Service Function Chaining P. Quinn, Ed.
Internet-Draft Cisco
Intended status: Standards Track U. Elzur, Ed.
Expires: February 13, 2018 Intel
C. Pignataro, Ed.
Cisco
August 12, 2017
Network Service Header (NSH)
draft-ietf-sfc-nsh-19
Abstract
This document describes a Network Service Header (NSH) inserted onto
packets or frames to realize service function paths. NSH also
provides a mechanism for metadata exchange along the instantiated
service paths. NSH is the SFC encapsulation required to support the
Service Function Chaining (SFC) architecture (defined in RFC7665).
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on February 13, 2018.
Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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include Simplified BSD License text as described in Section 4.e of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.2. Definition of Terms . . . . . . . . . . . . . . . . . . . 4
1.3. Problem Space . . . . . . . . . . . . . . . . . . . . . . 5
1.4. NSH-based Service Chaining . . . . . . . . . . . . . . . 5
2. Network Service Header . . . . . . . . . . . . . . . . . . . 6
2.1. Network Service Header Format . . . . . . . . . . . . . . 6
2.2. NSH Base Header . . . . . . . . . . . . . . . . . . . . . 7
2.3. Service Path Header . . . . . . . . . . . . . . . . . . . 9
2.4. NSH MD Type 1 . . . . . . . . . . . . . . . . . . . . . . 10
2.5. NSH MD Type 2 . . . . . . . . . . . . . . . . . . . . . . 11
2.5.1. Optional Variable Length Metadata . . . . . . . . . . 12
3. NSH Actions . . . . . . . . . . . . . . . . . . . . . . . . . 13
4. NSH Transport Encapsulation . . . . . . . . . . . . . . . . . 15
5. Fragmentation Considerations . . . . . . . . . . . . . . . . 15
6. Service Path Forwarding with NSH . . . . . . . . . . . . . . 16
6.1. SFFs and Overlay Selection . . . . . . . . . . . . . . . 16
6.2. Mapping NSH to Network Transport . . . . . . . . . . . . 19
6.3. Service Plane Visibility . . . . . . . . . . . . . . . . 20
6.4. Service Graphs . . . . . . . . . . . . . . . . . . . . . 20
7. Policy Enforcement with NSH . . . . . . . . . . . . . . . . . 20
7.1. NSH Metadata and Policy Enforcement . . . . . . . . . . . 20
7.2. Updating/Augmenting Metadata . . . . . . . . . . . . . . 22
7.3. Service Path Identifier and Metadata . . . . . . . . . . 24
8. Security Considerations . . . . . . . . . . . . . . . . . . . 24
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 26
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 28
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 28
11.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . 28
11.2. Network Service Header (NSH) Parameters . . . . . . . . 28
11.2.1. NSH Base Header Bits . . . . . . . . . . . . . . . . 29
11.2.2. NSH Version . . . . . . . . . . . . . . . . . . . . 29
11.2.3. MD Type Registry . . . . . . . . . . . . . . . . . . 29
11.2.4. MD Class Registry . . . . . . . . . . . . . . . . . 29
11.2.5. NSH Base Header Next Protocol . . . . . . . . . . . 30
11.2.6. New IETF Assigned Optional Variable Length Metadata
Type Registry . . . . . . . . . . . . . . . . . . . 31
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 31
12.1. Normative References . . . . . . . . . . . . . . . . . . 31
12.2. Informative References . . . . . . . . . . . . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 33
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1. Introduction
Service functions are widely deployed and essential in many networks.
These service functions provide a range of features such as security,
WAN acceleration, and server load balancing. Service functions may
be instantiated at different points in the network infrastructure
such as the wide area network, data center, campus, and so forth.
Prior to development of the SFC architecture [RFC7665] and the
protocol specified in this document, current service function
deployment models have been relatively static, and bound to topology
for insertion and policy selection. Furthermore, they do not adapt
well to elastic service environments enabled by virtualization.
New data center network and cloud architectures require more flexible
service function deployment models. Additionally, the transition to
virtual platforms demands an agile service insertion model that
supports dynamic and elastic service delivery. Specifically, the
following functions are necessary:
The movement of service functions and application workloads in the
network.
The ability to easily bind service policy to granular information,
such as per-subscriber state.
The capability to steer traffic to the requisite service
function(s).
The Network Service Header (NSH) specification defines a new protocol
for the creation of dynamic service chains, operating at the service
plane. NSH is composed of the following elements:
1. Service Function Path identification.
2. Indication of location within a Service Function Path.
3. Optional, per packet metadata (fixed length or variable).
NSH is designed to be easy to implement across a range of devices,
both physical and virtual, including hardware platforms.
The intended scope of NSH is for use within a single provider's
operational domain. This deployment scope is deliberatedly
constrained, as explained also in [RFC7665], and limited to a single
network administrative domain. In this context, a "domain" is a set
of network entities within a single administration. For example, a
network administrative domain can include a single data center, a
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campus physical network, or an overlay domain using virtual
connetions and tunnels. A corollary is that a network administrative
domain has a well defined perimeter.
An NSH-aware control plane is outside the scope of this document.
[RFC7665] provides an overview of a service chaining architecture
that clearly defines the roles of the various elements and the scope
of a service function chaining encapsulation. NSH is the SFC
encapsulation 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.
Classification: Defined in [RFC7665].
Classifier: Defined in [RFC7665].
Metadata: Defined in [RFC7665].
Network Locator: Dataplane address, typically IPv4 or IPv6, used to
send and receive network traffic.
Network Node/Element: Device that forwards packets or frames based
on an outer header (i.e., encapsulation) information.
