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Versions: (draft-quinn-sfc-nsh) 00 01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 RFC 8300

Network Working Group                                      P. Quinn, Ed.
Internet-Draft                                       Cisco Systems, Inc.
Intended status: Standards Track                           U. Elzur, Ed.
Expires: January 24, 2016                                          Intel
                                                           July 23, 2015


                         Network Service Header
                       draft-ietf-sfc-nsh-01.txt

Abstract

   This draft describes a Network Service Header (NSH) inserted onto
   encapsulated packets or frames to realize service function paths.
   NSH also provides a mechanism for metadata exchange along the
   instantiated service path.  NSH is the SFC encapsulation as per SFC
   Architecture [SFC-arch]


































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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 [RFC2119].

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
   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 January 24, 2016.

Copyright Notice

   Copyright (c) 2015 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.














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Table of Contents

   1.  Requirements Language  . . . . . . . . . . . . . . . . . . . .  2
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     2.1.  Definition of Terms  . . . . . . . . . . . . . . . . . . .  4
     2.2.  Problem Space  . . . . . . . . . . . . . . . . . . . . . .  7
     2.3.  NSH-based Service Chaining . . . . . . . . . . . . . . . .  8
   3.  Network Service Header . . . . . . . . . . . . . . . . . . . . 10
     3.1.  Network Service Header Format  . . . . . . . . . . . . . . 10
     3.2.  NSH Base Header  . . . . . . . . . . . . . . . . . . . . . 10
     3.3.  Service Path Header  . . . . . . . . . . . . . . . . . . . 12
     3.4.  NSH MD-type 1  . . . . . . . . . . . . . . . . . . . . . . 13
     3.5.  NSH MD-type 2  . . . . . . . . . . . . . . . . . . . . . . 13
       3.5.1.  Optional Variable Length Metadata  . . . . . . . . . . 14
   4.  NSH Actions  . . . . . . . . . . . . . . . . . . . . . . . . . 16
   5.  NSH Encapsulation  . . . . . . . . . . . . . . . . . . . . . . 18
   6.  Fragmentation Considerations . . . . . . . . . . . . . . . . . 19
   7.  Service Path Forwarding with NSH . . . . . . . . . . . . . . . 20
     7.1.  SFFs and Overlay Selection . . . . . . . . . . . . . . . . 20
     7.2.  Mapping NSH to Network Overlay . . . . . . . . . . . . . . 22
     7.3.  Service Plane Visibility . . . . . . . . . . . . . . . . . 23
     7.4.  Service Graphs . . . . . . . . . . . . . . . . . . . . . . 23
   8.  Policy Enforcement with NSH  . . . . . . . . . . . . . . . . . 26
     8.1.  NSH Metadata and Policy Enforcement  . . . . . . . . . . . 26
     8.2.  Updating/Augmenting Metadata . . . . . . . . . . . . . . . 27
     8.3.  Service Path ID and Metadata . . . . . . . . . . . . . . . 29
   9.  NSH Encapsulation Examples . . . . . . . . . . . . . . . . . . 31
     9.1.  GRE + NSH  . . . . . . . . . . . . . . . . . . . . . . . . 31
     9.2.  VXLAN-gpe + NSH  . . . . . . . . . . . . . . . . . . . . . 31
     9.3.  Ethernet + NSH . . . . . . . . . . . . . . . . . . . . . . 32
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 33
   11. Open Items for WG Discussion . . . . . . . . . . . . . . . . . 34
   12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 35
   13. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 38
   14. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 39
     14.1. NSH EtherType  . . . . . . . . . . . . . . . . . . . . . . 39
     14.2. Network Service Header (NSH) Parameters  . . . . . . . . . 39
       14.2.1. NSH Base Header Reserved Bits  . . . . . . . . . . . . 39
       14.2.2. MD Type Registry . . . . . . . . . . . . . . . . . . . 39
       14.2.3. TLV Class Registry . . . . . . . . . . . . . . . . . . 40
       14.2.4. NSH Base Header Next Protocol  . . . . . . . . . . . . 40
   15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 41
     15.1. Normative References . . . . . . . . . . . . . . . . . . . 41
     15.2. Informative References . . . . . . . . . . . . . . . . . . 41
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43






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2.  Introduction

   Service functions are widely deployed and essential in many networks.
   These service functions provide a range of features such as security,
   WAN acceleration, and server load balancing.  Service functions may
   be instantiated at different points in the network infrastructure
   such as the wide area network, data center, campus, and so forth.

   The current service function deployment models are relatively static,
   and bound to topology for insertion and policy selection.
   Furthermore, they do not adapt well to elastic service environments
   enabled by virtualization.

   New data center network and cloud architectures require more flexible
   service function deployment models.  Additionally, the transition to
   virtual platforms requires an agile service insertion model that
   supports dynamic and elastic service delivery; the movement of
   service functions and application workloads in the network and the
   ability to easily bind service policy to granular information such as
   per-subscriber state and steer traffic to the requisite service
   function(s) are necessary.

   NSH defines a new dataplane protocol specifically for the creation of
   dynamic service chains and is composed of the following elements:

   1.  Service Function Path identification

   2.  Transport independent service function chain

   3.  Per-packet network and service metadata or optional variable TLV
       metadata.

   NSH is designed to be easy to implement across a range of devices,
   both physical and virtual, including hardware platforms.

   An NSH aware control plane is outside the scope of this document.

   The SFC Architecture document [SFC-arch] provides an overview of a
   service chaining architecture that clearly defines the roles of the
   various elements and the scope of a service function chaining
   encapsulation.  NSH is the SFC encapsulation defined in that draft.

2.1.  Definition of Terms








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   Classification:  Locally instantiated matching of traffic flows
      against policy for subsequent application of the required set of
      network service functions.  The policy may be customer/network/
      service specific.

   Service Function Forwarder (SFF):  A service function forwarder is
      responsible for forwarding traffic to one or more connected
      service functions according to information carried in the NSH, as
      well as handling traffic coming back from the SF.  Additionally, a
      service function forwarder is responsible for transporting traffic
      to another SFF (in the same or different type of overlay), and
      terminating the SFP.

