Network Working Group Z. Li
Internet-Draft S. Peng
Intended status: Standards Track Huawei Technologies
Expires: September 12, 2019 March 11, 2019
Consideration of IPv6 Encapsulation for SFC and IFIT
draft-li-6man-ipv6-sfc-ifit-00
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
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on September 12, 2019.
Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
4. Design Consideration . . . . . . . . . . . . . . . . . . . . 3
4.1. Service Options . . . . . . . . . . . . . . . . . . . . . 4
4.2. IPv6 Metadata Header . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
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.
2. Terminology
SFC: Service Function Chaining
IFIT: In-situ Flow Information Telemetry
IOAM: In-situ OAM
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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 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 following
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.filsfils-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.
5. [I-D.guichard-spring-nsh-sr] is proposed for the solution to
encapsulate NSH in SRv6 to support SFC. But the encapsulation is not
defined yet.
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:
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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
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
Opt Data Len: 8 octets.
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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
Opt Data Len: 8 octets.
Other fields: refer to [I-D.ietf-ippm-ioam-data].
3. PBT 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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
Opt Data Len: 20 octets.
Other fields: refer to [I-D.song-ippm-postcard-based-telemetry].
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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
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.
4.2. IPv6 Metadata Header
IPv6 Metadata Header is defined as a new type of IPv6 extension
header shown in Figure 5. The metadata is the information recorded
by each hop for specific path services, The length of the metadata is
variable.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Header | Hdr Ext Len | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
. .
. Metadata Stack (Variable) .
. .
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. Metadata Header
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Next Header 8-bit selector. Identifies the type of header
immediately following the IPv6 metadata
header.
Hdr Ext Len 8-bit unsigned integer. Length of the
IPv6 metadata header in 8-octet units,
not including the first 8 octets.
Metadata Stack Variable-length field, of length such that the
complete IPv6 metadata header is an
integer multiple of 8 octets long. Contains
one or more type of path service metadata.
For specific path service, i.e. SFC/IOAM, the corresponding metadata
is defined as follows:
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 Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| Metadata (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6. Service Metadata
Service Type 8-bit selector. Identifies the type of
Service Metadata.
Length 16-bit unsigned integer. Length of the
Service metadata in 8-octet units,
not including the first 8 octets.
Metadata Variable-length field, of length such that the
complete IPv6 metadata header is an
integer multiple of 8 octets long.
5. IANA Considerations
TBD.
6. Security Considerations
TBD.
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7. References
7.1. 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>.
7.2. Informative References
[I-D.filsfils-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J.,
daniel.voyer@bell.ca, d., Matsushima, S., and Z. Li, "SRv6
Network Programming", draft-filsfils-spring-srv6-network-
programming-07 (work in progress), February 2019.
[I-D.guichard-spring-nsh-sr]
Guichard, J., Song, H., Tantsura, J., Halpern, J.,
Henderickx, W., and M. Boucadair, "NSH and Segment Routing
Integration for Service Function Chaining (SFC)", draft-
guichard-spring-nsh-sr-00 (work in progress), September
2018.
[]
Filsfils, C., Previdi, S., Leddy, J., Matsushima, S., and
d. daniel.voyer@bell.ca, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-16 (work in
progress), February 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-05 (work in progress), March 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., and J. Shin, "Postcard-based
In-band Flow Data Telemetry", draft-song-ippm-postcard-
based-telemetry-02 (work in progress), March 2019.
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[I-D.song-opsawg-ifit-framework]
Song, H., Li, Z., Zhou, T., Li, Z., and J. Shin, "In-situ
Flow Information Telemetry Framework", draft-song-opsawg-
ifit-framework-01 (work in progress), March 2019.
[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>.
[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>.
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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