Network Overlay: Logical network built on top of existing network
(the underlay). Packets are encapsulated or tunneled to create
the overlay network topology.
NSH-aware: NSH-aware means SFC-encapsulation-aware, with NSH as the
SFC encapsulation. This specification uses NSH-aware as a more
specific term from the more generic term SFC-aware [RFC7665].
Service Classifier: Logical entity providing classification
function. Since they are logical, classifiers may be co-resident
with SFC elements such as SFs or SFFs. Service classifiers
perform classification and impose NSH. The initial classifier
imposes the initial NSH and sends the NSH packet to the first SFF
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in the path. Non-initial (i.e., subsequent) classification can
occur as needed and can alter, or create a new service path.
Service Function (SF): Defined in [RFC7665].
Service Function Chain (SFC): Defined in [RFC7665].
Service Function Forwarder (SFF): Defined in [RFC7665].
Service Function Path (SFP): Defined in [RFC7665].
Service Plane: The collection of SFFs and associated SFs creates a
service-plane overlay in which all SFs reside [RFC7665].
SFC Proxy: Defined in [RFC7665].
1.3. Problem Space
NSH addresses several limitations associated with service function
deployments. [RFC7498] provides a comprehensive review of those
issues.
1.4. NSH-based Service Chaining
NSH creates a dedicated service plane, more specifically, NSH
enables:
1. Topological Independence: Service forwarding occurs within the
service plane, the underlying network topology does not require
modification. NSH provides an identifier used to select the
network overlay for network forwarding.
2. Service Chaining: NSH enables service chaining per [RFC7665].
NSH contains path identification information needed to realize a
service path. Furthermore, NSH provides the ability to monitor
and troubleshoot a service chain, end-to-end via service-specific
OAM messages. NSH fields can be used by administrators (via, for
example, a traffic analyzer) to verify (account, ensure correct
chaining, provide reports, etc.) the path specifics of packets
being forwarded along a service path.
3. NSH provides a mechanism to carry shared metadata between
participating entities and service functions. The semantics of
the shared metadata is communicated via a control plane, which is
outside the scope of this document, to participating nodes.
[I-D.ietf-sfc-control-plane] provides an example of such in
Section 3.3. Examples of metadata include classification
information used for policy enforcement and network context for
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forwarding post service delivery. Sharing the metadata allows
service functions to share initial and intermediate
classification results with downstream service functions saving
re-classification, where enough information was enclosed.
4. NSH offers a common and standards-based header for service
chaining to all network and service nodes.
5. Transport Agnostic: NSH is encapsulation-independent, meaning it
can be transported by a variety of protocols. An appropriate
(for a given deployment) encapsulation protocol can be used to
carry NSH-encapsulated traffic. This transport may form an
overlay network and if an existing overlay topology provides the
required service path connectivity, that existing overlay may be
used.
2. Network Service Header
NSH contains service path information and optionally metadata that
are added to a packet or frame and used to create a service plane.
An outer transport header is imposed, on NSH and the original packet/
frame, for network forwarding.
A Service Classifier adds NSH. NSH is removed by the last SFF in the
service chain or by an SF that consumes the packet.
2.1. Network Service Header Format
NSH is composed of a 4-byte Base Header, a 4-byte Service Path Header
and optional Context Headers, as shown in Figure 1 below.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Base Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Header |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Context Header(s) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Network Service Header
Base header: Provides information about the service header and the
payload protocol.
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Service Path Header: Provides path identification and location within
a service path.
Context header: Carries metadata (i.e., context data) along a service
path.
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|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: NSH Base Header
Base Header Field Descriptions:
Version: The version field is used to ensure backward compatibility
going forward with future NSH specification updates. It MUST be set
to 0x0 by the sender, in this first revision of NSH. Given the
widespread implementation of existing hardware that uses the first
nibble after an MPLS label stack for ECMP decision processing, this
document reserves version 01b and this value MUST NOT be used in
future versions of the protocol. Please see [RFC7325] for further
discussion of MPLS-related forwarding requirements.
O bit: Setting this bit indicates an Operations, Administration, and
Maintenance (OAM) packet. The actual format and processing of SFC
OAM packets is outside the scope of this specification (see for
example [I-D.ietf-sfc-oam-framework] for one approach).
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.
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
packets unmodified to the next element in the chain. Forwarding OAM
packets unmodified by SFC elements that do not support SFC OAM
procedures may be acceptable for a subset of OAM functions, but can
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.
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TTL: Indicates the maximum SFF hops for an SFP. This field is used
for service plane loop detection. The initial TTL value SHOULD be
configurable via the control plane; the configured initial value can
be specific to one or more SFPs. If no initial value is explicitly
provided, the default initial TTL value of 63 MUST 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, marked U, are unassigned and available for
future use, see Section 11.2.1. Unassigned bits MUST be set to zero
upon origination, and MUST be ignored and 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: The total length, in 4-byte words, of NSH including the Base
Header, the Service Path Header, the Fixed Length Context Header or
Variable Length Context Header(s). The length MUST be 0x6 for MD
Type equal to 0x1, and MUST be 0x2 or greater for MD Type equal to
0x2. The length of the NSH header MUST be an integer multiple of 4
bytes, thus variable length metadata is always padded out to a
multiple of 4 bytes.
MD Type: Indicates the format of NSH beyond the mandatory Base Header
and the Service Path Header. MD Type defines the format of the
metadata being carried. Please see the IANA Considerations
Section 11.2.3.
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 - This indicates that the format of the header includes a fixed
length Context Header (see Figure 4 below).
