Re: comments on draft-ietf-shim6-failure-detection-06.txt {2}

[Iljitsch van Beijnum <iljitsch@muada.com>]

On 30-sep-2006, at 16:47, Deguang Le wrote:

> This paragraph presents "SHIM6 needs to avoid sending packets
> concurrently over multiple path".

> However, in RFC 3582 - Goals for IPv6 Site-Multihoming Architectures,
> Load sharing is one of the goals of multihoming.
> 3.1.2.  Load Sharing
>    By multihoming, a site should be able to distribute both inbound  
> and
>    outbound traffic between multiple transit providers.  This goal is
>    for concurrent use of the multiple transit providers, not just the
>    usage of one provider over one interval of time and another  
> provider
>    over a different interval.

> Therfore, I would like to know if this sentence "SHIM6 needs to avoid
> sending packets concurrently over multiple path" means that SHIM6
> doesn't support load sharing?

The text you cite pertains to individual shim contexts. Often, a shim  
context will be used for a single TCP session, and it's considered  
suboptimal to have packets belonging to the same TCP session travel  
through different paths, because this introduces packet reordering  
which impedes TCP performance.

However, shim6 still supports load balancing by allowing different  
contexts to use different addresses, so that part of the contexts  
will generate traffic over one path and part of the contexts over  
another path.

Note though, that most traffic will be associated with contexts for  
which no shim6 address rewriting is active, so load balancing greatly  
depends on things outside the scope of shim6, such as information in  
the DNS and routing.

> -Page9
>    It is also necessary to
>    track remote address information from the peer.  For instance,  
> if the
>    peer's currently used address is no longer in use, mechanism to  
> relay
>    that information is needed.  The Update message in the SHIM6  
> protocol
>    is used for this purpose [I-D.ietf-shim6-proto].

> What is "Update message"?

I still have a review of the shim6 proto draft on my to do list, so  
I'll keep my eye out for this. Maybe Erik or Marcelo can answer this?

Thanks for the comments,

Iljitsch