I agree. I think introducing indexes especially that they do not solve all problems is not so great of an idea.
That is why I proposed a new clean complete label space for SR in draft-raszuk-mpls-domain-wide-labels. Of course an alternative is not to use mpls as a transport at all :-)) Cheers, R. On Fri, May 15, 2015 at 10:39 AM, Hannes Gredler <[email protected]> wrote: > hi martin, > > IMO context labels are the agreed-upon vehicle to disambiguate label-space. > in the past we have used that e.g. for egress-protection and upstream > label-allocation. > > /hannes > > On Fri, May 15, 2015 at 10:20:21AM +0300, Martin Horneffer wrote: > | Hello everyone, > | > | there is a problem for networks that use spring on the MPLS forwarding > | plane: It seems it would not be feasible to use anycast segments for > traffic > | engineering since we introduced indexed SIDs. > | > | I would really like to use of some well-defined anycast addresses to > solve a > | number of traffic engineering use cases. I.e. an anycast address would > stand > | for a certain property of possible paths and segment routing would be > | responsible to apply this property to the traffic which needs it. In > other > | words I want to use a path with one anycast segment, followed by the > usual > | node segment to the actual destination (typically an egress LER). > | > | The anycast segment itself is fine: it can be built in the usual way. > | However for the following node segment the spring source node cannot > | calculate the label value. The stack PUSHing router would not know at > which > | node the second segment would actually start, and thus which SRGB to > apply. > | > | If needed I could make a drawing to illustrate this problem. > | > | As I see it, there would be three different options to address this > problem: > | > | 1) Abandon anycast segments completely. > | This would greatly reduce the usefulness of segment routing in my > opinion. > | > | 2) Use a homogeneous SRGB, so that label values would effectively be the > | same for all nodes. > | But in this case, why did we introduce indexes at all? > | > | 3) Use a context label. E.g. as defined in > | draft-raszuk-mpls-domain-wide-labels. > | > | Since I really hate to add more labels to the stack than really needed, > | could we think of a way to only use context labels where needed? > | As far as I can see this would only be relevant for the segment > immediately > | following an anycast segment. > | > | Are there any other options? > | > | Best regards, Martin > | > | _______________________________________________ > | spring mailing list > | [email protected] > | https://www.ietf.org/mailman/listinfo/spring > > _______________________________________________ > spring mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/spring >
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