0x2 - This does not mandate any headers beyond the Base Header and
Service Path Header, but may contain optional variable length Context
Header(s). The semantics of the variable length Context Header(s)
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 0xF.
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The format of the Base Header and the Service Path Header is
invariant, and not affected by MD Type.
NSH MD Type 1 and MD Type 2 are described in detail in Sections 2.4
and 2.5, respectively. NSH implementations MUST support MD types 0x1
and 0x2 (where the length is 0x2). NSH implementations SHOULD
support MD Type 0x2 with length greater than 0x2. There exists,
however, a middle ground, wherein a device will support MD Type 0x1
(as per the MUST) metadata, yet be deployed in a network with MD Type
0x2 metadata packets. In that case, the MD Type 0x1 node, MUST
utilize the base header length field to determine the original
payload offset if it requires access to the original packet/frame.
This specification does not disallow the MD Type value from changing
along an SFP; however, the specification of the necessary mechanism
to allow the MD Type to change along an SFP are outside the scope of
this document, and would need to be defined for that functionality to
be available. Packets with MD Type values not supported by an
implementation MUST be silently dropped.
Next Protocol: indicates the protocol type of the encapsulated data.
NSH does not alter the inner payload, and the semantics on the inner
protocol remain unchanged due to NSH service function chaining.
Please see the IANA Considerations section below, Section 11.2.5.
This document defines the following Next Protocol values:
0x1: IPv4
0x2: IPv6
0x3: Ethernet
0x4: NSH
0x5: MPLS
0xFE: Experiment 1
0xFF: Experiment 2
Packets with Next Protocol values not supported SHOULD be silently
dropped by default, although an implementation MAY provide a
configuration parameter to forward them. Additionally, an
implementation not explicitly configured for a specific experiment
[RFC3692] SHOULD silently drop packets with Next Protocol values 0xFE
and 0xFF.
2.3. Service Path Header
Figure 3 shows the format of the Service Path Header:
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier (SPI) | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Service Path Identifier (SPI): 24 bits
Service Index (SI): 8 bits
Figure 3: NSH Service Path Header
The meaning of these fields is as follows:
Service Path Identifier (SPI): Identifies a service path.
Participating nodes MUST use this identifier for Service Function
Path selection. The initial classifier MUST set the appropriate SPI
for a given classification result.
Service Index (SI): Provides location within the SFP. The initial
classifier for a given SFP SHOULD set the SI to 255, however the
control plane MAY configure the initial value of SI as appropriate
(i.e., taking into account the length of the service function path).
The Service Index MUST be decremented by a value of 1 by Service
Functions or by SFC Proxy nodes after performing required services
and the new decremented SI value MUST be used in the egress packet's
NSH. The initial Classifier MUST send the packet to the first SFF in
the identified SFP for forwarding along an SFP. If re-classification
occurs, and that re-classification results in a new SPI, the
(re)classifier is, in effect, the initial classifier for the
resultant SPI.
The SI is used in conjunction the with Service Path Identifier for
Service Function Path Selection and for determining the next SFF/SF
in the path. The SI is also valuable when troubleshooting or
reporting service paths. Additionally, while the TTL field is the
main mechanism for service plane loop detection, the SI can also be
used for detecting service plane loops.
2.4. NSH MD Type 1
When the Base Header specifies MD Type = 0x1, a Fixed Length Context
Header (16-bytes) MUST be present immediately following the Service
Path Header, as per Figure 4. The value of a Fixed Length Context
Header that carries no metadata MUST be set to zero.
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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|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Fixed Length Context Header |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: NSH MD Type=0x1
This specification does not make any assumptions about the content of
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
the included metadata.
An SFC-aware SF MUST receive the data semantics first in order to
process the data placed in the mandatory context field. The data
semantics include both the allocation schema and the meaning of the
included data. How an SFC-aware SF gets the data semantics is
outside the scope of this specification.
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
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
the event occurs (subject to thresholding).
[I-D.guichard-sfc-nsh-dc-allocation] and
[I-D.napper-sfc-nsh-broadband-allocation] provide specific examples
of how metadata can be allocated.
2.5. NSH MD Type 2
When the base header specifies MD Type = 0x2, zero or more Variable
Length Context Headers MAY be added, immediately following the
Service Path Header (see Figure 5). Therefore, Length = 0x2,
indicates that only the Base Header followed by the Service Path
Header are present. The optional Variable Length Context Headers
MUST be of an integer number of 4-bytes. The base header Length
field MUST be used to determine the offset to locate the original
packet or frame for SFC nodes that require access to that
information.
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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|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Variable Length Context Headers (opt.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: NSH MD Type=0x2
2.5.1. Optional Variable Length Metadata
The format of the optional variable length Context Headers, is as
depicted in Figure 6.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Metadata Class | Type |U| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable Metadata |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Variable Context Headers
Metadata Class (MD Class): Defines the scope of the 'Type' field to
provide a hierarchical namespace. The IANA Considerations
Section 11.2.4 defines how the MD Class values can be allocated to
standards bodies, vendors, and others.
Type: Indicates the explicit type of metadata being carried. The
definition of the Type is the responsibility of the MD Class owner.
Unassigned bit: One unassigned bit is available for future use. This
bit MUST NOT be set, and MUST be ignored on receipt.
Length: Indicates the length of the variable metadata, in bytes. In
case the metadata length is not an integer number of 4-byte words,
the sender MUST add pad bytes immediately following the last metadata
byte to extend the metadata to an integer number of 4-byte words.
The receiver MUST round up the length field to the nearest 4-byte
word boundary, to locate and process the next field in the packet.