   Service Function (SF):  A function that is responsible for specific
      treatment of received packets.  A Service Function can act at
      various layers of a protocol stack (e.g., at the network layer or
      other OSI layers).  As a logical component, a Service Function can
      be realized as a virtual element or be embedded in a physical
      network element.  One or more Service Functions can be embedded in
      the same network element.  Multiple occurrences of the Service
      Function can exist in the same administrative domain.

      One or more Service Functions can be involved in the delivery of
      added-value services.  A non-exhaustive list of abstract Service
      Functions includes: firewalls, WAN and application acceleration,
      Deep Packet Inspection (DPI), LI (Lawful Intercept), server load
      balancing, NAT44 [RFC3022], NAT64 [RFC6146], NPTv6 [RFC6296],
      HOST_ID injection, HTTP Header Enrichment functions, TCP
      optimizer.

      An SF may be NSH-aware, that is it receives and acts on
      information in the NSH.  The SF may also be NSH-unaware in which
      case data forwarded to the SF does not contain NSH.

   Service Function Chain (SFC):  A service function chain defines an
      ordered set of abstract service functions (SFs) and ordering
      constraints that must be applied to packets and/or frames and/or
      flows selected as a result of classification.  An example of an
      abstract service function is "a firewall".  The implied order may
      not be a linear progression as the architecture allows for SFCs
      that copy to more than one branch, and also allows for cases where
      there is flexibility in the order in which service functions need
      to be applied.  The term service chain is often used as shorthand
      for service function chain.







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   Service Function Path (SFP):  The Service Function Path is a
      constrained specification of where packets assigned to a certain
      service function path must go.  While it may be so constrained as
      to identify the exact locations, it can also be less specific.
      The SFP provides a level of indirection between the fully abstract
      notion of service chain as a sequence of abstract service
      functions to be delivered, and the fully specified notion of
      exactly which SFF/SFs the packet will visit when it actually
      traverses the network.  By allowing the control components to
      specify this level of indirection, the operator may control the
      degree of SFF/SF selection authority that is delegated to the
      network.

   Network Node/Element:  Device that forwards packets or frames based
      on outer header information.

   Network Overlay:  Logical network built on top of existing network
      (the underlay).  Packets are encapsulated or tunneled to create
      the overlay network topology.

   Network Service Header:  provides SFP identification, and is used by
      the NSH-aware functions, such as the Classifier, SFF and NSH-aware
      SFs.  In addition to SFP identification, the NSH may carry data
      plane metadata.

   Service Classifier:  Logical function that performs classification
      and imposes an NSH.  The initial classifier imposes the initial
      NSH and sends the NSH packet to the first SFF in the path.  Non-
      initial (i.e. subsequent) classification can occur as needed and
      can alter, or create a new service path.

   Network Locator:  dataplane address, typically IPv4 or IPv6, used to
      send and receive network traffic.

   NSH Proxy:  Removes and inserts NSH on behalf of an NSH-unaware
      service function.  The proxy node removes the NSH header and
      delivers the original packet/frame via a local attachment circuit
      to the service function.  Examples of a local attachment circuit
      include, but are not limited to: VLANs, IP in IP, GRE, VXLAN.
      When complete, the Service Function returns the packet to the NSH
      proxy via the same or different attachment circuit.  The NSH
      Proxy, in turn, re-imposes NSH on the returned packets.  Often, an
      SFF will act as an NSH-proxy when required.








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2.2.  Problem Space

   Network Service Header (NSH) addresses several limitations associated
   with service function deployments today (i.e. prior to use of NSH).
   A short reference is included below, RFC 7498 [RFC7498], provides a
   more comprehensive review of the SFC Problem Statement.

   1.  Topological Dependencies: Network service deployments are often
       coupled to network topology.  Such a dependency imposes
       constraints on the service delivery, potentially inhibiting the
       network operator from optimally utilizing service resources, and
       reduces the flexibility.  This limits scale, capacity, and
       redundancy across network resources.

   2.  Service Chain Construction: Service function chains today are
       most typically built through manual configuration processes.
       These are slow and error prone.  With the advent of newer dynamic
       service deployment models, the control/management planes provide
       not only connectivity state, but will also be increasingly
       utilized for the creation of network services.  Such a control/
       management planes could be centralized, or be distributed.

   3.  Application of Service Policy: Service functions rely on topology
       information such as VLANs or packet (re) classification to
       determine service policy selection, i.e. the service function
       specific action taken.  Topology information is increasingly less
       viable due to scaling, tenancy and complexity reasons.  The
       topological information is often stale, providing the operator
       with inaccurate service Function (SF) placement that can result
       in suboptimal resource utilization.  Furthermore topology-centric
       information often does not convey adequate information to the
       service functions, forcing functions to individually perform more
       granular classification.

   4.  Per-Service (re)Classification: Classification occurs at each
       service function independent from previously applied service
       functions.  More importantly, the classification functionality
       often differs per service function and service functions may not
       leverage the results from other service functions.

   5.  Common Header Format: Various proprietary methods are used to
       share metadata and create service paths.  A standardized protocol
       provides a common format for all network and service devices.

   6.  Limited End-to-End Service Visibility: Troubleshooting service
       related issues is a complex process that involve both network-
       specific and service-specific expertise.  This is especially the
       case, when service function chains span multiple DCs, or across



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       administrative boundaries.  Furthermore, physical and virtual
       environments (network and service) can be highly divergent in
       terms of topology and that topological variance adds to these
       challenges.

   7.  Transport Dependence: Service functions can and will be deployed
       in networks with a range of transports requiring service
       functions to support and participate in many transports (and
       associated control planes) or for a transport gateway function to
       be present.

2.3.  NSH-based Service Chaining

   The NSH creates a dedicated service plane, that addresses many of the
   limitations highlighted in Section 2.2.  More specifically, NSH
   enables:

   1.  Topological Independence: Service forwarding occurs within the
       service plane, via a network overlay, the underlying network
       topology does not require modification.  NSH provides an
       identifier used to select the network overlay for network
       forwarding.

