Network Service Header TLVs
draft-ietf-sfc-nsh-tlv-02

Abstract

This draft describes Network Service Header (NSH) MD-Type 2 metadata TLVs that can be used within a service function path.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on September 5, 2020.

Copyright Notice

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Table of Contents

• 1. Introduction
• 2. Conventions used in this document
• 2.1. Terminology
• 2.2. Requirements Language
• 3. NSH Type 2 Format
• 4. NSH Type 2 TLVs
• 4.1. Forwarding Context
• 4.2. Tenant Identifier
• 4.3. Content Type
• 4.4. Ingress Network Information
• 4.5. Flow ID
• 4.6. Source and/or Destination Groups
• 4.7. Universal Resource Identifier
• 4.8. Policy Identifier (POLICY_ID)
• 5. Security Considerations
• 6. Acknowledgments
• 7. IANA Considerations
• 8. References
• 8.1. Normative References
• 8.2. Informative References
• Authors' Addresses

1. Introduction

Network Service Header (NSH) [RFC8300] is the Service Function Chaining (SFC) encapsulation protocol used to create Service Function Chains. As such, NSH provides two key elements:

1. Service Function Path identification
2. Metadata

[RFC8300] further defines two metadata formats (MD Types): 1 and 2. MD Type 1 defines fixed length, 16 bytes-long metadata, whereas MD Type 2 defines a variable-length TLV format for metadata. This draft defines some common TLVs for use with NSH MD Type 2.

This draft does not address metadata usage, updating/chaining of metadata or other SFP functions. Those topics are described in [RFC8300].

2. Conventions used in this document

2.1. Terminology

NSH: Network Service Header

MD Type: Metadata Format

CT: Context Type

TT: Tenant Type

URI: Universal Resource Identifier

SFC: Service Function Chaining

2.2. Requirements Language

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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. NSH Type 2 Format

    
    0                   1                   2                   3
    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    | Next Protocol |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: NSH Base Header

A NSH is composed of a 4-byte Base Header, a 4-byte Service Path Header and Context Headers. The Base Header identifies the MD-Type in use: [RFC8300] for a detailed header description.

    
     0                   1                   2                   3
     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
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Metadata Class       |      Type     |U|    Length   |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                   Variable-Length Metadata                    |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: NSH TLV Format

When the base header specifies MD Type = 0x2, zero or more Variable Length Context Headers MAY be added, immediately following the Service Path Header. Therefore, Length = 0x2 indicates that only the Base Header followed by the Service Path Header is present. The number, indicated in the Length field, of optional Variable Length Context Headers MUST be of an integer indicating length in 4-bytes words Figure 2 below depicts the format of the Context Header as defined in Section 2.5.1 of [RFC8300].

where

• Metadata Class (MD Class): Defines the scope of the Type field to provide a hierarchical namespace.
• Type - Indicates the explicit type of metadata being carried. The value is one from the Network Service Header (NSH) TLV Type registry (Section 7).
• Unassigned bit: One unassigned bit is available for future use. This bit MUST NOT be set, and it MUST be ignored on receipt.
• Length: Indicates the length of the variable-length metadata, in bytes. In case the metadata length is not an integer number of 4-byte words, the sender MUST add pad bytes immediately following the last metadata byte to extend the metadata to an integer number of 4-byte words. The receiver MUST round the Length field up to the nearest 4-byte-word boundary, to locate and process the next field in the packet. The receiver MUST access only those bytes in the metadata indicated by the Length field (i.e., actual number of bytes) and MUST ignore the remaining bytes up to the nearest 4-byte-word boundary. The length may be 0 or greater.
• A value of 0 denotes a Context Header without a Variable-Length Metadata field.

4. NSH Type 2 TLVs

In [RFC8300] defined that Metadata Class 0x0000 as IETF Base NSH MD Class. In this draft, metadata types are defined for the IETF Base NSH MD Class.

