draft-ietf-sfc-nsh-13.txt   draft-ietf-sfc-nsh-14.txt 
Service Function Chaining P. Quinn, Ed. Service Function Chaining P. Quinn, Ed.
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco
Intended status: Standards Track U. Elzur, Ed. Intended status: Standards Track U. Elzur, Ed.
Expires: January 1, 2018 Intel Expires: January 17, 2018 Intel
June 30, 2017 C. Pignataro, Ed.
Cisco
July 16, 2017
Network Service Header Network Service Header (NSH)
draft-ietf-sfc-nsh-13.txt draft-ietf-sfc-nsh-14
Abstract Abstract
This document describes a Network Service Header (NSH) inserted onto This document describes a Network Service Header (NSH) inserted onto
packets or frames to realize service function paths. NSH also packets or frames to realize service function paths. NSH also
provides a mechanism for metadata exchange along the instantiated provides a mechanism for metadata exchange along the instantiated
service path. NSH is the SFC encapsulation required to support the service paths. NSH is the SFC encapsulation required to support the
Service Function Chaining (SFC) Architecture (defined in RFC7665). Service Function Chaining (SFC) architecture (defined in RFC7665).
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 Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 1, 2018. This Internet-Draft will expire on January 17, 2018.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 4 1.2. Definition of Terms . . . . . . . . . . . . . . . . . . . 4
2.2. Problem Space . . . . . . . . . . . . . . . . . . . . . . 5 1.3. Problem Space . . . . . . . . . . . . . . . . . . . . . . 4
2.3. NSH-based Service Chaining . . . . . . . . . . . . . . . . 5 1.4. NSH-based Service Chaining . . . . . . . . . . . . . . . 5
3. Network Service Header . . . . . . . . . . . . . . . . . . . . 7 2. Network Service Header . . . . . . . . . . . . . . . . . . . 5
3.1. Network Service Header Format . . . . . . . . . . . . . . 7 2.1. Network Service Header Format . . . . . . . . . . . . . . 6
3.2. NSH Base Header . . . . . . . . . . . . . . . . . . . . . 7 2.2. NSH Base Header . . . . . . . . . . . . . . . . . . . . . 6
3.3. Service Path Header . . . . . . . . . . . . . . . . . . . 10 2.3. Service Path Header . . . . . . . . . . . . . . . . . . . 9
3.4. NSH MD Type 1 . . . . . . . . . . . . . . . . . . . . . . 10 2.4. NSH MD Type 1 . . . . . . . . . . . . . . . . . . . . . . 10
3.5. NSH MD Type 2 . . . . . . . . . . . . . . . . . . . . . . 11 2.5. NSH MD Type 2 . . . . . . . . . . . . . . . . . . . . . . 11
3.5.1. Optional Variable Length Metadata . . . . . . . . . . 12 2.5.1. Optional Variable Length Metadata . . . . . . . . . . 11
4. NSH Actions . . . . . . . . . . . . . . . . . . . . . . . . . 14 3. NSH Actions . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. NSH Encapsulation . . . . . . . . . . . . . . . . . . . . . . 16 4. NSH Transport Encapsulation . . . . . . . . . . . . . . . . . 14
6. Fragmentation Considerations . . . . . . . . . . . . . . . . . 17 5. Fragmentation Considerations . . . . . . . . . . . . . . . . 15
7. Service Path Forwarding with NSH . . . . . . . . . . . . . . . 18 6. Service Path Forwarding with NSH . . . . . . . . . . . . . . 15
7.1. SFFs and Overlay Selection . . . . . . . . . . . . . . . . 18 6.1. SFFs and Overlay Selection . . . . . . . . . . . . . . . 15
7.2. Mapping NSH to Network Transport . . . . . . . . . . . . . 20 6.2. Mapping NSH to Network Transport . . . . . . . . . . . . 18
7.3. Service Plane Visibility . . . . . . . . . . . . . . . . . 21 6.3. Service Plane Visibility . . . . . . . . . . . . . . . . 19
7.4. Service Graphs . . . . . . . . . . . . . . . . . . . . . . 21 6.4. Service Graphs . . . . . . . . . . . . . . . . . . . . . 19
8. Policy Enforcement with NSH . . . . . . . . . . . . . . . . . 22 7. Policy Enforcement with NSH . . . . . . . . . . . . . . . . . 19
8.1. NSH Metadata and Policy Enforcement . . . . . . . . . . . 22 7.1. NSH Metadata and Policy Enforcement . . . . . . . . . . . 19
8.2. Updating/Augmenting Metadata . . . . . . . . . . . . . . . 24 7.2. Updating/Augmenting Metadata . . . . . . . . . . . . . . 21
8.3. Service Path Identifier and Metadata . . . . . . . . . . . 25 7.3. Service Path Identifier and Metadata . . . . . . . . . . 23
9. Security Considerations . . . . . . . . . . . . . . . . . . . 27 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 27
12.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . . 32 11.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . 27
12.2. Network Service Header (NSH) Parameters . . . . . . . . . 32 11.2. Network Service Header (NSH) Parameters . . . . . . . . 27
12.2.1. NSH Base Header Reserved Bits . . . . . . . . . . . . 32 11.2.1. NSH Base Header Reserved Bits . . . . . . . . . . . 27
12.2.2. NSH Version . . . . . . . . . . . . . . . . . . . . . 32 11.2.2. NSH Version . . . . . . . . . . . . . . . . . . . . 27
12.2.3. MD Type Registry . . . . . . . . . . . . . . . . . . . 32 11.2.3. MD Type Registry . . . . . . . . . . . . . . . . . . 28
12.2.4. MD Class Registry . . . . . . . . . . . . . . . . . . 33 11.2.4. MD Class Registry . . . . . . . . . . . . . . . . . 28
12.2.5. NSH Base Header Next Protocol . . . . . . . . . . . . 33 11.2.5. NSH Base Header Next Protocol . . . . . . . . . . . 29
12.2.6. New IETF assigned MD Type Registry . . . . . . . . . . 34 11.2.6. New IETF assigned MD Type Registry . . . . . . . . . 29
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
13.1. Normative References . . . . . . . . . . . . . . . . . . . 35 12.1. Normative References . . . . . . . . . . . . . . . . . . 30
13.2. Informative References . . . . . . . . . . . . . . . . . . 35 12.2. Informative References . . . . . . . . . . . . . . . . . 30
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
2. Introduction 1. Introduction
Service functions are widely deployed and essential in many networks. Service functions are widely deployed and essential in many networks.
These service functions provide a range of features such as security, These service functions provide a range of features such as security,
WAN acceleration, and server load balancing. Service functions may WAN acceleration, and server load balancing. Service functions may
be instantiated at different points in the network infrastructure be instantiated at different points in the network infrastructure
such as the wide area network, data center, campus, and so forth. such as the wide area network, data center, campus, and so forth.
Prior to development of the SFC architecture [RFC7665] and the Prior to development of the SFC architecture [RFC7665] and the
protocol specified in this document, current service function protocol specified in this document, current service function
deployment models have been relatively static, and bound to topology deployment models have been relatively static, and bound to topology
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New data center network and cloud architectures require more flexible New data center network and cloud architectures require more flexible
service function deployment models. Additionally, the transition to service function deployment models. Additionally, the transition to
virtual platforms requires an agile service insertion model that virtual platforms requires an agile service insertion model that
supports dynamic and elastic service delivery; the movement of supports dynamic and elastic service delivery; the movement of
service functions and application workloads in the network and the service functions and application workloads in the network and the
ability to easily bind service policy to granular information such as ability to easily bind service policy to granular information such as
per-subscriber state and steer traffic to the requisite service per-subscriber state and steer traffic to the requisite service
function(s) are necessary. function(s) are necessary.
NSH defines a new service plane protocol specifically for the Network Service Header (NSH) defines a new service plane protocol
creation of dynamic service chains and is composed of the following specifically for the creation of dynamic service chains and is
elements: composed of the following elements:
1. Service Function Path identification 1. Service Function Path identification.
2. Indication of location within a Service Function Path. 2. Indication of location within a Service Function Path.
3. Optional, per packet metadata (fixed length or variable). 3. Optional, per packet metadata (fixed length or variable).
NSH is designed to be easy to implement across a range of devices, NSH is designed to be easy to implement across a range of devices,
both physical and virtual, including hardware platforms. both physical and virtual, including hardware platforms.
An NSH-aware control plane is outside the scope of this document. An NSH-aware control plane is outside the scope of this document.
[RFC7665] provides an overview of a service chaining architecture [RFC7665] provides an overview of a service chaining architecture
that clearly defines the roles of the various elements and the scope that clearly defines the roles of the various elements and the scope
of a service function chaining encapsulation. NSH is the SFC of a service function chaining encapsulation. NSH is the SFC
encapsulation referenced in RFC7665. encapsulation referenced in [RFC7665].
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 [RFC2119].
1.2. Definition of Terms
Byte: All references to "bytes" in this document refer to 8-bit
bytes, or octets.
2.1. Definition of Terms
Classification: Defined in [RFC7665]. Classification: Defined in [RFC7665].
Classifier: Defined in [RFC7665]. Classifier: Defined in [RFC7665].
Metadata: Defined in [RFC7665]. Metadata: Defined in [RFC7665].
Network Locator: dataplane address, typically IPv4 or IPv6, used to Network Locator: dataplane address, typically IPv4 or IPv6, used to
send and receive network traffic. send and receive network traffic.
Network Node/Element: Device that forwards packets or frames based Network Node/Element: Device that forwards packets or frames based
on outer header (i.e. transport) information. on an outer header (i.e., transport) information.
Network Overlay: Logical network built on top of existing network Network Overlay: Logical network built on top of existing network
(the underlay). Packets are encapsulated or tunneled to create (the underlay). Packets are encapsulated or tunneled to create
the overlay network topology. the overlay network topology.