   2.  Service Chaining: NSH contains path identification information
       needed to realize a service path.  Furthermore, NSH provides the
       ability to monitor and troubleshoot a service chain, end-to-end
       via service-specific OAM messages.  The NSH fields can be used by
       administrators (via, for example a traffic analyzer) to verify
       (account, ensure correct chaining, provide reports, etc.) the
       path specifics of packets being forwarded along a service path.

   3.  NSH provides a mechanism to carry shared metadata between network
       devices and service function, and between service functions.  The
       semantics of the shared metadata is communicated via a control
       plane to participating nodes.  Examples of metadata include
       classification information used for policy enforcement and
       network context for forwarding post service delivery.

   4.  Classification and re-classification: sharing the metadata allows
       service functions to share initial and intermediate
       classification results with downstream service functions saving
       re-classification, where enough information was enclosed.

   5.  NSH offers a common and standards based header for service
       chaining to all network and service nodes.

   6.  Transport Agnostic: NSH is transport independent and is carried
       in an overlay, over existing underlays.  If an existing overlay



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       topology provides the required service path connectivity, that
       existing overlay may be used.

















































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3.  Network Service Header

   A Network Service Header (NSH) contains service path information and
   optionally metadata that are added to a packet or frame and used to
   create a service plane.  The original packets preceded by NSH, are
   then encapsulated in an outer header for transport.

   NSH is added by a Service Classifier.  The NSH header is removed by
   the last SFF in the chain or by a SF that consumes the packet.

3.1.  Network Service Header Format

   A NSH is composed of a 4-byte Base Header, a 4-byte Service Path
   Header and Context Headers, as shown in Figure 1 below.


    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Base Header                                    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Service Path Header                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   ~                Context Headers                                ~
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 1: Network Service Header

   Base header: provides information about the service header and the
   payload protocol.

   Service Path Header: provide path identification and location within
   a path.

   Context headers: carry opaque metadata and variable length encoded
   information.

3.2.  NSH Base Header



      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 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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                         Figure 2: NSH Base Header

   Base Header Field Descriptions:

   Version: The version field is used to ensure backward compatibility
   going forward with future NSH updates.  It MUST be set to 0x0 by the
   sender, in this first revision of NSH.

   O bit: when set to 0x1 indicates that this packet is an operations
   and management (OAM) packet.  The receiving SFF and SFs nodes MUST
   examine the payload and take appropriate action (e.g. return status
   information).

   OAM message specifics and handling details are outside the scope of
   this document.

   C bit: Indicates that a critical metadata TLV is present (see Section
   3.4.2).  This bit acts as an indication for hardware implementers to
   decide how to handle the presence of a critical TLV without
   necessarily needing to parse all TLVs present.  The C bit MUST be set
   to 0x0 when MD Type= 0x01 and MAY be used with MD Type = 0x2 and MUST
   be set to 0x1 if one or more critical TLVs are present.

   All other flag fields are reserved.

   Length: total length, in 4-byte words, of NSH including the Base
   Header, the Service Path Header and the optional variable TLVs.  The
   Length MUST be of value 0x6 for MD Type = 0x1 and MUST be of value
   0x2 or higher for MD Type = 0x2.  The NSH header length MUST be an
   integer number of 4 bytes.

   MD Type: indicates the format of NSH beyond the mandatory Base Header
   and the Service Path Header.  MD Type defines the format of the
   metadata being carried.  A new registry will be requested from IANA
   for the MD Type.

   NSH defines two MD types:

   0x1 - which indicates that the format of the header includes fixed
   length context headers (see Figure 4 below).

   0x2 - which does not mandate any headers beyond the Base Header and
   Service Path Header, and may contain optional variable length context
   information.

   The format of the base header and the service path header is
   invariant, and not affected by MD Type.




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   NSH implementations MUST support MD-Type = 0x1, and SHOULD support
   MD- Type = 0x2.

   Next Protocol: indicates the protocol type of the original packet.  A
   new IANA registry will be created for protocol type.

   This draft defines the following Next Protocol values:

   0x1 : IPv4
   0x2 : IPv6
   0x3 : Ethernet
   0x253: Experimental

3.3.  Service Path Header



      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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |          Service Path ID                      | Service Index |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Service path ID (SPI): 24 bits
   Service index (SI): 8 bits

                     Figure 3: NSH Service Path Header

   Service Path Identifier (SPI): identifies a service path.
   Participating nodes MUST use this identifier for Service Function
   Path selection.

   Service Index (SI): provides location within the SFP.  The first
   Classifier (i.e. at the boundary of the NSH domain)in the NSH Service
   Function Path, SHOULD set the SI to 255, however the control plane
   MAY configure the initial value of SI as appropriate (i.e. taking
   into account the length of the service function path).  A Classifier
   MUST send the packet to the first SFF in the chain.  Service index
   MUST be decremented by service functions or proxy nodes after
   performing required services and the new decremented SI value MUST be
   reflected in the egress NSH packet.  SI MAY be used in conjunction
   with Service Path ID for Service Function Path selection.  Service
   Index (SI) is also valuable when troubleshooting/reporting service
   paths.  In addition to indicating the location within a Service
   Function Path, SI can be used for loop detection.






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3.4.  NSH MD-type 1

   When the Base Header specifies MD Type = 0x1, four Context Header,
   4-byte each, MUST be added immediately following the Service Path
   Header, as per Figure 4.  Context Headers that carry no metadata MUST
   be set to zero.


     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=0x1  | Next Protocol |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |          Service Path ID                      | Service Index |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Mandatory Context Header                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Mandatory Context Header                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Mandatory Context Header                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
    |                Mandatory Context Header                       |
    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                         Figure 4: NSH MD-type=0x1



   Draft-dc [dcalloc] and draft-mobility [moballoc] provide specific
   examples of how metadata can be allocated.

3.5.  NSH MD-type 2

   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 are present.  The
   optional Variable Length Context Headers MUST be of an integer number
   of 4-bytes.












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        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=0x2  | Next Protocol |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          Service Path ID                      | Service Index |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       ~              Variable Length Context Headers  (opt.)          ~
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+




                         Figure 5: NSH MD-type=0x2

3.5.1.  Optional Variable Length Metadata

   The format of the optional variable length context headers, is as
   described below.

