agent to forward messages to the mobile device. A separate address is required because the IP address of the device that is used as host identification is topologically incorrect - it does not match the network of attachment. The care-of address splits the dual nature of an IP address, that is, its use is to identify the host and the location within the global IP network.
Subnetwork
An IPv4 subnet mask is 32 bits, a sequence of ones (1) followed by a block of zeros (0). The ones indicate bits in the address used for the network prefix and the trailing block of zeros designates that part as being the host identifier.
Semiconductor intellectual property core
In electronic design a semiconductor intellectual property core, IP core, or IP block is a reusable unit of logic, cell, or integrated circuit (commonly called a "chip") layout design that is the intellectual property of one party. IP cores may be licensed to another party or can be owned and used by a single party alone. The term is derived from the licensing of the patent and/or source code copyright that exist in the design. IP cores can be used as building blocks within application-specific integrated circuit (ASIC) designs or field-programmable gate array (FPGA) logic designs.
Mobile web analytics
For desktop web browsing, the network address of the client machine usually gives some form of user identification and location. For mobile web browsing, the client IP address refers to the internet gateway machine owned by the network operator. For devices such as the BlackBerry or for phones using Opera Mini browser software, the IP address refers to an operator-owned internet gateway machine in Canada or Norway.
Node (computer science)
A node is a basic unit used in computer science. Nodes are devices or data points on a larger network. Devices such as a personal computer, cell phone, or printer are nodes. When defining nodes on the Internet, a node is anything that has an IP address. Nodes are individual parts of a larger data structure, such as linked lists and tree data structures. Nodes contain data and also may link to other nodes. Links between nodes are often implemented by pointers.
IP address
An Internet Protocol address (IP address) is a numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication.
An IP address serves two principal functions: host or network interface identification and location addressing.
IPv6 address
There are a number of addresses with special meaning in IPv6. They represent less than 2% of the entire address space:
IPv6 address
A 64-bit interface identifier is most commonly derived from its 48-bit MAC address. A MAC address is turned into a 64-bit EUI-64 by inserting in the middle: . When this EUI-64 is used to form an IPv6 address it is modified: the meaning of the "Universal/Local" bit (the 7th most significant bit of the EUI-64, starting from 1) is inverted, so that a 1 now means "Universal". To create an IPv6 address with the network prefix it yields the address (with the "Universal/Local" bit, the second-least-significant bit of the underlined quartet, inverted to 1 in this case because the MAC address is universally unique).
Network address translation
IP masquerading is a technique that hides an entire IP address space, usually consisting of private IP addresses, behind a single IP address in another, usually public address space. The address that has to be hidden is changed into a single (public) IP address as "new" source address of the outgoing IP packet so it appears as originating not from the hidden host but from the routing device itself. Because of the popularity of this technique to conserve IPv4 address space, the term "NAT" has become virtually synonymous with IP masquerading.
IP address
The most common concept of an IP address is in unicast addressing, available in both IPv4 and IPv6. It normally refers to a single sender or a single receiver, and can be used for both sending and receiving. Usually, a unicast address is associated with a single device or host, but a device or host may have more than one unicast address. Some individual PCs have several distinct unicast addresses, each for its own distinct purpose. Sending the same data to multiple unicast addresses requires the sender to send all the data many times over, once for each recipient.
Hosts (file)
The hosts file is one of several system facilities that assists in addressing network nodes in a computer network. It is a common part of an operating system's Internet Protocol (IP) implementation, and serves the function of translating human-friendly hostnames into numeric protocol addresses, called IP addresses, that identify and locate a host in an IP network.
IP aliasing
IP aliasing can be used to provide multiple network addresses on a single physical interface. This demonstrates using IP version 4 addresses only. One reason for using this could be to make a computer look as though it is multiple computers, so for example you could have one server that is acting as both a gateway (router) and a DHCP server and DNS using 3 different IP addresses, perhaps with a future plan to use a hardware router and to move the functionality to separate DNS and DHCP servers. Or indeed the opposite you could decide to replace the 3 different hardware devices with a single server to reduce the administration overhead. In this case you can have 3 different addresses which are all on the same computer without having to install lots of physical network interfaces. Another reason is that you want to have the computer on two different logical network subnets whilst using a single physical interface.
IPv4
A broadcast address is an address that allows information to be sent to all interfaces in a given subnet, rather than a specific machine. Generally, the broadcast address is found by obtaining the bit complement of the subnet mask and performing a bitwise OR operation with the network identifier. In other words, the broadcast address is the last address in the address range of the subnet. For example, the broadcast address for the network 192.168.5.0 is 192.168.5.255. For networks of size /24 or larger, the broadcast address always ends in 255.
Home page
In the early days of the World Wide Web in the first half of the 1990s, an important part of web pages belonged to students or teachers with a UNIX account in their university. System administrators of such systems installed an HTTP server pointing its root directory to the directory containing the users accounts. On UNIX, the base directory of an account is called "home", and the codice_1 environment variable contains its path (for example codice_2). The URL of the home page usually has the format codice_3. Thus the term home page appeared and then spread to its current usage.