Service Classifier: Logical entity providing classification Service Classifier: Logical entity providing classification
function. Since they are logical, classifiers may be co-resident function. Since they are logical, classifiers may be co-resident
with SFC elements such as SFs or SFFs. Service classifiers with SFC elements such as SFs or SFFs. Service classifiers
perform classification and impose NSH. The initial classifier perform classification and impose NSH. The initial classifier
imposes the initial NSH and sends the NSH packet to the first SFF imposes the initial NSH and sends the NSH packet to the first SFF
in the path. Non-initial (i.e. subsequent) classification can in the path. Non-initial (i.e. subsequent) classification can
occur as needed and can alter, or create a new service path. occur as needed and can alter, or create a new service path.
Service Function (SF): Defined in [RFC7665]. Service Function (SF): Defined in [RFC7665].
Service Function Chain (SFC): Defined in [RFC7665]. Service Function Chain (SFC): Defined in [RFC7665].
Service Function Forwarder (SFF): Defined in [RFC7665]. Service Function Forwarder (SFF): Defined in [RFC7665].
Service Function Path (SFP): Defined in [RFC7665]. Service Function Path (SFP): Defined in [RFC7665].
SFC Proxy: Defined in [RFC7665]. SFC Proxy: Defined in [RFC7665].
2.2. Problem Space 1.3. Problem Space
Network Service Header (NSH) addresses several limitations associated NSH addresses several limitations associated with service function
with service function deployments. [RFC7498] provides a deployments. [RFC7498] provides a comprehensive review of those
comprehensive review of those issues. issues.
2.3. NSH-based Service Chaining 1.4. NSH-based Service Chaining
NSH creates a dedicated service plane, more specifically, NSH NSH creates a dedicated service plane, more specifically, NSH
enables: enables:
1. Topological Independence: Service forwarding occurs within the 1. Topological Independence: Service forwarding occurs within the
service plane, the underlying network topology does not require service plane, the underlying network topology does not require
modification. NSH provides an identifier used to select the modification. NSH provides an identifier used to select the
network overlay for network forwarding. network overlay for network forwarding.
2. Service Chaining: NSH enables service chaining per [RFC7665]. 2. Service Chaining: NSH enables service chaining per [RFC7665].
skipping to change at page 6, line 19 skipping to change at page 5, line 28
and troubleshoot a service chain, end-to-end via service-specific and troubleshoot a service chain, end-to-end via service-specific
OAM messages. NSH fields can be used by administrators (via, for OAM messages. NSH fields can be used by administrators (via, for
example, a traffic analyzer) to verify (account, ensure correct example, a traffic analyzer) to verify (account, ensure correct
chaining, provide reports, etc.) the path specifics of packets chaining, provide reports, etc.) the path specifics of packets
being forwarded along a service path. being forwarded along a service path.
3. NSH provides a mechanism to carry shared metadata between 3. NSH provides a mechanism to carry shared metadata between
participating entities and service functions. The semantics of participating entities and service functions. The semantics of
the shared metadata is communicated via a control plane, which is the shared metadata is communicated via a control plane, which is
outside the scope of this document, to participating nodes. outside the scope of this document, to participating nodes.
[SFC-CP] provides an example of such in section 3.3. Examples of [I-D.ietf-sfc-control-plane] provides an example of such in
metadata include classification information used for policy Section 3.3. Examples of metadata include classification
enforcement and network context for forwarding post service information used for policy enforcement and network context for
delivery. Sharing the metadata allows service functions to share forwarding post service delivery. Sharing the metadata allows
initial and intermediate classification results with downstream service functions to share initial and intermediate
service functions saving re-classification, where enough classification results with downstream service functions saving
information was enclosed. re-classification, where enough information was enclosed.
4. NSH offers a common and standards-based header for service 4. NSH offers a common and standards-based header for service
chaining to all network and service nodes. chaining to all network and service nodes.
5. Transport Agnostic: NSH is transport independent. An appropriate 5. Transport Agnostic: NSH is transport-independent. An appropriate
(for a given deployment) network transport protocol can be used (for a given deployment) network transport protocol can be used
to transport NSH-encapsulated traffic. This transport may form to transport NSH-encapsulated traffic. This transport may form
an overlay network and if an existing overlay topology provides an overlay network and if an existing overlay topology provides
the required service path connectivity, that existing overlay may the required service path connectivity, that existing overlay may
be used. be used.
3. Network Service Header 2. Network Service Header
A Network Service Header (NSH) contains service path information and NSH contains service path information and optionally metadata that
optionally metadata that are added to a packet or frame and used to are added to a packet or frame and used to create a service plane.
create a service plane. An outer transport header is imposed, on NSH An outer transport header is imposed, on NSH and the original packet/
and the original packet/frame, for network forwarding. frame, for network forwarding.
A Service Classifier adds NSH. NSH is removed by the last SFF in the A Service Classifier adds NSH. NSH is removed by the last SFF in the
service chain or by a SF that consumes the packet. service chain or by an SF that consumes the packet.
3.1. Network Service Header Format 2.1. Network Service Header Format
NSH is composed of a 4-byte (all references to bytes in this document NSH is composed of a 4-byte Base Header, a 4-byte Service Path Header
refer to 8-bit bytes, or octets) Base Header, a 4-byte Service Path and optional Context Headers, as shown in Figure 1 below.
Header and optional 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 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
| Base Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Base Header |
| Service Path Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path Header |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Context Header(s) ~ | |
| | ~ Context Header(s) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Network Service Header Figure 1: Network Service Header
Base header: provides information about the service header and the Base header: provides information about the service header and the
payload protocol. payload protocol.
Service Path Header: provide path identification and location within Service Path Header: provides path identification and location within
a service path. a service path.
Context header: carry metadata (i.e. context data) along a service Context header: carries metadata (i.e., context data) along a service
path. path.
3.2. NSH Base Header 2.2. NSH Base Header
Figure 2 depicts the NSH base header:
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|R| TTL | Length |R|R|R|R|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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|R| TTL | Length |R|R|R|R|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: NSH Base Header Figure 2: NSH Base Header
Base Header Field Descriptions: Base Header Field Descriptions:
Version: The version field is used to ensure backward compatibility Version: The version field is used to ensure backward compatibility
going forward with future NSH updates. It MUST be set to 0x0 by the going forward with future NSH specification updates. It MUST be set
sender, in this first revision of NSH. Given the widespread to 0x0 by the sender, in this first revision of NSH. Given the
implementation of existing hardware that uses the first nibble after widespread implementation of existing hardware that uses the first
an MPLS label stack for ECMP decision processing, this document nibble after an MPLS label stack for ECMP decision processing, this
reserves version 01 and this value MUST NOT be used in future document reserves version 01 and this value MUST NOT be used in
versions of the protocol. Please see [RFC7325] for further future versions of the protocol. Please see [RFC7325] for further
discussion of MPLS-related forwarding requirements. discussion of MPLS-related forwarding requirements.
O bit: Setting this bit indicates an Operations, Administration, and O bit: Setting this bit indicates an Operations, Administration, and
Maintenance (OAM) packet. The actual packet format and processing of Maintenance (OAM) packet. The actual format and processing of SFC
SFC OAM messages is outside the scope of this specification (see OAM packets is outside the scope of this specification (see for
[oam-frame]). example [I-D.ietf-sfc-oam-framework] for one approach).
SF/SFF/SFC Proxy/Classifer implementations that do not support SFC The O bit MUST be set for OAM packets and MUST NOT be set for non-OAM
OAM procedures SHOULD discard packets with O-bit set, but MAY support packets. The O bit MUST NOT be modified along the SFP.
SF/SFF/SFC Proxy/Classifier implementations that do not support SFC
OAM procedures SHOULD discard packets with O bit set, but MAY support
a configurable parameter to enable forwarding received SFC OAM a configurable parameter to enable forwarding received SFC OAM
packets unmodified to the next element in the chain. Forwarding OAM packets unmodified to the next element in the chain. Forwarding OAM
packets unmodified by SFC elements that do not support SFC OAM packets unmodified by SFC elements that do not support SFC OAM
procedures may be acceptable for a subset of OAM functions, but can procedures may be acceptable for a subset of OAM functions, but can
result in unexpected outcomes for others, thus it is recommended to result in unexpected outcomes for others, thus it is recommended to
analyze the impact of forwarding an OAM packet for all OAM functions analyze the impact of forwarding an OAM packet for all OAM functions
prior to enabling this behavior. The configurable parameter MUST be prior to enabling this behavior. The configurable parameter MUST be
disabled by default. disabled by default.
The O-bit MUST be set for OAM packets and MUST NOT be set for non-OAM
packets. The O-bit MUST NOT be modified along the SFP.
TTL: Indicates the maximum SFF hops for an SFP. The initial TTL TTL: Indicates the maximum SFF hops for an SFP. The initial TTL
value SHOULD be configurable via the control plane; the configured value SHOULD be configurable via the control plane; the configured
initial value can be specific to one or more SFPs. If no initial initial value can be specific to one or more SFPs. If no initial
value is explicitly provided, the default initial TTL value 63 MUST value is explicitly provided, the default initial TTL value 63 MUST
be used. Each SFF involved in forwarding an NSH packet MUST be used. Each SFF involved in forwarding an NSH packet MUST
decrement the TTL value by 1 prior to NSH forwarding lookup. decrement the TTL value by 1 prior to NSH forwarding lookup.
Decrementing by 1 from an incoming value of 0 shall result in a TTL Decrementing by 1 from an incoming value of 0 shall result in a TTL
value of 63. The packet MUST NOT be forwarded if TTL is, after value of 63. The packet MUST NOT be forwarded if TTL is, after
decrement, 0. decrement, 0.
All other flag fields are reserved for future use. Reserved bits All other flag fields are reserved for future use. Reserved bits
MUST be set to zero upon origination and MUST be preserved unmodified MUST be set to zero upon origination and MUST be preserved unmodified
by other NSH supporting elements. Elements which do not understand by other NSH supporting elements. Elements which do not understand
the meaning of any of these bits MUST not modify their actions based the meaning of any of these bits MUST NOT modify their actions based
on those unknown bits. on those unknown bits.
Length: The total length, in 4-byte words, of the NSH including the Length: The total length, in 4-byte words, of NSH including the Base
Base Header, the Service Path Header, the Fixed Length Context Header Header, the Service Path Header, the Fixed Length Context Header or
or Variable Length Context Header(s). The length MUST be of value Variable Length Context Header(s). The length MUST be of value 0x6
0x6 for MD Type equal to 0x1, and MUST be of value 0x2 or greater for for MD Type equal to 0x1, and MUST be of value 0x2 or greater for MD
MD Type equal to 0x2. The length of the NSH header MUST be an Type equal to 0x2. The length of the NSH header MUST be an integer
integer multiple of 4 bytes, thus variable length metadata is always multiple of 4 bytes, thus variable length metadata is always padded
padded out to a multiple of 4 bytes. out to a multiple of 4 bytes.
MD Type: indicates the format of NSH beyond the mandatory Base Header MD Type: indicates the format of NSH beyond the mandatory Base Header
and the Service Path Header. MD Type defines the format of the and the Service Path Header. MD Type defines the format of the
metadata being carried. Please see IANA Considerations section metadata being carried. Please see the IANA Considerations
below. Section 11.2.3.
This document defines two MD Type values: This document specifies the following four MD Type values:
0x0 - this is a reserved value. Implementations SHOULD silently
discard packets with MD Type 0x0.
0x1 - which indicates that the format of the header includes a fixed 0x1 - which indicates that the format of the header includes a fixed
length Context Header (see Figure 4 below). length Context Header (see Figure 4 below).
0x2 - which does not mandate any headers beyond the Base Header and 0x2 - which does not mandate any headers beyond the Base Header and
Service Path Header, but may contain optional variable length Context Service Path Header, but may contain optional variable length Context
Header(s). The semantics of the variable length Context Header(s) Header(s). The semantics of the variable length Context Header(s)
are not defined in this document are not defined in this document. The format of the optional
variable length Context Headers is provided in Section 2.5.1.
0xF - this value is reserved for experimentation and testing, as per
[RFC3692]. Implementations not explicitly configured to be part of
an experiment SHOULD silently discard packets with MD Type 0x15.
The format of the Base Header and the Service Path Header is The format of the Base Header and the Service Path Header is
invariant, and not affected by MD Type. invariant, and not affected by MD Type.
NSH implementations MUST support MD type = 0x1 and MD Type 0x2 (where NSH implementations MUST support MD type = 0x1 and MD Type = 0x2
the length is of value 0x2). NSH implementations SHOULD support MD (where the length is of value 0x2). NSH implementations SHOULD
Type 0x2 with length > 0x2. There exists, however, a middle ground, support MD Type 0x2 with length > 0x2. There exists, however, a
wherein a device will support MD Type 0x1 (as per the MUST) metadata, middle ground, wherein a device will support MD Type 0x1 (as per the
yet be deployed in a network with MD Type 0x2 metadata packets. In MUST) metadata, yet be deployed in a network with MD Type 0x2
that case, the MD Type 0x1 node, MUST utilize the base header length metadata packets. In that case, the MD Type 0x1 node, MUST utilize
field to determine the original payload offset if it requires access the base header length field to determine the original payload offset
to the original packet/frame. if it requires access to the original packet/frame.
Next Protocol: indicates the protocol type of the encapsulated data. Next Protocol: indicates the protocol type of the encapsulated data.
NSH does not alter the inner payload, and the semantics on the inner NSH does not alter the inner payload, and the semantics on the inner
protocol remain unchanged due to NSH service function chaining. protocol remain unchanged due to NSH service function chaining.
Please see IANA Considerations section below. Please see the IANA Considerations section below, Section 11.2.5.
This document defines the following Next Protocol values: This document defines the following Next Protocol values:
0x0: Reserved
0x1: IPv4 0x1: IPv4
0x2: IPv6 0x2: IPv6
0x3: Ethernet 0x3: Ethernet
0x4: NSH 0x4: NSH
0x5: MPLS 0x5: MPLS
0xFE: Experiment 1
0xFF: Experiment 2
3.3. Service Path Header An implementation not explicitly configured for a specific experiment
[RFC3692] SHOULD NOT attempt to process Next Protocol values 0xFE and
0xFF.
2.3. Service Path Header
Figure 3 shows the format of the Service Path Header:
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 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 Identifier (SPI) | Service Index | | Service Path Identifier (SPI) | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Path Identifier (SPI): 24 bits Service Path Identifier (SPI): 24 bits
Service Index (SI): 8 bits Service Index (SI): 8 bits
Figure 3: NSH Service Path Header Figure 3: NSH Service Path Header
The meaning of these fields is as follows:
Service Path Identifier (SPI): identifies a service path. Service Path Identifier (SPI): identifies a service path.
Participating nodes MUST use this identifier for Service Function Participating nodes MUST use this identifier for Service Function
Path selection. The initial classifier MUST set the appropriate SPI Path selection. The initial classifier MUST set the appropriate SPI
for a given classification result. for a given classification result.
Service Index (SI): provides location within the SFP. The initial Service Index (SI): provides location within the SFP. The initial
classifier for a given SFP SHOULD set the SI to 255, however the classifier for a given SFP SHOULD set the SI to 255, however the
control plane MAY configure the initial value of SI as appropriate control plane MAY configure the initial value of SI as appropriate
(i.e. taking into account the length of the service function path). (i.e., taking into account the length of the service function path).
Service Index MUST be decremented by a value of 1 by Service Service Index MUST be decremented by a value of 1 by Service
Functions or by SFC Proxy nodes after performing required services Functions or by SFC Proxy nodes after performing required services
and the new decremented SI value MUST be used in the egress NSH and the new decremented SI value MUST be used in the egress NSH
packet. The initial Classifier MUST send the packet to the first SFF packet. The initial Classifier MUST send the packet to the first SFF
in the identified SFP for forwarding along an SFP. If re- in the identified SFP for forwarding along an SFP. If re-
classification occurs, and that re-classification results in a new classification occurs, and that re-classification results in a new
SPI, the (re)classifier is, in effect, the initial classifier for the SPI, the (re)classifier is, in effect, the initial classifier for the
resultant SPI. resultant SPI.
SI is used in conjunction with Service Path Identifier for Service The SI is used in conjunction with Service Path Identifier for
Function Path Selection and for determining the next SFF/SF in the Service Function Path Selection and for determining the next SFF/SF
path. Service Index (SI) is also valuable when troubleshooting/ in the path. The SI is also valuable when troubleshooting/ reporting
reporting service paths. In addition to indicating the location service paths. In addition to indicating the location within a
within a Service Function Path, SI can be used for service plane loop Service Function Path, SI can be used for service plane loop
detection. detection.
3.4. NSH MD Type 1 2.4. NSH MD Type 1
When the Base Header specifies MD Type = 0x1, a Fixed Length Context When the Base Header specifies MD Type = 0x1, a Fixed Length Context
Header (16-bytes) MUST be present immediately following the Service Header (16-bytes) MUST be present immediately following the Service
Path Header, as per Figure 4. A Fixed Length Context Header that Path Header, as per Figure 4. A Fixed Length Context Header that
carries no metadata MUST be set to zero. carries 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 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|R| TTL | Length |R|R|R|R|MD Type| Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|R| TTL | Length |R|R|R|R|MD Type| Next Protocol |
| Service Path Identifer | Service Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path Identifier | Service Index |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Fixed Length Context Header | | |
| | | Fixed Length Context Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: NSH MD Type=0x1 Figure 4: NSH MD Type=0x1
This specification does not make any assumptions about the content of This specification does not make any assumptions about the content of
the 16 byte Context Header that must be present when the MD Type the 16 byte Context Header that must be present when the MD Type
field is set to 1, and does not describe the structure or meaning of field is set to 1, and does not describe the structure or meaning of
the included metadata. the included metadata.
An SFC-aware SF MUST receive the data semantics first in order to An SFC-aware SF MUST receive the data semantics first in order to
process the data placed in the mandatory context field. The data process the data placed in the mandatory context field. The data
semantics include both the allocation schema and the meaning of the semantics include both the allocation schema and the meaning of the
included data. How an SFC-aware SF gets the data semantics is included data. How an SFC-aware SF gets the data semantics is
outside the scope of this specification. outside the scope of this specification.
An SF or SFC Proxy that does not know the format or semantics of the An SF or SFC Proxy that does not know the format or semantics of the
Context Header for an NSH with MD Type 1 MUST discard any packet with Context Header for an NSH with MD Type 1 MUST discard any packet with
such an NSH (i.e., MUST NOT ignore the metadata that it cannot such an NSH (i.e., MUST NOT ignore the metadata that it cannot
process), and MUST log the event at least once per the SPI for which process), and MUST log the event at least once per the SPI for which
the event occurs (subject to thresholding). the event occurs (subject to thresholding).
[dcalloc] and [broadalloc] provide specific examples of how metadata [I-D.guichard-sfc-nsh-dc-allocation] and
can be allocated. [I-D.napper-sfc-nsh-broadband-allocation] provide specific examples
of how metadata can be allocated.
3.5. NSH MD Type 2 2.5. NSH MD Type 2
When the base header specifies MD Type= 0x2, zero or more Variable When the base header specifies MD Type = 0x2, zero or more Variable
Length Context Headers MAY be added, immediately following the Length Context Headers MAY be added, immediately following the
Service Path Header. Therefore, Length = 0x2, indicates that only Service Path Header (see Figure 5). Therefore, Length = 0x2,
the Base Header followed by the Service Path Header are present. The indicates that only the Base Header followed by the Service Path
optional Variable Length Context Headers MUST be of an integer number Header are present. The optional Variable Length Context Headers
of 4-bytes. The base header Length field MUST be used to determine MUST be of an integer number of 4-bytes. The base header Length
the offset to locate the original packet or frame for SFC nodes that field MUST be used to determine the offset to locate the original
require access to that information. packet or frame for SFC nodes that require access to that
information.