The receiver MUST access only those bytes in the metadata indicated
by the length field (i.e., actual number of bytes) and MUST ignore
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the remaining bytes up to the nearest 4-byte word boundary. The
Length may be 0 or greater.
A value of 0 denotes a Context Header without a Variable Metadata
field.
This specification does not make any assumption about Context Headers
that are mandatory-to-implement or those that are mandatory-to-
process. These considerations are deployment-specific. However, the
control plane is entitled to instruct SFC-aware SFs with the data
structure of context header together with its scoping (see
Section 3.3.3 of [I-D.ietf-sfc-control-plane]).
Upon receipt of a packet that belongs to a given SFP, if a mandatory-
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
for which the mandatory metadata is missing.
If multiple mandatory-to-process context headers are required for a
given SFP, the control plane MAY instruct the SFC-aware SF with the
order to consume these Context Headers. If no instructions are
provided, the SFC-aware SF MUST process these Context Headers in the
order they 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 the first instance and ignore
subsequent instances.
3. NSH Actions
NSH-aware nodes are the only nodes that may alter the content of NSH
headers. NSH-aware nodes include: service classifiers, SFFs, SFs and
SFC proxies. These nodes have several possible NSH-related actions:
1. Insert or remove NSH: These actions can occur respectively at the
start and end of a service path. Packets are classified, and if
determined to require servicing, NSH will be imposed. A service
classifier MUST insert NSH at the start of an SFP. An imposed
NSH MUST contain both a valid Base Header and Service Path
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
before forwarding or delivering the un-encapsulated packet.
Multiple logical classifiers may exist within a given service
path. Non-initial classifiers may re-classify data and that re-
classification MAY result in the selection of a different Service
Function Path. When the logical classifier performs re-
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classification that results in a change of service path, it MUST
remove the existing NSH and MUST impose a new NSH with the Base
Header and Service Path Header reflecting the new service path
information and MUST set the initial SI. Metadata MAY be
preserved in the new NSH.
2. Select service path: The Service Path Header provides service
path information and is used by SFFs to determine correct service
path selection. SFFs MUST use the Service Path Header for
selecting the next SF or SFF in the service path.
3. Update NSH: SFs MUST decrement the service index by one. If an
SFF receives a packet with an SPI and SI that do not correspond
to a valid next hop in a valid Service Function Path, that packet
MUST be dropped by the SFF.
Classifiers MAY update Context Headers if new/updated context is
available.
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 Index and MAY update contexts. When an SFC proxy
receives an NSH-encapsulated packet, it MUST remove NSH before
forwarding it to an NSH unaware SF. When the SFC Proxy receives
a packet back from an NSH unaware SF, it MUST re-encapsulate it
with the correct NSH, and MUST decrement the Service Index by
one.
4. Service policy selection: Service Functions derive policy (i.e.,
service actions such as permit or deny) selection and enforcement
from NSH. Metadata shared in NSH can provide a range of service-
relevant information such as traffic classification.
Figure 7 maps each of the four actions above to the components in the
SFC architecture that can perform it.
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+----------------+---------------+-------+----------------+---------+
| | Insert |Forward| Update |Service |
| | or remove NSH |NSH | NSH |policy |
| | |Packets| |selection|
| Component +-------+-------+ +----------------+ |
| | | | | Dec. |Update | |
| |Insert |Remove | |Service |Context| |
| | | | | Index |Header | |
+----------------+-------+-------+-------+--------+-------+---------+
| | + | + | | | + | |
|Classifier | | | | | | |
+----------------+-------+-------+-------+--------+-------+---------+
|Service Function| | + | + | | | |
|Forwarder(SFF) | | | | | | |
+----------------+-------+-------+-------+--------+-------+---------+
|Service | | | | + | + | + |
|Function (SF) | | | | | | |
+----------------+-------+-------+-------+--------+-------+---------+
|SFC Proxy | + | + | | + | + | |
+----------------+-------+-------+-------+--------+-------+---------+
Figure 7: NSH Action and Role Mapping
4. NSH Transport Encapsulation
Once NSH is added to a packet, an outer encapsulation is used to
forward the original packet and the associated metadata to the start
of a service chain. The encapsulation serves two purposes:
1. Creates a topologically independent services plane. Packets are
forwarded to the required services without changing the
underlying network topology.
2. Transit network nodes simply forward the encapsulated packets
without modification.
The service header is independent of the encapsulation used and is
encapsulated in existing transports. The presence of NSH is
indicated via protocol type or other indicator in the outer
encapsulation.
5. Fragmentation Considerations
NSH and the associated transport header are "added" to the
encapsulated packet/frame. This additional information increases the
size of the packet.
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As discussed in [I-D.ietf-rtgwg-dt-encap], within an administrative
domain, an operator can ensure that the underlay MTU is sufficient to
carry SFC traffic without requiring fragmentation.
However, there will be cases where the underlay MTU is not large
enough to carry the NSH traffic. Since NSH does not provide
fragmentation support at the service plane, the transport/overlay
layer MUST provide the requisite fragmentation handling. Section 9
of [I-D.ietf-rtgwg-dt-encap] provides guidance for those scenarios.
For example, when NSH is encapsulated in IP, IP-level fragmentation
coupled with Path MTU Discovery (PMTUD) is used. When, on the other
hand, the underlay does not support fragmentation procedures, an
error message SHOULD be logged when dropping a packet too big.
Lastly, NSH-specific fragmentation and reassembly methods may be
defined as well, but these methods are outside the scope of this
document.
