Trouble Ahead for Internet Routing Tables?

joabj writes: "This article in Light Reading, a fiber optics news page, claims that the Internet's routing tables are ballooning in size and within a couple of years "equipment won't have enough processor power and memory to handle them." The article draws its conclusions from the dramatic increase in the number of BGP routing tables over the last six years and the predicted need for more IP addresses for all those pervasive computing goodies we've been promised."

Comments

Routing table is _already_ affecting performance.

[Phizzy]

Alright.. so first off, this isn't news. Anyone following the NANOG list knows that the routing table is increasing exponentially with the rest of the internet. There isn't anything that can be done about that, realistically. The aggregation Nazis will scream day and night that they can fix the Internet if you would just let them aggregate things properly. Fine, but that would require a total renumbering of the internet, so it isn't at all possible with IPv4, unless everyone out there really feels like renumbering every machine on their network with a publicly addressable IP. Think about that for a minute. They'll scream that they can do it without renumbering, but they're wrong. The routing table is an intricate mesh of advertisements and if everything was aggregated, nothing would work right. BGP's first method of selection of routes is the longest match rule, whereby when you're choosing a route to pass traffic on, you choose the most specific advertisement, eg choose a class C rather than a class B advertisement. If everything was aggregated into /20 or larger blocks, there would be no practical way to load balance traffic in a multihomed environment (when you have transit through more than one ISP).

And secondly, BGP isn't the cause for the routing table growing, it is the cure. There is no way we would still be using IPv4 without BGP. It saved the internet by introducing classless routing.

The answer to this is simple.. upgrade, upgrade, upgrade. There are routers out there that can handle far more than the internet has to throw at them right now.. it's just that Cisco doesn't make them. Juniper does.. check them out. They built a router off some sweet hardware and BSD. You can type 'start shell' in the router and drop to a BSD shell, and they have the route processor to chew through a routing table many times the size of our current table.

ISPs need to keep up with the growth and upgrade their routers, or they will have problems. Much of the instability of the 'net is due to that now, routers get overloaded and reboot and cause all kinds of churn in the network, which overloads other routers, which reload.. you can see the cascading effect. The ISP I work for had to upgrade all of our older routers to 128m of ram and newer route processors.. if all the ISPs did this, there would be no routing table problems. They just don't want to spend the millions they need to to upgrade their infrastructure, unless the users start screaming. So start screaming at your ISP! (unless it's mine. ;)

//Phizzy

Re:Some quick thinking....

[CoreDump]

1.BGP isn't working. Well, fortunately, there are a lot of other protocols out there to choose from.

Really, pray tell what these are? Apart from draft proposals, please tell me what these other protocols are? BGP does work. No, it is not perfect, but it works and it's failure modes are pretty well defined. The fact of no legitimate alternatives also poses a problem. :\

2.Routers will need "gigabits" of memory within two years.

Assuming cisco, which is pretty much the standard, you are going to have trouble fitting a full BGP table into less than 128 MB today. So what? That doesn't mean the sky is falling.

3.In 6 years we went from 10,000 to 100,000 entries.

Yes, for a good statistical analysis of this growth please see:

• http://www.telstra.net/ops/bgptable.html
• http://www.employees.org/~tbates/cidr.hist.plot. html

Now, how did the number of end users on the "Internet" grow during the same period?

4. ... Part of the reason the routing tables are growing so much is because IPv4 does not make routing tables very efficient.

Not the case at all. IPv6 is going to save nothing. Greater than 1/2 of the current routing table is announced as /24 or longer prefixes. Aggregation can cut the routing table size. Please see the CIDR report for the worst abusers of de-aggregation. The worst offender is announcing ~430 blocks when they could aggregate those into ~150 blocks, without losing any routing stability. The CIDR report is available at:

CIDR Report

IPv4 has a long way to go still before we are in dire straights. Let's not forget what 2^32 gives us, and what we are using now out of that.

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