Advertising Service Functions Using IS-IS

describes a particular use case for SPRING where the Segment Routing (SR) mechanism is leveraged to realize the service path layer functionality of the Service Function Chaining (SFC), i.e, steering traffic through the service function path. To allow the service classifier to encode the segment list represeting a particular service function path, the classifier needs to know on which service node(s) a given service function is located and what segment ID (SID) is used to indicate that service function on a given service node. This document describes how to advertise service functions and their corresponding SIDs using IS-IS.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119.

This memo makes use of the terms defined in .

Service nodes within the network need to advertise each service function they are offering by using a new sub-TLV of the IS-IS Router CAPABILITY TLV . This new sub-TLV is called as Service Function sub-TLV. The Service Function sub-TLV could appear multiple times wihin a given IS-IS Router CAPABILITY TLV when more than one service function needs to be advertised by a given service node. The scope of the advertisement depends on the application but it is recommended that it SHOULD be domain-wide. Furthermore, service nodes need to allocate a corresponding SID to each service function they are offering and advertise it by using a sub-TLV of the above Service Function sub-TLV, called Service Function SID sub-TLV. In the MPLS-SR case, service nodes within the network would allocate a locally significant MPLS label to each service function they are offering. In the IPv6-SR case, service nodes within the network would allocate a locally unique link-local IPv6 address to each service function they are offering. For a given service function, the service node offering that service function could advertise the corresponding SID in the MPLS label format or in the IPv6 address format, or both.

Type: TBD. Length: variable. Service Function Identifier: A unique identifier that represents a service function within an SFC-enabled domain. Sub-TLVs: contains zero or more sub-TLVs related to service functions. Besides the Service Function SID sub-TLVs as defined in Section 3.2, other sub-TLVs (to be defined in future) which are used to describe some characters of a given service function could also be added.

Type: TBD. Length: variable (3 or 16). Value: if the Length is set to 3, the 20 rightmost bits represent a MPLS label. If the length is set to 16, the value represents an IPv6 address.

TBD.

This memo includes a request to IANA to allocate one sub-TLV type codes within the IS-IS Router Capability TLV for the Service Function sub-TLV, and one sub-TLV type code within the Service Function sub-TLV for the Service Function SID sub-TLV.

This document does not introduce any new security risk.