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 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|R| TTL | Length |R|R|R|R|MD Type| Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|R| TTL | Length |R|R|R|R|MD Type| Next Protocol |
| Service Path Identifier | Service Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path Identifier | Service Index |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Variable Length Context Headers (opt.) ~ | |
| | ~ Variable Length Context Headers (opt.) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: NSH MD Type=0x2 Figure 5: NSH MD Type=0x2
3.5.1. Optional Variable Length Metadata 2.5.1. Optional Variable Length Metadata
The format of the optional variable length Context Headers, is as The format of the optional variable length Context Headers, is as
described below. depicted in Figure 6.
0 1 2 3 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 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 |R| Len | | Metadata Class | Type |R| Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Metadata | | Variable Metadata |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Variable Context Headers Figure 6: Variable Context Headers
Metadata Class (MD Class): The MD Class defines the scope of the Metadata Class (MD Class): defines the scope of the 'Type' field to
'Type' field to provide a hierarchical namespace. The IANA provide a hierarchical namespace. The IANA Considerations
Considerations section defines how the MD Class values can be Section 11.2.4 defines how the MD Class values can be allocated to
allocated to standards bodies, vendors, and others. standards bodies, vendors, and others.
Type: indicates the explicit type of metadata being carried and is Type: indicates the explicit type of metadata being carried and is
the responsibility of the MD Class owner. the responsibility of the MD Class owner.
Reserved bit: one reserved bit is present for future use. The Reserved bit: one reserved bit is present for future use. The
reserved bits MUST be set to 0x0. reserved bits MUST be set to 0x0.
Length: Length of the variable metadata, in single byte words. In Length: indicates the length of the variable metadata, in single byte
case the metadata length is not an integer number of 4-byte words, words. In case the metadata length is not an integer number of
the sender MUST add pad bytes immediately following the last metadata 4-byte words, the sender MUST add pad bytes immediately following the
byte to extend the metadata to an integer number of 4-byte words. last metadata byte to extend the metadata to an integer number of
4-byte words. The receiver MUST round up the length field to the
The receiver MUST round up the length field to the nearest 4-byte nearest 4-byte word boundary, to locate and process the next field in
word boundary, to locate and process the next field in the packet. the packet. The receiver MUST access only those bytes in the
The receiver MUST access only those bytes in the metadata indicated metadata indicated by the length field (i.e., actual number of single
by the length field (i.e. actual number of single byte words) and byte words) and MUST ignore the remaining bytes up to the nearest
MUST ignore the remaining bytes up to the nearest 4-byte word 4-byte word boundary. The Length may be 0 or greater.
boundary. The Length may be 0 or greater.
A value of 0x0 denotes a Context Header without a Variable Metadata A value of 0x0 denotes a Context Header without a Variable Metadata
field. field.
This specification does not make any assumption about Context Headers This specification does not make any assumption about Context Headers
that are mandatory-to-implement or those that are mandatory-to- that are mandatory-to-implement or those that are mandatory-to-
process. These considerations are deployment-specific. However, the process. These considerations are deployment-specific. However, the
control plane is entitled to instruct SFC-aware SFs with the data control plane is entitled to instruct SFC-aware SFs with the data
structure of context header together with their scoping (see Section structure of context header together with their scoping (see
3.3.3 of [SFC-CP]). Section 3.3.3 of [I-D.ietf-sfc-control-plane]).
Upon receipt of a packet that belong to a given SFP, if a mandatory- Upon receipt of a packet that belong to a given SFP, if a mandatory-
to-process context header is missing in that packet, the SFC-aware SF to-process context header is missing in that packet, the SFC-aware SF
MUST NOT process the packet and MUST log at least once per the SPI MUST NOT process the packet and MUST log at least once per the SPI
for which a mandatory metadata is missing. for which a mandatory metadata is missing.
If multiple mandatory-to-process context headers are required for a If multiple mandatory-to-process context headers are required for a
given SFP, the control plane MAY instruct the SFC-aware SF with the given SFP, the control plane MAY instruct the SFC-aware SF with the
order to consume these Context Headers. If no instructions are order to consume these Context Headers. If no instructions are
provided, the SFC-aware SF MUST process these Context Headers in the provided, the SFC-aware SF MUST process these Context Headers in the
order their appear in an NSH packet. order their appear in an NSH packet.
If multiple instances of the same metadata are included in an NSH If multiple instances of the same metadata are included in an NSH
packet, but the definition of that context header does not allow for packet, but the definition of that context header does not allow for
it, the SFC-aware SF MUST process first instance and ignore it, the SFC-aware SF MUST process first instance and ignore
subsequent instances. subsequent instances.
4. NSH Actions 3. NSH Actions
NSH-aware nodes are the only nodes that may alter the content of NSH NSH-aware nodes are the only nodes that may alter the content of NSH
headers. NSH-aware nodes include: service classifiers, SFF, SF and headers. NSH-aware nodes include: service classifiers, SFF, SF and
SFC proxies. These nodes have several possible header related SFC proxies. These nodes have several possible NSH-related actions:
actions:
1. Insert or remove NSH: These actions can occur at the start and 1. Insert or remove NSH: These actions can occur at the start and
end respectively of a service path. Packets are classified, and end respectively of a service path. Packets are classified, and
if determined to require servicing, NSH will be imposed. A if determined to require servicing, NSH will be imposed. A
service classifier MUST insert NSH at the start of an SFP. An service classifier MUST insert NSH at the start of an SFP. An
imposed NSH MUST contain valid Base Header and Service Path imposed NSH MUST contain valid Base Header and Service Path
Header. At the end of a service function path, a SFF, MUST be Header. At the end of a service function path, an SFF, MUST be
the last node operating on the service header and MUST remove NSH the last node operating on the service header and MUST remove NSH
before forwarding or delivering the un-encapsulated packet before forwarding or delivering the un-encapsulated packet
Multiple logical classifiers may exist within a given service Multiple logical classifiers may exist within a given service
path. Non-initial classifiers may re-classify data and that re- path. Non-initial classifiers may re-classify data and that re-
classification MAY result in the selection a different Service classification MAY result in the selection a different Service
Function Path. When the logical classifier performs re- Function Path. When the logical classifier performs re-
classification that results in a change of service path, it MUST classification that results in a change of service path, it MUST
remove the existing NSH and MUST impose a new NSH with the Base remove the existing NSH and MUST impose a new NSH with the Base
Header and Service Path Header reflecting the new service path Header and Service Path Header reflecting the new service path
skipping to change at page 15, line 5 skipping to change at page 13, line 43
If an SFC proxy is in use (acting on behalf of a NSH unaware If an SFC proxy is in use (acting on behalf of a NSH unaware
service function for NSH actions), then the proxy MUST update service function for NSH actions), then the proxy MUST update
Service Index and MAY update contexts. When an SFC proxy Service Index and MAY update contexts. When an SFC proxy
receives an NSH-encapsulated packet, it MUST remove NSH before receives an NSH-encapsulated packet, it MUST remove NSH before
forwarding it to an NSH unaware SF. When the SFC Proxy receives forwarding it to an NSH unaware SF. When the SFC Proxy receives
a packet back from an NSH unaware SF, it MUST re-encapsulates it a packet back from an NSH unaware SF, it MUST re-encapsulates it
with the correct NSH, and MUST decrement the Service Index by with the correct NSH, and MUST decrement the Service Index by
one. one.
4. Service policy selection: Service Functions derive policy (i.e. 4. Service policy selection: Service Functions derive policy (i.e.,
service actions such as permit or deny) selection and enforcement service actions such as permit or deny) selection and enforcement
from NSH. Metadata shared in NSH can provide a range of service- from NSH. Metadata shared in NSH can provide a range of service-
relevant information such as traffic classification. relevant information such as traffic classification.
Figure 7 maps each of the four actions above to the components in the Figure 7 maps each of the four actions above to the components in the
SFC architecture that can perform it. SFC architecture that can perform it.
+---------------+------------------+-------+----------------+---------+ +----------------+---------------+-------+----------------+---------+
| | Insert |Forward| Update |Service | | | Insert |Forward| Update |Service |
| | or remove NSH |NSH | NSH |policy | | | or remove NSH |NSH | NSH |policy |
| | |Packets| |selection| | | |Packets| |selection|
| Component +--------+--------+ +----------------+ | | Component +-------+-------+ +----------------+ |
| | | | | Dec. |Update | | | | | | | Dec. |Update | |
| | Insert | Remove | |Service |Context| | | |Insert |Remove | |Service |Context| |
| | | | | Index |Header | | | | | | | Index |Header | |
+----------------+--------+--------+-------+--------+-------+---------+ +----------------+-------+-------+-------+--------+-------+---------+
| | + | + | | | + | | | | + | + | | | + | |
|Classifier | | | | | | | |Classifier | | | | | | |
+--------------- +--------+--------+-------+--------+-------+---------+ +--------------- +-------+-------+-------+--------+-------+---------+
|Service Function| | + | + | | | | |Service Function| | + | + | | | |
|Forwarder(SFF) | | | | | | | |Forwarder(SFF) | | | | | | |
+--------------- +--------+--------+-------+--------+-------+---------+ +--------------- +-------+-------+-------+--------+-------+---------+
|Service | | | | + | + | + | |Service | | | | + | + | + |
|Function (SF) | | | | | | | |Function (SF) | | | | | | |
+--------------- +--------+--------+-------+--------+-------+---------+ +--------------- +-------+-------+-------+--------+-------+---------+
|SFC Proxy | + | + | | + | + | | |SFC Proxy | + | + | | + | + | |
+----------------+--------+--------+-------+--------+-------+---------+ +----------------+-------+-------+-------+--------+-------+---------+
Figure 7: NSH Action and Role Mapping Figure 7: NSH Action and Role Mapping
5. NSH Encapsulation 4. NSH Transport Encapsulation
Once NSH is added to a packet, an outer encapsulation is used to Once NSH is added to a packet, an outer encapsulation is used to
forward the original packet and the associated metadata to the start forward the original packet and the associated metadata to the start
of a service chain. The encapsulation serves two purposes: of a service chain. The encapsulation serves two purposes:
1. Creates a topologically independent services plane. Packets are 1. Creates a topologically independent services plane. Packets are
forwarded to the required services without changing the forwarded to the required services without changing the
underlying network topology underlying network topology
2. Transit network nodes simply forward the encapsulated packets as 2. Transit network nodes simply forward the encapsulated packets as
is. is.
