Service Function Chaining J. Napper
Internet-Draft Cisco Systems, Inc.
Intended status: Standards Track S. Kumar
Expires: December 21, 2018 Individual Contributor
P. Muley
W. Hendericks
Nokia
M. Boucadair
Orange
June 19, 2018
NSH Context Header Allocation for Broadband
draft-ietf-sfc-nsh-broadband-allocation-01
Abstract
This document provides a recommended allocation of Network Service
Header (NSH) context headers within the broadband service provider
network context. Both fixed and mobile deployments are considered.
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 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 21, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Network Service Header (NSH) Context Headers: A Reminder . . 3
4. Recommended Context Allocation For Broadband . . . . . . . . 4
4.1. MD Type 0x01 Allocation Specifics . . . . . . . . . . . . 4
4.2. MD Type 0x02 Allocation Specifics . . . . . . . . . . . . 6
5. Context Allocation and Control Plane Considerations . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 7
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
9.1. Normative References . . . . . . . . . . . . . . . . . . 8
9.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Service Function Chaining (SFC) [RFC7665] provides a mechanism for
network traffic to be steered through an ordered list of Service
Functions (SFs). Furthermore, SFC allows to share metadata among
involved SFC data functional elements (classifiers and SFs).
Particularly, the Network Service Header (NSH, [RFC8300]) provides
support for carrying shared metadata either using a fixed context
header or as optional TLVs.
This document describes a recommended default allocation scheme for
the fixed-length context header used for SFC within fixed and mobile
broadband service provider networks. Also, the document defines
companion TLV types when MD Type 0x02 is used. The use cases
describing the need for metadata in these deployment contexts are
described in [I-D.ietf-sfc-use-case-mobility].
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This document does not address control plane considerations. The
reader may refer to [I-D.ietf-sfc-control-plane].
2. Terminology
This document makes use of the terms as defined in [RFC7498],
[RFC7665], and [RFC8300].
3. Network Service Header (NSH) Context Headers: A Reminder
The NSH is composed of a 4-byte base header (BH1), a 4-byte service
path header (SH1), and a fixed 16-byte context header in the case of
MD Type 0x01 or optional TLVs in the case of MD Type 0x02 [RFC8300].
Figure 1 shows the format of the MD Type 0x01 NSH header.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | BH1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier | Service Index | SH1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Fixed |
+ Context Header +
| (16 Bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Network Service Header (MD Type 0x01)
Figure 2 shows the MD Type 0x02 NSH header format.
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 | BH1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier | Service Index | SH1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
~ Variable Length Context Headers (opt.) ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Network Service Header (MD Type 0x02)
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4. Recommended Context Allocation For Broadband
The following header allocations provide information to support
service function chaining in a service provider network, for example
as described for mobility in [I-D.ietf-sfc-use-case-mobility].
The set of metadata headers can be delivered to SFs that can use the
metadata within to enforce service policy, communicate between
service functions, provide subscriber information, and other
functionality. Several of the headers are typed allowing for
different metadata to be provided to different SFs or even to the
same SF but on different packets within a flow.
Which metadata are sent to which SFs is decided in the SFC control
plane and is thus out of the scope of this document.
4.1. MD Type 0x01 Allocation Specifics
Figure 3 provides a high-level description of the fields in the
recommended allocation of the fixed sixteen byte context header for a
broadband context. Each four byte word in the sixteen byte context
header is referred to as CH1, CH2, CH3, and CH4, respectively.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| R | Sub | Tag | Context ID | CH1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub/Endpoint ID ~ CH2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Sub/Endpoint ID (cont.) | CH3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Information | CH4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: NSH Context Allocation
The intended use for each of the context header fields is as follows:
R: MUST be set to zero upon origination, and they MUST be ignored and
preserved unmodified by other NSH supporting elements.
Sub: Sub/Endpoint ID type field. These bits determine the type of
the 64-bit Sub/Endpoint ID field that spans CH2 and CH3.
000: The 64-bit Sub/Endpoint ID field is an opaque field that can
be used or ignored by SFs as determined by the control plane.
001: The Sub/Endpoint ID field contains an IMSI [itu-e-164].
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010: The Sub/Endpoint ID field contains an MSISDN (8-15 digit)
[itu-e-164].
011: The Sub/Endpoint ID field contains a 64-bit identifier that
can be used to group flows (e.g., in Machine-to-Machine (M2M)
contexts).
100: The Sub/Endpoint IP field contains a wireline subscriber ID
in CH2, and CH3 contains the line identifier.
101-111: Reserved.
Tag: Indicates the type of the Service Information field in CH4.
The following values are defined:
000: If the Tag field is not set, the Service Information field
in CH4 is an opaque field that can be used or ignored by SFs as
determined by the control plane.
001: The Service Information field in CH4 contains information
related to the Access Network (AN) for the subscriber. This is
shown in Figure 4 for a 3GPP Radio Access Network (RAN).
