[c-nsp] LAM / Mobile IP in modern times

[David Freedman]

I should have mentioned that my target trains are 12.2SX and 12.2SR :)


> 
> 1. OTV 
> <http://www.ciscosistemi.net/en/US/prod/switches/ps9441/nexus7000_promo.html>
> 2. EoMPLSoGRE 
> <http://www.cisco.com/en/US/prod/collateral/switches/ps5718/ps708/white_paper_
> c11_493718.pdf>


Great, but both layer 2 solutions and both suffering from the same l3
symmetry issue. 

This is an MPLS network and as such the VPLS sledgehammer could be
brandished, I'm just trying to avoid it.


> you have a few options.
> 1. deaggregate / announce host routes (may work ok for an enterprise, less so
> for other environments)

Don't see this as being a problem in a well managed SP network.


> 2. announce the server subnet out both/multiple locations with same metric,
> return traffic will arrive at closest site or loadbalance across them with
> ECMP.

Similar problems as with layer 2, return traffic has to come back to a deagg
of some sort or be bridged across to where it needs to go somehow

> 
> since they probably aren't palatable to you, we also have another way on the
> way.
> 
> 3. LISP. <http://lisp4.cisco.com/index.html>

LISP/HIP is great, but quite far from production use, especially in this
scenario (but I have been following your LISP efforts with great interest)

> 
> 
>> I personally think LAM and
>> sufficiently convergence tuned network should be almost if not as good.
> 
> LAM is for unicast traffic only and IP unicast traffic to be precise.  there
> are many protocols / use-cases where that is not sufficient.
> i think its widely acknowledged that it doesn't really scale.

Disagree, we are only talking about host route deaggregation for hosts which
need to migrate for some reason or another, it doesn't appear to be a
complicated or dangerous thing to do providing active number of deaggregates
is managed, granted point about the multicast but don't think it will hamper
the product much (inter-datacenter multicast isn't a problem anyway)

I note from 
http://www.cisco.com/en/US/docs/ios/ipmobility/command/reference/imo_01.html
it seems to have made it into XE, quite why this was chosen (and not SX/SR)
is beyond me!


Appreciate the advice.


Dave.