An Examination of the Internet's BGP Table Behaviour in 2001

During the Asia Pacific Regional Internet Conference on Operational Technologies in March 2002, Geoff Huston presented An Examination of the Internet's BGP Table Behaviour in 2001. It seems the growth in the routing table slowed down considerably to 8%. The two previous years saw a 55% growth rate.

Yes, it took the news some time to reach BGPexpert. There are some other interesting presentations available on the APRICOT 2002 web site as well.

RIAA sues transit networks to have Chinese site blocked

On August 15th, the Recording Industry Association of America (RIAA) filed a complaint against AT&T Broadband, Cable & Wireless USA, Sprint and UUNET, asking for a court order to make those networks to block an MP3 web site operated in China. BGP is even mentioned on page 11 of the complaint.

This, and other recent RIAA initiatives such as their plans to hack MP3 swapper's PC's, has made the RIAA very unpopular on the NANOG list. The pros and cons of blocking RIAA and record label web sites were discussed at length.

When the offending web site went offline, the RIAA dropped the lawsuit. But I'm sure the net hasn't seen the last of the RIAA lawyers.

Large AT&T outage / no more IGPs

On August 28th, AT&T had an outage in Chicago that affected a large part of their network. It took them two hours to fix this, and after this they released a fairly detailed description of what happened: network statements in the OSPF configuration of their backbone routers had been deleted by accident.

AT&T was praised by some on the NANOG list for their openness, but others were puzzled how a problem like this could have such wide spread repercussions. This evolved into a discussion about the merits of interior routing protocols. Alex Yuriev brought up the point that when IGPs fail, they do so in a very bad way, his conclusion being it's better to run without any. This led to some "static routing is stupid" remarks. However, it is possible to run a large network without an IGP and not rely on static routes. This should work as follows:

• There must be a confederation
• Routers separated by a point-to-point link must be in different confederation sub-ASes
• All IBGP sessions are configured with next-hop-self
• The Multi Exit Discriminator metric is increased by each router

That way, you never talk (I)BGP with a router you're not directly connected to, so you don't need loopback routes to find BGP peers. Because of the next-hop-self on every session, you don't need "redistribute connected" either so you've eliminated the need for an IGP. Since the MED is increased at each hop, it functions exactly the same way as the OSPF or IS-IS cost and the shortest path is preferred.

Ownership of address space

In the first week of May, a message was posted on the NANOG list by someone who had a dispute with one of his ISPs. When it became obvious this dispute wasn't going to be resolved, the ISP wasn't content with no longer providing any service, but they also contacted the other ISP this network connected to, and asked them to stop routing the /22 out of their range the (ex-)customer was using. The second ISP complied and the customer network was cut off from the internet. (This all happened on a sunday afternoon, so it is likely there is more to the story than what was posted on the NANOG list.)

The surprising thing was that many people on the list didn't think this was a very unreasonable thing to do. It is generally accepted that a network using an ISP's address space should stop using these addresses when it no longer connects to that ISP, but in the cases I have been involved with there was always a reasonable time to renumber. Obviously depending on such a grace period is a very dangerous thing to do. You have been warned.

Packet reordering

During the second week of April there was some discussion on reordering of packets on parallel links at Internet Exchanges. Equipment vendors try very hard to make sure this doesn't happen, but this has the risk that balancing traffic over parallel links doesn't work as good as it should. It is generally accepted that reordering leeds to inefficiency or even slowdowns in TCP implementations, but it seems unlikely reordering will happen much hosts are connected at the speed of the parallel links (ie, Gigabit Ethernet) or there is significant congestion.

Telephony best practices for IP

In March, the NANOG list focussed some of its attention on efforts of the telephony world to com up with "best practices" about packet networks/the internet. (Network Reliability and Interoperability Council publications) In meeting minutes, 100% of the carriers reported to abide by these best practices, which include firewalling routers and DNS servers.

There were discussions about the merits of filtering/firewalling at OC-192 (10 Gbps) speeds (which, depending on your definition of "firewall" may be impossible to do) and about out-of-band versus in-band management. The former is always used in the telephony world, the latter often in IP. The main problem with out of band management is that the management network may be unavailable when the network is in critical need of being "managed". Also, many vendors do not support a clear separation between production and for-management interfaces.