[AusNOG] Asymmetric BGP question

[Jason Sinclair]

Something I have done in the past when really stuck is "experimented" with sending a community to a provider/upstream to see what they supported. Now obviously you want to be careful of sending arbitrary communities for production routes but you will generally find that a lot of providers use communities without advertising the fact. The most common ones appear to be local pref manipulation which is generally done by AS:local_pref ie community xx:110 would set the local pref to 110 for provider xx..........

Another common one is xx:1 or xx:2 or xx:3 which prepends the route 1, 2 or 3 times....

Might help if you get really stuck.

Jas

-----Original Message-----
From: ausnog-bounces at lists.ausnog.net [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Nick @ Deltaband
Sent: Monday, 3 August 2009 7:20 PM
To: ausnog at ausnog.net
Subject: Re: [AusNOG] Asymmetric BGP question

Good idea.

Sadly it seems AS2 don't publicly announce any supported communities,
that i can find anyhow. Same goes for the transit provider... :(

On Mon, Aug 3, 2009 at 7:10 PM, Matthew Moyle-Croft<mmc at internode.com.au> wrote:
> A good place to find community defs is ONESC's
> page: http://www.onesc.net/communities/
> MMC
> On 03/08/2009, at 6:11 PM, Sean K. Finn wrote:
>
> Can you use AS2's communities (If they have any) to influence how they
> return traffic to AS1 ?
>
> E.g. take a look at Jason Sinclair from Pipe Networks presentation from
> AUSNog last year on Communities.
> http://www.ausnog.net/media/images/ausnog-02/presentations/AusNOG02-Sinclair-BGP%20Communities.pdf
>
> Community attributes stack, so you can tag AS1:community and AS2:community
> to influence how AS2 treats your routes, and yes it works multiple hops
> away, as long as any intermediaries aren't stripping community tags.
>
> -S
>
> -----Original Message-----
> From: ausnog-bounces at lists.ausnog.net
> [mailto:ausnog-bounces at lists.ausnog.net] On Behalf Of Nick @ Deltaband
> Sent: Monday, 3 August 2009 6:28 PM
> To: ausnog at ausnog.net
> Subject: [AusNOG] Asymmetric BGP question
>
> Hi,
>
> So i have this BGP problem...
>
> Traffic going between AS1 and AS2 has an asymmetric path of latency and
> doom.
>
> On the outbound path it goes something like this:
>
> AS1 > Transit Provider(AS1) > Equinix Sydney > AS2 - Perfect all is
> kept nicely on this side of the pacific.
>
> The return path is like this:
>
> AS2 > Transit Provider(AS1) > AS1 - The transit provider peers
> directly with AS2. Great. The problem is, it's in the US. So the
> traffic on the return path is laggy as hell because it's got to cross
> the pacific twice.
>
> You'd think AS2, that's predominately based in Australia, would be
> localpref'ing routes learnt from Australian IX's over US IX's but I
> guess they probably have their reasons not to.
>
> My question is: Other than asking the transit provider for AS1 to add
> an AS path prepend to the route being advertised to AS2 in the US, do
> I have any other options?
>
> MED would only work if the transit provider peered with AS2 directly
> in Aus as well right? Rather than via Equinix?
>
> Cheers,
>
> Nick
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> --
> Matthew Moyle-Croft
> Networks, Internode/Agile
> Level 5, 162 Grenfell Street, Adelaide, SA 5000 Australia
> Email: mmc at internode.com.au    Web: http://www.on.net
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