> On Nov 17, 2015, at 3:52 PM, Eric C Rosen <ero...@juniper.net> wrote: > > [Eric] Do you have an example in mind where it is useful to advertise > an Originator SRGB when the prefix in the NLRI is not a host > address? > > [Stefano] in fact I don’t have any good example where a /32 (/128) must be > enforced… > > Well, that's not the question I asked ;-) > > Given that the SRGB is a property of a node, it seems to make sense to > associate an advertised SRGB with the address of a node.
to me it makes sense to advertise the SRGB along with ANY prefix originated by that node, regardless the mask-length. s. > As I explained, one can use this by pushing on a label that is computed by > combining a domain-wide unique SID with the node's SRGB, and then pushing on > a label that causes the packet to be delivered to the node in question. > > However, I can see Acee's point that (if I understand it correctly) that all > the nodes on a given subnet might use the same SRGB. > > Suppose we modify my suggested text as follows: > > --------------------------- > OLD > > When a BGP speaker attaches a Prefix-SID attribute to a given route, > the Originator SRGB TLV MUST NOT be included in the attribute unless > the following conditions hold: > > - The prefix field of the route's NLRI contains a host address > (i.e., a /32 IPv4 address or a /128 IPv6 address). > > - The value of the Originator SRGB TLV specifies the SRGB of the node > that is identified by the prefix field of the NLRI. > > If a BGP route is received that contains a Prefix-SID attribute with > an Originator SRGB TLV, but the prefix field of the NLRI does not > contain a host address, the attribute SHOULD be regarded as > malformed. If aPrefix-SID attribute contains more than one SRGB TLV, > it SHOULD be regarded as malformed. See section 7 for the treatment > of a malformed Prefix-SID attribute. > > When a route carrying the Prefix-SID attribute is propagated, the > Originator SRGB TLV (if present) MUST NOT be changed. > > NEW > > If a BGP speaker attaches a Prefix-SID attribute to a given route, and if the > Prefix-SID attribute includes the Originator SRGB TLV, then: > > - If the prefix field of the route's NLRI contains a host address > (i.e., a /32 IPv4 address or a /128 IPv6 address), the Originator SRGB TLV > specifies the SRGB of the node to whom the host address belongs > > - If the prefix field of the route's NLRI does not contain a host address, > the Originator SRGB TLV specifies the SRGB that is used by the set of nodes > whose host addresses match the prefix, but for which there is no "more > specific" match that specifies a different Originator SRGB. > > When a route carrying the Prefix-SID attribute is propagated, the > Originator SRGB TLV (if present) MUST NOT be changed. > > -------------------- > > This new text omits the enforcement, allows an SRGB to be advertised for an > entire subnet (as suggested by Acee), but still explains how to figure out > which nodes are using the specified SRGB. > > Does this modification satisfy your objection? > > > > _______________________________________________ spring mailing list spring@ietf.org https://www.ietf.org/mailman/listinfo/spring