The service header is independent of the encapsulation used and is The service header is independent of the encapsulation used and is
encapsulated in existing transports. The presence of NSH is encapsulated in existing transports. The presence of NSH is
indicated via protocol type or other indicator in the outer indicated via protocol type or other indicator in the outer
encapsulation. encapsulation.
6. Fragmentation Considerations 5. Fragmentation Considerations
NSH and the associated transport header are "added" to the NSH and the associated transport header are "added" to the
encapsulated packet/frame. This additional information increases the encapsulated packet/frame. This additional information increases the
size of the packet. size of the packet.
As discussed in [encap-considerations], within an administrative As discussed in [I-D.ietf-rtgwg-dt-encap], within an administrative
domain, an operator can ensure that the underlay MTU is sufficient to domain, an operator can ensure that the underlay MTU is sufficient to
carry SFC traffic without requiring fragmentation. carry SFC traffic without requiring fragmentation.
However, there will be cases where the underlay MTU is not large However, there will be cases where the underlay MTU is not large
enough to carry the NSH traffic. Since NSH does not provide enough to carry the NSH traffic. Since NSH does not provide
fragmentation support at the service plane, the transport/overlay fragmentation support at the service plane, the transport/overlay
layer MUST provide the requisite fragmentation handling. Section 6 layer MUST provide the requisite fragmentation handling. Section 6
of [encap-considerations] provides guidance for those scenarios. of [I-D.ietf-rtgwg-dt-encap] provides guidance for those scenarios.
7. Service Path Forwarding with NSH 6. Service Path Forwarding with NSH
7.1. SFFs and Overlay Selection 6.1. SFFs and Overlay Selection
As described above, NSH contains a Service Path Identifier (SPI) and As described above, NSH contains a Service Path Identifier (SPI) and
a Service Index (SI). The SPI is, as per its name, an identifier. 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. The SPI alone cannot be used to forward packets along a service path.
Rather the SPI provide a level of indirection between the service Rather the SPI provides a level of indirection between the service
path/topology and the network transport. Furthermore, there is no path/topology and the network transport. Furthermore, there is no
requirement, or expectation of an SPI being bound to a pre-determined requirement, or expectation of an SPI being bound to a pre-determined
or static network path. or static network path.
The Service Index provides an indication of location within a service The Service Index provides an indication of location within a service
path. The combination of SPI and SI provides the identification of a 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 logical SF and its order within the service plane, and is used to
select the appropriate network locator(s) for overlay forwarding. select the appropriate network locator(s) for overlay forwarding.
The logical SF may be a single SF, or a set of eligible SFs that are The logical SF may be a single SF, or a set of eligible SFs that are
equivalent. In the latter case, the SFF provides load distribution equivalent. In the latter case, the SFF provides load distribution
amongst the collection of SFs as needed. amongst the collection of SFs as needed.
SI serves as a mechanism for detecting invalid service function path. SI serves as a mechanism for detecting invalid service function path.
In particular, an SI value of zero indicates that forwarding is In particular, an SI value of zero indicates that forwarding is
incorrect and the packet must be discarded incorrect and the packet must be discarded
This indirection -- path ID to overlay -- creates a true service This indirection -- SPI to overlay -- creates a true service plane.
plane. That is the SFF/SF topology is constructed without impacting That is the SFF/SF topology is constructed without impacting the
the network topology but more importantly service plane only network topology but more importantly service plane only participants
participants (i.e. most SFs) need not be part of the network overlay (i.e., most SFs) need not be part of the network overlay topology and
topology and its associated infrastructure (e.g. control plane, its associated infrastructure (e.g., control plane, routing tables,
routing tables, etc.). SFs need to be able to return a packet to an etc.) SFs need to be able to return a packet to an appropriate SFF
appropriate SFF (i.e. has the requisite NSH information) when service (i.e., has the requisite NSH information) when service processing is
processing is complete. This can be via the over or underlay and in complete. This can be via the over or underlay and in some case
some case require additional configuration on the SF. As mentioned require additional configuration on the SF. As mentioned above, an
above, an existing overlay topology may be used provided it offers existing overlay topology may be used provided it offers the
the requisite connectivity. requisite connectivity.
The mapping of SPI to transport occurs on an SFF (as discussed above, 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 the first SFF in the path gets a NSH encapsulated packet from the
Classifier). The SFF consults the SPI/ID values to determine the Classifier). The SFF consults the SPI/ID values to determine the
appropriate overlay transport protocol (several may be used within a appropriate overlay transport protocol (several may be used within a
given network) and next hop for the requisite SF. Figure 8 below given network) and next hop for the requisite SF. Table 1 below
depicts an example of a single next-hop SPI/SI to network overlay depicts an example of a single next-hop SPI/SI to network overlay
network locator mapping. network locator mapping.
+-------------------------------------------------------+ +------+------+---------------------+-------------------+
| SPI | SI | Next hop(s) | Transport | | SPI | SI | Next hop(s) | Transport |
+-------------------------------------------------------+ +------+------+---------------------+-------------------+
| 10 | 255 | 192.0.2.1 | VXLAN-gpe | | 10 | 255 | 192.0.2.1 | VXLAN-gpe |
| 10 | 254 | 198.51.100.10 | GRE | | | | | |
| 10 | 251 | 198.51.100.15 | GRE | | 10 | 254 | 198.51.100.10 | GRE |
| 40 | 251 | 198.51.100.15 | GRE | | | | | |
| 50 | 200 | 01:23:45:67:89:ab | Ethernet | | 10 | 251 | 198.51.100.15 | GRE |
| 15 | 212 | Null (end of path) | None | | | | | |
+-------------------------------------------------------+ | 40 | 251 | 198.51.100.15 | GRE |
| | | | |
| 50 | 200 | 01:23:45:67:89:ab | Ethernet |
| | | | |
| 15 | 212 | Null (end of path) | None |
+------+------+---------------------+-------------------+
Figure 8: SFF NSH Mapping Example Table 1: SFF NSH Mapping Example
Additionally, further indirection is possible: the resolution of the Additionally, further indirection is possible: the resolution of the
required SF network locator may be a localized resolution on an SFF, required SF network locator may be a localized resolution on an SFF,
rather than a service function chain control plane responsibility, as rather than a service function chain control plane responsibility, as
per figures 9 and 10 below. per Table 2 and Table 3 below.
Please note: VXLAN-gpe and GRE in the above table refer to Please note: VXLAN-gpe and GRE in the above table refer to
[VXLAN-gpe] and [RFC2784], respectively. [I-D.ietf-nvo3-vxlan-gpe] and [RFC2784], respectively.
+----------------------------+ +------+-----+----------------+
| SPI | SI | Next hop(s) | | SPI | SI | Next hop(s) |
+----------------------------+ +------+-----+----------------+
| 10 | 3 | SF2 | | 10 | 3 | SF2 |
| 245 | 12 | SF34 | | | | |
| 40 | 9 | SF9 | | 245 | 12 | SF34 |
+----------------------------+ | | | |
| 40 | 9 | SF9 |
+------+-----+----------------+
Figure 9: NSH to SF Mapping Example Table 2: NSH to SF Mapping Example
+----------------------------------------+ +------+-------------------+-------------+
| SF | Next hop(s) | Transport | | SF | Next hop(s) | Transport |
+----------------------------------------| +------+-------------------+-------------+
| SF2 | 192.0.2.2 | VXLAN-gpe | | SF2 | 192.0.2.2 | VXLAN-gpe |
| SF34| 198.51.100.34 | UDP | | | | |
| SF9 | 2001:db8::1 | GRE | | SF34 | 198.51.100.34 | UDP |
+--------------------------+------------- | | | |
= | SF9 | 2001:db8::1 | GRE |
Figure 10: SF Locator Mapping Example +------+-------------------+-------------+
Table 3: SF Locator Mapping Example
Since the SPI is a representation of the service path, the lookup may 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 return more than one possible next-hop within a service path for a
given SF, essentially a series of weighted (equally or otherwise) given SF, essentially a series of weighted (equally or otherwise)
paths to be used (for load distribution, redundancy or policy), see paths to be used (for load distribution, redundancy or policy), see
Figure 11. The metric depicted in Figure 11 is an example to help Table 4. The metric depicted in Table 4 is an example to help
illustrated weighing SFs. In a real network, the metric will range illustrated weighing SFs. In a real network, the metric will range
from a simple preference (similar to routing next- hop), to a true from a simple preference (similar to routing next- hop), to a true
dynamic composite metric based on some service function-centric state dynamic composite metric based on some service function-centric state
(including load, sessions state, capacity, etc.) (including load, sessions state, capacity, etc.)
+------+-----+--------------+---------+
| SPI | SI | NH | Metric |
+------+-----+--------------+---------+
| 10 | 3 | 203.0.113.1 | 1 |
| | | | |
| | | 203.0.113.2 | 1 |
| | | | |
| 20 | 12 | 192.0.2.1 | 1 |
| | | | |
| | | 203.0.113.4 | 1 |
| | | | |
| 30 | 7 | 192.0.2.10 | 10 |
| | | | |
| | | 198.51.100.1 | 5 |
+------+-----+--------------+---------+
+----------------------------------+ (encapsulation type omitted for formatting)
| SPI | SI | NH | Metric |
+----------------------------------+
| 10 | 3 | 203.0.113.1 | 1 |
| | | 203.0.113.2 | 1 |
| | | | |
| 20 | 12 | 192.0.2.1 | 1 |
| | | 203.0.113.4 | 1 |
| | | | |
| 30 | 7 | 192.0.2.10 | 10 |
| | | 198.51.100.1| 5 |
+----------------------------------+
(encapsulation type omitted for formatting)
Figure 11: NSH Weighted Service Path Table 4: NSH Weighted Service Path
7.2. Mapping NSH to Network Transport 6.2. Mapping NSH to Network Transport
As described above, the mapping of SPI to network topology may result As described above, the mapping of SPI to network topology may result
in a single path, or it might result in a more complex topology. in a single path, or it might result in a more complex topology.
