Service Function Chaining E. Wang
Internet-Draft K. Leung
Intended status: Informational A. Ossipov
Expires: December 30, 2017 Cisco Systems Inc.
June 28, 2017

Network Service Header (NSH) Context Header Allocation (Network Security)


This document provides a recommended default allocation of the mandatory fixed context headers for a Network Service Header (NSH) relevant to Service Function Chaining (SFC) for network security Service Functions. NSH is defined in [I-D.ietf-sfc-nsh]. This allocation is intended to support the use cased described in [].

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Table of Contents

1. Introduction

Service Function Chaining (SFC) provides a mechanism for network traffic to go through a set of Service Functions in sequence. Network Service Header (NSH) allows metadata to be shared between Service Functions along with the packets. Such metadata is carried by either a fixed number of 32-bit context headers (MD-Type 1) or a variable number of TLVs (MD-Type 2), as defined in NSH. This document provides a recommended default allocation of the fixed size context headers for network security Service Functions forming a Service Function Chain. The allocation may also form a MD-Type 2 metadata TLV. Supporting use cases for a metadata definition in this context are described in SFC-NS-Use-Cases . This document does not define any other variable TLVs. It does not address the control plane mechanisms.

1.1. Requirements Language

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.

2. Definition Of Terms

This document uses the terms as defined in RFC 7498, [RFC7665] and [I-D.ietf-sfc-nsh].

3. Network Service Header (NSH) Context Headers

NSH MD-Type 1 is composed of three parts as described in [I-D.ietf-sfc-nsh]: a 4-byte base header, a 4-byte service path header, and four 4-byte mandatory context headers.

 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 = 1  | Next Protocol |
|          Service Path ID                      | Service Index |
|                Mandatory Context Header                       |
|                Mandatory Context Header                       |
|                Mandatory Context Header                       |
|                Mandatory Context Header                       |

Figure 1: Network Service Header - MD-Type 1

4. Recommended Security Mandatory Context Allocation

The following context header allocation provides information used to support SFC operation within a generic network security environment. The 16-byte context headers are used to deliver metadata and classification results between security Service Functions. Service Functions may use the metadata for local policy enforcement, security actions, classification refinement, and other functionality.

  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
 |                          Session ID                           |
 |D|P|                 Application Session ID                    |
 | Destination Class / Reserved  |        Source Class           |
 |B|U|T|D| Rsvd  |       Tenant ID       | Dst Score | Src Score |

Figure 2: NSH Security Context Allocation

4.1. Network Security Allocation Specifics

The specific 16-byte allocation of the mandatory context headers is as follows:

5. Context Allocation and Control Plane Considerations

This document describes an allocation scheme for the NSH context headers in the context of network security SFC use cases.

The suggested allocation in this document would be considered as a guideline only. Some of the allocated fields are specific to certain use cases. A control plane mechanism is required to ensure consistency among the SFC components participating in the allocation scheme. The actual control plane mechanism is out of the scope of this document.

6. Security Considerations

The SFC control plane responsible for identifying and distributing the allocation scheme should ensure the communication mechanism is secure.

The metadata defined in this document carries important information for participating Service Functions to make security policy decisions. Some of the metadata such as the security score may be accumulated before a Service Function takes an action. There is a risk that the metadata may be intercepted or even spoofed by an unauthorized party. Proper precaution must be taken to ensure the confidentiality and integrity of the metadata fields.

7. Acknowledgments

Authors would like to thank Jeremy Felix and Jay Iyer for their contributions.

8. IANA Considerations

This document includes no request to IANA.

9. References

9.1. Normative References

[I-D.ietf-sfc-nsh] Quinn, P. and U. Elzur, "Network Service Header", Internet-Draft draft-ietf-sfc-nsh-12, February 2017.
[I-D.kumar-sfc-offloads] Surendra, S., Guichard, J., Quinn, P., Halpern, J. and S. Majee, "Service Function Simple Offloads", Internet-Draft draft-kumar-sfc-offloads-03, October 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997.
[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.

9.2. Informative References

[] Wang, E., Leung, K., Felix, J. and J. Iyer, "Service Function Chaining Use Cases for Network Security", Internet-Draft draft-wang-sfc-ns-use-cases-02, October 2016.

Authors' Addresses

Eric Wang Cisco Systems Inc. 170 W Tasman Dr San Jose, CA 95134 U.S.A. EMail:
Kent Leung Cisco Systems Inc. 170 W Tasman Dr San Jose, CA 95134 U.S.A. EMail:
Andrew Ossipov Cisco Systems Inc. 170 W Tasman Dr San Jose, CA 95134 U.S.A. EMail: