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-02Abstract
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 working documents as Internet-Drafts. The list of current Internet- 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 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. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
Li, et al. Expires March 13, 2020 [Page 1]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
Table of Contents1. 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.
Li, et al. Expires March 13, 2020 [Page 2]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019 2. TerminologySFC: 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.
Li, et al. Expires March 13, 2020 [Page 3]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019 4. Design ConsiderationTo 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
Li, et al. Expires March 13, 2020 [Page 4]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
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 instructionsOption 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 instructionsOption Type: TBD_1
Opt Data Len: 8 octets.
Other fields: refer to [I-D.ietf-ippm-ioam-data].
3. PBT Service Option
Li, et al. Expires March 13, 2020 [Page 5]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
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 instructionsOption 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_3Opt 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.
Li, et al. Expires March 13, 2020 [Page 6]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019 4.2. IPv6 Service Metadata OptionsAs 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 MetadataSFC 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].
Li, et al. Expires March 13, 2020 [Page 7]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019 4.2.2. IOAM Service Metadata OptionFor 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 MetadataIOAM 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.
Li, et al. Expires March 13, 2020 [Page 8]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
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 MetadataIFA 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 Li, et al. Expires March 13, 2020 [Page 9]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
[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.
[I-D.ietf-6man-segment-routing-header]
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>.
Li, et al. Expires March 13, 2020 [Page 10]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines forWriting 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 FunctionChaining (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 Kihoon LEE LG U+ 71, Magokjungang 8-ro, Gangseo-gu Seoul Republic of Korea
Li, et al. Expires March 13, 2020 [Page 11]
Internet-Draft IPv6 Encaps for SFC and IFIT September 2019
Email: soho8416@lguplus.co.krLi, et al. Expires March 13, 2020 [Page 12]
