Network Working Group Z. Li
Internet-Draft S. Peng
Intended status: Standards Track Huawei Technologies
Expires: March 13, 2020 K. LEE
LG U+
September 10, 2019
IPv6 Encapsulation for SFC and IFIT
draft-li-6man-ipv6-sfc-ifit-02
Abstract
Service Function Chaining (SFC) and In-situ Flow Information
Telemetry (IFIT) are important path services along with the packets.
In order to support these services, several encapsulations have been
defined. The document analyzes the problems of these encapsulations
in the IPv6 scenario and proposes the possible optimized
encapsulation for IPv6.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 13, 2020.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
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(https://trustee.ietf.org/license-info) in effect on the date of
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Design Consideration . . . . . . . . . . . . . . . . . . . . 4
4.1. Service Options . . . . . . . . . . . . . . . . . . . . . 4
4.2. IPv6 Service Metadata Options . . . . . . . . . . . . . . 7
4.2.1. SFC Service Metadata Option . . . . . . . . . . . . . 7
4.2.2. IOAM Service Metadata Option . . . . . . . . . . . . 8
4.2.3. IFA Service Metadata Option . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 11
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
1. Introduction
Service Function Chaining (SFC) [RFC7665] and In-situ Flow
Information Telemetry (IFIT) [I-D.song-opsawg-ifit-framework] are
important path services along with the packets. In order to support
these services, several encapsulations have been defined. Network
Service Header (NSH) is defined in [RFC8300] as the encapsulation for
SFC. For IFIT encapsulations, In-situ OAM (iOAM) Header is defined
in [I-D.ietf-ippm-ioam-data] and Postcard-Based Telemetry (PBT)
Header is defined in [I-D.song-ippm-postcard-based-telemetry].
Inband Flow Analyzer (IFA) is also defined in [I-D.kumar-ippm-ifa] to
record flow specific information from an end station and/or switches
across a network. In the application scenario of IPv6, these
encapsulations propose challenges for the data plane. The document
analyzes the problems and proposes the possible optimized
encapsulation for IPv6.
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2. Terminology
SFC: Service Function Chaining
IFIT: In-situ Flow Information Telemetry
IOAM: In-situ OAM
PBT: Postcard-Based Telemetry
IFA: Inband Flow Analyzer
SRH: Segment Routing Header
3. Problem Statement
The problems posed by the current encapsulations for SFC and IFIT in
the application scenarios of IPv6 and SRv6 include:
1. According to the encapsulation order recommended in [RFC8200], if
the IOAM is encapsulated in the IPv6 Hop-by-Hop options header, in
the incremental trace mode of IOAM as the number of nodes traversed
by the IPv6 packets increases, the recorded IOAM information will
increase accordingly. This will increase the length of the Hop-by-
Hop options header and cause increasing difficulties in reading the
subsequent Segment Routing Extension Header (SRH)
[I-D.ietf-6man-segment-routing-header] and thereby reduce the
forwarding performance of the data plane greatly.
2. With the introduction of SRv6 network programming
[I-D.ietf-spring-srv6-network-programming], the path services along
with the IPv6 packets can be processed at all the IPv6 network nodes
or only at the SRv6 enabled network nodes along the path. It is
necessary to distinguish the encapsulations for the specific path
service which should be processed by the IPv6 path or the SRv6 path.
3. Both NSH and IOAM need the Metadata field to record metadata
information. However currently these metadata has to be recorded
separately which may generate redundant metadata information or
increase the cost of process.
4. There is unnecessary inconsistency in the current encapsulations
for IOAM, IFA and PBT in the IPv6 scenario. Especially it seems
unnecessary to define a new specific IPv6 header for IFA, i.e. IFA
header.
