Hi Xu, How to simply use the MPLS label stack to realize the SFC has been > described in http://tools.ietf.org/html/draft-xu-spring-sfc-use-case-00. > Any comments are welcome. >
The draft says: "that packet, SN1 could further consume the metadata contained in the NSH and meanwhile decrease the service index value within the NSH by on e " I would observe after reading this draft that S x service node may not be capable of handling NSH of any sort (including SR header - be it MPLS label stack or IPv6 EHs) therefor much more then just decreasing the index value is required at SNx. It seems that to realize any service chain via most of today's service nodes a full removal of NSH and re-application is required at directly attached SNs. That actually means that network needs to carry the state pretty much out of band. Such state could be carried within routing protocols (today BGP is used for that in L3VPN case) or by new overlay control plane - same as is used to carry the metadata. Cheers, R.
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