Reimagining the future of routers
"What modern IP routers do is exactly this. Every forwarding entry has to be fast. Analysis of real backbone traffic data, says it does not have to be. For all practical purposes, today, forwarding tables are oversized by a factor of 10x today."<p>What he is suggesting will drastically impact the latency of packets as well as the throughput. Following his analogy of cache hierarchies in a regular computer, some prefix lookups are going to be 'downgraded' to the main memory and will take maybe 100x the time.<p>If a router is forwarding at 10gbps it has ~51 nanoseconds in worst case (64 byte packets). So this is the overhead you can probably expect at each router as your traffic traverses the net. I'm 17 hops from my old university's network. That's just under a microsecond of lookup times. Not bad thanks to TCAM or other specialized lookup chips.<p>If all of these routers adopted this, my lowly traffic would have to read from main memory on each route lookup because I would never be in the top tier for bandwidth usage even if I was connected all day long. A full routing table is >600k addresses now[1] so each lookup may have to reference main memory several times as it walks a trie. Let's assume about 10 times to be generous which (at 100ns a reference) comes to about 1 microsecond. This is just for 1 packet.<p>As you start to pile on the thousands of other small connections (we're talking about provider network routers) that would be put into this steerage class, there is going to be contention and queuing that could easily push it into 1ms-10ms depending on bursts.<p>So if my whole path adopted these routers, I could experience jitter of ~170ms or worse. Gross.<p>This is essentially turning into a crappy QoS system where the biggest bandwidth hogs get the good service and everything else gets garbage.<p>Thumbs down from me.<p>1. <a href="http://www.cidr-report.org/as2.0/" rel="nofollow">http://www.cidr-report.org/as2.0/</a>