Note that these values should correspond to those that can be
obtained for the flow from the corresponding 3GPP PCRF (Policy
and Charging Rules Function) component using Diameter as
described in [TS.29.230].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CAN | QoS/DSCP | Con | App Id | Rsvd | CH4
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Service Information RAN Allocation
CAN: IP-CAN-Type for IP Connectivity Access Network (Diameter
AVP code 1027).
QoS: QoS-Class-Identifier AVP (Diameter AVP code 1028) or
Differentiated Services Code Point (DSCP) marking as
described in [RFC2474].
Con: Access congestion level. An Access Congestion level
'000' means an unknown/undefined congestion level. An
Access Congestion level '001' means no congestion. For
other values of Access Congestion level, a higher value
indicates a higher level of congestion.
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App Id: Application ID describing the flow type. Allocation
of IDs is done using the control plane and is out of the
scope of this document.
Rsvd: Reserved.
010-111: Reserved.
Context ID: The Context ID field allows the Sub/Endpoint ID field to
be scoped. For example, the Context ID field may contain the
incoming VRF, VxLAN VNID, VLAN, or a policy identifier within
which the Sub/Endpoint ID field is defined.
Sub/Endpoint ID: 64-bit length Subscriber/Endpoint identifier (e.g.,
IMSI, MSISDN, or implementation-specific Endpoint ID) of the
corresponding subscriber/machine/application for the flow.
Service Information: The Service Information field is a unique
identifier that can carry metadata specific to the flow or
subscriber identified in the Sub/Endpoint ID field.
4.2. MD Type 0x02 Allocation Specifics
Figure 5 depictes the format of the recommended allocation of the
variable length headers for a mobility context.
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TLV Class = 3GPP |C| Type |U|U|U| Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data ...
+-+-+-+-+-+-+-+-+
Figure 5: TLV Allocation
The intended use of the header is for TLVs associated with 3GPP Radio
Access Networks as described in [TS.29.230]. This TLV can be used by
3GPP to extend the metadata as per use cases. Having this TLV helps
to carry more information that does not fit within the MD Type 0x01.
The Len field carries the total length. Type = 0x01 is reserved. If
set to 0x01, the TLV carries the 4 context headers as defined in
Section 4.1.
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5. Context Allocation and Control Plane Considerations
This document describes an allocation scheme for both the fixed
context header (MD Type#1) and optional TLV headers (MD Type#2) in
the context of broadband service providers. This allocation of
headers should be considered as a guideline and may vary depending on
the use case.
The control plane aspects of specifying and distributing the
allocation scheme among different SFs within the Service Function
Chaining environment to guarantee consistent semantics for the
metadata is beyond the scope of this document.
6. Security Considerations
This specification relies on NSH to share metadata among SFC data
plane elements. Security-related consideration discussed in
[RFC8300] MUST be followed.
The recommended header allocation in this document includes sensitive
information that MUST NOT be revealed outside an SFC-enabled domain.
Those considerations are already discussed in [RFC8300]. NSH allows
by design to remove any NSH data before existing an SFC-enabled
domain.
Furthermore, means to prevent that illegitimate nodes insert spoofed
data MUST be supported. As a reminder, the NSH specification assumes
ingress boundary nodes strip any NSH data that may be present in a
packet. Misbehaving nodes from within an SFC-enabled domain may
alter the content of the NSH data. Such treats are discussed in
[RFC8300]. This document does not introduce new treats compared to
those discussed in [RFC8300].
7. IANA Considerations
This document requests IANA to assign a TLV class for 3GPP to be used
for its use cases.
8. Acknowledgments
The authors would like to thank Jim Guichard for his assistance
structuring the document.
9. References
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9.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665,
DOI 10.17487/RFC7665, October 2015,
<https://www.rfc-editor.org/info/rfc7665>.
[RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed.,
"Network Service Header (NSH)", RFC 8300,
DOI 10.17487/RFC8300, January 2018,
<https://www.rfc-editor.org/info/rfc8300>.
9.2. Informative References
[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-use-case-mobility]
Haeffner, W., Napper, J., Stiemerling, M., Lopez, D., and
J. Uttaro, "Service Function Chaining Use Cases in Mobile
Networks", draft-ietf-sfc-use-case-mobility-08 (work in
progress), May 2018.
[itu-e-164]
"The international public telecommunication numbering
plan", ITU-T E.164, November 2010.
[RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black,
"Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers", RFC 2474,
DOI 10.17487/RFC2474, December 1998,
<https://www.rfc-editor.org/info/rfc2474>.
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498,
DOI 10.17487/RFC7498, April 2015,
<https://www.rfc-editor.org/info/rfc7498>.
[TS.29.230]
"Diameter applications; 3GPP specific codes and
identifiers", 3GPP TS 29.230 14.5.0, July 2017.
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Authors' Addresses
Jeffrey Napper
Cisco Systems, Inc.
Email: jenapper@cisco.com
Surendra Kumar
Individual Contributor
Email: surendra.stds@gmail.com
Praveen Muley
Nokia
Email: praveen.muley@nokia.com
Wim Hendericks
Nokia
Email: Wim.Henderickx@nokia.com
Mohamed Boucadair
Orange
France
Email: mohamed.boucadair@orange.com
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