Exodus/C&W Depeering

Mailman List Mirror (Read Only)
1

This isn't something I really care to make a big argument of, but my point
was that for many ISPs, the path will go from:

   SELF - EXODUS

to:

   SELF - OTHER BACKBONE - C&W

for a net increase in average path length.

Are we talking AS_Path attributes here? If so, all this means
is that now we don't announce OTHER BACKBONE routes to C&W/EXODUS,
which we probably weren't doing anyway.

Or are we talking forwarding paths, which are _different_ (and not
necessarily stable even in the presence of perfect AS_Path stability)?
If so, have we added any bottlenecks or sources of packet corruption?
If none have been added, a change in the number of links and routers
traversed is meaningless.
(Note that it is possible that the number of links and routers DECREASES).

  Sean.

2

>
>> This isn't something I really care to make a big argument of, but my point
>> was that for many ISPs, the path will go from:
>>
>> SELF - EXODUS
>>
>> to:
>>
>> SELF - OTHER BACKBONE - C&W
>>
>> for a net increase in average path length.
>
>Are we talking AS_Path attributes here? If so, all this means
>is that now we don't announce OTHER BACKBONE routes to C&W/EXODUS,
>which we probably weren't doing anyway.

Actually, it also mean a reduction in the possible paths presented to my router for computation. Some would say this is a good thing. Me, I like having multiple choices / redundancy. Better to have two ways to get to EXDS than one. IMHO, of course.

>Or are we talking forwarding paths, which are _different_ (and not
>necessarily stable even in the presence of perfect AS_Path stability)?
>If so, have we added any bottlenecks or sources of packet corruption?
>If none have been added, a change in the number of links and routers
>traversed is meaningless.

The *number* of routers and links is probably irrelevant. However, given C&W's history and current connectivity to "OTHER BACKBONES", it is likely a bottleneck, or extra fiber miles, or some other "problem" will be introduced into the forwarding path causing extra latency, packet loss, etc. for some portion of traffic.

Question is, do these problems affect enough traffic for anyone at C&W (or their customers) to notice / care? If not, then C&W probably has nothing to worry about.

BTW: I am interested in what portion of traffic does not get forwarded along the expected AS Path. Does anyone have an idea?

>(Note that it is possible that the number of links and routers DECREASES).

Is is also possible the air molecules in the room where I now sit will suddenly all congregate into a 1 square inch space in the corner over there. Although I admit your possibility is *slightly* more likely.

3

In my experience, the odds of any given path sucking are far greater than
the odds of that path going away. Therefore I would rather have one path
which doesn't suck than two paths which may.

4

Date: Tue, 26 Mar 2002 19:58:40 -0500
From: Richard A Steenbergen <ras@e-gerbil.net>

In my experience, the odds of any given path sucking are far
greater than the odds of that path going away. Therefore I
would rather have one path which doesn't suck than two paths
which may.

!
route-map blah 100
match suckage high
set local-pref 10
!
route-map blah 110
match suckage medium
set local-pref 20
!
! put rest of route map entries here

Eddy

Brotsman & Dreger, Inc. - EverQuick Internet Division
Phone: +1 (316) 794-8922 Wichita/(Inter)national
Phone: +1 (785) 865-5885 Lawrence

5

>> >Are we talking AS_Path attributes here? If so, all this means
>> >is that now we don't announce OTHER BACKBONE routes to C&W/EXODUS,
>> >which we probably weren't doing anyway.
>>
>> Actually, it also mean a reduction in the possible paths presented to my
>> router for computation. Some would say this is a good thing. Me, I like
>> having multiple choices / redundancy. Better to have two ways to get to
>> EXDS than one. IMHO, of course.
>
>In my experience, the odds of any given path sucking are far greater than
>the odds of that path going away. Therefore I would rather have one path
>which doesn't suck than two paths which may.

So would I. Doubt anyone would rather have two sucky paths than one good one.

However, in my experience, I would rather have to chose between me -> EXDS and me -> upstream -> EXDS, than be forced to use me -> upstream -> C&W.