draft-ietf-sfc-nsh-12.txt   draft-ietf-sfc-nsh-13.txt 
Service Function Chaining P. Quinn, Ed. Service Function Chaining P. Quinn, Ed.
Internet-Draft Cisco Systems, Inc. Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track U. Elzur, Ed. Intended status: Standards Track U. Elzur, Ed.
Expires: August 27, 2017 Intel Expires: January 1, 2018 Intel
February 23, 2017 June 30, 2017
Network Service Header Network Service Header
draft-ietf-sfc-nsh-12.txt draft-ietf-sfc-nsh-13.txt
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 path. 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 1. Requirements Language
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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 August 27, 2017. This Internet-Draft will expire on January 1, 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.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 28
11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 31
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32
12.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . . 32 12.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . . 32
12.2. Network Service Header (NSH) Parameters . . . . . . . . . 32 12.2. Network Service Header (NSH) Parameters . . . . . . . . . 32
12.2.1. NSH Base Header Reserved Bits . . . . . . . . . . . . 32 12.2.1. NSH Base Header Reserved Bits . . . . . . . . . . . . 32
12.2.2. NSH Version . . . . . . . . . . . . . . . . . . . . . 32 12.2.2. NSH Version . . . . . . . . . . . . . . . . . . . . . 32
12.2.3. MD Type Registry . . . . . . . . . . . . . . . . . . . 32 12.2.3. MD Type Registry . . . . . . . . . . . . . . . . . . . 32
12.2.4. MD Class Registry . . . . . . . . . . . . . . . . . . 33 12.2.4. MD Class Registry . . . . . . . . . . . . . . . . . . 33
12.2.5. NSH Base Header Next Protocol . . . . . . . . . . . . 33 12.2.5. NSH Base Header Next Protocol . . . . . . . . . . . . 33
12.2.6. New IETF assigned MD Type Registry . . . . . . . . . . 34
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 35
13.1. Normative References . . . . . . . . . . . . . . . . . . . 35 13.1. Normative References . . . . . . . . . . . . . . . . . . . 35
13.2. Informative References . . . . . . . . . . . . . . . . . . 35 13.2. Informative References . . . . . . . . . . . . . . . . . . 35
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 37
2. Introduction 2. 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
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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 NSH defines a new service plane protocol specifically for the
creation of dynamic service chains and is composed of the following creation of dynamic service chains and is composed of the following
elements: elements:
1. Service Function Path identification 1. Service Function Path identification
2. Transport independent service function chain 2. Indication of location within a Service Function Path.
3. Per-packet network and service metadata or optional variable 3. Optional, per packet metadata (fixed length or variable).
type-length-value (TLV) metadata.
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.
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SFC Proxy: Defined in [RFC7665]. SFC Proxy: Defined in [RFC7665].
2.2. Problem Space 2.2. Problem Space
Network Service Header (NSH) addresses several limitations associated Network Service Header (NSH) addresses several limitations associated
with service function deployments. [RFC7498] provides a with service function deployments. [RFC7498] provides a
comprehensive review of those issues. comprehensive review of those issues.
2.3. NSH-based Service Chaining 2.3. NSH-based Service Chaining
The 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].
NSH contains path identification information needed to realize a NSH contains path identification information needed to realize a
service path. Furthermore, NSH provides the ability to monitor service path. Furthermore, NSH provides the ability to monitor
and troubleshoot a service chain, end-to-end via service-specific and troubleshoot a service chain, end-to-end via service-specific
OAM messages. The NSH fields can be used by administrators (via, OAM messages. NSH fields can be used by administrators (via, for
for example, a traffic analyzer) to verify (account, ensure example, a traffic analyzer) to verify (account, ensure correct
correct chaining, provide reports, etc.) the path specifics of chaining, provide reports, etc.) the path specifics of packets
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 [SFC-CP] provides an example of such in section 3.3. Examples of
metadata include classification information used for policy metadata include classification information used for policy
enforcement and network context for forwarding post service enforcement and network context for forwarding post service
delivery. delivery. Sharing the metadata allows service functions to share
initial and intermediate classification results with downstream
4. Classification and re-classification: sharing the metadata allows service functions saving re-classification, where enough
service functions to share initial and intermediate information was enclosed.
classification results with downstream service functions saving
re-classification, where enough information was enclosed.
