SFC Working Group G. Van de Velde, Ed. Internet-Draft M. Vigoureux Intended status: Standards Track P. Mulay Expires: April 20, 2017 Nokia October 17, 2016 Network Services Header Context Allocation Identifier draft-vandevelde-sfc-nsh-length-overload-00 Abstract The specification of the NSH MD Type 1 header [draft-ietf-sfc-nsh] mandates four Context Headers, 4-byte each, and they MUST be added immediately following the Service Path Header. As direct consequence, an NSH MD Type 1 header is always Length 0x6 (six 4-byte words). As a result, the Length field of the NSH MD Type 1 header provides an information which is known by simply looking at the "MD Type" field. However, while [draft-ietf-sfc-nsh] does not specify the encoding of these Context Headers, other specifications have started to do so. A need to distinguish types of Context Headers therefore arises. This draft proposes to overload the Length field of an NSH MD Type 1 as Meta-Data context allocation identifier and to create a IANA repository for NSH MD Type 1 allocation schemes. The NSH MD Type 1 Length field overload intends to allow universal understanding at any network location and by any network device of the context allocation structure. 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 [1]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any Van de Velde, et al. Expires April 20, 2017 [Page 1] Internet-Draft NSH MD Type-1 Context Allocation Identifier October 2016 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on April 20, 2017. Copyright Notice Copyright (c) 2016 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 6.1. Normative References . . . . . . . . . . . . . . . . . . 4 6.2. Informative References . . . . . . . . . . . . . . . . . 4 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction The specification of the NSH MD Type 1 header [draft-ietf-sfc-nsh] mandates four Context Headers, 4-byte each, and they MUST be added immediately following the Service Path Header. As direct consequence, an NSH MD Type 1 header is always Length 0x6 (six 4-byte words). As a result, the Length field of the NSH MD Type 1 header provides an information which is known by simply looking at the "MD Type" field. However, while [draft-ietf-sfc-nsh] does not specify the encoding of these Context Headers, other specifications have started to do so. A need to distinguish types of Context Headers therefore arises. This draft proposes to overload the Length field of an NSH MD Type 1 as Meta-Data context allocation identifier and to create a IANA repository for NSH MD Type 1 allocation schemes. The NSH MD Type 1 Van de Velde, et al. Expires April 20, 2017 [Page 2] Internet-Draft NSH MD Type-1 Context Allocation Identifier October 2016 Length field overload intends to allow universal understanding at any network location and by any network device of the context allocation structure. The capability of overloading the NSH MD Type 1 Length field as context allocation identifier is particular useful in networks environments where multiple different NSH MD Type 1 allocation schemes exist simultaneously. For example in Datacenters where data- flows are serviced and allocations are based upon either [draft- guichard-sfc-nsh-dc-allocation] or [draft-napper-sfc-nsh-broadband- allocation]. Without Length field overload, it is for a servicing node non-trivial to know how the NSH Meta Data is structured and how the Meta Data should be consumed without provisioning of additional context information to understand the NSH embedded Meta-Data. In addition, this document serves as anchor-point to request an IANA repository for NSH MD Type 1 allocation schemes. 2. Operation The Length field in the NSH Base header intends to provide the length of the NSH header including the Base header itself in 4-byte words. According [draft-ietf-sfc-nsh] the NSH MD Type 1 the value within the Length field MUST always be 0x6. This note proposes a different usage for the length field taking backward compatibility into account. This draft proposes to use the Length field of a fixed length NSH MD Type 1 header as indication of the Meta Data allocation scheme. The allocation scheme context overloading of the length field does not modify the fixed length of the NSH MD Type 1 fields and expected Meta Data fields is fixed at four words of 4-byte data. The different from 0x6 value represents the Meta Data allocation scheme used for the NSH MD Type 1 header. To avoid compatibility issues with older NSH MD Type implementations the Length value of 0x6 is reserved and allows existing NSH MD Type 1 usage to carry opaque Meta Data. The following MD allocation types have been defined: 0x0: draft-guichard-sfc-nsh-dc-allocation 0x1: draft-napper-sfc-nsh-broadband-allocation 0x6: draft-ietf-sfc-nsh Van de Velde, et al. Expires April 20, 2017 [Page 3] Internet-Draft NSH MD Type-1 Context Allocation Identifier October 2016 3. Security Considerations tbc 4. Acknowledgements tbc 5. IANA Considerations This document requests IANA to setup a central repository to keep track of the different NSH MD Type 1 allocation schemes 6. References 6.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . 6.2. Informative References [2] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, . Authors' Addresses Gunter Van de Velde (editor) Nokia Antwerp Belgium Email: gunter.van_de_velde@nokia.com Martin Vigoureux Nokia Route de Villejust Nozay 91620 France Email: martin.vigoureux@nokia.com Van de Velde, et al. Expires April 20, 2017 [Page 4] Internet-Draft NSH MD Type-1 Context Allocation Identifier October 2016 Praveen Mulay Nokia Mountain View USA Email: praveen.muley@nokia.com Van de Velde, et al. Expires April 20, 2017 [Page 5]