[AusNOG] Asymmetric BGP question

[Nick @ Deltaband]

Hi Sean,

You don't know the half of it... the problem got way more complex when
it turned out AS2 also bought transit from the same provider as AS1.
That provider then in turn ended up being a collection of ASs around
the globe that had supposedly merged, but hadn't. I almost had to
reach for the old Sam Halabi bible ;)

Anyhow after some off list mails, AS2 provided some regexp access-list
localpref route map action and the packets are currently staying
within a 10ms latency of their endpoints.

The transit in question, after 48 hours are still trying to find
someone who knows what an as-path pre-pend is... i haven't got the
heart to tell them it's not needed at this late stage.


On Wed, Aug 5, 2009 at 3:41 PM, Sean K. Finn<sean.finn at ozservers.com.au> wrote:
> Hrrm,
>
> This is really a boggle, and one I cant stop thinking about.
>
> Now, if AS1 wasn't using outgoing BGP to dump its traffic onto AS1 TRANSIT PROVIDER, you could POSSIBLY, although not NICELY, pre-pend AS1-TransitProvider to *your* BGP path and see-what-happens.
>
> This may make AS2 drop AS1-TRANSIT-PROVIDER as the return path, and dump your traffic into Equinix, although, I'm not sure how this would get you back to AS1.
>
> Could you perhaps talk to the NOC's of AS1-TRANSIT-PROVIDER or AS2, or possible get AS1 to escalate a job request to the NOC's on your behalf?
>
> I'm sure if you got through to speaking to a sane person capable of making a change, they would see how silly it was to have the traffic doubling back.
>
> Better yet, if you know AS1-TRANSIT-PROVIDER or AS2 and could publicly disclose, then maybe someone lurking on this list is that sane person you need to reach, or has had a beer with them recently at the very least.
>
> -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 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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>>
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