| Service Function Chaining | J. Napper |
| Internet-Draft | S. Kumar |
| Intended status: Informational | Cisco Systems, Inc. |
| Expires: May 7, 2016 | P. Muley |
| W. Hendericks | |
| Alcatel-Lucent | |
| November 4, 2015 |
NSH Context Header Allocation -- Mobility
draft-napper-sfc-nsh-mobility-allocation-02
This document provides a recommended allocation of the mandatory fixed context headers for a Network Service Header (NSH) within the mobility service provider network context. NSH is described in detail in [ietf-sfc-nsh]. This allocation is intended to support uses cases as defined in [ietf-sfc-use-case-mobility].
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 [RFC2119].
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This Internet-Draft will expire on May 7, 2016.
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Service function chaining provides a mechanism for network traffic to be forced through multiple service functions in a sequence. Metadata can be useful to service functions. Network Service Headers (NSH) provides support for carrying shared metadata between service functions (and devices) using 4 fixed-length 32-bit context headers as defined in [ietf-sfc-nsh]. NSH is then encapsulated within an outer header for transport.
This document provides a recommended default allocation scheme for the fixed-length context headers in the context of service chaining within fixed and mobile broadband service provider networks. Supporting use cases describing the need for a metadata header in these contexts are described in [ietf-sfc-use-case-mobility]. This draft does not address control plane mechanisms.
This document uses the terms as defined in [RFC7498] and [RFC7665].
In Service Function Chaining, the Network Service Header is composed of a 4-byte base header (BH1), a 4-byte service path header (SH1) and four mandatory 4-byte context headers (CH1-CH4) as described in [ietf-sfc-nsh].
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|C|R|R|R|R|R|R| Length | MD Type = 0x01| Next Protocol | BH1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path ID | Service Index | SH1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header 1 | CH1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header 2 | CH2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header 3 | CH3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header 4 | CH4 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Network Service Header - MD Type 0x01
The following context header allocation provides information to support service function chaining in a mobile service provider network as described in [ietf-sfc-use-case-mobility].
The set of context headers can be delivered to service functions that can use the metadata within to enforce policy, communicate between service functions, provide subscriber information and other functionality. Several of the context headers are typed allowing for different metadata to be provided to different service functions or even to the same service function but on different packets within a flow. Which metadata are sent to which service functions is decided in the SFC control plane and is thus out of the scope of this document.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | R | Sub | Tag | Context ID | CH1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sub/Endpoint ID ~ CH2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Sub/Endpoint ID (cont.) | CH3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ServiceTag | CH4 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: NSH Mobility Context Allocation
Figure 2 provides a high-level description of the fields in the recommended allocation of the fixed context headers for a mobility context.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | CAN | QoS |U| Con | App Id | Rsvd | CH4 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Service Tag RAN Allocation
The intended use for each of the context header allocations is as follows:
This document describes an allocation scheme for the mandatory context headers in the context of mobile service providers. This suggested allocation of context headers should be considered as a guideline and may vary depending on the use case. The control plane aspects of specifying and distributing the allocation scheme among different service functions within the Service Function Chaining environment to guarantee consistent semantics for the metadata is beyond the scope of this document.
The context header allocation recommended by this document includes numbers that must be distributed consistently across a Service Function Chaining environment. Protocols for distributing these numbers securely are required in the control plane, but are out of scope of this document.
Furthermore, some of the metadata carried in the context headers require secure methods to prevent spoofing or modification by service function elements that may themselves be exposed to subscriber traffic and thus might be compromised. This document does not address such security concerns.
This document has no actions for IANA.
The authors would like to thank Jim Guichard for his assistance structuring the document.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997. |
| [ietf-sfc-nsh] | Quinn, P. and U. Elzur, Network Service Header", I-D draft-ietf-sfc-nsh-01 (work in progress), July 2015. |
| [ietf-sfc-use-case-mobility] | Haeffner, W., Napper, J., Stiemerling, M., Lopez, D. and J. Uttaro, "Service Function Chaining Use Cases in Mobile Networks", I-D draft-ietf-sfc-use-case-mobility-05 (work in progress), January 2015. |
| [itu-e-164] | The international public telecommunication numbering plan", ITU-T E.164, November 2010. | , "
| [RFC7498] | Quinn, P. and T. Nadeau, "Problem Statement for Service Function Chaining", RFC 7498, DOI 10.17487/RFC7498, April 2015. |
| [RFC7665] | Halpern, J. and C. Pignataro, Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015. |
| [TS.29.230] | Diameter applications; 3GPP specific codes and identifiers", 3GPP TS 29.230 13.2.0, September 2015. | , "