5. NSH offers a common and standards-based header for service 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.
6. 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 3. Network Service Header
A Network Service Header (NSH) contains service path information and A Network Service Header (NSH) contains service path information and
optionally metadata that are added to a packet or frame and used to optionally metadata that are added to a packet or frame and used to
create a service plane. An outer transport header is imposed, on NSH create a service plane. An outer transport header is imposed, on NSH
and the original packet/frame, for network forwarding. and the original packet/frame, for network forwarding.
A Service Classifier adds the NSH. The NSH is removed by the last A Service Classifier adds NSH. NSH is removed by the last SFF in the
SFF in the service chain or by a SF that consumes the packet. service chain or by a SF that consumes the packet.
3.1. Network Service Header Format 3.1. Network Service Header Format
An NSH is composed of a 4-byte (all references to bytes in this draft NSH is composed of a 4-byte (all references to bytes in this document
refer to 8-bit bytes, or octets) Base Header, a 4-byte Service Path refer to 8-bit bytes, or octets) Base Header, a 4-byte Service Path
Header and 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 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 Headers ~ ~ 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: provide path identification and location within
a service path. a service path.
Context headers: carry metadata (i.e. context data) along a service Context header: carry metadata (i.e. context data) along a service
path. path.
3.2. NSH Base Header 3.2. NSH Base Header
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|C|R|R|R|R|R|R| Length | MD Type | Next Protocol | |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 updates. It MUST be set to 0x0 by the
sender, in this first revision of NSH. Given the widespread sender, in this first revision of NSH. Given the widespread
implementation of existing hardware that uses the first nibble after implementation of existing hardware that uses the first nibble after
an MPLS label stack for ECMP decision processing, this document an MPLS label stack for ECMP decision processing, this document
reserves version 01 and this value MUST NOT be used in future reserves version 01 and this value MUST NOT be used in future
versions of the protocol. Please see [RFC7325] for further 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 packet format and processing of
SFC OAM messages is outside the scope of this specification (see [I- SFC OAM messages is outside the scope of this specification (see
D.ietf-sfc-oam-framework]). [oam-frame]).
SF/SFF/SFC Proxy/Classifer implementations, which do not support SFC
OAM procedures, SHALL discard packets with O-bit set.
SF/SFF/SFC Proxy/Classifer implementations MAY support a configurable SF/SFF/SFC Proxy/Classifer implementations that do not support SFC
parameter to enable forwarding received SFC OAM packets unmodified to OAM procedures SHOULD discard packets with O-bit set, but MAY support
the next element in the chain. Such behavior may be acceptable for a a configurable parameter to enable forwarding received SFC OAM
subset of OAM functions, but can result in unexpected outcomes for packets unmodified to the next element in the chain. Forwarding OAM
others, thus it is recommended to analyze the impact of forwarding an packets unmodified by SFC elements that do not support SFC OAM
OAM packet for all OAM functions prior to enabling this behavior. procedures may be acceptable for a subset of OAM functions, but can
The configurable parameter MUST be disabled by default. result in unexpected outcomes for others, thus it is recommended to
analyze the impact of forwarding an OAM packet for all OAM functions
prior to enabling this behavior. The configurable parameter MUST be
disabled by default.
For non OAM packets, the O-bit MUST be cleared and MUST NOT be The O-bit MUST be set for OAM packets and MUST NOT be set for non-OAM
modified along the SFP. packets. The O-bit MUST NOT be modified along the SFP.
C bit: Indicates that a critical metadata TLV is present. This bit TTL: Indicates the maximum SFF hops for an SFP. The initial TTL
acts as an indication for hardware implementers to decide how to value SHOULD be configurable via the control plane; the configured
handle the presence of a critical TLV without necessarily needing to initial value can be specific to one or more SFPs. If no initial
parse all TLVs present. For an MD Type of 0x1 (i.e. no variable value is explicitly provided, the default initial TTL value 63 MUST
length metadata is present), the C bit MUST be set to 0x0. be used. Each SFF involved in forwarding an NSH packet MUST
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
value of 63. The packet MUST NOT be forwarded if TTL is, after
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 when sent and MUST be ignored upon receipt. MUST be set to zero upon origination and MUST be preserved unmodified
by other NSH supporting elements. Elements which do not understand
the meaning of any of these bits MUST not modify their actions based
on those unknown bits.
