[88200] in North American Network Operators' Group
Re: T1 bonding
daemon@ATHENA.MIT.EDU (PC)
Tue Jan 24 20:17:47 2006
Date: Tue, 24 Jan 2006 18:15:17 -0700
From: PC <mailinglists@pc.boise.id.us>
To: nanog@merit.edu
In-Reply-To: <3CB5335E037F5544BA279A8DB9B52C3C531B99@dc-mail.onelegal.com>
Errors-To: owner-nanog@merit.edu
Is it AT&T?
If so, they only use Cisco Express Forwarding on the router, or so
that's at least what I was told by the level 1 techs. If packet order
reassembly is a an issue and the link is oversubscribed (IE: Heavy
VoIP/gaming use), this method isn't the greatest over others like MLPPP,
or per-flow CEF, but in 99% of circumstances it works great (and has
other advantages). Can you max out the T-1 with two or three separate
"flows" (IE: simultaneous transfers?) If so, it is possible that they
are doing per flow and not per-packet load balancing. It should be per
packet.
Call them up. Once you get screened and transferred to a Cisco guy,
fire away with your questions -- they know their stuff in my
experience. Or if is your equipment, log into the router and see if ip
load-sharing per-packet is set (assuming it is CEF), and confirm they
did the same.
Off topic, but in my experience MLPPP usually does a better job of
getting 190% of a T-1's speed with two of them. CEF usually tops out at
around 160-170% with a single flow, but will max out with as little as
two flows. I don't know why though, and haven't cared since I've never
really had a dual T-1 all to myself without any other users. 2.5
megabit seems to be the single flow norm on our AT&T Circuits at 3 AM
with no usage., 2.8-2.9 with two or three flows.
As for the technical details, here is some reading material that
explains it quite nicely.
http://www.cisco.com/en/US/products/hw/modules/ps2033/products_white_paper09186a0080091d4b.shtml
http://www.swcp.com/~jgentry/cisco/cisco-load.html
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120limit/120s/120s21/pplb.htm
Test file here for speed tests:
ftp://ftp1.optonline.net/test64
Matt Bazan wrote:
> Can someone shed some technical light on the details of how two T1's are
> bonded (typically). We've got two sets of T's at two different location
> with vendor 'X' (name starts w/ an 'A') and it appears that we're really
> only getting about 1 full T's worth of bandwidth and maybe 20% of the
> second.
>
> Seems like they're bonded perhaps using destination IP? It's a vendor
> managed solution and I need to get some answers faster than they're
> coming in. Thanks.
>
> Matt
>
Matt Bazan wrote:
> Can someone shed some technical light on the details of how two T1's are
> bonded (typically). We've got two sets of T's at two different location
> with vendor 'X' (name starts w/ an 'A') and it appears that we're really
> only getting about 1 full T's worth of bandwidth and maybe 20% of the
> second.
>
> Seems like they're bonded perhaps using destination IP? It's a vendor
> managed solution and I need to get some answers faster than they're
> coming in. Thanks.
>
> Matt
>
