The Routing Over Large Clouds Mailing List Archive by date

[Andy Malis <malis@maelstrom.timeplex.com>]

Joachim,

> >Analyze and propose enhancements to IP [and IPng] routing over large
> >Analyze and propose enhancements to IP [and IPng] routing over large
> >``shared media'' link layer (with respect to IP) networks (ATM, Frame
> >``shared media'' link layer (with respect to IP) networks (ATM, Frame
> >Relay, X.25, SMDS, etc.).
> 
> Wide-area links connected via wide-area MAC-bridges running a path
> Wide-area links connected via wide-area MAC-bridges running a path
> selection protocol like spanning tree or source routing can be used
> to build the switching fabric of a "Large Cloud" and should be added
> to the considerations of ROLC.

That case (a bridged WAN network) is meant to be covered by the "etc."
That case (a bridged WAN network) is meant to be covered by the "etc."
above, and in fact has already been discussed during working group
sessions.

> >Avoid ``extra hops'' when routing IP. Extra hops are defined as points
> >Avoid ``extra hops'' when routing IP. Extra hops are defined as points
> >where an IP datagram leaves and re-enters the same link-layer-cloud as a
> >result of an IP routing decision, such as when routing between different
> >IP subnets overlaid on the same cloud.
> 
> Such a rule or recommendation is inappropriate.  This issue is a question
> of  internet design and not a question of protocol standardization.
> 
> It might make perfect sense to leave and reenter the "cloud" if selecting
> a path which remains within the cloud necessitates transversal of a link
> which has extremely low data rate or some other negative characteristic
> whereas the path which requires the external hop uses links of appropriate
> characterists.

Yes.  The term as used above should actually be more precise, and I'll
fix the charter text to reflect this after the upcoming meeting.  What
we're actually talking about is the IP datagram leaving and reentering
the WAN through the EXACT SAME physical interface, because IP routing
the WAN through the EXACT SAME physical interface, because IP routing
forced it to make a router hop from one IP subnet to another, where
both subnets are overlayed on the same physical WAN, and are
both subnets are overlayed on the same physical WAN, and are
interconnected (using one physical WAN interface) by the router in
interconnected (using one physical WAN interface) by the router in
question.  Our goal is to eliminate such hops if possible.

Thanks for your comments.

Cheers,
Andy
Andy