Length: total length, in 4-byte words, of NSH including the Base Length: The total length, in 4-byte words, of the NSH including the
Header, the Service Path Header and the context headers or optional Base Header, the Service Path Header, the Fixed Length Context Header
variable length metadata. The Length MUST be of value 0x6 for MD or Variable Length Context Header(s). The length MUST be of value
Type equal to 0x1 and MUST be of value 0x2 or greater for MD Type 0x6 for MD Type equal to 0x1, and MUST be of value 0x2 or greater for
equal to 0x2. The NSH header length MUST be an integer number of 4 MD Type equal to 0x2. The length of the NSH header MUST be an
bytes. The length field indicates the "end" of NSH and where the integer multiple of 4 bytes, thus variable length metadata is always
original packet/frame begins. padded 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 IANA Considerations section
below. below.
NSH defines two MD types: This document defines two MD Type values:
0x1 - which indicates that the format of the header includes fixed 0x1 - which indicates that the format of the header includes a fixed
length context headers (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
information. Header(s). The semantics of the variable length Context Header(s)
are not defined in this document
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 SHOULD support MD NSH implementations MUST support MD type = 0x1 and MD Type 0x2 (where
Type = 0x2. There exists, however, a middle ground, wherein a device the length is of value 0x2). NSH implementations SHOULD support MD
will support MD Type 0x1 (as per the MUST) metadata, yet be deployed Type 0x2 with length > 0x2. There exists, however, a middle ground,
in a network with MD Type 0x2 metadata packets. In that case, the MD wherein a device will support MD Type 0x1 (as per the MUST) metadata,
Type 0x1 node, MUST utilize the base header length field to determine yet be deployed in a network with MD Type 0x2 metadata packets. In
the original payload offset if it requires access to the original that case, the MD Type 0x1 node, MUST utilize the base header length
packet/frame. field to determine the original payload offset 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 IANA Considerations section below.
This draft defines the following Next Protocol values: This document defines the following Next Protocol values:
0x1 : IPv4 0x1: IPv4
0x2 : IPv6 0x2: IPv6
0x3 : Ethernet 0x3: Ethernet
0x4: NSH 0x4: NSH
0x5: MPLS 0x5: MPLS
0x6-0xFD: Unassigned
0xFE-0xFF: Experimental
3.3. Service Path Header 3.3. Service Path Header
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 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
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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 Service Functions or by SFC Service Index MUST be decremented by a value of 1 by Service
Proxy nodes after performing required services and the new Functions or by SFC Proxy nodes after performing required services
decremented SI value MUST be used in the egress NSH packet. The and the new decremented SI value MUST be used in the egress NSH
initial Classifier MUST send the packet to the first SFF in the packet. The initial Classifier MUST send the packet to the first SFF
identified SFP for forwarding along an SFP. If re-classification in the identified SFP for forwarding along an SFP. If re-
occurs, and that re-classification results in a new SPI, the classification occurs, and that re-classification results in a new
(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 SHOULD be used in conjunction with Service Path Identifier for SI is used in conjunction with Service Path Identifier for Service
Service Function Path Selection and for determining the next SFF/SF Function Path Selection and for determining the next SFF/SF in the
in the path. Service Index (SI) is also valuable when path. Service Index (SI) is also valuable when troubleshooting/
troubleshooting/ reporting service paths. In addition to indicating reporting service paths. In addition to indicating the location
the location within a Service Function Path, SI can be used for within a Service Function Path, SI can be used for service plane loop
service plane loop detection. detection.