        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |          TLV Class            |C|    Type     |R|R|R|   Len   |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                      Variable Metadata                        |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



                    Figure 6: Variable Context Headers

   TLV Class: describes the scope of the "Type" field.  In some cases,
   the TLV Class will identify a specific vendor, in others, the TLV
   Class will identify specific standards body allocated types.  A new
   IANA registry will be created for TLV Class type.

   Type: the specific type of information being carried, within the
   scope of a given TLV Class.  Value allocation is the responsibility
   of the TLV Class owner.

   Encoding the criticality of the TLV within the Type field is
   consistent with IPv6 option types: the most significant bit of the
   Type field indicates whether the TLV is mandatory for the receiver to
   understand/process.  This effectively allocates Type values 0 to 127
   for non-critical options and Type values 128 to 255 for critical
   options.  Figure 7 below illustrates the placement of the Critical



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   bit within the Type field.

     +-+-+-+-+-+-+-+-+
     |C|     Type    |
     +-+-+-+-+-+-+-+-+


        Figure 7: Critical Bit Placement Within the TLV Type Field


   If a receiver receives an encapsulated packet containing a TLV with
   the Critical bit set to 0x1 in the Type field and it does not
   understand how to process the Type, it MUST drop the packet.  Transit
   devices MUST NOT drop packets based on the setting of this bit.

   Reserved bits: three reserved bit are present for future use.  The
   reserved bits MUST be set to 0x0.

   Length: Length of the variable metadata, in 4-byte words.  A value of
   0x0 or higher can be used.  A value of 0x0 denotes a TLV header
   without a Variable Metadata field.






























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4.  NSH Actions

   NSH-aware nodes are the only nodes that MAY alter the content of the
   NSH headers.  NSH-aware nodes include: service classifiers, SFF, SF
   and NSH proxies.  These nodes have several possible header related
   actions:

   1.  Insert or remove NSH: These actions can occur at the start and
       end respectively of a service path.  Packets are classified, and
       if determined to require servicing, NSH will be imposed.  A
       service classifier MUST insert NSH at the start of an SFP.  An
       imposed NSH MUST contain valid Base Header and Service Path
       Header.  At the end of a service function path, a SFF, MUST be
       the last node operating on the service header and MUST remove it.

       Multiple logical classifiers may exist within a given service
       path.  Non-initial classifiers may re-classify data and that re-
       classification MAY result in a new Service Function Path.  When
       the logical classifier performs re-classification that results in
       a change of service path, it MUST remove the existing NSH and
       MUST impose a new NSH with the Base Header and Service Path
       Header reflecting the new service path information and set the SI
       to 255.  Metadata MAY be preserved in the new NSH.


   2.  Select service path: The Service Path Header provides service
       chain information and is used by SFFs to determine correct
       service path selection.  SFFs MUST use the Service Path Header
       for selecting the next SF or SFF in the service path.

   3.  Update a Service Path Header: NSH aware service functions (SF)
       MUST decrement the service index.  A service index = 0x0
       indicates that a packet MUST be dropped by the SFF.

       Classifier(s) MAY update Context Headers if new/updated context
       is available.

       If an NSH proxy (see Section 7) is in use (acting on behalf of a
       non-NSH-aware service function for NSH actions), then the proxy
       MUST update Service Index and MAY update contexts.  When an NSH
       proxy receives an NSH-encapsulated packet, it MUST remove the NSH
       headers before forwarding it to an NSH unaware SF.  When the NSH
       Proxy receives a packet back from an NSH unaware SF, it MUST re-
       encapsulate it with the correct NSH, and MUST also decrement the
       Service Index.






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   4.  Service policy selection: Service Function instances derive
       policy (i.e. service actions such as permit or deny) selection
       and enforcement from the service header.  Metadata shared in the
       service header can provide a range of service-relevant
       information such as traffic classification.  Service functions
       SHOULD use NSH to select local service policy.

   Figure 8 maps each of the four actions above to the components in the
   SFC architecture that can perform it.

 +---------------+------------------+-------+----------------+---------+
 |                |  Insert         |Select |   Update       |Service  |
 |                |  or remove NSH  |Service|    NSH         |policy   |
 |                |                 |Function|               |selection|
 | Component      +--------+--------+Path   +----------------+         |
 |                |        |        |       | Dec.   |Update |         |
 |                | Insert | Remove |       |Service |Context|         |
 |                |        |        |       | Index  |Header |         |
 +----------------+--------+--------+-------+--------+-------+---------+
 |                |   +    |   +    |       |        |   +   |         |
 |Classifier      |        |        |       |        |       |         |
 +--------------- +--------+--------+-------+--------+-------+---------+
 |Service Function|        |   +    |  +    |        |       |         |
 |Forwarder(SFF)  |        |        |       |        |       |         |
 +--------------- +--------+--------+-------+--------+-------+---------+
 |Service         |        |        |       |   +    |       |   +     |
 |Function  (SF)  |        |        |       |        |       |         |
 +--------------- +--------+--------+-------+--------+-------+---------+
 |NSH Proxy       |   +    |   +    |       |   +    |       |         |
 +----------------+--------+--------+-------+--------+-------+---------+



                   Figure 8: NSH Action and Role Mapping

















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5.  NSH Encapsulation

   Once NSH is added to a packet, an outer encapsulation is used to
   forward the original packet and the associated metadata to the start
   of a service chain.  The encapsulation serves two purposes:

   1.  Creates a topologically independent services plane.  Packets are
       forwarded to the required services without changing the
       underlying network topology

   2.  Transit network nodes simply forward the encapsulated packets as
       is.

   The service header is independent of the encapsulation used and is
   encapsulated in existing transports.  The presence of NSH is
   indicated via protocol type or other indicator in the outer
   encapsulation.

   See Section 9 for NSH encapsulation examples.
































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6.  Fragmentation Considerations

   Work in progress: discussion of jumbo frames and PMTUD implications.
















































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7.  Service Path Forwarding with NSH

7.1.  SFFs and Overlay Selection

   As described above, NSH contains a Service Path Identifier (SPI) and
   a Service Index (SI).  The SPI is, as per its name, an identifier.
   The SPI alone cannot be used to forward packets along a service path.
   Rather the SPI provide a level of indirection between the service
   path/topology and the network transport.  Furthermore, there is no
   requirement, or expectation of an SPI being bound to a pre-determined
   or static network path.