6. Service Path Forwarding with NSH
6.1. SFFs and Overlay Selection
As described above, NSH contains a Service Path Identifier (SPI) and
a Service Index (SI). The SPI is, as per its name, an identifier.
The SPI alone cannot be used to forward packets along a service path.
Rather the SPI provides a level of indirection between the service
path/topology and the network transport. Furthermore, there is no
requirement, or expectation of an SPI being bound to a pre-determined
or static network path.
The Service Index provides an indication of location within a service
path. The combination of SPI and SI provides the identification of a
logical SF and its order within the service plane, and is used to
select the appropriate network locator(s) for overlay forwarding.
The logical SF may be a single SF, or a set of eligible SFs that are
equivalent. In the latter case, the SFF provides load distribution
amongst the collection of SFs as needed.
SI serves as a mechanism for detecting invalid service function
paths. In particular, an SI value of zero indicates that forwarding
is incorrect and the packet must be discarded.
This indirection -- SPI to overlay -- creates a true service plane.
That is, the SFF/SF topology is constructed without impacting the
network topology but more importantly, service plane only
participants (i.e., most SFs) need not be part of the network overlay
topology and its associated infrastructure (e.g., control plane,
routing tables, etc.) SFs need to be able to return a packet to an
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appropriate SFF (i.e., has the requisite NSH information) when
service processing is complete. This can be via the overlay 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 first SFF in the path gets an NSH encapsulated packet from the
Classifier). The SFF consults the SPI/ID values to determine the
appropriate overlay transport protocol (several may be used within a
given network) and next hop for the requisite SF. Table 1 below
depicts an example of a single next-hop SPI/SI to network overlay
network locator mapping.
+------+------+---------------------+-------------------+
| SPI | SI | Next hop(s) | Transport |
+------+------+---------------------+-------------------+
| 10 | 255 | 192.0.2.1 | VXLAN-gpe |
| | | | |
| 10 | 254 | 198.51.100.10 | GRE |
| | | | |
| 10 | 251 | 198.51.100.15 | GRE |
| | | | |
| 40 | 251 | 198.51.100.15 | GRE |
| | | | |
| 50 | 200 | 01:23:45:67:89:ab | Ethernet |
| | | | |
| 15 | 212 | Null (end of path) | None |
+------+------+---------------------+-------------------+
Table 1: SFF NSH Mapping Example
Additionally, further indirection is possible: the resolution of the
required SF network locator may be a localized resolution on an SFF,
rather than a service function chain control plane responsibility, as
per Table 2 and Table 3 below.
Please note: VXLAN-gpe and GRE in the above table refer to
[I-D.ietf-nvo3-vxlan-gpe] and [RFC2784] [RFC7676], respectively.
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+------+-----+----------------+
| SPI | SI | Next hop(s) |
+------+-----+----------------+
| 10 | 3 | SF2 |
| | | |
| 245 | 12 | SF34 |
| | | |
| 40 | 9 | SF9 |
+------+-----+----------------+
Table 2: NSH to SF Mapping Example
+------+-------------------+-------------+
| SF | Next hop(s) | Transport |
+------+-------------------+-------------+
| SF2 | 192.0.2.2 | VXLAN-gpe |
| | | |
| SF34 | 198.51.100.34 | UDP |
| | | |
| SF9 | 2001:db8::1 | GRE |
+------+-------------------+-------------+
Table 3: SF Locator Mapping Example
Since the SPI is a representation of the service path, the lookup may
return more than one possible next-hop within a service path for a
given SF, essentially a series of weighted (equally or otherwise)
paths to be used (for load distribution, redundancy, or policy), see
Table 4. The metric depicted in Table 4 is an example to help
illustrated weighing SFs. In a real network, the metric will range
from a simple preference (similar to routing next-hop), to a true
dynamic composite metric based on some service function-centric state
(including load, sessions state, capacity, etc.)
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+------+-----+--------------+---------+
| 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)
Table 4: NSH Weighted Service Path
6.2. Mapping NSH to Network Transport
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.
Furthermore, the SPI to overlay mapping occurs at each SFF
independently. Any combination of topology selection is possible.
Please note, there is no requirement to create a new overlay topology
if a suitable one already exists. NSH packets can use any (new or
existing) overlay provided the requisite connectivity requirements
are satisfied.
Examples of mapping for a topology:
1. Next SF is located at SFFb with locator 2001:db8::1
SFFa mapping: SPI=10 --> VXLAN-gpe, dst-ip: 2001:db8::1
2. Next SF is located at SFFc with multiple network locators for
load distribution purposes:
SFFb mapping: SPI=10 --> VXLAN-gpe, dst_ip:203.0.113.1,
203.0.113.2, 203.0.113.3, equal cost
3. Next SF is located at SFFd with two paths from SFFc, one for
redundancy:
SFFc mapping: SPI=10 --> VXLAN-gpe, dst_ip:192.0.2.10 cost=10,
203.0.113.10, cost=20
In the above example, each SFF makes an independent decision about
the network overlay path and policy for that path. In other words,
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there is no a priori mandate about how to forward packets in the
network (only the order of services that must be traversed).
The network operator retains the ability to engineer the network
paths as required. For example, the overlay path between SFFs may
utilize traffic engineering, QoS marking, or ECMP, without requiring
complex configuration and network protocol support to be extended to
the service path explicitly. In other words, the network operates as
expected, and evolves as required, as does the service plane.
6.3. Service Plane Visibility
The SPI and SI serve an important function for visibility into the
service topology. An operator can determine what service path a
packet is "on", and its location within that path simply by viewing
NSH information (packet capture, IPFIX, etc.) The information can be
used for service scheduling and placement decisions, troubleshooting,
and compliance verification.