3.4. NSH MD Type 1 3.4. NSH MD Type 1
When the Base Header specifies MD Type = 0x1, four Context Headers, When the Base Header specifies MD Type = 0x1, a Fixed Length Context
4-byte each, MUST be added immediately following the Service Path Header (16-bytes) MUST be present immediately following the Service
Header, as per Figure 4. Context Headers that carry no metadata MUST Path Header, as per Figure 4. A Fixed Length Context Header that
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 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|C|R|R|R|R|R|R| Length | MD type=0x1 | Next Protocol | |Ver|O|R| TTL | Length |R|R|R|R|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifer | Service Index | | Service Path Identifer | 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 assumption about the content This specification does not make any assumptions about the content of
placed in the mandatory context field of the NSH header, and does not the 16 byte Context Header that must be present when the MD Type
describe the structure or meaning of the included metadata. field is set to 1, and does not describe the structure or meaning of
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.
Upon receiving an NSH MD-type 1 packet, if the SFC-aware SF is An SF or SFC Proxy that does not know the format or semantics of the
configured for mandatory use of metadata but does not yet receive the Context Header for an NSH with MD Type 1 MUST discard any packet with
data semantics for the mandatory context field, it MUST NOT process such an NSH (i.e., MUST NOT ignore the metadata that it cannot
the packet and MUST log at least once per the SPI for which a process), and MUST log the event at least once per the SPI for which
mandatory metadata is missing. the event occurs (subject to thresholding).
[dcalloc] and [broadalloc] provide specific examples of how metadata [dcalloc] and [broadalloc] provide specific examples of how metadata
can be allocated. can be allocated.
3.5. NSH MD Type 2 3.5. 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. Therefore, Length = 0x2, indicates that only
the Base Header followed by the Service Path Header are present. The the Base Header followed by the Service Path Header are present. The
optional Variable Length Context Headers MUST be of an integer number optional Variable Length Context Headers MUST be of an integer number
of 4-bytes. The base header length field MUST be used to determine of 4-bytes. The base header Length field MUST be used to determine
the offset to locate the original packet or frame for SFC nodes that the offset to locate the original packet or frame for SFC nodes that
require access to that information. 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 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|C|R|R|R|R|R|R| Length | MD Type=0x2 | Next Protocol | |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 3.5.1. 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. described below.
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 |C| 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): The MD Class defines the scope of the
'Type' field to provide a hierarchical namespace. The IANA 'Type' field to provide a hierarchical namespace. The IANA
Considerations section defines how the MD Class values can be Considerations section defines how the MD Class values can be
allocated to standards bodies, vendors, and others. allocated to standards bodies, vendors, and others.
Type: the Type field is split into two ranges - 0 to 127 for non- Type: indicates the explicit type of metadata being carried and is
critical options and 128-255 for critical options. While the value the responsibility of the MD Class owner.
allocation is the responsibility of the MD Class owner, critical
options MUST NOT be allocated from the 0 to 127 range and non-
critical options MUST NOT be allocated from the 128-255 range.
Figure 7 below illustrates the placement of the Critical bit within
the Type field.
+-+-+-+-+-+-+-+-+
|C| Type |
+-+-+-+-+-+-+-+-+
Figure 7: Critical Bit Placement Within the TLV Type Field
If an NSH-aware node receives an encapsulated packet containing a TLV
with the Critical bit set to 0x1 in the Type field and it does not
understand how to process the Type, it MUST drop the packet. Transit
devices (i.e. network nodes that do not participate in the service
plane) MUST NOT drop packets based on the setting of this bit.
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: Length of the variable metadata, in single byte words. In
case the metadata length is not an integer number of 4-byte words, case the metadata length is not an integer number of 4-byte words,
the sender MUST add pad bytes immediately following the last metadata the sender MUST add pad bytes immediately following the last metadata
byte to extend the metadata to an integer number of 4-byte words. byte to extend the metadata to an integer number of 4-byte words.
The receiver MUST round up the length field to the nearest 4-byte The receiver MUST round up the length field to the nearest 4-byte
word boundary, to locate and process the next field in the packet. word boundary, to locate and process the next field in the packet.
The receiver MUST access only those bytes in the metadata indicated The receiver MUST access only those bytes in the metadata indicated
by the length field (i.e. actual number of single byte words) and by the length field (i.e. actual number of single byte words) and
MUST ignore the remaining bytes up to the nearest 4-byte word MUST ignore the remaining bytes up to the nearest 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 TLV 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 TLVs that are This specification does not make any assumption about Context Headers
mandatory-to-implement or those that are mandatory-to-process. These that are mandatory-to-implement or those that are mandatory-to-
considerations are deployment-specific. However, the control plane process. These considerations are deployment-specific. However, the
is entitled to instruct SFC-aware SFs with the data structure of TLVs control plane is entitled to instruct SFC-aware SFs with the data
together with their scoping (see Section 3.3.3 of [SFC-CP]). structure of context header together with their scoping (see Section
3.3.3 of [SFC-CP]).
