RE: Executive summary of: RE: hard questions: request routing

[DonE@activate.net]

I vote for proposal 1.

Also, I think it is the case, but I just wanted to make sure, that all
proposals would work with L7-based RR as well as DNS-based RR.  Any that
wouldn't should be ruled out.

Don

> -----Original Message-----
> From: Oliver Spatscheck [mailto:spatsch@research.att.com]
> Sent: Tuesday, April 03, 2001 2:12 PM
> To: cdn@ops.ietf.org
> Subject: Executive summary of: RE: hard questions: request routing
> 
> 
> 
> Enclosed the executive summary of the discussion about loop 
> avoidance in
> request routing. I think I finally understood Abbie's 
> solution after talking
> to him and we think it is time that the group agrees which 
> method we should use
> to move on. The candidates which crystallized so far:
> 
> 
> 1. Restrict the topology.
> 
>    This solution statically restricts the depth of request 
> routing to one (or
>    maybe two). This avoids loops due to its static 
> limitation, however, it is
>    the most restrictive one. On the other hand the protcol 
> overhead is zero.
> 
> 2. Recursive request routing
> 
>    The request is handled by the first CDN contacted by a 
> client.  The CDN
>    will ask other CDN's recursively to resolve to an A 
> record.  This recursive
>    request includes a request path which can be used to 
> prevent loops. This
>    avoids the DNS hack issue, however, it requires a new 
> protocol (or DNS
>    extension) to carry the path information.
> 
> 3. Abbie's proposal
> 
>    A matrix is distributed to all participants representing 
> the relationships
>    between individual CDNs for a particular set of content.  
> This matrix is
>    used to encode the path info as set of CNAMEs in a 
> structured way. So this
>    solution is similar to Brad's suggestion, except it adds 
> structure to the
>    CNAME encoding (see Abbie's email for more data).
> 
> 4. Abbie's proposal as I understood it first..... .
> 
>    A cycle free graph is generated based on the matrix every 
> time a CDN starts
>    or stops serving a particular set of content. This cycle 
> free graph is
>    distributed to all CDN's involved atomically. Request 
> routing is now a
>    traversal of this cycle free graph. This is basically a 
> variant of a link
>    state protocol, but the atomic requirement makes it rather 
> expensive.
> 
> 
> I think we discarded already the path vector with common metric
> approach. So at this point we have to decide which way we want
> to go. PLEASE VOTE NOW!
> 
> Oliver 
>