query about determining ingress interface

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1

Hi

Is there a way for an ISP to determine the ingress router interface at
its network border that will carry IP traffic _from_ an IP address not
owned by it?

I don't want to assume the path is the same in both directions, and tools
such as CAIDA's skitter plot paths from specific sources. One approach
might be deriving network paths from CAIDA's data, perhaps someone has
already done this?

Thanks.
Rajesh.

2

Rajesh,

Hi there..

Are you asking to determine the interface that "will" or "is" passing said
traffic?

I think it depends on what you're trying to do- Are you trying to track
an individual src at one given point, or collect some stats/trends on where
various srcs are entering your network?

I.e, for an individual src/dst (maybe you're tracing a DoS, etc..) there are
a number of ways to use filters and other mechanisms to log/count packets
matching some known charachteristics (src/dst, length, etc..)

There are various ways to do things like this, it depends on what exactly you're
trying to track though.

..Dylan

3

Is there a way for an ISP to determine the ingress router interface at
its network border that will carry IP traffic _from_ an IP address not
owned by it?

traceroute -g, which is what insisting on lsr is all about

randy

4

indeed, altho you will have to go back to filters if you want to do this
on an IP more than a couple of hops away, I tend to find most of my peers
allow it a little way into their network and it either stops or it stops
at the next network boundary..

Steve

5

Wouldn't it be nice for router vendors to include traceroute servers into
basic router features, and bury the expensive (in silicon) and dangerous
(for inattentive sysadmins) source-routing IP options?

(...keeps dreaming... :slight_smile:

--vadim