If multiple mandatory-to-process TLVs are required for a given SFP, Upon receipt of a packet that belong to a given SFP, if a mandatory-
the control plane MAY instruct the SFC-aware SF with the order to to-process context header is missing in that packet, the SFC-aware SF
consume these TLVs. If no instructions are provided, the SFC-aware MUST NOT process the packet and MUST log at least once per the SPI
SF MUST process these TLVs in the order their appear in the NSH for which a mandatory metadata is missing.
packet.
If multiple instances of the same TLV are included in an NSH packet, If multiple mandatory-to-process context headers are required for a
but the definition of that TLV does not allow for it, the SFC-aware given SFP, the control plane MAY instruct the SFC-aware SF with the
SF MUST NOT process the packet and MUST log at least once per the SPI order to consume these Context Headers. If no instructions are
for which multiple instances of that TLV is supplied. provided, the SFC-aware SF MUST process these Context Headers in the
order their appear in an NSH packet.
If multiple instances of the same metadata are included in an NSH
packet, but the definition of that context header does not allow for
it, the SFC-aware SF MUST process first instance and ignore
subsequent instances.
4. NSH Actions 4. NSH Actions
NSH-aware nodes are the only nodes that MAY alter the content of the NSH-aware nodes are the only nodes that may alter the content of NSH
NSH headers. NSH-aware nodes include: service classifiers, SFF, SF headers. NSH-aware nodes include: service classifiers, SFF, SF and
and SFC proxies. These nodes have several possible header related SFC proxies. These nodes have several possible header 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, a SFF, MUST be
the last node operating on the service header and MUST remove it. the last node operating on the service header and MUST remove NSH
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 a new Service Function Path. When classification MAY result in the selection a different Service
the logical classifier performs re-classification that results in Function Path. When the logical classifier performs re-
a change of service path, it MUST remove the existing NSH and classification that results in a change of service path, it MUST
MUST impose a new NSH with the Base Header and Service Path remove the existing NSH and MUST impose a new NSH with the Base
Header reflecting the new service path information and set the Header and Service Path Header reflecting the new service path
initial SI. Metadata MAY be preserved in the new NSH. information and set the initial SI. Metadata MAY be preserved in
the new NSH.
2. Select service path: The Service Path Header provides service 2. Select service path: The Service Path Header provides service
chain information and is used by SFFs to determine correct path information and is used by SFFs to determine correct service
service path selection. SFFs MUST use the Service Path Header path selection. SFFs MUST use the Service Path Header for
for selecting the next SF or SFF in the service path. selecting the next SF or SFF in the service path.
3. Update NSH: NSH-aware service functions (SF) MUST decrement the 3. Update NSH: SFs MUST decrement the service index by one. If an
service index. If an SFF receives a packet with an SPI and SI SFF receives a packet with an SPI and SI that do not correspond
that do not correspond to a valid next hop in a valid Service to a valid next hop in a valid Service Function Path, that packet
Function Path, that packet MUST be dropped by the SFF. MUST be dropped by the SFF.
Classifier(s) MAY update Context Headers if new/updated context Classifiers MAY update Context Headers if new/updated context is
is available. available.
If an SFC proxy is in use (acting on behalf of a non-NSH-aware 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 the NSH receives an NSH-encapsulated packet, it MUST remove NSH before
headers before forwarding it to an NSH unaware SF. When the SFC forwarding it to an NSH unaware SF. When the SFC Proxy receives
Proxy receives a packet back from an NSH unaware SF, it MUST re- a packet back from an NSH unaware SF, it MUST re-encapsulates it
encapsulates it with the correct NSH, and MUST decrement the with the correct NSH, and MUST decrement the Service Index by
Service Index. one.
