Re: [Idr] Robustness of NLRI encoding in draft-ietf-idr-add-paths

[John Scudder <[e-mail]>]

Robert,

On Nov 23, 2010, at 8:48 AM, Robert Raszuk wrote:
...
> So while we are looking to change the NLRI format let me point out 
> another observation of current add-paths proposal .. it allows to work 
> on a per AFI/SAFI level only. If I have 1 million of IPv4 routes and 
> 10-50 voice gateways prefixes I particularly care about I do not have a 
> way to continue sending my 1 million of IPv4 routes (less the 50 voice 
> gateways) the old MP_REACH way with single best path only, with packing 
> enabled and without path_id attached.

I don't know what you mean by "with packing enabled"?  You are correct that if you enable add-paths for a given AFI/SAFI the path_id as to be attached for all routes of that AFI/SAFI; however, there isn't any requirement to send multiple paths for all routes.  If you didn't want to send multiple paths, you could certainly send the path_id as zero (or any other fixed value) and essentially ignore it in every other respect.

> Add-paths must be as defined today enabled for all IPv4 unicast SAFI 

I'm not sure what you mean by this either.  There is no requirement in the spec to enable it for any particular AFI/SAFI.

> and
> what's worse with current implementations enabled uniformly ... that 
> means if I need to send all paths for my voice gateways it will also 
> result in distribution of all paths for the entire address family.
...

As you observe, this is an implementation choice and not fundamental to the protocol.  As I point out above, an implementation is free to pick and choose which prefixes it sends multiple paths for.  (This might be a topic to be mentioned in the add-paths-guidelines draft, though?)

Regards,

--John