6.4. Service Graphs
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
collection of service function paths, with the interconnection
provided by classifiers (in-service path, non-initial
reclassification). These internal reclassifiers examine the packet
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
new NSH with new values is implementation specific) to reflect the
"result" of the classification. These classifiers may also of course
modify the metadata associated with the packet.
[RFC7665], Section 2.1 describes Service Graphs in detail.
7. Policy Enforcement with NSH
7.1. NSH Metadata and Policy Enforcement
As described in Section 2, NSH provides the ability to carry metadata
along a service path. This metadata may be derived from several
sources, common examples include:
Network nodes/devices: Information provided by network nodes can
indicate network-centric information (such as VRF or tenant) that
may be used by service functions, or conveyed to another network
node post service path egress.
External (to the network) systems: External systems, such as
orchestration systems, often contain information that is valuable
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for service function policy decisions. In most cases, this
information cannot be deduced by network nodes. For example, a
cloud orchestration platform placing workloads "knows" what
application is being instantiated and can communicate this
information to all NSH nodes via metadata carried in the context
header(s).
Service Functions: A classifier co-resident with Service Functions
often perform very detailed and valuable classification.
Regardless of the source, metadata reflects the "result" of
classification. The granularity of classification may vary. For
example, a network switch, acting as a classifier, might only be able
to classify based on a 5-tuple, whereas, a service function may be
able to inspect application information. Regardless of granularity,
the classification information can be represented in NSH.
Once the data is added to NSH, it is carried along the service path,
NSH-aware SFs receive the metadata, and can use that metadata for
local decisions and policy enforcement. Figure 8 and Figure 9
highlight the relationship between metadata and policy:
+-------+ +-------+ +-------+
| SFF )------->( SFF |------->| SFF |
+---+---+ +---+---+ +---+---+
^ | |
,-|-. ,-|-. ,-|-.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ ify / \ / \ /
`---' `---' `---'
5-tuple: Permit Inspect
Tenant A Tenant A AppY
AppY
Figure 8: Metadata and Policy
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+-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+
^ | |
,-+-. ,-+-. ,-+-.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ ify / \ / \ /
`-+-' `---' `---'
| Permit Deny AppZ
+---+---+ employees
| |
+-------+
External
system:
Employee
AppZ
Figure 9: External Metadata and Policy
In both of the examples above, the service functions perform policy
decisions based on the result of the initial classification: the SFs
did not need to perform re-classification, rather they rely on a
antecedent classification for local policy enforcement.
Depending on the information carried in the metadata, data privacy
considerations may need to be considered. For example, if the
metadata conveys tenant information, that information may need to be
authenticated and/or encrypted between the originator and the
intended recipients (which may include intended SFs only) . NSH
itself does not provide privacy functions, rather it relies on the
transport/overlay layer. An operator can select the appropriate
transport to ensure confidentially (and other security)
considerations are met. Metadata privacy and security considerations
are a matter for the documents that define metadata format.
7.2. Updating/Augmenting Metadata
Post-initial metadata imposition (typically performed during initial
service path determination), the metadata may be augmented or
updated:
1. Metadata Augmentation: Information may be added to NSH's existing
metadata, as depicted in Figure 10. For example, if the initial
classification returns the tenant information, a secondary
classification (perhaps co-resident with DPI or SLB) may augment
the tenant classification with application information, and
impose that new information in NSH metadata. The tenant
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classification is still valid and present, but additional
information has been added to it.
2. Metadata Update: Subsequent classifiers may update the initial
classification if it is determined to be incorrect or not
descriptive enough. For example, the initial classifier adds
metadata that describes the traffic as "Internet" but a security
service function determines that the traffic is really "attack".
Figure 11 illustrates an example of updating metadata.
+-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+
^ | |
,---. ,---. ,---.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ / \ / \ /
`-+-' `---' `---'
| Inspect Deny
+---+---+ employees employee+
| | Class=AppZ appZ
+-------+
External
system:
Employee
Figure 10: Metadata Augmentation
+-----+ +-----+ +-----+
| SFF |---------> | SFF |----------> | SFF |
+--+--+ +--+--+ +--+--+
^ | |
,---. ,---. ,---.
/ \ / \ / \
( Class ) ( SF1 ) ( SF2 )
\ / \ / \ /
`---' `---' `---'
5-tuple: Inspect Deny
Tenant A Tenant A attack
--> attack
Figure 11: Metadata Update
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7.3. Service Path Identifier and Metadata
Metadata information may influence the service path selection since
the Service Path Identifier values can represent the result of
classification. A given SPI can be defined based on classification
results (including metadata classification). The imposition of the
SPI and SI results in the packet being placed on the newly specified
SFP at the position indicated by the imposed SPI and SI.
This relationship provides the ability to create a dynamic service
plane based on complex classification without requiring each node to
be capable of such classification, or requiring a coupling to the
network topology. This yields service graph functionality as
described in Section 6.4. Figure 12 illustrates an example of this
behavior.
+-----+ +-----+ +-----+
| SFF |---------> | SFF |------+---> | SFF |
+--+--+ +--+--+ | +--+--+
| | | |
,---. ,---. | ,---.
/ \ / SF1 \ | / \
( SCL ) ( + ) | ( SF2 )
\ / \SCL2 / | \ /
`---' `---' +-----+ `---'
5-tuple: Inspect | SFF | Original
Tenant A Tenant A +--+--+ next SF
--> DoS |
V
,-+-.