SIP URI scheme
As a SIP address is text, much like an e-mail address, it may contain non-numeric characters. As the client may be a SIP phone or other device with just a numeric, telephone-like keypad, various schemes exist to associate an entirely numeric identifier to a publicly reachable SIP address. These include the iNum Initiative (which issues E.164-formatted numbers, where the corresponding SIP address is the number '@sip.inum.net'), SIP Broker-style services (which associate a numeric *prefix to the SIP domain name) and the e164.org and e164.arpa domain name servers (which convert numbers to addresses one-by-one as DNS reverse-lookups).
Zero-configuration networking
Both IPv4 and IPv6 hosts may randomly generate the host-specific part of an autoconfigured address. IPv6 hosts generally combine a prefix of up to 64 bits with a 64-bit EUI-64 derived from the factory-assigned 48-bit IEEE MAC address. The MAC address has the advantage of being globally unique, a basic property of the EUI-64. The IPv6 protocol stack also includes duplicate address detection to avoid conflicts with other hosts. In IPv4, the method is called "link-local address autoconfiguration". However, Microsoft refers to this as "Automatic Private IP Addressing" (APIPA) or "Internet Protocol Automatic Configuration" (IPAC). The feature is supported in Windows since at least Windows 98.
Subnetwork
An address fulfills the functions of identifying the host and locating it on the network. The most common network addressing architecture is Internet Protocol version 4 (IPv4), but its successor, IPv6, has been increasingly deployed since approximately 2006. An IPv4 address consists of 32 bits, for readability written in a form consisting of four decimal octets separated by dots, called dot-decimal notation. An IPv6 address consists of 128 bits written in a hexadecimal notation and groupings of 16 bits, called hextets, separated by colons.
An IP address is divided into two logical parts, the "network prefix" and the "host identifier". All hosts on a subnetwork have the same network prefix. This prefix occupies the most-significant bits of the address. The number of bits allocated within a network to the prefix may vary between subnets, depending on the network architecture. The host identifier is a unique local identification and is either a host number on the local network or an interface identifier.
Anonymous blog
An IP address is a unique numerical label assigned to a computer connected to a computer network that uses the Internet Protocol for communication. The most popular implementation of the Internet Protocol would be the Internet (capitalized, to differentiate it from smaller internetworks). Internet Service Providers (ISPs) are allocated chunks of IP addresses by a Regional Internet registry, which they then assign to customers. However, ISPs do not have enough addresses to give the customers their own address. Instead, DHCP is used; a customer's device (typically a modem or router) is assigned an IP address from a pool of available addresses. It keeps that address for a certain amount of time (e.g., two weeks). If the device is still active at the end of the lease, it can renew its connection and keep the same IP address. Otherwise, the IP address is collected and added to the pool to be redistributed. Thus, IP addresses provide regional information (through Regional Internet registries) and, if the ISP has logs, specific customer information. While this does not prove that a specific person was the originator of a blog post (it could have been someone else using that customer's Internet, after all), it provides powerful circumstantial evidence.
IP address
Two versions of the Internet Protocol are in common use in the Internet today. The original version of the Internet Protocol that was first deployed in 1983 in the ARPANET, the predecessor of the Internet, is Internet Protocol version 4 (IPv4).
IPv6
Internet Protocol Version 4 (IPv4) was the first publicly used version of the Internet Protocol. IPv4 was developed as a research project by the Defense Advanced Research Projects Agency (DARPA), a United States Department of Defense agency, before becoming the foundation for the Internet and the World Wide Web. IPv4 includes an addressing system that uses numerical identifiers consisting of 32 bits. These addresses are typically displayed in quad-dotted notation as decimal values of four octets, each in the range 0 to 255, or 8 bits per number. Thus, IPv4 provides an addressing capability of 2 or approximately 4.3 billion addresses. Address exhaustion was not initially a concern in IPv4 as this version was originally presumed to be a test of DARPA's networking concepts. During the first decade of operation of the Internet, it became apparent that methods had to be developed to conserve address space. In the early 1990s, even after the redesign of the addressing system using a classless network model, it became clear that this would not suffice to prevent IPv4 address exhaustion, and that further changes to the Internet infrastructure were needed.
IP fragmentation attack
The source system sets "Identification" field in each packet to a unique value for all packets which use the same source IP address, destination IP address, and "Protocol" values, for the lifetime of the packet on the internet. This way the destination can distinguish which incoming fragments belong to a unique packet and buffer all of them until the last fragment is received. The last fragment sets the "More Fragment" bit to 0 and this tells the receiving station to start reassembling the data if all fragments have been received.
IPv6 address
In the Domain Name System, hostnames are mapped to IPv6 addresses by "AAAA" resource records, so-called "quad-A" records.
