Subject: Re: New Routing Header!!!

From: Tim Enos <[email-masked]>
Date: Tue, 04 Sep 2007 11:50:04 -0500 (CDT)

Hi all,

>Hi bill, Hi Stig, Hi *,
>
>bill fumerola <[email-masked]> writes:
>
>> On Fri, Aug 31, 2007 at 03:58:54AM +0200, Stig Venaas wrote:
>>> I'm not arguing for keeping source routing here, but one quite useful
>>> thing it can be used for is traceroute. You can for instance trace from
>>> a remote point in the network towards yourself. This can be very helpful
>>> when debugging routing problems.
>
>First, thank you both for the feedback.
>
>Having spent quite some time doing that on the IPv6 internet, i basically
>got to the conclusion that if you don't precisely know the router you
>send your packets to (the waypoint that will bounce your traffic based
>on RH content), you spend more time debugging the reaction of that
>router than what happens on the path.

First, a qualifier: my own IPv6 knowledge and experience is and has been (and FWIW will likely remain) in R&D, not operations.

That said, the above point seems brilliant in its simplicity. The effectiveness of traceroute from A <-> B would have to be delimited by the intermediate nodes(s) 'willingness' &/or ability to forward these IPv6 packets (containing RH0), as well as the destination's 'willingness' &/or ability to process them.

_Not_ rhetorical: I'm wondering how often (and what percentage of times) such a use of RH0 would have to be successful in order for it to be (at least generally) considered an example of a valid use case.

There are routers that drops
>traffic, others that reply with ICMPv6 error packets indicating an
>administratively prohibited condition, others that don't have a route to
>your next destination, others that do have a route (default ?) but which
>won't go far, etc 
>
>When you include multiple waypoints, this gets even more difficult to
>get some precise information (Even if your tool does not try to be smart
>on what comes back).
>
>I understand the interest and like the boomerang traceroute too but i'm
>surprised network operators do not have better tools than that to debug
>and monitor things.
>
>> engineers also can use it when setting up, debugging, or for periodic
>> testing of peering sessions to make sure that the other side isn't doing
>> anything against the contractual terms of the peer (e.g. overriding the
>> normal policies that result from standard RIB->FIB route selection).
>>
>> examples:
>> http://ptd.mbo.ma.rcn.net/peerinfo/
>>
>> All peers are requested to enable LSRR on router interfaces facing RCN
>> peering sessions to facilitate network diagnostics at least during session
>> activation.
>>
>> http://www.via.net/support/support_peer.html 
>> We require that our peers permit LSR, loose source routing, at least at the border.
>>
>> http://www.noc.wiscnet.net/peering/
>> We require that our peers permit LSR, loose source routing, at least at
>> the border for diagnostic purposes.
>
>Some questions:
>
>- can anyone send LSR traffic to those routers? is it limited?  
>- If it is limited in some way, how is it done? 
>- What tools do you use to test that and what is the frequency of use?
>  (Only traceroute when you have a doubt?)
>
>> i don't have an ACM account, but:
>> http://portal.acm.org/citation.cfm?coll=GUIDE&dl=GUIDE&id=1016718
>
>Don't have either. I won't give credit only based on the abstract ;-)
>
>> without comparable functionality in IPv6, we lose a feature actively in
>> use (through IPv4) by some networks for verification of proper peering.
>
>Is there any place one can ask operators or people that provide peering
>at exchange points on that. Basically, my question is: is there any
>consensus on the use of source routing among those people? I know people
>that prohibit their use.
>
>> if i'm out of touch with current policies on peering & LSRR, please let
>> me know.
>
>a+
>

Best Regards,

Tim Enos
Rom 8:28

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