[109938] in North American Network Operators' Group
Re: Gigabit Linux Routers
daemon@ATHENA.MIT.EDU (Eugeniu Patrascu)
Wed Dec 17 11:43:11 2008
Date: Wed, 17 Dec 2008 18:43:00 +0200
From: Eugeniu Patrascu <eugen@imacandi.net>
To: Florian Weimer <fweimer@bfk.de>
In-Reply-To: <82oczaq0zj.fsf@mid.bfk.de>
Cc: nanog list <nanog@nanog.org>
Errors-To: nanog-bounces@nanog.org
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.