For reverse lookup the IETF reserved the domain ip6.arpa, where the name space is hierarchically divided by the 1-digit hexadecimal representation of nibble units (4 bits) of the IPv6 address.
Differentiated services
The Class Selector code points are of the binary form 'xxx000'. The first three bits are the IP precedence bits. Each IP precedence value can be mapped into a DiffServ class. CS0 equals to IP precedence 0, CS1 to IP precedence 1, and so on. If a packet is received from a non-DiffServ aware router that used IP precedence markings, the DiffServ router can still understand the encoding as a Class Selector code point.
Interested Parties Information
The IP Name Number is the code for a name or pseudonym related to an entity (natural person or a legal entity). One entity can have several names. Prince for example has the IPI-codes
00045620792 (Nelson Prince Rogers), 00052210040 (Prince) and 00334284961 (Nelson Prince R).
The IPI Name Number is composed of eleven numeric digits.
Root name server
The DNS is a hierarchical naming system for computers, services, or any resource participating in the Internet. The top of that hierarchy is the root domain. The root domain does not have a formal name and its label in the DNS hierarchy is an empty string. All fully qualified domain names (FQDNs) on the Internet can be regarded as ending with this empty string for the root domain, and therefore ending in a full stop character (the label delimiter), e.g., "www.example.com.". This is generally implied rather than explicit, as modern DNS software does not actually require that the terminating dot be included when attempting to translate a domain name to an IP address.
IPv6 address
The size of a block of addresses is specified by writing a slash (/) followed by a number in decimal whose value is the length of the network prefix in bits, rather than by explicitly specifying which addresses are in the block. For example, an address block with 48 bits in the prefix is indicated by . Such a block contains 2 = 2 addresses. The smaller the value of the network prefix, the larger the block: a block is 8 times larger than a block.
Internet Control Message Protocol
The ICMP header starts after the IPv4 header and is identified by IP protocol number '1'. All ICMP packets have an 8-byte header and variable-sized data section. The first 4 bytes of the header have fixed format, while the last 4 bytes depend on the type/code of that ICMP packet.ICMP error messages contain a data section that includes a copy of the entire IPv4 header, plus at least the first eight bytes of data from the IPv4 packet that caused the error message. The maximum length of ICMP error messages is 576 bytes. This data is used by the host to match the message to the appropriate process. If a higher level protocol uses port numbers, they are assumed to be in the first eight bytes of the original datagram's data.
Classless Inter-Domain Routing
IP addresses are described as consisting of two groups of bits in the address: the most significant bits are the network prefix, which identifies a whole network or subnet, and the least significant set forms the "host identifier", which specifies a particular interface of a host on that network. This division is used as the basis of traffic routing between IP networks and for address allocation policies.
Geolocation software
An IP address is assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. The protocol specifies that each IP packet must have a header which contains, among other things, the IP address of the sender of the packet.
6to4
Most IPv6 networks use autoconfiguration, which requires the last 64 bits of the address for the host. The first 64 bits are the IPv6 prefix. The first 16 bits of the prefix are always :, the next 32 bits are the IPv4 address, and the last 16 bits of the prefix are available for addressing multiple IPv6 subnets behind the same 6to4 router. Since the IPv6 hosts using autoconfiguration already have determined the unique 64 bit host portion of their address, they must simply wait for a Router Advertisement indicating the first 64 bits of prefix to have a complete IPv6 address. A 6to4 router will know to send an encapsulated packet directly over IPv4 if the first 16 bits are , using the next 32 as the destination, or otherwise send the packet to a well-known relay server, which has access to native IPv6.
Net neutrality
Internet routers forward packets according to the diverse peering and transport agreements that exist between network operators. Many networks using Internet protocols now employ quality of service (QoS), and Network Service Providers frequently enter into Service Level Agreements with each other embracing some sort of QoS. There is no single, uniform method of interconnecting networks using IP, and not all networks that use IP are part of the Internet. IPTV networks are isolated from the Internet and are therefore not covered by network neutrality agreements. The IP datagram includes a 3-bit wide Precedence field and a larger DiffServ Code Point (DSCP) that are used to request a level of service, consistent with the notion that protocols in a layered architecture offer services through Service Access Points. This field is sometimes ignored, especially if it requests a level of service outside the originating network's contract with the receiving network. It is commonly used in private networks, especially those including Wi-Fi networks where priority is enforced. While there are several ways of communicating service levels across Internet connections, such as SIP, RSVP, IEEE 802.11e, and MPLS, the most common scheme combines SIP and DSCP. Router manufacturers now sell routers that have logic enabling them to route traffic for various Classes of Service at "wire-speed".