Furthermore, the SPI to overlay mapping occurs at each SFF Furthermore, the SPI to overlay mapping occurs at each SFF
independently. Any combination of topology selection is possible. independently. Any combination of topology selection is possible.
Please note, there is no requirement to create a new overlay topology 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 if a suitable one already existing. NSH packets can use any (new or
existing) overlay provided the requisite connectivity requirements existing) overlay provided the requisite connectivity requirements
are satisfied. are satisfied.
skipping to change at page 21, line 27 skipping to change at page 19, line 14
there is no a priori mandate about how to forward packets in the there is no a priori mandate about how to forward packets in the
network (only the order of services that must be traversed). network (only the order of services that must be traversed).
The network operator retains the ability to engineer the network The network operator retains the ability to engineer the network
paths as required. For example, the overlay path between SFFs may paths as required. For example, the overlay path between SFFs may
utilize traffic engineering, QoS marking, or ECMP, without requiring utilize traffic engineering, QoS marking, or ECMP, without requiring
complex configuration and network protocol support to be extended to complex configuration and network protocol support to be extended to
the service path explicitly. In other words, the network operates as the service path explicitly. In other words, the network operates as
expected, and evolves as required, as does the service plane. expected, and evolves as required, as does the service plane.
7.3. Service Plane Visibility 6.3. Service Plane Visibility
The SPI and SI serve an important function for visibility into the The SPI and SI serve an important function for visibility into the
service topology. An operator can determine what service path a service topology. An operator can determine what service path a
packet is "on", and its location within that path simply by viewing packet is "on", and its location within that path simply by viewing
NSH information (packet capture, IPFIX, etc.). The information can NSH information (packet capture, IPFIX, etc.) The information can be
be used for service scheduling and placement decisions, used for service scheduling and placement decisions, troubleshooting
troubleshooting and compliance verification. and compliance verification.
7.4. Service Graphs 6.4. Service Graphs
While a given realized service function path is a specific sequence While a given realized service function path is a specific sequence
of service functions, the service as seen by a user can actually be a of service functions, the service as seen by a user can actually be a
collection of service function paths, with the interconnection collection of service function paths, with the interconnection
provided by classifiers (in-service path, non-initial provided by classifiers (in-service path, non-initial
reclassification). These internal reclassifiers examine the packet reclassification). These internal reclassifiers examine the packet
at relevant points in the network, and, if needed, SPI and SI are at relevant points in the network, and, if needed, SPI and SI are
updated (whether this update is a re-write, or the imposition of a updated (whether this update is a re-write, or the imposition of a
new NSH with new values is implementation specific) to reflect the new NSH with new values is implementation specific) to reflect the
"result" of the classification. These classifiers may also of course "result" of the classification. These classifiers may also of course
modify the metadata associated with the packet. modify the metadata associated with the packet.
RFC7665, section 2.1 describes Service Graphs in detail. [RFC7665], Section 2.1 describes Service Graphs in detail.
8. Policy Enforcement with NSH 7. Policy Enforcement with NSH
8.1. NSH Metadata and Policy Enforcement 7.1. NSH Metadata and Policy Enforcement
As described in Section 3, NSH provides the ability to carry metadata As described in Section 3, NSH provides the ability to carry metadata
along a service path. This metadata may be derived from several along a service path. This metadata may be derived from several
sources, common examples include: sources, common examples include:
Network nodes/devices: Information provided by network nodes can Network nodes/devices: Information provided by network nodes can
indicate network-centric information (such as VRF or tenant) that indicate network-centric information (such as VRF or tenant) that
may be used by service functions, or conveyed to another network may be used by service functions, or conveyed to another network
node post service path egress. node post service path egress.
skipping to change at page 22, line 41 skipping to change at page 20, line 25
Regardless of the source, metadata reflects the "result" of Regardless of the source, metadata reflects the "result" of
classification. The granularity of classification may vary. For classification. The granularity of classification may vary. For
example, a network switch, acting as a classifier, might only be able 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 to classify based on a 5-tuple, whereas, a service function may be
able to inspect application information. Regardless of granularity, able to inspect application information. Regardless of granularity,
the classification information can be represented in NSH. the classification information can be represented in NSH.
Once the data is added to NSH, it is carried along the service path, 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 NSH-aware SFs receive the metadata, and can use that metadata for
local decisions and policy enforcement. The following two examples local decisions and policy enforcement. Figure 8 and Figure 9
highlight the relationship between metadata and policy: highlight the relationship between metadata and policy:
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+
| SFF )------->( SFF |------->| SFF | | SFF )------->( SFF |------->| SFF |
+---^---+ +---|---+ +---|---+ +---^---+ +---|---+ +---|---+
,-|-. ,-|-. ,-|-. ,-|-. ,-|-. ,-|-.
/ \ / \ / \ / \ / \ / \
( Class ) SF1 ) ( SF2 ) ( Class ) ( SF1 ) ( SF2 )
\ ify / \ / \ / \ ify / \ / \ /
`---' `---' `---' `---' `---' `---'
5-tuple: Permit Inspect 5-tuple: Permit Inspect
Tenant A Tenant A AppY Tenant A Tenant A AppY
AppY AppY
Figure 12: Metadata and Policy Figure 8: Metadata and Policy
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF | | SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
^ | | ^ | |
,-+-. ,-+-. ,-+-. ,-+-. ,-+-. ,-+-.
/ \ / \ / \ / \ / \ / \
( Class ) ( SF1 ) ( SF2 ) ( Class ) ( SF1 ) ( SF2 )
\ ify / \ / \ / \ ify / \ / \ /
`-+-' `---' `---' `-+-' `---' `---'
| Permit Deny AppZ | Permit Deny AppZ
+---+---+ employees +---+---+ employees
| | | |
+-------+ +-------+
external external
system: system:
Employee Employee
AppZ AppZ
Figure 13: External Metadata and Policy Figure 9: External Metadata and Policy
In both of the examples above, the service functions perform policy In both of the examples above, the service functions perform policy
decisions based on the result of the initial classification: the SFs decisions based on the result of the initial classification: the SFs
did not need to perform re-classification, rather they rely on a did not need to perform re-classification, rather they rely on a
antecedent classification for local policy enforcement. antecedent classification for local policy enforcement.
Depending on the information carried in the metadata, data privacy Depending on the information carried in the metadata, data privacy
considerations may need to be considered. For example, if the considerations may need to be considered. For example, if the
metadata conveys tenant information, that information may need to be metadata conveys tenant information, that information may need to be
authenticated and/or encrypted between the originator and the authenticated and/or encrypted between the originator and the
intended recipients (which may include intended SFs only) . NSH intended recipients (which may include intended SFs only) . NSH
itself does not provide privacy functions, rather it relies on the itself does not provide privacy functions, rather it relies on the
transport/overlay layer. An operator can select the appropriate transport/overlay layer. An operator can select the appropriate
transport to ensure the confidentially (and other security) transport to ensure the confidentially (and other security)
considerations are met. Metadata privacy and security considerations considerations are met. Metadata privacy and security considerations
are a matter for the documents that define metadata format. are a matter for the documents that define metadata format.
8.2. Updating/Augmenting Metadata 7.2. Updating/Augmenting Metadata
Post-initial metadata imposition (typically performed during initial Post-initial metadata imposition (typically performed during initial
service path determination), metadata may be augmented or updated: service path determination), metadata may be augmented or updated:
1. Metadata Augmentation: Information may be added to NSH's existing 1. Metadata Augmentation: Information may be added to NSH's existing
metadata, as depicted in Figure 14. For example, if the initial metadata, as depicted in Figure 10. For example, if the initial
classification returns the tenant information, a secondary classification returns the tenant information, a secondary
classification (perhaps co-resident with DPI or SLB) may augment classification (perhaps co-resident with DPI or SLB) may augment
the tenant classification with application information, and the tenant classification with application information, and
impose that new information in NSH metadata. The tenant impose that new information in NSH metadata. The tenant
classification is still valid and present, but additional classification is still valid and present, but additional
information has been added to it. information has been added to it.
2. Metadata Update: Subsequent classifiers may update the initial 2. Metadata Update: Subsequent classifiers may update the initial
classification if it is determined to be incorrect or not classification if it is determined to be incorrect or not
descriptive enough. For example, the initial classifier adds descriptive enough. For example, the initial classifier adds
metadata that describes the traffic as "internet" but a security metadata that describes the traffic as "internet" but a security
service function determines that the traffic is really "attack". service function determines that the traffic is really "attack".
Figure 15 illustrates an example of updating metadata. Figure 11 illustrates an example of updating metadata.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF | | SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
^ | | ^ | |
,---. ,---. ,---. ,---. ,---. ,---.
/ \ / \ / \ / \ / \ / \
( Class ) ( SF1 ) ( SF2 ) ( Class ) ( SF1 ) ( SF2 )
\ / \ / \ / \ / \ / \ /
`-+-' `---' `---' `-+-' `---' `---'
| Inspect Deny | Inspect Deny
+---+---+ employees employee+ +---+---+ employees employee+
| | Class=AppZ appZ | | Class=AppZ appZ
+-------+ +-------+
external external
system: system:
Employee Employee
Figure 14: Metadata Augmentation
+-----+ +-----+ +-----+ Figure 10: Metadata Augmentation
| SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+
^ | |
,---. ,---. ,---.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ / \ / \ /
`---' `---' `---'
5-tuple: Inspect Deny
Tenant A Tenant A attack
--> attack
Figure 15: Metadata Update +-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+
^ | |
,---. ,---. ,---.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ / \ / \ /
`---' `---' `---'
5-tuple: Inspect Deny
Tenant A Tenant A attack
--> attack
8.3. Service Path Identifier and Metadata Figure 11: Metadata Update
7.3. Service Path Identifier and Metadata
Metadata information may influence the service path selection since Metadata information may influence the service path selection since
the Service Path Identifier values can represent the result of the Service Path Identifier values can represent the result of
classification. A given SPI can be defined based on classification classification. A given SPI can be defined based on classification
results (including metadata classification). The imposition of the results (including metadata classification). The imposition of the
SPI and SI results in the packet being placed on the newly specified SPI and SI results in the packet being placed on the newly specified
SFP at the position indicated by the imposed SPI and SI. SFP at the position indicated by the imposed SPI and SI.