4. Service policy selection: Service Function instances derive 4. Service policy selection: Service Functions derive policy (i.e.
policy (i.e. service actions such as permit or deny) selection service actions such as permit or deny) selection and enforcement
and enforcement from the service header. Metadata shared in the from NSH. Metadata shared in NSH can provide a range of service-
service header can provide a range of service-relevant relevant information such as traffic classification.
information such as traffic classification. Service functions
SHOULD use NSH to select local service policy.
Figure 8 maps each of the four actions above to the components in the 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 |Select | Update |Service | | | Insert |Forward| Update |Service |
| | or remove NSH |Service| NSH |policy | | | or remove NSH |NSH | NSH |policy |
| | |Function| |selection| | | |Packets| |selection|
| Component +--------+--------+Path +----------------+ | | 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 8: NSH Action and Role Mapping Figure 7: NSH Action and Role Mapping
5. NSH Encapsulation 5. NSH 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
skipping to change at page 18, line 34 skipping to change at page 18, line 34
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 -- path ID to overlay -- creates a true service
plane. That is the SFF/SF topology is constructed without impacting plane. That is the SFF/SF topology is constructed without impacting
the network topology but more importantly service plane only the network topology but more importantly service plane only
participants (i.e. most SFs) need not be part of the network overlay participants (i.e. most SFs) need not be part of the network overlay
topology and its associated infrastructure (e.g. control plane, topology and its associated infrastructure (e.g. control plane,
routing tables, etc.). As mentioned above, an existing overlay routing tables, etc.). SFs need to be able to return a packet to an
topology may be used provided it offers the requisite connectivity. appropriate SFF (i.e. has the requisite NSH information) when service
processing is complete. This can be via the over or underlay and in
some case require additional configuration on the SF. As mentioned
above, an existing overlay topology may be used provided it offers
the requisite connectivity.
The mapping of SPI to transport occurs on an SFF (as discussed above, The 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 9 below given network) and next hop for the requisite SF. Figure 8 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 | 254 | 198.51.100.10 | GRE |
| 10 | 251 | 198.51.100.15 | GRE | | 10 | 251 | 198.51.100.15 | GRE |
| 40 | 251 | 198.51.100.15 | GRE | | 40 | 251 | 198.51.100.15 | GRE |
| 50 | 200 | 01:23:45:67:89:ab | Ethernet | | 50 | 200 | 01:23:45:67:89:ab | Ethernet |
| 15 | 212 | Null (end of path) | None | | 15 | 212 | Null (end of path) | None |
+-------------------------------------------------------+ +-------------------------------------------------------+
Figure 9: SFF NSH Mapping Example Figure 8: 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 10 and 11 below. per figures 9 and 10 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. [VXLAN-gpe] and [RFC2784], respectively.
+----------------------------+ +----------------------------+
| SPI | SI | Next hop(s) | | SPI | SI | Next hop(s) |
+----------------------------+ +----------------------------+
| 10 | 3 | SF2 | | 10 | 3 | SF2 |
| 245 | 12 | SF34 | | 245 | 12 | SF34 |
| 40 | 9 | SF9 | | 40 | 9 | SF9 |
+----------------------------+ +----------------------------+
Figure 10: NSH to SF Mapping Example Figure 9: 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 | | SF34| 198.51.100.34 | UDP |
| SF9 | 2001:db8::1 | GRE | | SF9 | 2001:db8::1 | GRE |
+--------------------------+------------- +--------------------------+-------------
= =
Figure 11: SF Locator Mapping Example Figure 10: 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 12. The metric depicted in Figure 12 is an example to help Figure 11. The metric depicted in Figure 11 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 | | SPI | SI | NH | Metric |
+----------------------------------+ +----------------------------------+
| 10 | 3 | 203.0.113.1 | 1 | | 10 | 3 | 203.0.113.1 | 1 |
| | | 203.0.113.2 | 1 | | | | 203.0.113.2 | 1 |
| | | | | | | | | |
| 20 | 12 | 192.0.2.1 | 1 | | 20 | 12 | 192.0.2.1 | 1 |
| | | 203.0.113.4 | 1 | | | | 203.0.113.4 | 1 |
| | | | | | | | | |
| 30 | 7 | 192.0.2.10 | 10 | | 30 | 7 | 192.0.2.10 | 10 |
| | | 198.51.100.1| 5 | | | | 198.51.100.1| 5 |
+----------------------------------+ +----------------------------------+
(encapsulation type omitted for formatting) (encapsulation type omitted for formatting)
Figure 12: NSH Weighted Service Path Figure 11: NSH Weighted Service Path
7.2. Mapping NSH to Network Transport 7.2. 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
skipping to change at page 21, line 32 skipping to change at page 21, line 32
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 7.3. 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
the NSH information (packet capture, IPFIX, etc.). The information NSH information (packet capture, IPFIX, etc.). The information can
can be used for service scheduling and placement decisions, be used for service scheduling and placement decisions,
troubleshooting and compliance verification. troubleshooting and compliance verification.