DNS zone
Although the administrative structure of this domain and its sub-domains is different, the technical delegation into zones of responsibility is similar and the DNS tools and servers used are identical to any other zone. Sub-zones are delegated by components of the respective resources. For example, 8.8.2.5.5.2.2.0.0.8.1.e164.arpa., which might represent an E.164 telephone number in the ENUM system, might be sub-delegated at suitable boundaries of the name. An example of an IP addresses in the reverse DNS zone is 166.188.77.208.in-addr.arpa, which represents the address 208.77.188.166 and resolves to the domain name "www.example.com". In the case of IP addresses, the reverse zones are delegated to the Internet service provider (ISP) to which the IP address block is assigned. When an ISP allocates a range to a customer, it usually also delegates the management of that space to the customer by insertion of name server resource records pointing to the customer's DNS facilities into their zone, or provides other management tools. Allocations of single IP addresses for networks connected through network address translation (NAT) typically do not provide such facilities.
IEEE 802.1ah-2008
The idea of PBB is to offer complete separation of customer and provider domains. For this purpose, a new Ethernet header has been defined. This header may take multiple different forms, but the main components of the header are:PBB defines a 48 bit B-DA and 48 bit B-SA to indicate the backbone source and destination MAC addresses. It also defines a 12 bit B-VID (backbone VLAN ID) and 24 bit I-SID (Service Instance VLAN ID). The bridges in the PBB domain switch based on the B-VID and B-DA values, which contain 60 bits total. Bridges learn based on the B-SA and ingress port value and hence is completely unaware of the customer MAC addresses. I-SID allows distinguishing the services within a PBB domain.
IPv4 shared address space
The use of shared address space is one of the various methods to allow transition from IPv4 to IPv6.
Its main purpose is to postpone the depletion of IPv4 addresses, by allowing ISPs to introduce a second layer of NATting.
Common practice is to give CPEs a unique IPv4 address on their internet facing interface and use NAT to hide all addresses on the home LAN.
Since public IPv4 addresses are growing scarce rapidly, it is no longer possible for some ISPs to assign unique IPv4 addresses to CPEs, due to the fact that there are none left to them.
Instead, an address in the range is assigned on the CPE's internet facing interface, and this address is translated again to one of the public IPv4 address of the ISP's core routers.
This scheme hides a large number of IP addresses behind a small set of public addresses, the same way the CPE does this locally, slowing down the rate IPv4 addresses are depleted.
The shared address space contains 2 or addresses, so each ISP is able to connect over 4 million subscribers this way.
Transmission Control Protocol
While IP handles actual delivery of the data, TCP keeps track of 'segments' - the individual units of data transmission that a message is divided into for efficient routing through the network. For example, when an HTML file is sent from a web server, the TCP software layer of that server divides the sequence of file octets into segments and forwards them individually to the IP software layer (Internet Layer). The Internet Layer encapsulates each TCP segment into an IP packet by adding a header that includes (among other data) the destination IP address. When the client program on the destination computer receives them, the TCP layer (Transport Layer) re-assembles the individual segments and ensures they are correctly ordered and error-free as it streams them to an application.
Name server
An example of a name server is the server component of the Domain Name System (DNS), one of the two principal namespaces of the Internet. The most important function of DNS servers is the translation (resolution) of human-memorable domain names and hostnames into the corresponding numeric Internet Protocol (IP) addresses, the second principal name space of the Internet which is used to identify and locate computer systems and resources on the Internet.
Simple Key-Management for Internet Protocol
The first node is called Node I. Node I has a public component Ki and a private component i. The second node is called Node J. Node J has a public component Kj and a private component j.
Internet Connection Sharing
ICS routes TCP/IP packets from a small LAN to the Internet. ICS provides NAT services, mapping individual IP addresses of local computers to unused port numbers in the sharing computer. Because of the nature of the NAT, IP addresses on the local computer are not visible on the Internet. All packets leaving or entering the LAN are sent from or to the IP address of the external adapter on the ICS host computer.
IPv6 address
Every IPv6 address, except the unspecified address (), has a "scope", which specifies in which part of the network it is valid.
Open Shortest Path First
Areas are uniquely identified with 32-bit numbers. The area identifiers are commonly written in the dot-decimal notation, familiar from IPv4 addressing. However, they are not IP addresses and may duplicate, without conflict, any IPv4 address. The area identifiers for IPv6 implementations (OSPFv3) also use 32-bit identifiers written in the same notation. When dotted formatting is omitted, most implementations expand area "1" to the area identifier "0.0.0.1", but some have been known to expand it as "1.0.0.0".
IP multicast
IPv4 multicast packets are delivered using the Ethernet MAC address range 01:00:5e:00:00:00–01:00:5e:7f:ff:ff (with an OUI owned by the IANA). This range has 23 bits of available address space. The first octet (01) includes the broadcast/multicast bit. The lower 23 bits of the 28-bit multicast IP address are mapped into the 23 bits of available Ethernet address space. This means that there is ambiguity in delivering packets. If two hosts on the same subnet each subscribe to a different multicast group whose address differs only in the first 5 bits, Ethernet packets for both multicast groups will be delivered to both hosts, requiring the network software in the hosts to discard the unrequired packets.