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4. Design Consideration
To solve the problems stated above, in the application scenarios of
IPv6 and SRv6, the encapsulations of SFC and IFIT can be optimized
with the following design considerations:
o To separate the SFC/IFIT path service into two parts, i.e.
instruction and recording parts. The instruction part (normally
with fixed length) can be placed in the front IPv6 extension
headers including Hop-by-Hop options header, Destination options
header, Routing header, etc. while the recording part can be
placed in the back IPv6 extension headers such as being placed
after IPv6 Routing Header. In this way the path service
instruction in the IPv6 extension headers can be fixed as much as
possible to facilitate hardware process to keep forwarding
performance while the SFC/IFIT metadata recording part is placed
afterwards which enables to stop recording when too much recording
information has to be carried to reach the limitation of hardware
process.
o To define SFC/IFIT path service instructions as IPv6 options
uniformly whichs can be placed either in the Hop-by-hop options
which indicates the path service processed by all IPv6 enabled
nodes along the path or in the SRH option TLVs which indicates the
path service processed only by the SRv6 nodes along the SRv6 path
indicated by the Segment List in the SRH.
o To define a unified IPv6 metadata header which can be used as a
container to record the service metadata of SFC, IFIT and other
possible path services.
According to the above design optimization consideration, in the
application scenarios of IPv6 and SRv6 the encapsulations for SFC and
IFIT can be defined as below.
4.1. Service Options
1. NSH Service Option
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1. IPv6 Options with NSH instructions
Option Type: TBD_0
Opt Data Len: 8 octets.
Other fields: refer to [RFC8300].
2. IOAM Service Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Namespace-ID |NodeLen | Flags | RemainingLen|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM-Trace-Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2. IPv6 Options with IOAM instructions
Option Type: TBD_1
Opt Data Len: 8 octets.
Other fields: refer to [I-D.ietf-ippm-ioam-data].
3. PBT Service Option
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | TIH Length | Reserved | Hop Count |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flow ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Data Set ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3. IPv6 Options with PBT instructions
Option Type: TBD_2
Opt Data Len: 20 octets.
Other fields: refer to [I-D.song-ippm-postcard-based-telemetry].
4. IFA Service Option
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Option Type | Opt Data Len |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Ver=2.0| GNS |NextHdr = IP_xx|R|R|R|M|T|I|T|C| Max Length |
| | | | | | |F|S| |A| | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4. IPv6 Options with IFA instructions
Option Type: TBD_3
Opt Data Len: 4 octets.
Other fields: refer to [I-D.kumar-ippm-ifa].
These options can be put in the IPv6 Hop-by-Hop Options Header or SRH
TLV.
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4.2. IPv6 Service Metadata Options
As introduced in [I-D.li-6man-enhanced-extension-header], IPv6
Metadata Header is defined as a new type of IPv6 extension header.
The metadata is the information recorded by each hop for specific
path services, and carried in corresponding service metadata options.
The length of the metadata is variable.
4.2.1. SFC Service Metadata Option
For the SFC service, the corresponding SFC service metadata option is
defined as shown in Figure 5.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SFC Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SFC Metadata Class | Type |U| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Variable-Length Metadata |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. SFC Service Metadata
SFC Type 8-bit identifier of the service type, i.e. SFC.
The value is TBD-4.
Length 8-bit unsigned integer. Length of the
Service Metadata field, in octets.
Metadata Class Defines the scope of the Type field to
provide a hierarchical namespace. IANA has
set up the "NSH MD Class" registry, which
contains 16-bit values [RFC8300].
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 it MUST be
ignored on receipt.
Length Indicates the length of the variable-length
metadata, in bytes. Detailed specification
in [RFC8300].
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4.2.2. IOAM Service Metadata Option
For the IOAM service, the corresponding IOAM service metadata option
is defined as shown 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IOAM Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| IOAM Service Metadata Options (variable) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6. IOAM Service Metadata
IOAM Type 8-bit identifier of the IOAM Service Metadata
type. The value is TBD-5.
Length 8-bit unsigned integer. Length of the
IOAM Service Metadata field, in octets.
RESERVED 8-bit reserved field MUST be set to zero upon
transmission and ignored upon receipt.
