[ppml] Various IPv6 issues

Scott Leibrand sleibrand at internap.com
Fri Aug 24 01:21:59 EDT 2007

mack wrote:
> 5) Geographically dispersed organizations will need more than a single /32 if a /32 is the
> smallest announcement and we do not wish to de-aggregate.  Traffic engineering is also
> going to require either A) a new routing protocol, B) changes to BGP, C) deaggregation
> or D) multiple /32s.

Deaggregation need not be global...

> We need some policy with this in mind.
> Example with two locations, 2 transit providers and a link:
> Transit1 in location A.
> Transit2 in location B.
> Transport between A and B via Layer 2 connection (billed at 95th).
> Advertising the same prefix in both locations means that traffic
> from Transit2 will exit only in location B.
> But may actually be destined for A.
> The obvious solution is to apply for a second /32.

That's one solution.  Another would be to subnet the /32, announce your 
/32 from both locations, and also announce the subnets, each from its 
own location.  Assuming you pay them to do so, your transit providers 
will be happy to accept your subnets from you and, importantly, from 
each other.   They may also announce the routes to their peers, who may 
accept them.  If they do, they'll route your traffic optimally the whole 
way through.  If not, then some of the time the traffic will get routed 
to the wrong transit provider, who will have to hot-potato it off to the 
correct transit provider via the more-specific subnet.  Assuming the two 
transit providers are relatively peered, this will result in minimal 
suboptimal routing.

To me, that sounds a whole lot easier than designing and implementing a 
new or improved routing protocol, and a lot more flexible for preventing 
routing table explosion than giving applicants more space than they need 
so they can get avoid prefix length filters.


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