   The Service Index provides an indication of location within a service
   path.  The combination of SPI and SI provides the identification of a
   logical SF and its order within the service plane, and is used to
   select the appropriate network locator(s) for overlay forwarding.
   The logical SF may be a single SF, or a set of SFs that are
   equivalent.  In the latter case, the SFF provides load distribution
   amongst the collection of SFs as needed.  SI may also serve as a
   mechanism for loop detection within a service path since each SF in
   the path decrements the index; an Service Index of 0 indicates that a
   loop occurred and packet must be discarded.

   This indirection -- path ID to overlay -- creates a true service
   plane.  That is the SFF/SF topology is constructed without impacting
   the network topology but more importantly service plane only
   participants (i.e. most SFs) need not be part of the network overlay
   topology and its associated infrastructure (e.g. control plane,
   routing tables, etc.).  As mentioned above, an existing overlay
   topology may be used provided it offers the requisite connectivity.

   The mapping of SPI to transport occurs on an SFF (as discussed above,
   the first SFF in the path gets a NSH encapsulated packet from the
   Classifier).  The SFF consults the SPI/ID values to determine the
   appropriate overlay transport protocol (several may be used within a
   given network) and next hop for the requisite SF.  Figure 9 below
   depicts a simple, single next-hop SPI/SI to network overlay network
   locator mapping.













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   +-------------------------------------------------------+
   |  SPI |  SI |  NH                 |   Transport        |
   +-------------------------------------------------------+
   |  10  | 255 |  1.1.1.1            |   VXLAN-gpe        |
   |  10  | 254 |  2.2.2.2            |   nvGRE            |
   |  10  | 251 |  10.1.2.3           |   GRE              |
   |  40  | 251 |  10.1.2.3           |   GRE              |
   |  50  | 200 |  01:23:45:67:89:ab  |   Ethernet         |
   |  15  | 212 |  Null (end of path) |   None             |
   +-------------------------------------------------------+


                     Figure 9: SFF NSH Mapping Example

   Additionally, further indirection is possible: the resolution of the
   required SF network locator may be a localized resolution on an SFF,
   rather than a service function chain control plane responsibility, as
   per figures 10 and 11 below.


    +-------------------+
    | SPI |  SI |  NH   |
    +-------------------+
    | 10  |  3  |  SF2  |
    | 245 |  12 |  SF34 |
    | 40  |  9  |  SF9  |
    +-------------------+



                   Figure 10: NSH to SF Mapping Example



    +-----------------------------------+
    |  SF  |  NH          |  Transport  |
    +-----------------------------------|
    |  SF2 |  10.1.1.1    |  VXLAN-gpe  |
    |  SF34|  192.168.1.1 |  UDP        |
    |  SF9 |  1.1.1.1     |  GRE        |
    +-----------------------------------+



                   Figure 11: SF Locator Mapping Example

   Since the SPI is a representation of the service path, the lookup may
   return more than one possible next-hop within a service path for a



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   given SF, essentially a series of weighted (equally or otherwise)
   overlay links to be used (for load distribution, redundancy or
   policy), see Figure 12.  The metric depicted in Figure 12 is an
   example to help illustrated weighing SFs.  In a real network, the
   metric will range from a simple preference (similar to routing next-
   hop), to a true dynamic composite metric based on some service
   function-centric state (including load, sessions state, capacity,
   etc.)


    +----------------------------------+
    | SPI | SI |   NH        |  Metric |
    +----------------------------------+
    | 10  |  3 | 10.1.1.1    |  1      |
    |     |    | 10.1.1.2    |  1      |
    |     |    |             |         |
    | 20  | 12 | 192.168.1.1 |  1      |
    |     |    | 10.2.2.2    |  1      |
    |     |    |             |         |
    | 30  |  7 | 10.2.2.3    |  10     |
    |     |    | 10.3.3.3    |  5      |
    +----------------------------------+
     (encap type omitted for formatting)



                   Figure 12: NSH Weighted Service Path

7.2.  Mapping NSH to Network Overlay

   As described above, the mapping of SPI to network topology may result
   in a single overlay path, or it might result in a more complex
   topology.  Furthermore, the SPIx to overlay mapping occurs at each
   SFF independently.  Any combination of topology selection is
   possible.  Please note, there is no requirement to create a new
   overlay topology if a suitable one already existing.  NSH packets can
   use any (new or existing) overlay provided the requisite connectivity
   requirements are satisfied.

   Examples of mapping for a topology:

   1.  Next SF is located at SFFb with locator 10.1.1.1
       SFFa mapping: SPI=10 --> VXLAN-gpe, dst-ip: 10.1.1.1

   2.  Next SF is located at SFFc with multiple network locators for
       load distribution purposes:
       SFFb mapping: SPI=10 --> VXLAN-gpe, dst_ip:10.2.2.1, 10.2.2.2,
       10.2.2.3, equal cost



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   3.  Next SF is located at SFFd with two paths to SFFc, one for
       redundancy:
       SFFc mapping: SPI=10 --> VXLAN-gpe, dst_ip:10.1.1.1 cost=10,
       10.1.1.2, cost=20

   In the above example, each SFF makes an independent decision about
   the network overlay path and policy for that path.  In other words,
   there is no a priori mandate about how to forward packets in the
   network (only the order of services that must be traversed).

   The network operator retains the ability to engineer the overlay
   paths as required.  For example, the overlay path between service
   functions forwarders may utilize traffic engineering, QoS marking, or
   ECMP, without requiring complex configuration and network protocol
   support to be extended to the service path explicitly.  In other
   words, the network operates as expected, and evolves as required, as
   does the service function plane.

7.3.  Service Plane Visibility

   The SPI and SI serve an important function for visibility into the
   service topology.  An operator can determine what service path a
   packet is "on", and its location within that path simply by viewing
   the NSH information (packet capture, IPFIX, etc.).  The information
   can be used for service scheduling and placement decisions,
   troubleshooting and compliance verification.