Address space
An address space usually provides (or allows) a partitioning to several regions according to the mathematical structure it has. In the case of total order, as for memory addresses, these are simply chunks. Some nested domain hierarchies appear in the case of directed ordered tree as for the Domain Name System or a directory structure; this is similar to the hierarchical design of postal addresses. In the Internet, for example, the Internet Assigned Numbers Authority (IANA) allocates ranges of IP addresses to various registries in order to enable them to each manage their parts of the global Internet address space.
List of IP protocol numbers
Below are the Internet Protocol numbers found in the "Protocol" field of the IPv4 header and the "Next Header" field of the IPv6 header. The same values are used in both versions of the field and define the layout of the header that will immediately follow the IPv4 or IPv6 header. Both the "Protocol" and "Next Header" fields are eight bits wide. The numbers used in these fields are managed and assigned by the Internet Assigned Numbers Authority (IANA).
IPv6 address
An IP address serves the purpose of identifying an individual network interface of a host, locating it on the network, and thus permitting the routing of IP packets between hosts. For routing, IP addresses are present in fields of the packet header where they indicate the source and destination of the packet.
Host Identity Protocol
The Host Identity Protocol (HIP) is a host identification technology for use on Internet Protocol (IP) networks, such as the Internet. The Internet has two main name spaces, IP addresses and the Domain Name System. HIP separates the end-point identifier and locator roles of IP addresses. It introduces a Host Identity (HI) name space, based on a public key security infrastructure.
IP traceback
Belenky and Ansari, outline a deterministic packet marking scheme. They describe a more realistic topology for the Internet – that is composed of LANs and ASs with a connective boundary – and attempt to put a single mark on inbound packets at the point of network ingress. Their idea is to put, with random probability of .5, the upper or lower half of the IP address of the ingress interface into the fragment id field of the packet, and then set a reserve bit indicating which portion of the address is contained in the fragment field. By using this approach they claim to be able to obtain 0 false positives with .99 probability after only 7 packets.
IP fragmentation attack
IP fragmentation is the process of breaking up a single Internet Protocol (IP) packet into multiple packets of smaller size. Every network link has a characteristic size of messages that may be transmitted, called the maximum transmission unit (MTU).
NetBIOS
This suffix describes the service or name record type such as host record, master browser record, or domain controller record or other services. The host name (or short host name) is specified when Windows networking is installed/configured, the suffixes registered are determined by the individual services supplied by the host. In order to connect to a computer running TCP/IP via its NetBIOS name, the name must be resolved to a network address. Today this is usually an IP address (the NetBIOS name to IP address resolution is often done by either broadcasts or a WINS Server – NetBIOS Name Server). A computer's NetBIOS name is often the same as that computer's host name (see below), although truncated to 15 characters, but it may also be completely different.
IP fragmentation attack
Part of the TCP/IP suite is the Internet Protocol (IP) which resides at the Internet Layer of this model. IP is responsible for the transmission of packets between network end points. IP includes some features which provide basic measures of fault-tolerance (time to live, checksum), traffic prioritization (type of service) and support for the fragmentation of larger packets into multiple smaller packets (ID field, fragment offset). The support for fragmentation of larger packets provides a protocol allowing routers to fragment a packet into smaller packets when the original packet is too large for the supporting datalink frames. IP fragmentation exploits (attacks) use the fragmentation protocol within IP as an attack vector.
Locator/Identifier Separation Protocol
Locator/ID Separation Protocol (LISP) () is a "map-and-encapsulate" protocol which is developed by the Internet Engineering Task Force LISP Working Group. The basic idea behind the separation is that the Internet architecture combines two functions, routing locators (where a client is attached to the network) and identifiers (who the client is) in one number space: the IP address. LISP supports the separation of the IPv4 and IPv6 address space following a network-based map-and-encapsulate scheme (). In LISP, both identifiers and locators can be IP addresses or arbitrary elements like a set of GPS coordinates or a MAC address.
Port (computer networking)
The Telnet service received the first official assignment of the value 1.
In detail, the first set of assignments was:
In the early ARPANET, the AEN was also called a "socket name", and was used with the Initial Connection Protocol (ICP), a component of the Network Control Program (NCP). NCP was the forerunner of the modern Internet protocols. Today the terminology "service name" is still closely connected with port numbers, the former being text strings used in some network functions to represent a numerical port number.
Host (network)
Computers participating in networks that use the Internet protocol suite may also be called "IP hosts". Specifically, computers participating in the Internet are called Internet hosts, sometimes "Internet nodes". Internet hosts and other IP hosts have one or more IP addresses assigned to their network interfaces. The addresses are configured either manually by an administrator, automatically at startup by means of the Dynamic Host Configuration Protocol (DHCP), or by stateless address autoconfiguration methods.