/ \
( SF10 )
\ /
`---'
DoS
"Scrubber"
Figure 12: Path ID and Metadata
Specific algorithms for mapping metadata to an SPI are outside the
scope of this document.
8. Security Considerations
As with many other protocols, the NSH encapsulation could be spoofed
or otherwise modified in transit. However, the deployment scope (as
defined in [RFC7665]) of the NSH encapsulation is limited to a single
network administrative domain as a controlled environment, with
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trusted devices (e.g., a data center) thus mitigating the risk of
unauthorized manipulation of the encapsulation headers or metadata.
NSH is always encapsulated in a transport protocol (as detailed in
Section 4 of this specification) and therefore, when required,
existing security protocols that provide authenticity (e.g.,
[RFC6071]) can be used. Similarly, if confidentiality is required,
existing encryption protocols can be used in conjunction with the NSH
encapsulation.
Further, existing best practices, such as [BCP38] SHOULD be deployed
at the network layer to ensure that traffic entering the service path
is indeed "valid". [I-D.ietf-rtgwg-dt-encap] provides additional
transport encapsulation considerations.
Even though much of the metadata carried within the NSH encapsulation
is derived from the packet contents, and thus is not privacy or
security sensitive, NSH metadata authenticity and confidentiality
must be considered as well. In order to protect the metadata, an
operator can leverage the aforementioned mechanisms provided by the
transport layer including authenticity and/or confidentiality. An
operator MUST carefully select the transport/underlay services to
ensure end-to-end security services, when those are sought. For
example, if [RFC6071] is used, the operator MUST ensure it can be
supported by the transport/underlay of all relevant network segments
as well as SFFs and SFs in the service path. Further, as described
under the "SFC Encapsulation" area of the Security Considerations of
[RFC7665], operators can and should use indirect identification for
metadata deemed to be sensitive (such as personally identifying
information), thus significantly mitigating the risk of privacy
violation. In particular, subscriber identifying information should
be handled carefully, and in general should be obfuscated. This is
covered in the Security Considerations of [RFC7665]. For those
situations where obfuscation is either inapplicable or judged to be
insufficient, one can also encrypt the metadata. An approach to an
optional capability to do this was explored
[I-D.reddy-sfc-nsh-encrypt]. Means to prevent leaking privacy-
related information outside an administrative domain are natively
supported by NSH given that the last SFF of a servicepath will
systematically remove the NSH encapsulation before forwarding a
packet exiting the service path.
Lastly, SF security, although out of scope of this document, should
be considered, particularly if an SF needs to access, authenticate,
or update the NSH encapsulation or metadata. However, again the
placement of SFs is assumed to be bounded within the scope of a
single administrative domain and therefore under direct control of
the operator.
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9. Contributors
This WG document originated as draft-quinn-sfc-nsh and had the
following co-authors and contributors. The editors of this document
would like to thank and recognize them and their contributions.
These co-authors and contributors provided invaluable concepts and
content for this document's creation.
Surendra Kumar
Cisco Systems
smkumar@cisco.com
Michael Smith
Cisco Systems
michsmit@cisco.com
Jim Guichard
Huawei
james.n.guichard@huawei.com
Rex Fernando
Cisco Systems
Email: rex@cisco.com
Navindra Yadav
Cisco Systems
Email: nyadav@cisco.com
Wim Henderickx
Alcatel-Lucent
wim.henderickx@alcatel-lucent.com
Andrew Dolganow
Alcaltel-Lucent
Email: andrew.dolganow@alcatel-lucent.com
Praveen Muley
Alcaltel-Lucent
Email: praveen.muley@alcatel-lucent.com
Tom Nadeau
Brocade
tnadeau@lucidvision.com
Puneet Agarwal
puneet@acm.org
Rajeev Manur
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Broadcom
rmanur@broadcom.com
Abhishek Chauhan
Citrix
Abhishek.Chauhan@citrix.com
Joel Halpern
Ericsson
joel.halpern@ericsson.com
Sumandra Majee
F5
S.Majee@f5.com
David Melman
Marvell
davidme@marvell.com
Pankaj Garg
Microsoft
pankajg@microsoft.com
Brad McConnell
Rackspace
bmcconne@rackspace.com
Chris Wright
Red Hat Inc.
chrisw@redhat.com
Kevin Glavin
Riverbed
kevin.glavin@riverbed.com
Hong (Cathy) Zhang
Huawei US R&D
cathy.h.zhang@huawei.com
Louis Fourie
Huawei US R&D
louis.fourie@huawei.com
Ron Parker
Affirmed Networks
ron_parker@affirmednetworks.com
Myo Zarny
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Goldman Sachs
myo.zarny@gs.com
10. Acknowledgments
The authors would like to thank Sunil Vallamkonda, Nagaraj Bagepalli,
Abhijit Patra, Peter Bosch, Darrel Lewis, Pritesh Kothari, Tal
Mizrahi and Ken Gray for their detailed review, comments and
contributions.
A special thank you goes to David Ward and Tom Edsall for their
guidance and feedback.
Additionally the authors would like to thank Larry Kreeger for his
invaluable ideas and contributions which are reflected throughout
this document.
Loa Andersson provided a thorough review and valuable comments, we
thank him for that.
Reinaldo Penno deserves a particular thank you for his architecture
and implementation work that helped guide the protocol concepts and
design.
The editors also acknowledge comprehensive reviews and respective
suggestions by Med Boucadair, Adrian Farrel, Juergen Schoenwaelder,
and Acee Lindem.
Lastly, David Dolson has provides significant review, feedback and
suggestions throughout the evolution of this document. His
contributions are very much appreciated.