7.4.  Service Graphs

   In some cases, a service path is exactly that -- a linear list of
   service functions that must be traversed.  However, the "path" is
   actually a directed graph.  Furthermore, within a given service
   topology several directed graphs may exist with packets moving
   between graphs based on non-initial classification (in Figure 13, co-
   located with the SFs).
















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                     ,---.          ,---.            ,---.
                   /     \        /     \          /     \
                  (  SF2  +------+  SF7  +--------+  SF3  )
            ,------\     /        \     /       /-+      /
           ;        |---'          `---'\      /    `-+-'
           |        :                    \    /
           |         \                /---:---
         ,-+-.        `.     ,---.   /     :
        /     \         '---+     \/        \
       (  SF1  )           (  SF6  )        \
        \     /             \     +--.       :
         `---'               `---'    `-.  ,-+-.
                                         `+     \
                                         (  SF4  )
                                          \     /
                                           `---'



                     Figure 13: Service Graph Example

   The SPI/SI combination provides a simple representation of a directed
   graph, the SPI represents a graph ID; and the SI a node ID.  The
   service topology formed by SPI/SI support cycles, weighting, and
   alternate topology selection, all within the service plane.  The
   realization of the network topology occurs as described above: SPI/ID
   mapping to an appropriate transport and associated next network hops.

   NSH-aware services receive the entire header, including the SPI/SI.
   An non-initial logical classifier (in many deployment, this
   classifier will be co-resident with a SF) can now, based on local
   policy, alter the SPI, which in turn effects both the service graph,
   and in turn the selection of overlay at the SFF.  The figure below
   depicts the policy associated with the graph in Figure 13 above.
   Note: this illustrates multiple graphs and their representation; it
   does not depict the use of metadata within a single service function
   graph.














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   SF1:
       SPI: 10
           NH: SF2
   SF2:
       Class: Bad
               SPI: 20
               NH: SF6
        Class: Good
               SPI: 30
               NH: SF7
   SF6:
        Class: Employee
               SPI: 21
               NH: SF4
        Class: Guest
               SPI: 22
               NH: SF3
   SF7:
        Class: Employee
               SPI: 31
               NH: SF4
        Class: Guest
                  SPI: 32
              NH: SF3

                    Figure 14: Service Graphs Using SPI

   This example above does not show the mapping of the service topology
   to the network overlay topology.  As discussed in the sections above,
   the overlay selection occurs as per network policy.





















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8.  Policy Enforcement with NSH

8.1.  NSH Metadata and Policy Enforcement

   As described in Section 3, NSH provides the ability to carry metadata
   along a service path.  This metadata may be derived from several
   sources, common examples include:

      Network nodes/devices: Information provided by network nodes can
      indicate network-centric information (such as VRF or tenant) that
      may be used by service functions, or conveyed to another network
      node post service path egress.

      External (to the network) systems: External systems, such as
      orchestration systems, often contain information that is valuable
      for service function policy decisions.  In most cases, this
      information cannot be deduced by network nodes.  For example, a
      cloud orchestration platform placing workloads "knows" what
      application is being instantiated and can communicate this
      information to all NSH nodes via metadata carried in the context
      header(s).

      Service Functions: A classifier co-resident with Service Functions
      often perform very detailed and valuable classification.  In some
      cases they may terminate, and be able to inspect encrypted
      traffic.

   Regardless of the source, metadata reflects the "result" of
   classification.  The granularity of classification may vary.  For
   example, a network switch, acting as a classifier, might only be able
   to classify based on a 5-tuple, whereas, a service function may be
   able to inspect application information.  Regardless of granularity,
   the classification information can be represented in NSH.

   Once the data is added to NSH, it is carried along the service path,
   NSH-aware SFs receive the metadata, and can use that metadata for
   local decisions and policy enforcement.  The following two examples
   highlight the relationship between metadata and policy:













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    +-------+        +-------+        +-------+
    |  SFF  )------->(  SFF  |------->|  SFF  |
    +---^---+        +---|---+        +---|---+
      ,-|-.            ,-|-.            ,-|-.
     /     \          /     \          /     \
    ( Class )           SF1  )        (  SF2  )
     \ ify /          \     /          \     /
      `---'            `---'            `---'
     5-tuple:        Permit             Inspect
     Tenant A        Tenant A           AppY
     AppY


                      Figure 15: Metadata and Policy



       +-----+           +-----+            +-----+
       | SFF |---------> | SFF |----------> | SFF |
       +--+--+           +--+--+            +--+--+
          ^                 |                  |
        ,-+-.             ,-+-.              ,-+-.
       /     \           /     \            /     \
      ( Class )         (  SF1  )          (  SF2  )
       \ ify /           \     /            \     /
        `-+-'             `---'              `---'
          |              Permit            Deny AppZ
      +---+---+          employees
      |       |
      +-------+
      external
      system:
      Employee
      AppZ


                  Figure 16: External Metadata and Policy

   In both of the examples above, the service functions perform policy
   decisions based on the result of the initial classification: the SFs
   did not need to perform re-classification, rather they rely on a
   antecedent classification for local policy enforcement.

8.2.  Updating/Augmenting Metadata

   Post-initial metadata imposition (typically performed during initial
   service path determination), metadata may be augmented or updated:




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   1.  Metadata Augmentation: Information may be added to NSH's existing
       metadata, as depicted in Figure 17.  For example, if the initial
       classification returns the tenant information, a secondary
       classification (perhaps co-resident with DPI or SLB) may augment
       the tenant classification with application information, and
       impose that new information in the NSH metadata.  The tenant
       classification is still valid and present, but additional
       information has been added to it.

   2.  Metadata Update: Subsequent classifiers may update the initial
       classification if it is determined to be incorrect or not
       descriptive enough.  For example, the initial classifier adds
       metadata that describes the traffic as "internet" but a security
       service function determines that the traffic is really "attack".
       Figure 18 illustrates an example of updating metadata.