7.4. Service Graphs 7.4. 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
skipping to change at page 23, line 17 skipping to change at page 23, line 17
+---^---+ +---|---+ +---|---+ +---^---+ +---|---+ +---|---+
,-|-. ,-|-. ,-|-. ,-|-. ,-|-. ,-|-.
/ \ / \ / \ / \ / \ / \
( 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 13: Metadata and Policy Figure 12: 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 14: External Metadata and Policy Figure 13: 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. considerations are met. Metadata privacy and security considerations
are a matter for the documents that define metadata format.
8.2. Updating/Augmenting Metadata 8.2. 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 15. For example, if the initial metadata, as depicted in Figure 14. 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 the 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 16 illustrates an example of updating metadata. Figure 15 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 15: Metadata Augmentation
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF | | SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+ +--+--+ +--+--+ +--+--+
^ | | ^ | |
,---. ,---. ,---. ,---. ,---. ,---.
/ \ / \ / \ / \ / \ / \
( Class ) ( SF1 ) ( SF2 ) ( Class ) ( SF1 ) ( SF2 )
\ / \ / \ / \ / \ / \ /
`---' `---' `---' `---' `---' `---'
5-tuple: Inspect Deny 5-tuple: Inspect Deny
Tenant A Tenant A attack Tenant A Tenant A attack
--> attack --> attack
Figure 16: Metadata Update Figure 15: Metadata Update
8.3. Service Path Identifier and Metadata 8.3. 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 17 illustrates an example of this described in Section 7.4. Figure 16 illustrates an example of this
behavior. behavior.
+-----+ +-----+ +-----+ +-----+ +-----+ +-----+
| SFF |---------> | SFF |------+---> | SFF | | SFF |---------> | SFF |------+---> | SFF |
+--+--+ +--+--+ | +--+--+ +--+--+ +--+--+ | +--+--+
| | | | | | | |
,---. ,---. | ,---. ,---. ,---. | ,---.
/ \ / SF1 \ | / \ / \ / SF1 \ | / \
( SCL ) ( + ) | ( SF2 ) ( SCL ) ( + ) | ( SF2 )
\ / \SCL2 / | \ / \ / \SCL2 / | \ /
skipping to change at page 26, line 26 skipping to change at page 26, line 26
--> DoS | --> DoS |
V V
,-+-. ,-+-.
/ \ / \
( SF10 ) ( SF10 )
\ / \ /
`---' `---'
DoS DoS
"Scrubber" "Scrubber"
Figure 17: Path ID and Metadata Figure 16: 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 9. 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.
skipping to change at page 28, line 22 skipping to change at page 28, line 22
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
james.n.guichard@huawei.com
Carlos Pignataro
Cisco Systems Cisco Systems
jguichar@cisco.com 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
skipping to change at page 31, line 15 skipping to change at page 31, line 15
11. Acknowledgments 11. 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 Carlos Pignataro and Additionally the authors would like to thank Larry Kreeger for his
Larry Kreeger for their invaluable ideas and contributions which are invaluable ideas and contributions which are reflected throughout
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.
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
skipping to change at page 32, line 20 skipping to change at page 32, line 20
12.2. Network Service Header (NSH) Parameters 12.2. 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 12.2.1. NSH Base Header Reserved Bits
There are ten bits at the beginning of the NSH Base Header. New bits There are five reserved bits in the NSH Base Header. New bits are
are assigned via Standards Action [RFC5226]. assigned via Standards Action [RFC5226].