This relationship provides the ability to create a dynamic service This relationship provides the ability to create a dynamic service
plane based on complex classification without requiring each node to plane based on complex classification without requiring each node to
be capable of such classification, or requiring a coupling to the be capable of such classification, or requiring a coupling to the
network topology. This yields service graph functionality as network topology. This yields service graph functionality as
described in Section 7.4. Figure 16 illustrates an example of this described in Section 7.4. Figure 12 illustrates an example of this
behavior. behavior.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| SFF |---------> | SFF |------+---> | SFF | | SFF |---------> | SFF |------+---> | SFF |
+--+--+ +--+--+ | +--+--+ +--+--+ +--+--+ | +--+--+
| | | | | | | |
,---. ,---. | ,---. ,---. ,---. | ,---.
/ \ / SF1 \ | / \ / \ / SF1 \ | / \
( SCL ) ( + ) | ( SF2 ) ( SCL ) ( + ) | ( SF2 )
\ / \SCL2 / | \ / \ / \SCL2 / | \ /
`---' `---' +-----+ `---' `---' `---' +-----+ `---'
5-tuple: Inspect | SFF | Original 5-tuple: Inspect | SFF | Original
Tenant A Tenant A +--+--+ next SF Tenant A Tenant A +--+--+ next SF
--> DoS | --> DoS |
V V
,-+-. ,-+-.
/ \ / \
( SF10 ) ( SF10 )
\ / \ /
`---' `---'
DoS DoS
"Scrubber" "Scrubber"
Figure 16: Path ID and Metadata Figure 12: Path ID and Metadata
Specific algorithms for mapping metadata to an SPI are outside the Specific algorithms for mapping metadata to an SPI are outside the
scope of this document. scope of this document.
9. Security Considerations 8. Security Considerations
As with many other protocols, NSH data can be spoofed or otherwise As with many other protocols, NSH data can be spoofed or otherwise
modified. In many deployments, NSH will be used in a controlled modified. In many deployments, NSH will be used in a controlled
environment, with trusted devices (e.g. a data center) thus environment, with trusted devices (e.g., a data center) thus
mitigating the risk of unauthorized header manipulation. mitigating the risk of unauthorized header manipulation.
NSH is always encapsulated in a transport protocol and therefore, NSH is always encapsulated in a transport protocol and therefore,
when required, existing security protocols that provide authenticity when required, existing security protocols that provide authenticity
(e.g. [RFC6071]) can be used. Similarly, if confidentiality is (e.g., [RFC6071]) can be used. Similarly, if confidentiality is
required, existing encryption protocols can be used in conjunction required, existing encryption protocols can be used in conjunction
with encapsulated NSH. with encapsulated NSH.
Further, existing best practices, such as [BCP38] should be deployed Further, existing best practices, such as [BCP38] should be deployed
at the network layer to ensure that traffic entering the service path at the network layer to ensure that traffic entering the service path
is indeed "valid". [encap-considerations] provides additional is indeed "valid". [I-D.ietf-rtgwg-dt-encap] provides additional
transport encapsulation considerations. transport encapsulation considerations.
NSH metadata authenticity and confidentially must be considered as NSH metadata authenticity and confidentially must be considered as
well. In order to protect the metadata, an operator can leverage the well. In order to protect the metadata, an operator can leverage the
aforementioned mechanisms provided the transport layer, authenticity aforementioned mechanisms provided the transport layer, authenticity
and/or confidentiality. An operator MUST carefully select the and/or confidentiality. An operator MUST carefully select the
transport/underlay services to ensure end to end security services, transport/underlay services to ensure end to end security services,
when those are sought after. For example, if [RFC6071] is used, the when those are sought after. For example, if [RFC6071] is used, the
operator MUST ensure it can be supported by the transport/underlay of operator MUST ensure it can be supported by the transport/underlay of
all relevant network segments as well as SFF and SFs. Further, as all relevant network segments as well as SFF and SFs. Further, as
described in [section 8.1], operators can and should use indirect described in Section 8.1, operators can and should use indirect
identification for personally identifying information, thus identification for personally identifying information, thus
significantly mitigating the risk of privacy violation. significantly mitigating the risk of privacy violation. Means to
prevent leaking privacy-related information outside an administrative
domain are natively supported by NSH given that the last SFF of a
path will systematically remove the NSH header before forwarding a
packet upstream.
Lastly, SF security, although out of scope of this document, should Lastly, SF security, although out of scope of this document, should
be considered, particularly if an SF needs to access, authenticate or be considered, particularly if an SF needs to access, authenticate or
update NSH metadata. update NSH metadata.
10. Contributors 9. Contributors
This WG document originated as draft-quinn-sfc-nsh and had the This WG document originated as draft-quinn-sfc-nsh and had the
following co-authors and contributors. The editors of this document following co-authors and contributors. The editors of this document
would like to thank and recognize them and their contributions. would like to thank and recognize them and their contributions.
These co-authors and contributors provided invaluable concepts and These co-authors and contributors provided invaluable concepts and
content for this document's creation. content for this document's creation.
Surendra Kumar Surendra Kumar
Cisco Systems Cisco Systems
smkumar@cisco.com smkumar@cisco.com
Michael Smith Michael Smith
Cisco Systems Cisco Systems
michsmit@cisco.com michsmit@cisco.com
Jim Guichard Jim Guichard
Huawei Huawei
james.n.guichard@huawei.com james.n.guichard@huawei.com
Carlos Pignataro
Cisco Systems
cpignata@cisco.com
Rex Fernando Rex Fernando
Cisco Systems Cisco Systems
Email: rex@cisco.com Email: rex@cisco.com
Navindra Yadav Navindra Yadav
Cisco Systems Cisco Systems
Email: nyadav@cisco.com Email: nyadav@cisco.com
Wim Henderickx Wim Henderickx
Alcatel-Lucent Alcatel-Lucent
skipping to change at page 31, line 5 skipping to change at page 26, line 38
louis.fourie@huawei.com louis.fourie@huawei.com
Ron Parker Ron Parker
Affirmed Networks Affirmed Networks
ron_parker@affirmednetworks.com ron_parker@affirmednetworks.com
Myo Zarny Myo Zarny
Goldman Sachs Goldman Sachs
myo.zarny@gs.com myo.zarny@gs.com
11. Acknowledgments 10. Acknowledgments
The authors would like to thank Sunil Vallamkonda, Nagaraj Bagepalli, The authors would like to thank Sunil Vallamkonda, Nagaraj Bagepalli,
Abhijit Patra, Peter Bosch, Darrel Lewis, Pritesh Kothari, Tal Abhijit Patra, Peter Bosch, Darrel Lewis, Pritesh Kothari, Tal
Mizrahi and Ken Gray for their detailed review, comments and Mizrahi and Ken Gray for their detailed review, comments and
contributions. contributions.
A special thank you goes to David Ward and Tom Edsall for their A special thank you goes to David Ward and Tom Edsall for their
guidance and feedback. guidance and feedback.
Additionally the authors would like to thank Larry Kreeger for his Additionally the authors would like to thank Larry Kreeger for his
invaluable ideas and contributions which are reflected throughout invaluable ideas and contributions which are reflected throughout
this document. this document.
Loa Andersson provided a thorough review and valuable comments, we Loa Andersson provided a thorough review and valuable comments, we
thank him for that. thank him for that.
Reinaldo Penno deserves a particular thank you for his architecture Reinaldo Penno deserves a particular thank you for his architecture
and implementation work that helped guide the protocol concepts and and implementation work that helped guide the protocol concepts and
design. design.
The editors also acknowledge a comprehensive review and respective
suggestions by Med Boucadair.
Lastly, David Dolson has provides significant review, feedback and Lastly, David Dolson has provides significant review, feedback and
suggestions throughout the evolution of this document. His suggestions throughout the evolution of this document. His
contributions are very much appreciated. contributions are very much appreciated.
12. IANA Considerations 11. IANA Considerations
12.1. NSH EtherType 11.1. NSH EtherType
An IEEE EtherType, 0x894F, has been allocated for NSH. An IEEE EtherType, 0x894F, has been allocated for NSH.
12.2. Network Service Header (NSH) Parameters 11.2. Network Service Header (NSH) Parameters
IANA is requested to create a new "Network Service Header (NSH) IANA is requested to create a new "Network Service Header (NSH)
Parameters" registry. The following sub-sections request new Parameters" registry. The following sub-sections request new
registries within the "Network Service Header (NSH) Parameters " registries within the "Network Service Header (NSH) Parameters "
registry. registry.
12.2.1. NSH Base Header Reserved Bits 11.2.1. NSH Base Header Reserved Bits
There are five reserved bits in the NSH Base Header. New bits are There are five reserved bits in the NSH Base Header. New bits are
assigned via Standards Action [RFC5226]. assigned via Standards Action [RFC8126].
Bit 3 - Reserved Bit 3 - Reserved
Bits 16-19 - Reserved Bits 16-19 - Reserved
12.2.2. NSH Version 11.2.2. NSH Version
IANA is requested to setup a registry of "NSH Version". New values IANA is requested to setup a registry of "NSH Version". New values
are assigned via Standards Action [RFC5226]. are assigned via Standards Action [RFC8126].
Version 00: This protocol version. This document. Version 00: This protocol version. This document.
Version 01: Reserved. This document. Version 01: Reserved. This document.
Version 10: Unassigned. Version 10: Unassigned.
Version 11: Unassigned. Version 11: Unassigned.
12.2.3. MD Type Registry 11.2.3. MD Type Registry
IANA is requested to set up a registry of "MD Types". These are IANA is requested to set up a registry of "MD Types". These are
4-bit values. MD Type values 0, 1, 2, 15, and 16 are specified in 4-bit values. MD Type values 0, 1, 2, and 15 are specified in this
this document. Registry entries are assigned by using the "IETF document, see Table 5. Registry entries are assigned by using the
Review" policy defined in RFC 5226 [RFC5226]. "IETF Review" policy defined in RFC 8126 [RFC8126].