        +-----+           +-----+            +-----+
        | SFF |---------> | SFF |----------> | SFF |
        +--+--+           +--+--+            +--+--+
          ^                 |                  |
         ,---.             ,---.              ,---.
        /     \           /     \            /     \
       ( Class )         (  SF1  )          (  SF2  )
        \     /           \     /            \     /
         `-+-'             `---'              `---'
          |              Inspect           Deny
       +---+---+          employees         employee+
       |       |          Class=AppZ        appZ
       +-------+
       external
       system:
       Employee


                     Figure 17: Metadata Augmentation













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       +-----+           +-----+            +-----+
       | SFF |---------> | SFF |----------> | SFF |
       +--+--+           +--+--+            +--+--+
          ^                 |                  |
        ,---.             ,---.              ,---.
       /     \           /     \            /     \
      ( Class )         (  SF1  )          (  SF2  )
       \     /           \     /            \     /
        `---'             `---'              `---'
     5-tuple:            Inspect             Deny
     Tenant A            Tenant A            attack
                          --> attack


                        Figure 18: Metadata Update

8.3.  Service Path ID and Metadata

   Metadata information may influence the service path selection since
   the Service Path Identifier can represent the result of
   classification.  A given SPI can represent all or some of the
   metadata, and be updated based on metadata classification results.
   This relationship provides the ability to create a dynamic services
   plane based on complex classification without requiring each node to
   be capable of such classification, or requiring a coupling to the
   network topology.  This yields service graph functionality as
   described in Section 7.4.  Figure 19 illustrates an example of this
   behavior.























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       +-----+           +-----+            +-----+
       | SFF |---------> | SFF |------+---> | SFF |
       +--+--+           +--+--+      |     +--+--+
          |                 |         |        |
        ,---.             ,---.       |      ,---.
       /     \           /     \      |     /     \
      (  SCL  )         (  SF1  )     |    (  SF2  )
       \     /           \     /      |     \     /
        `---'             `---'    +-----+   `---'
     5-tuple:            Inspect   | SFF |    Original
     Tenant A            Tenant A  +--+--+    next SF
                          --> DoS     |
                                      V
                                    ,-+-.
                                   /     \
                                  (  SF10 )
                                   \     /
                                    `---'
                                     DoS
                                  "Scrubber"



                      Figure 19: Path ID and Metadata

   Specific algorithms for mapping metadata to an SPI are outside the
   scope of this draft.
























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9.  NSH Encapsulation Examples

9.1.  GRE + NSH


    IPv4 Packet:
   +----------+--------------------+--------------------+
   |L2 header | L3 header, proto=47|GRE header,PT=0x894F|
   +----------+--------------------+--------------------+
   --------------+----------------+
   NSH, NP=0x1   |original packet |
   --------------+----------------+



    L2 Frame:
    +----------+--------------------+--------------------+
    |L2 header | L3 header, proto=47|GRE header,PT=0x894F|
    +----------+--------------------+--------------------+
    ---------------+---------------+
    NSH, NP=0x3    |original frame |
    ---------------+---------------+


                           Figure 20: GRE + NSH

9.2.  VXLAN-gpe + NSH

    IPv4 Packet:
    +----------+------------------------+---------------------+
    |L2 header | IP + UDP dst port=4790 |VXLAN-gpe NP=0x4(NSH)|
    +----------+------------------------+---------------------+
    --------------+----------------+
    NSH, NP=0x1   |original packet |
    --------------+----------------+


    L2 Frame:
    +----------+------------------------+---------------------+
    |L2 header | IP + UDP dst port=4790 |VXLAN-gpe NP=0x4(NSH)|
    +----------+------------------------+---------------------+
    ---------------+---------------+
    NSH,NP=0x3     |original frame |
    ---------------+---------------+


                        Figure 21: VXLAN-gpe + NSH




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9.3.  Ethernet + NSH


  IPv4 Packet:
  +-------------------------------+---------------+--------------------+
  |Outer Ethernet, ET=0x894F      | NSH, NP = 0x1 | original IP Packet |
  +-------------------------------+---------------+--------------------+


  L2 Frame:
  +-------------------------------+---------------+----------------+
  |Outer Ethernet, ET=0x894F      | NSH, NP = 0x3 | original frame |
  +-------------------------------+---------------+----------------+



                         Figure 22: Ethernet + NSH


































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10.  Security Considerations

   As with many other protocols, NSH data can be spoofed or otherwise
   modified.  In many deployments, NSH will be used in a controlled
   environment, with trusted devices (e.g. a data center) thus
   mitigating the risk of unauthorized header manipulation.

   NSH is always encapsulated in a transport protocol and therefore,
   when required, existing security protocols that provide authenticity
   (e.g.  RFC 2119 [RFC6071]) can be used.

   Similarly if confidentiality is required, existing encryption
   protocols can be used in conjunction with encapsulated NSH.






































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11.  Open Items for WG Discussion

   1.  MD type 1 metadata semantics specifics

   2.  Bypass bit in NSH.

   3.  Rendered Service Path ID (RSPID).












































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12.  Contributors

   This WG document originated as draft-quinn-sfc-nsh and had the
   following co-authors and contributors.  The editors of this document
   would like to thank and recognize them and their contributions.
   These co-authors and contributors provided invaluable concepts and
   content for this document's creation.

   Surendra Kumar
   Cisco Systems
   smkumar@cisco.com

   Michael Smith
   Cisco Systems
   michsmit@cisco.com

   Jim Guichard
   Cisco Systems
   jguichar@cisco.com

   Rex Fernando
   Cisco Systems
   Email: rex@cisco.com

   Navindra Yadav
   Cisco Systems
   Email: nyadav@cisco.com

   Wim Henderickx
   Alcatel-Lucent
   wim.henderickx@alcatel-lucent.com

   Andrew Dolganow
   Alcaltel-Lucent
   Email: andrew.dolganow@alcatel-lucent.com

   Praveen Muley
   Alcaltel-Lucent
   Email: praveen.muley@alcatel-lucent.com

   Tom Nadeau
   Brocade
   tnadeau@lucidvision.com

   Puneet Agarwal
   puneet@acm.org

   Rajeev Manur



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   Broadcom
   rmanur@broadcom.com

