Subject: [P2PSIP] draft-ietf-p2psip-base-20: fragmentation and via lists

From: André Becker <[email-masked]>
Date: Thu, 2 Feb 2012 23:38:09 +0100

Hi,

I'm currently implementing parts of RELOAD as my bachelor thesis and 
stumbled upon an ambiguity concerning answers to fragmented requests. 
Section 5.2.2 states:

    When a peer sends a response to a request using this routing
    algorithm, it MUST construct the destination list by reversing the
    order of the entries on the via list.  This has the result that the
    response traverses the same peers as the request traversed, except in
    reverse order (symmetric routing).

However, neither this section nor section 5.7 (which covers 
fragmentation) clarifies which via list should be used if the message 
was fragmented. As intermediate nodes handle each fragment 
independently, different fragments of the same request might take 
different routes in the overlay. So for the receiving node it remains 
unclear which via list should be used for the answer.

Proposal: Add the following text to section 5.2.2:

     If the request was fragmented and for that had to be reassembled by the
     receiving node, the via lists of the fragments may differ. The 
receiving Node
     SHOULD use the via list of the last fragment, as determined by the last
     fragment bit; See Section 5.7

This should be a good approach, because for the last fragment's route 
the probability is high to still be available.

Regards,
   André

---

From: Bruce Lowekamp <[email-masked]>
Date: Sat, 18 Feb 2012 13:55:37 -0500

André,

I agree.  Added some text to 5.2.2

Bruce

On Thu, Feb 2, 2012 at 5:38 PM, André Becker
<[email-masked]> wrote:
> However, neither this section nor section 5.7 (which covers fragmentation)
> clarifies which via list should be used if the message was fragmented. As
> intermediate nodes handle each fragment independently, different fragments
> of the same request might take different routes in the overlay. So for the
> receiving node it remains unclear which via list should be used for the
> answer.
>
>    receiving node, the via lists of the fragments may differ. The receiving
> Node
> This should be a good approach, because for the last fragment's route the
> probability is high to still be available.
>
> Regards,
>  André
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