11. IANA Considerations
11.1. NSH EtherType
An IEEE EtherType, 0x894F, has been allocated for NSH.
11.2. Network Service Header (NSH) Parameters
IANA is requested to create a new "Network Service Header (NSH)
Parameters" registry. The following sub-sections request new
registries within the "Network Service Header (NSH) Parameters "
registry.
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11.2.1. NSH Base Header Bits
There are five unassigned bits (U bits) in the NSH Base Header, and
one assigned bit (O bit). New bits are assigned via Standards Action
[RFC8126].
Bit 2 - O (OAM) bit
Bit 3 - Unassigned
Bits 16-19 - Unassigned
11.2.2. NSH Version
IANA is requested to setup a registry of "NSH Version". New values
are assigned via Standards Action [RFC8126].
Version 00b: This protocol version. This document.
Version 01b: Reserved. This document.
Version 10b: Unassigned.
Version 11b: Unassigned.
11.2.3. MD Type Registry
IANA is requested to set up a registry of "MD Types". These are
4-bit values. MD Type values 0x0, 0x1, 0x2, and 0xF are specified in
this document, see Table 5. Registry entries are assigned by using
the "IETF Review" policy defined in RFC 8126 [RFC8126].
+----------+-----------------+---------------+
| MD Type | Description | Reference |
+----------+-----------------+---------------+
| 0x0 | Reserved | This document |
| | | |
| 0x1 | NSH MD Type 1 | This document |
| | | |
| 0x2 | NSH MD Type 2 | This document |
| | | |
| 0x3..0xE | Unassigned | |
| | | |
| 0xF | Experimentation | This document |
+----------+-----------------+---------------+
Table 5: MD Type Values
11.2.4. MD Class Registry
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
following policies:
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0x0000 to 0x01ff: IETF Review
0x0200 to 0xfff5: Expert Review
0xfff6 to 0xfffe: Experimental
0xffff: Reserved
IANA is requested to assign the values as per Table 6::
+-----------+-----------------------------+------------+
| MD Class | Meaning | Reference |
+-----------+-----------------------------+------------+
| 0x0000 | IETF Base NSH MD Class | This.I-D |
+-----------+-----------------------------+------------+
Table 6: MD Class Value
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.
11.2.5. NSH Base Header Next Protocol
IANA is requested to set up a registry of "Next Protocol". These are
8-bit values. Next Protocol values 0, 1, 2, 3, 4 and 5 are defined
in this document (see Table 7. New values are assigned via "Expert
Reviews" as per [RFC8126].
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+---------------+--------------+---------------+
| Next Protocol | Description | Reference |
+---------------+--------------+---------------+
| 0x0 | Unassigned | |
| | | |
| 0x1 | IPv4 | This document |
| | | |
| 0x2 | IPv6 | This document |
| | | |
| 0x3 | Ethernet | This document |
| | | |
| 0x4 | NSH | This document |
| | | |
| 0x5 | MPLS | This document |
| | | |
| 0x6..0xFD | Unassigned | |
| | | |
| 0xFE | Experiment 1 | This document |
| | | |
| 0xFF | Experiment 2 | This document |
+---------------+--------------+---------------+
Table 7: NSH Base Header Next Protocol Values
11.2.6. New IETF Assigned Optional Variable Length Metadata 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 Optional Variable Length Metadata Type Registry", as
specified in Section 2.5.1.
The type values are assigned via Standards Action [RFC8126].
No initial values are assigned at the creation of the registry.
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
Quinn, et al. Expires February 13, 2018 [Page 31]
Internet-Draft Network Service Header (NSH) August 2017
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<http://www.rfc-editor.org/info/rfc7665>.
[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.
Quinn, et al. Expires February 13, 2018 [Page 32]
Internet-Draft Network Service Header (NSH) August 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-03 (work in
progress), July 2017.
[I-D.reddy-sfc-nsh-encrypt]
Reddy, T., Patil, P., Fluhrer, S., and P. Quinn,
"Authenticated and encrypted NSH service chains", draft-
reddy-sfc-nsh-encrypt-00 (work in progress), April 2015.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
DOI 10.17487/RFC2784, March 2000,
<http://www.rfc-editor.org/info/rfc2784>.
[RFC3692] Narten, T., "Assigning Experimental and Testing Numbers
Considered Useful", BCP 82, RFC 3692,
DOI 10.17487/RFC3692, January 2004,
<http://www.rfc-editor.org/info/rfc3692>.
[RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and
Internet Key Exchange (IKE) Document Roadmap", RFC 6071,
DOI 10.17487/RFC6071, February 2011,
<http://www.rfc-editor.org/info/rfc6071>.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <http://www.rfc-editor.org/info/rfc7325>.
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498,
DOI 10.17487/RFC7498, April 2015,
<http://www.rfc-editor.org/info/rfc7498>.
[RFC7676] Pignataro, C., Bonica, R., and S. Krishnan, "IPv6 Support
for Generic Routing Encapsulation (GRE)", RFC 7676,
DOI 10.17487/RFC7676, October 2015,
<http://www.rfc-editor.org/info/rfc7676>.
Authors' Addresses
Paul Quinn (editor)
Cisco Systems, Inc.
Email: paulq@cisco.com
Quinn, et al. Expires February 13, 2018 [Page 33]
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Uri Elzur (editor)
Intel
Email: uri.elzur@intel.com
Carlos Pignataro (editor)
Cisco Systems, Inc.
Email: cpignata@cisco.com
Quinn, et al. Expires February 13, 2018 [Page 34]