Bits 0-1 - Version Bit 3 - Reserved
Bit 2 - OAM (O bit) Bits 16-19 - Reserved
Bit 3 - Critical TLV (C bit)
Bits 4-9 - Reserved
12.2.2. NSH Version 12.2.2. 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 [RFC5226].
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 12.2.3. 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
8-bit values. MD Type values 0, 1, 2, 254, and 255 are specified in 4-bit values. MD Type values 0, 1, 2, 15, and 16 are specified in
this document. Registry entries are assigned by using the "IETF this document. Registry entries are assigned by using the "IETF
Review" policy defined in RFC 5226 [RFC5226]. Review" policy defined in RFC 5226 [RFC5226].
+---------+--------------+---------------+ +---------+--------------+---------------+
| MD Type | Description | Reference | | MD Type | Description | Reference |
+---------+--------------+---------------+ +---------+--------------+---------------+
| 0 | Reserved | This document | | 0 | Reserved | This document |
| | | | | | | |
| 1 | NSH | This document | | 1 | NSH | This document |
| | | | | | | |
| 2 | NSH | This document | | 2 | NSH | This document |
| | | | | | | |
| 3..253 | Unassigned | | | 3..14 | Unassigned | |
| | | | | | | |
| 254 | Experiment 1 | This document | | 15 | Experiment 1 | This document |
| | | | | | | |
| 255 | Experiment 2 | This document | | 16 | Experiment 2 | This document |
+---------+--------------+---------------+ +---------+--------------+---------------+
Table 1 Table 1
12.2.4. MD Class Registry 12.2.4. 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. MD Classes defined by this document are assigned as bit values. New allocations are to be made according to the
follows: 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:
MD Class | Meaning | Reference
---------+----------------------------+-----------
0x0000 | IETF Base NSH MD Class | [This.I-D]
Designated Experts evaluating new allocation requests from the
"Expert Review" range should principally consider whether a new MD
class is needed compared to adding MD types to an existing class.
The Designated Experts should also encourage the existence of an
associated and publicly visible registry of MD types although this
registry need not be maintained by IANA.
12.2.5. NSH Base Header Next Protocol 12.2.5. 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 draft. New values are assigned via "Expert Reviews" as per
[RFC5226]. [RFC5226].
+---------------+--------------+---------------+ +---------------+--------------+---------------+
| Next Protocol | Description | Reference | | Next Protocol | Description | Reference |
+---------------+--------------+---------------+ +---------------+--------------+---------------+
skipping to change at page 35, line 5 skipping to change at page 34, line 31
| | | | | | | |
| 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 2
12.2.6. New IETF assigned MD Type Registry
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
Assigned MD Type Registry."
The type values are assigned via Standards Action [RFC5226].
No initial values are assigned at the creation of the registry.
13. References 13. References
13.1. Normative References 13.1. 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, DOI 10.17487/
RFC2119, March 1997, 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 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226, IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008, DOI 10.17487/RFC5226, May 2008,
<http://www.rfc-editor.org/info/rfc5226>. <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, DOI 10.17487/
RFC7665, October 2015, RFC7665, October 2015,
<http://www.rfc-editor.org/info/rfc7665>. <http://www.rfc-editor.org/info/rfc7665>.
13.2. Informative References 13.2. Informative References
skipping to change at page 37, line 5 skipping to change at page 36, line 41
L., Garg, P., Thaler, P., and T. Herbert, "Encapsulation L., Garg, P., Thaler, P., and T. Herbert, "Encapsulation
Considerations", <https://datatracker.ietf.org/doc/ Considerations", <https://datatracker.ietf.org/doc/
draft-ietf-rtgwg-dt-encap/>. draft-ietf-rtgwg-dt-encap/>.
[nsh-env-req] [nsh-env-req]
Migault, D., Pignataro, C., Reddy, T., and C. Inacio, "SFC Migault, D., Pignataro, C., Reddy, T., and C. Inacio, "SFC
environment Security requirements", 2016, <https:// environment Security requirements", 2016, <https://
www.ietf.org/id/ www.ietf.org/id/
draft-mglt-sfc-security-environment-req-02.txt>. 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
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