North American Network Operators Group

Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical

Re: Gigabit Linux Routers

  • From: Eugeniu Patrascu
  • Date: Wed Dec 17 11:43:06 2008

Florian Weimer wrote:
* Eugeniu Patrascu:

You can also use a kernel with LC-Trie as route hashing algorithm to
improve FIB lookups.

Do you know if it's possible to switch of the route cache? Based on my past experience, it was a major source of routing performance dependency on traffic patterns (it's basically flow-based forwarding).

I don't understand your question.


In kernel, when you compile it, you have two options:
- hash based route algorithm
- lc-trie based route algorithm

From what I've read on the internet about the latter algorithm, it's supposed to be faster regarding route lookups with large routing tables (like a global routing table).



Anyway, with very few flows, we get quite decent performance (several hundred megabits five-minute peak, and we haven't bothered tuning yet), running on mid-range single-socket server boards and Intel NICs (PCI-X, this is all 2006 hardware). We use a router-on-a-stick configuration with VLAN separation between all hosts to get a decent number of ports.

In that configuration you'll split available bandwidth on the NIC and also have less throughput because server NICs are not optimized for "same interface switching".



My concern with PC routing (in the WAN area) is a lack of WAN NICs with properly maintained kernel drivers.


Usually it's better to get a dedicated router for that kind of stuff than bother with PC WAN cards.