]> China Mobile

xuxiaohu@cmss.chinamobile.com

Huawei

hongyi.huang@huawei.com

Ciena

hshah@ciena.com

Telefonica I+D

luismiguel.contrerasmurillo@telefonica.com

Routing Area LSR Working Group Sample The MPLS source routing mechanism developed by Source Packet Routing in Networking (SPRING) WG can be leveraged to realize a unified source routing instruction which works across both IPv4 and IPv6 underlays in addition to the MPLS underlay. The unified source routing instruction can be used to realize a transport-independent service function chaining by encoding the service function path information or service function chain information as an MPLS label stack. This document describes how to advertise service functions and their corresponding attributes (e.g., service function label) using IS-IS.

Introduction describes how to leverage the unified source routing instruction to realize a transport-independent service function chaining by encoding the Service Function Path (SFP) or Service Function Chain (SFC) information as an MPLS label stack. To allow a service classifier to attach the MPLS label stack which represents a particular SFP or SFC to the selected traffic, the service classifier needs to know on which Service Function Forwarder (SFF) a given Service Function (SF) is located and what service function label is used to indicate that SF. This document describes how to advertise SFs and their corresponding attributes (e.g., service function label) using IS-IS.

Terminology This memo makes use of the terms defined in and . The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Solution Description SFFs within the SFC domain need to advertise each SF 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 within a given IS-IS Router CAPABILITY TLV when more than one SF needs to be advertised. The scope of the advertisement depends on the application but it is recommended that it SHOULD be domain-wide. To support the approach of encoding SFP information in the form of an MPLS label stack as described in , SFFs SHOULD allocate a locally significant MPLS label to each SF they are offering. Therefore, SFFs need to advertise the corresponding service function label to each SF they are offering by using a sub-TLV of the above Service Function sub-TLV, called SF Label sub-TLV.

Service Function Sub-TLV

• Type: TBD1.

• Length: variable.

• Service Function Identifier: A unique identifier that represents an SF within an SFC-enabled domain.

• Sub-TLVs: contains zero or more sub-TLVs corresponding to the particular attributes of a given SF. The SF Label sub-TLV as defined in Section 3.2 is one such sub-TLV. Other sub-TLVs are to be defined in the future.

SF Label Sub-TLV

• Type: TBD2.

• Length: 3.

• Value: The rightmost 20 bits represent an MPLS label which is the SF Label of the corresponding SF.

IANA Considerations This document includes a request to IANA for allocating type codes for the Service Function sub-TLV and the SF Label sub-TLV.

Security Considerations This document does not introduce any new security risk.

Acknowledgements TBD.

Contributors Nan Wu
Huawei
eric.wu@huawei.com

References Normative References This document defines a new optional Intermediate System to Intermediate System (IS-IS) TLV named CAPABILITY, formed of multiple sub-TLVs, which allows a router to announce its capabilities within an IS-IS level or the entire routing domain. This document obsoletes RFC 4971. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References This document describes an architecture for the specification, creation, and ongoing maintenance of Service Function Chains (SFCs) in a network. It includes architectural concepts, principles, and components used in the construction of composite services through deployment of SFCs, with a focus on those to be standardized in the IETF. This document does not propose solutions, protocols, or extensions to existing protocols. Cisco Systems, Inc. China Mobile Cisco Systems, Inc. Bell Canada Huawei Orange Mellanox AT&T Nokia Universita di Roma "Tor Vergata" This document defines data plane functionality required to implement service segments and achieve service programming in SR-enabled MPLS and IPv6 networks, as described in the Segment Routing architecture. MPLS Segment Routing (SR-MPLS) is a method of source routing a packet through an MPLS data plane by imposing a stack of MPLS labels on the packet to specify the path together with any packet-specific instructions to be executed on it. SR-MPLS can be leveraged to realize a source-routing mechanism across MPLS, IPv4, and IPv6 data planes by using an MPLS label stack as a source-routing instruction set while making no changes to SR-MPLS specifications and interworking with SR-MPLS implementations. This document describes how SR-MPLS-capable routers and IP-only routers can seamlessly coexist and interoperate through the use of SR-MPLS label stacks and IP encapsulation/tunneling such as MPLS-over-UDP as defined in RFC 7510.