+---------+--------------+---------------+ +---------+-----------------+---------------+
| MD Type | Description | Reference | | MD Type | Description | Reference |
+---------+--------------+---------------+ +---------+-----------------+---------------+
| 0 | Reserved | This document | | 0 | Reserved | This document |
| | | | | | | |
| 1 | NSH | This document | | 1 | NSH MD Type 1 | This document |
| | | | | | | |
| 2 | NSH | This document | | 2 | NSH MD Type 2 | This document |
| | | | | | | |
| 3..14 | Unassigned | | | 3..14 | Unassigned | |
| | | | | | | |
| 15 | Experiment 1 | This document | | 15 | Experimentation | This document |
| | | | +---------+-----------------+---------------+
| 16 | Experiment 2 | This document |
+---------+--------------+---------------+
Table 1 Table 5: MD Type Values
12.2.4. MD Class Registry 11.2.4. MD Class Registry
IANA is requested to set up a registry of "MD Class". These are 16- IANA is requested to set up a registry of "MD Class". These are 16-
bit values. New allocations are to be made according to the bit values. New allocations are to be made according to the
following policies: following policies:
0x0000 to 0x01ff: IETF Review 0x0000 to 0x01ff: IETF Review
0x0200 to 0xfff5: Expert Review 0x0200 to 0xfff5: Expert Review
0xfff6 to 0xfffe: Experimental 0xfff6 to 0xfffe: Experimental
0xffff: Reserved 0xffff: Reserved
IANA is requested to assign the following value: IANA is requested to assign the values as per Table 6::
MD Class | Meaning | Reference +-----------+-----------------------------+------------+
---------+----------------------------+----------- | MD Class | Meaning | Reference |
0x0000 | IETF Base NSH MD Class | [This.I-D] +-----------+-----------------------------+------------+
| 0x0000 | IETF Base NSH MD Class | This.I-D |
+-----------+-----------------------------+------------+
Table 6: MD Class Value
Designated Experts evaluating new allocation requests from the Designated Experts evaluating new allocation requests from the
"Expert Review" range should principally consider whether a new MD "Expert Review" range should principally consider whether a new MD
class is needed compared to adding MD types to an existing class. class is needed compared to adding MD types to an existing class.
The Designated Experts should also encourage the existence of an The Designated Experts should also encourage the existence of an
associated and publicly visible registry of MD types although this associated and publicly visible registry of MD types although this
registry need not be maintained by IANA. registry need not be maintained by IANA.
12.2.5. NSH Base Header Next Protocol 11.2.5. NSH Base Header Next Protocol
IANA is requested to set up a registry of "Next Protocol". These are IANA is requested to set up a registry of "Next Protocol". These are
8-bit values. Next Protocol values 0, 1, 2, 3, 4 and 5 are defined 8-bit values. Next Protocol values 0, 1, 2, 3, 4 and 5 are defined
in this draft. New values are assigned via "Expert Reviews" as per in this document (see Table 7. New values are assigned via "Expert
[RFC5226]. Reviews" as per [RFC8126].
+---------------+--------------+---------------+ +---------------+--------------+---------------+
| Next Protocol | Description | Reference | | Next Protocol | Description | Reference |
+---------------+--------------+---------------+ +---------------+--------------+---------------+
| 0 | Reserved | This document | | 0 | Reserved | This document |
| | | | | | | |
| 1 | IPv4 | This document | | 1 | IPv4 | This document |
| | | | | | | |
| 2 | IPv6 | This document | | 2 | IPv6 | This document |
| | | | | | | |
skipping to change at page 34, line 29 skipping to change at page 29, line 36
| | | | | | | |
| 5 | MPLS | This document | | 5 | MPLS | This document |
| | | | | | | |
| 6..253 | Unassigned | | | 6..253 | Unassigned | |
| | | | | | | |
| 254 | Experiment 1 | This document | | 254 | Experiment 1 | This document |
| | | | | | | |
| 255 | Experiment 2 | This document | | 255 | Experiment 2 | This document |
+---------------+--------------+---------------+ +---------------+--------------+---------------+
Table 2 Table 7: NSH Base Header Next Protocol Values
12.2.6. New IETF assigned MD Type Registry 11.2.6. New IETF assigned MD Type Registry
This document requests IANA to create a registry for the type values This document requests IANA to create a registry for the type values
owned by the IETF (i.e., MD Class set to 0x0000) called the "IETF owned by the IETF (i.e., MD Class set to 0x0000) called the "IETF
Assigned MD Type Registry." Assigned MD Type Registry."
The type values are assigned via Standards Action [RFC5226]. The type values are assigned via Standards Action [RFC8126].
No initial values are assigned at the creation of the registry. No initial values are assigned at the creation of the registry.
13. References 12. References
13.1. Normative References 12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/ Chaining (SFC) Architecture", RFC 7665,
RFC7665, October 2015, DOI 10.17487/RFC7665, October 2015,
<http://www.rfc-editor.org/info/rfc7665>. <http://www.rfc-editor.org/info/rfc7665>.
13.2. Informative References [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<http://www.rfc-editor.org/info/rfc8126>.
12.2. Informative References
[BCP38] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827,
May 2000, <http://www.rfc-editor.org/info/rfc2827>.
[I-D.guichard-sfc-nsh-dc-allocation]
Guichard, J., Smith, M., Surendra, S., Majee, S., Agarwal,
P., Glavin, K., and Y. Laribi, "Network Service Header
(NSH) Context Header Allocation (Data Center)", draft-
guichard-sfc-nsh-dc-allocation-05 (work in progress),
August 2016.
[I-D.ietf-nvo3-vxlan-gpe]
Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol
Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-04 (work
in progress), April 2017.
[I-D.ietf-rtgwg-dt-encap]
Nordmark, E., Tian, A., Gross, J., Hudson, J., Kreeger,
L., Garg, P., Thaler, P., and T. Herbert, "Encapsulation
Considerations", draft-ietf-rtgwg-dt-encap-02 (work in
progress), October 2016.
[I-D.ietf-sfc-control-plane]
Boucadair, M., "Service Function Chaining (SFC) Control
Plane Components & Requirements", draft-ietf-sfc-control-
plane-08 (work in progress), October 2016.
[I-D.ietf-sfc-oam-framework]
Aldrin, S., Pignataro, C., Kumar, N., Akiya, N., Krishnan,
R., and A. Ghanwani, "Service Function Chaining Operation,
Administration and Maintenance Framework", draft-ietf-sfc-
oam-framework-02 (work in progress), July 2017.
[I-D.napper-sfc-nsh-broadband-allocation]
Napper, J., Kumar, S., Muley, P., Henderickx, W., and M.
Boucadair, "NSH Context Header Allocation -- Broadband",
draft-napper-sfc-nsh-broadband-allocation-02 (work in
progress), January 2017.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000, DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>. <http://www.rfc-editor.org/info/rfc2784>.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering: [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Defeating Denial of Service Attacks which employ IP Source Considered Useful", BCP 82, RFC 3692,
Address Spoofing", BCP 38, RFC 2827, DOI 10.17487/RFC2827, DOI 10.17487/RFC3692, January 2004,
May 2000, <http://www.rfc-editor.org/info/rfc2827>. <http://www.rfc-editor.org/info/rfc3692>.
[RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and [RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", RFC 6071, Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
DOI 10.17487/RFC6071, February 2011, DOI 10.17487/RFC6071, February 2011,
<http://www.rfc-editor.org/info/rfc6071>. <http://www.rfc-editor.org/info/rfc6071>.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A., [RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325, Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <http://www.rfc-editor.org/info/rfc7325>. August 2014, <http://www.rfc-editor.org/info/rfc7325>.
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498, DOI 10.17487/ Service Function Chaining", RFC 7498,
RFC7498, April 2015, DOI 10.17487/RFC7498, April 2015,
<http://www.rfc-editor.org/info/rfc7498>. <http://www.rfc-editor.org/info/rfc7498>.
[SFC-CP] Boucadair, M., "Service Function Chaining (SFC) Control
Plane Components & Requirements", 2016, <https://
datatracker.ietf.org/doc/draft-ietf-sfc-control-plane/>.
[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/>.
[bcp38] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", 2000,
<https://tools.ietf.org/html/bcp38>.
[broadalloc]
Napper, J., Kumar, S., Muley, P., and W. Hendericks, "NSH
Context Header Allocation -- Mobility", 2016, <https://
datatracker.ietf.org/doc/
draft-napper-sfc-nsh-broadband-allocation/>.
[dcalloc] Guichard, J., Smith, M., and et al., "Network Service
Header (NSH) Context Header Allocation (Data Center)",
2016, <https://datatracker.ietf.org/doc/
draft-guichard-sfc-nsh-dc-allocation/>.
[encap-considerations]
Nordmark, E., Tian, A., Gross, J., Hudson, J., Kreeger,
L., Garg, P., Thaler, P., and T. Herbert, "Encapsulation
Considerations", <https://datatracker.ietf.org/doc/
draft-ietf-rtgwg-dt-encap/>.
[nsh-env-req]
Migault, D., Pignataro, C., Reddy, T., and C. Inacio, "SFC
environment Security requirements", 2016, <https://
www.ietf.org/id/
draft-mglt-sfc-security-environment-req-02.txt>.
[oam-frame]
Aldrin, S., Krishnan, R., Akiya, N., Pignataro, C., and A.
Ghanwani, "Service Function Chaining Operation,
Administration and Maintenance Framework", 2016, <https://
tools.ietf.org/html/draft-ietf-sfc-oam-framework-01/>.
Authors' Addresses Authors' Addresses
Paul Quinn (editor) Paul Quinn (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
Email: paulq@cisco.com Email: paulq@cisco.com
Uri Elzur (editor) Uri Elzur (editor)
Intel Intel
Email: uri.elzur@intel.com Email: uri.elzur@intel.com
Carlos Pignataro (editor)
Cisco Systems, Inc.
Email: cpignata@cisco.com
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