IOAM Service IOAM option data is present as specified by the
Metadata Options IOAM Type field, and is defined in Section 4 of
[I-D.ietf-ippm-ioam-data].
All the IOAM IPv6 options require 4n alignment. This ensures that 4
octet fields specified in [I-D.ietf-ippm-ioam-data] such as transit
delay are aligned at a multiple-of-4 offset from the start of the
IPv6 Metadata header.
In addition, to maintain IPv6 extension header 8-octet alignment and
avoid the need to add or remove padding at every hop, the Trace-Type
for Incremental Tracing Option in IPv6 MUST be selected such that the
IOAM node data length is a multiple of 8-octets.
4.2.3. IFA Service Metadata Option
For the IOAM service, the corresponding IOAM service metadata option
is defined as shown in Figure 6.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IFA Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| IFA Service Metadata Options (variable) |
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6. IFA Service Metadata
IFA Type 8-bit identifier of the IFA Service Metadata
type. The value is TBD-6.
Length 8-bit unsigned integer. Length of the
IOAM Service Metadata field, in octets.
RESERVED 8-bit reserved field MUST be set to zero upon
transmission and ignored upon receipt.
IFA Service IFA option data is present as specified by the
Metadata Options IFA Type field.
5. IANA Considerations
Value Description Reference
---------------------------------------------------------------------
TBD_0 NSH Service Option [This draft]
TBD_1 IOAM Service Option [This draft]
TBD_2 PBT Service Option [This draft]
TBD_3 IFA Service Option [This draft]
TBD_4 SFC Service Metadata Type [This draft]
TBD_5 IOAM Service Metadata Type [This draft]
TBD_6 IFA Service Metadata Type [This draft]
6. Security Considerations
TBD.
7. References
7.1. Normative References
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[I-D.guichard-spring-nsh-sr]
Guichard, J., Song, H., Tantsura, J., Halpern, J.,
Henderickx, W., Boucadair, M., and S. Hassan, "NSH and
Segment Routing Integration for Service Function Chaining
(SFC)", draft-guichard-spring-nsh-sr-01 (work in
progress), March 2019.
[]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and d. daniel.voyer@bell.ca, "IPv6 Segment
Routing Header (SRH)", draft-ietf-6man-segment-routing-
header-22 (work in progress), August 2019.
[I-D.ietf-ippm-ioam-data]
Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
P., Chang, R., daniel.bernier@bell.ca, d., and J. Lemon,
"Data Fields for In-situ OAM", draft-ietf-ippm-ioam-
data-06 (work in progress), July 2019.
[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J.,
daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
Network Programming", draft-ietf-spring-srv6-network-
programming-01 (work in progress), July 2019.
[I-D.kumar-ippm-ifa]
Kumar, J., Anubolu, S., Lemon, J., Manur, R., Holbrook,
H., Ghanwani, A., Cai, D., Ou, H., and L. Yizhou, "Inband
Flow Analyzer", draft-kumar-ippm-ifa-01 (work in
progress), February 2019.
[I-D.song-ippm-postcard-based-telemetry]
Song, H., Zhou, T., Li, Z., Shin, J., and K. Lee,
"Postcard-based On-Path Flow Data Telemetry", draft-song-
ippm-postcard-based-telemetry-04 (work in progress), June
2019.
[I-D.song-opsawg-ifit-framework]
Song, H., Li, Z., Zhou, T., Qin, F., Shin, J., and J. Jin,
"In-situ Flow Information Telemetry Framework", draft-
song-opsawg-ifit-framework-04 (work in progress),
September 2019.
[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>.
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[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,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
[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>.
7.2. Informative References
[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>.
Authors' Addresses
Zhenbin Li
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
Shuping Peng
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: pengshuping@huawei.com
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Kihoon LEE
LG U+
71, Magokjungang 8-ro, Gangseo-gu
Seoul
Republic of Korea
Email: soho8416@lguplus.co.kr
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