IP in IP
Source IP Address: 32 bits
This field is the IP address of the encapsulator
IP address
A host may use geolocation software to deduce the geolocation of its communicating peer.
A public IP address, in common parlance, is a globally routable unicast IP address, meaning that the address is not an address reserved for use in private networks, such as those reserved by , or the various IPv6 address formats of local scope or site-local scope, for example for link-local addressing. Public IP addresses may be used for communication between hosts on the global Internet.
IPv4
The primary address pool of the Internet, maintained by IANA, was exhausted on 3 February 2011, when the last 5 blocks were allocated to the 5 RIRs. APNIC was the first RIR to exhaust its regional pool on 15 April 2011, except for a small amount of address space reserved for the transition to IPv6, which will be allocated under a much more restricted policy.
Inter-domain
Inter-domain is data flow control and interaction between Primary Domain Controller (PDC) computers. This type of computer uses various computer protocols and services to operate. It is most commonly used to multicast between internet domains.
An Internet service provider, ISP, is provided with a unique URL access address. This address is a unique number. The number for each ISP is stored within a DNS server. The DNS servers interpret the ISP URL Domain name and provide the appropriate IP address number. The Domain is under the control of a specialised computer, called a PDC, (primary domain controller). This computer holds records of all the user accounts within the domain, their rights to access information, and lists of approved System Operatives. This PDC is backed up by a SDC, (a secondary domain controller), this computer synchronises itself with the PDC and takes over the role in the event of a PDC failure. Multiple replication servers connect to these control computers and they are routed to the Internet backbone to provide the requested data to and from the domain. 
Internet protocols that are focused on inter-domain functions include: Border Gateway Multicast Protocol, Classless Inter-Domain Routing, Multicast Source Discovery Protocol, and Protocol Independent Multicast.
A PDC uses a number of special computer programs to announce its presence to other domain controllers. It uses Windows Internet naming service WINS and Browser services to allow other computers to gain access to digital information that it has control over.
IPv6 packet
A packet containing a fragment of an original (larger) packet consists of two parts: the unfragmentable part of the original packet (which is the same for all fragments), and a piece of the fragmentable part of the original packet, identified by a Fragment Offset. The Fragment Offset of the first ("leftmost") fragment is 0.
IPv6
The fixed header occupies the first 40 octets (320 bits) of the IPv6 packet. It contains the source and destination addresses, traffic classification options, a hop counter, and the type of the optional extension or payload which follows the header. This "Next Header" field tells the receiver how to interpret the data which follows the header. If the packet contains options, this field contains the option type of the next option. The "Next Header" field of the last option, points to the upper-layer protocol that is carried in the packet's payload.
IP address
Classful network design allowed for a larger number of individual network assignments and fine-grained subnetwork design. The first three bits of the most significant octet of an IP address were defined as the "class" of the address. Three classes ("A", "B", and "C") were defined for universal unicast addressing. Depending on the class derived, the network identification was based on octet boundary segments of the entire address. Each class used successively additional octets in the network identifier, thus reducing the possible number of hosts in the higher order classes ("B" and "C"). The following table gives an overview of this now obsolete system.
IPv6 address
Unicast and anycast addresses are typically composed of two logical parts: a 64-bit network prefix used for routing, and a 64-bit interface identifier used to identify a host's network interface.
The "network prefix" (the "routing prefix" combined with the "subnet id") is contained in the most significant 64 bits of the address. The size of the routing prefix may vary; a larger prefix size means a smaller subnet id size. The bits of the "subnet id" field are available to the network administrator to define subnets within the given network. The 64-bit "interface identifier" is either automatically generated from the interface's MAC address using the modified EUI-64 format, obtained from a DHCPv6 server, automatically established randomly, or assigned manually.
Port (computer networking)
The term "port number" was not yet used at this time. It was preceded by the use of the term "socket number" in the early development stages of the network. A socket number for a remote host was a 40-bit quantity. The first 32 bits were similar to today's IPv4 address, but at the time the most-significant 8 bits were the host number. The least-significant portion of the socket number (bits 33 through 40) was an entity called "Another Eightbit Number", abbreviated AEN. Today, "network socket" refers to a related but distinct concept, namely the internal address of an endpoint (used within the node only).
IP address
Three non-overlapping ranges of IPv4 addresses for private networks are reserved. These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry. Any user may use any of the reserved blocks. Typically, a network administrator will divide a block into subnets; for example, many home routers automatically use a default address range of through ().
Classful network
In the original address definition, the most significant eight bits of the 32-bit IPv4 address was the "network number" field which specified the particular network a host was attached to. The remaining 24 bits specified the local address, also called "rest field" (the rest of the address), which uniquely identified a host connected to that network. This format was sufficient at a time when only a few large networks existed, such as the ARPANET (network number 10), and before the wide proliferation of local area networks (LANs). As a consequence of this architecture, the address space supported only a low number (254) of independent networks.