4.1. Forwarding Context

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x01  |U|  Length = 8 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |   CT  |             Reserved                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                      Tenant ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Forwarding Context

This TLV carries a network-centric forwarding context, used for segregation and forwarding scope. Forwarding context can take several forms depending on the network environment. Commonly used data includes VXLAN/VXLAN- GPE VNID, VRF identification or VLAN.

where:

• Context Type (CT) is four bits-long field that defines the length and the interpretation of the Tenant ID field. This document defines these CT values:
  • 0x0 - 24 bits-long VXLAN/LISP virtual network identifier (VNI)
  • 0x1 - 32 bits-long MPLS VPN label
  • 0x2 - VLAN

4.2. Tenant Identifier

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x02  |U|  Length=12  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  TT   |             Reserved                                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Tenant ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         Tenant ID                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 4: Tenant Identifier List

Tenant identification is often used for segregation within a multi-tenant environment. Orchestration system-generated tenant IDs are an example of such data.

where:

• Tenant Type (TT) is four bits-long field that specifies the length of the Tenant ID field. This document defines the following values for TT:
  • 0x0 - 32 bits-long Tenant ID
  • 0x1 - 64 bits-long Tenant ID

4.3. Content Type

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x03  |U|  Length = 4 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Content Type                              |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 5: Content Type

Provides explicit information about the content being carried, for example, type of video or content value for billing purposes.

4.4. Ingress Network Information

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x04  |U|  Length = 8 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Node ID                                |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Source Interface/Port                     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 6: Ingress Network Information

This data identifies the ingress network node, and, if required, ingress interface.

4.5. Flow ID

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x05  |U|  Length = 4 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     Flow ID                                   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 7: Flow ID

Flow ID provides a representation of the flow. Akin, but not identical to the usage described in [RFC6437].

4.6. Source and/or Destination Groups

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x06  |U|  Length=12  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  GT   |                Reserved                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Source Group                           |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                        Dest Group                             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 8: End Point Group

Intent-based systems can use this data to express the logical grouping of source and/or destination objects. [GROUPBASEDPOLICY] and [GROUPPOLICY] provide examples of such a system.

where:

• Group Type (GT) is four bits-long field that specifies the the interpretation of Source Group and/or Destination Group fields. This document defines the following values for GT:
  • 0x1 - Group Based Policy (GBP) end point group (EPG)

4.7. Universal Resource Identifier

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x07  |U|  Length=var |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  UT   |                URI                                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                        URI                                    ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 9: Universal Resource Identifier

where

• URI (Universal Resource Identifier) Type is four bits-long field that specifies the format of the URI field. This document defines the following values for the URI Type field:
  • 0x1: URI in standard string format as defined in [RFC3986].
  • 0x2: URI represented in a compacted hash format.

4.8. Policy Identifier (POLICY_ID)

    
    0                   1                   2                   3
    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Metadata Class = 0x0000    |  Type = 0x08  |U|  Length=var |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                     POLICY_ID                                 |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                     POLICY_ID                                  ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 10: POLICY_ID

The policy is often referred by a system-generated identifier which is then used by the devices to lookup the content of the policy locally. For example, this identifier could be an index to an array, a lookup key, a database Id. The identifier allows enforcement agents or services to lookup up the content of their part of the policy quite efficiently.

5. Security Considerations

[RFC8300] describes the requisite security considerations for protecting NSH metadata.

6. Acknowledgments

The authors would like to thank Paul Quinn for contributing to the draft and thank Behcet Sarikaya, Dirk von Hugo and Mohamed Boucadair for their work regarding usage of subscriber and host information TLVs.

7. IANA Considerations

IANA is requested to create a new "Network Service Header (NSH) TLV Type" registry according to Table 1.

This document defines the following new values (Table 2) in the Network Service Header (NSH) TLV Type registry:

8. References

8.1. Normative References

8.2. Informative References

Authors' Addresses