   Abhishek Chauhan
   Citrix
   Abhishek.Chauhan@citrix.com

   Joel Halpern
   Ericsson
   joel.halpern@ericsson.com

   Sumandra Majee
   F5
   S.Majee@f5.com

   David Melman
   Marvell
   davidme@marvell.com

   Pankaj Garg
   Microsoft
   Garg.Pankaj@microsoft.com

   Brad McConnell
   Rackspace
   bmcconne@rackspace.com

   Chris Wright
   Red Hat Inc.
   chrisw@redhat.com

   Kevin Glavin
   Riverbed
   kevin.glavin@riverbed.com

   Hong (Cathy) Zhang
   Huawei US R&D
   cathy.h.zhang@huawei.com

   Louis Fourie
   Huawei US R&D
   louis.fourie@huawei.com

   Ron Parker
   Affirmed Networks
   ron_parker@affirmednetworks.com

   Myo Zarny



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   Goldman Sachs
   myo.zarny@gs.com

















































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13.  Acknowledgments

   The authors would like to thank Nagaraj Bagepalli, Abhijit Patra,
   Peter Bosch, Darrel Lewis, Pritesh Kothari, Tal Mizrahi and Ken Gray
   for their detailed review, comments and contributions.

   A special thank you goes to David Ward and Tom Edsall for their
   guidance and feedback.

   Additionally the authors would like to thank Carlos Pignataro and
   Larry Kreeger for their invaluable ideas and contributions which are
   reflected throughout this draft.

   Lastly, Reinaldo Penno deserves a particular thank you for his
   architecture and implementation work that helped guide the protocol
   concepts and design.



































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14.  IANA Considerations

14.1.  NSH EtherType

   An IEEE EtherType, 0x894F, has been allocated for NSH.

14.2.  Network Service Header (NSH) Parameters

   IANA is requested to create a new "Network Service Header (NSH)
   Parameters" registry.  The following sub-sections request new
   registries within the "Network Service Header (NSH) Parameters "
   registry.

14.2.1.  NSH Base Header Reserved Bits

   There are ten bits at the beginning of the NSH Base Header.  New bits
   are assigned via Standards Action [RFC5226].

   Bits 0-1 - Version
   Bit 2 - OAM (O bit)
   Bits 2-9 - Reserved

14.2.2.  MD Type Registry

   IANA is requested to set up a registry of "MD Types".  These are
   8-bit values.  MD Type values 0, 1, 2, 254, and 255 are specified in
   this document.  Registry entries are assigned by using the "IETF
   Review" policy defined in RFC 5226 [RFC5226].

                +---------+--------------+---------------+
                | MD Type | Description  | Reference     |
                +---------+--------------+---------------+
                | 0       | Reserved     | This document |
                |         |              |               |
                | 1       | NSH          | This document |
                |         |              |               |
                | 2       | NSH          | This document |
                |         |              |               |
                | 3..253  | Unassigned   |               |
                |         |              |               |
                | 254     | Experiment 1 | This document |
                |         |              |               |
                | 255     | Experiment 2 | This document |
                +---------+--------------+---------------+

                                  Table 1





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14.2.3.  TLV Class Registry

   IANA is requested to set up a registry of "TLV Types".  These are 16-
   bit values.  Registry entries are assigned by using the "IETF Review"
   policy defined in RFC 5226 [RFC5226].

14.2.4.  NSH Base Header Next Protocol

   IANA is requested to set up a registry of "Next Protocol".  These are
   8-bit values.  Next Protocol values 0, 1, 2 and 3 are defined in this
   draft.  New values are assigned via Standards Action [RFC5226].

              +---------------+-------------+---------------+
              | Next Protocol | Description | Reference     |
              +---------------+-------------+---------------+
              | 0             | Reserved    | This document |
              |               |             |               |
              | 1             | IPv4        | This document |
              |               |             |               |
              | 2             | IPv6        | This document |
              |               |             |               |
              | 3             | Ethernet    | This document |
              |               |             |               |
              | 4..253        | Unassigned  |               |
              +---------------+-------------+---------------+

                                  Table 2
























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15.  References

15.1.  Normative References

   [RFC0791]  Postel, J., "Internet Protocol", STD 5, RFC 791,
              DOI 10.17487/RFC0791, September 1981,
              <http://www.rfc-editor.org/info/rfc791>.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

15.2.  Informative References

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              DOI 10.17487/RFC2784, March 2000,
              <http://www.rfc-editor.org/info/rfc2784>.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              DOI 10.17487/RFC5226, May 2008,
              <http://www.rfc-editor.org/info/rfc5226>.

   [RFC6071]  Frankel, S. and S. Krishnan, "IP Security (IPsec) and
              Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
              DOI 10.17487/RFC6071, February 2011,
              <http://www.rfc-editor.org/info/rfc6071>.

   [RFC7498]  Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
              Service Function Chaining", RFC 7498, DOI 10.17487/
              RFC7498, April 2015,
              <http://www.rfc-editor.org/info/rfc7498>.

   [SFC-arch]
              Quinn, P., Ed. and J. Halpern, Ed., "Service Function
              Chaining (SFC) Architecture", 2014,
              <http://datatracker.ietf.org/doc/draft-quinn-sfc-arch>.

   [VXLAN-gpe]
              Quinn, P., Manur, R., Agarwal, P., Kreeger, L., Lewis, D.,
              Maino, F., Smith, M., Yong, L., Xu, X., Elzur, U., Garg,
              P., and D. Melman, "Generic Protocol Extension for VXLAN",
              <https://datatracker.ietf.org/doc/
              draft-ietf-nvo3-vxlan-gpe/>.

   [dcalloc]  Guichard, J., Smith, M., and S. Kumar, "Network Service



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              Header (NSH) Context Header Allocation (Data Center)",
              2014, <https://datatracker.ietf.org/doc/
              draft-guichard-sfc-nsh-dc-allocation/>.

   [moballoc]
              Napper, J. and S. Kumar, "NSH Context Header Allocation --
              Mobility", 2014, <https://datatracker.ietf.org/doc/
              draft-napper-sfc-nsh-mobility-allocation/>.











































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Authors' Addresses

   Paul Quinn (editor)
   Cisco Systems, Inc.

   Email: paulq@cisco.com


   Uri Elzur (editor)
   Intel

   Email: uri.elzur@intel.com







































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