IP address
Just as IPv4 reserves addresses for private networks, blocks of addresses are set aside in IPv6. In IPv6, these are referred to as unique local addresses (ULAs). The routing prefix is reserved for this block, which is divided into two blocks with different implied policies. The addresses include a 40-bit pseudorandom number that minimizes the risk of address collisions if sites merge or packets are misrouted.
IPv6 address
IPv6 is the successor to the first addressing infrastructure of the Internet, Internet Protocol version 4 (IPv4). In contrast to IPv4, which defined an IP address as a 32-bit value, IPv6 addresses have a size of 128 bits. Therefore, IPv6 has a vastly enlarged address space compared to IPv4.
IPv4
An IP packet consists of a header section and a data section.
Anonymity
However, the Internet was not designed for anonymity: IP addresses serve as virtual mailing addresses, which means that any time any resource on the Internet is accessed, it is accessed from a particular IP address, and the data traffic patterns to and from IP addresses can be intercepted, monitored, and analysed, even if the content of that traffic is encrypted. This address can be mapped to a particular Internet Service Provider (ISP), and this ISP can then provide information about what customer that IP address was leased to. This does not necessarily implicate a specific individual (because other people could be using that customer's connection, especially if the customer is a public resource, such as a library), but it provides regional information and serves as powerful circumstantial evidence.
History of the Internet
Over time, after consultation with the IANA, the IETF, RIPE NCC, APNIC, and the Federal Networking Council (FNC), the decision was made to separate the management of domain names from the management of IP numbers. Following the examples of RIPE NCC and APNIC, it was recommended that management of IP address space then administered by the InterNIC should be under the control of those that use it, specifically the ISPs, end-user organizations, corporate entities, universities, and individuals. As a result, the American Registry for Internet Numbers (ARIN) was established as in December 1997, as an independent, not-for-profit corporation by direction of the National Science Foundation and became the third Regional Internet Registry.
IP Pascal
The '_' (break) character can be included anywhere in a number except for the first digit. It is ignored, and serves only to separate digits in the number.
Broadcast address
A special definition exists for the IP address . It is the broadcast address of the "zero network" or , which in Internet Protocol standards stands for "this network", i.e. the local network. Transmission to this address is limited by definition, in that it is never forwarded by the routers connecting the local network to other networks.
IPv6 rapid deployment
The default allocation of IPv6 space by a Regional Internet Registry (RIR) is a 32-bit prefix. Since it takes 32 bits to map an IPv4 address with 6rd, this implies that an ISP would only be able to allocate 64-bit IPv6 prefixes to its customers if it were to use entire IPv4 addresses. 6rd, however, allows any redundant part of an IPv4 address to be discarded: For example, if the IPv4 addresses an ISP issues to its customers all share the same first eighteen bits, a 6rd prefix only need include the remaining fourteen bits. Without this flexibility, Free originally assigned 64-bit IPv6 prefixes to its customers but was able to assign them shorter prefixes once it obtained a larger allocation of IPv6 space (a 26-bit prefix) from the RIPE NCC.
Graduated response
In a number of European countries early attempts to implement a graduated response have led to court cases to establish under which circumstances an ISP may provide subscriber data to the content industry. In order to pursue those that download copyrighted material the individual committing the infringing must be identified. Internet users are often only identifiable by their Internet Protocol address (IP address), which distinguishes the virtual location of a particular computer. Many ISPs allocate a pool of IP addresses as needed, rather than assigning each computer a never-changing static IP address. Using ISP subscriber information the content industry has thought to remedy copyright infringement, assuming that the ISPs are legally responsible for end user activity, therefore commuting an offence, and that the end user is responsible for all illegal activity connected to his or hers IP address. And if you commit such crime, you could be sentenced to up to 45 years in incarceration.
Ping of death
When fragmentation is performed, each IP fragment needs to carry information about which part of the original IP packet it contains. This information is kept in the Fragment Offset field, in the IP header. The field is 13 bits long, and contains the offset of the data in the current IP fragment, in the original IP packet. The offset is given in units of 8 bytes. This allows a maximum offset of 65,528 ((2-1)*8). Then when adding 20 bytes of IP header, the maximum will be 65,548 bytes, which exceeds the maximum frame size. This means that an IP fragment with the maximum offset should have data no larger than 7 bytes, or else it would exceed the limit of the maximum packet length. A malicious user can send an IP fragment with the maximum offset and with much more data than 8 bytes (as large as the physical layer allows it to be).
IP address
Today, these two versions of the Internet Protocol are in simultaneous use. Among other technical changes, each version defines the format of addresses differently. Because of the historical prevalence of IPv4, the generic term "IP address" typically still refers to the addresses defined by IPv4. The gap in version sequence between IPv4 and IPv6 resulted from the assignment of version 5 to the experimental Internet Stream Protocol in 1979, which however was never referred to as IPv5.
