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

[Eric Dean <eric@crystalballinc.com>]

1.

On Tue, 3 Apr 2001, Oliver Spatscheck wrote:

> 
> 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 
> 

Eric Dean
President, Crystal Ball Inc.
W 703-322-8000
F 703-322-8010 
M 703-597-6921