Classless Inter-Domain Routing
The IP address is expressed according to the standards of IPv4 or IPv6. The address may denote a single, distinct interface address or the beginning address of an entire network. The aggregation of these bits is often called the "host identifier".
Multicast address
IPv4 multicast addresses are defined by the most-significant bit pattern of "1110". This originates from the classful network design of the early Internet when this group of addresses was designated as "Class D". The CIDR notation for this group is . The group includes the addresses from to . Address assignments from within this range are specified in RFC 5771, an Internet Engineering Task Force (IETF) "Best Current Practice" document (BCP 51).
Slash (punctuation)
The slash in an IP address (e.g., 192.0.2.0/29) indicates the prefix size in CIDR notation. The number of addresses of a subnet may be calculated as 2, in which the address size is 128 for IPv6 and 32 for IPv4. For example, in IPv4, the prefix size /29 gives: 2 = 2 = 8 addresses.
IP address
The IP address space is managed globally by the Internet Assigned Numbers Authority (IANA), and by five regional Internet registries (RIRs) responsible in their designated territories for assignment to end users and local Internet registries, such as Internet service providers. IPv4 addresses have been distributed by IANA to the RIRs in blocks of approximately 16.8 million addresses each. Each ISP or private network administrator assigns an IP address to each device connected to its network. Such assignments may be on a "static" (fixed or permanent) or "dynamic" basis, depending on its software and practices.
Subnetwork
The "routing prefix" may be expressed in Classless Inter-Domain Routing (CIDR) notation written as the first address of a network, followed by a slash character ("/"), and ending with the bit-length of the prefix. For example, is the prefix of the Internet Protocol version 4 network starting at the given address, having 24 bits allocated for the network prefix, and the remaining 8 bits reserved for host addressing. Addresses in the range to belong to this subnet. The IPv6 address specification is a large address block with 2 addresses, having a 32-bit routing prefix.
Internet Protocol
IP addressing entails the assignment of IP addresses and associated parameters to host interfaces. The address space is divided into subnetworks, involving the designation of network prefixes. IP routing is performed by all hosts, as well as routers, whose main function is to transport packets across network boundaries. Routers communicate with one another via specially designed routing protocols, either interior gateway protocols or exterior gateway protocols, as needed for the topology of the network.
Root name server
A root name server is a name server for the root zone of the Domain Name System (DNS) of the Internet. It directly answers requests for records in the root zone and answers other requests by returning a list of the authoritative name servers for the appropriate top-level domain (TLD). The root name servers are a critical part of the Internet infrastructure because they are the first step in translating (resolving) human readable host names into IP addresses that are used in communication between Internet hosts.
IP address
IPv4 addresses are usually represented in dot-decimal notation, consisting of four decimal numbers, each ranging from 0 to 255, separated by dots, e.g., . Each part represents a group of 8 bits (an octet) of the address. In some cases of technical writing, IPv4 addresses may be presented in various hexadecimal, octal, or binary representations.
Dot-decimal notation
IP addresses in the dot-decimal notation are also presented in CIDR notation, in which the IP address is suffixed with a slash and a number, used to specify the length of the associated routing prefix. For example, 127.0.0.1/8 specifies that the IP address has an 8-bit routing prefix, and therefore the subnet mask 255.0.0.0.
ARP spoofing
When an Internet Protocol (IP) datagram is sent from one host to another in a local area network, the destination IP address must be resolved to a MAC address for transmission via the data link layer. When another host's IP address is known, and its MAC address is needed, a broadcast packet is sent out on the local network. This packet is known as an "ARP request". The destination machine with the IP in the ARP request then responds with an "ARP reply" that contains the MAC address for that IP.
IPv6
The last unassigned top-level address blocks of 16 million IPv4 addresses were allocated in February 2011 by the Internet Assigned Numbers Authority (IANA) to the five regional Internet registries (RIRs). However, each RIR still has available address pools and is expected to continue with standard address allocation policies until one /8 Classless Inter-Domain Routing (CIDR) block remains. After that, only blocks of 1024 addresses (/22) will be provided from the RIRs to a local Internet registry (LIR). As of September 2015, all of Asia-Pacific Network Information Centre (APNIC), the Réseaux IP Européens Network Coordination Centre (RIPE_NCC), Latin America and Caribbean Network Information Centre (LACNIC), and American Registry for Internet Numbers (ARIN) have reached this stage. This leaves African Network Information Center (AFRINIC) as the sole regional internet registry that is still using the normal protocol for distributing IPv4 addresses. As of November 2018, AFRINIC's minimum allocation is /22 or 1024 IPv4 addresses. A LIR may receive additional allocation when about 80% of all the address space has been utilized.
Address pool
In the context of the Internet addressing structure, an address pool is a set of Internet Protocol addresses available at any level in the IP address allocation hierarchy. At the top level, the IP address pool is managed by the Internet Assigned Numbers Authority (IANA). The total IPv4 address pool contains (2) addresses, while the size of the IPv6 address pool is 2 () addresses.