SFC OAM for path consistency
draft-ao-sfc-oam-path-consistency-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Ting Ao , Greg Mirsky , Zhonghua Chen | ||
| Last updated | 2018-10-19 | ||
| Replaced by | draft-ietf-sfc-multi-layer-oam, draft-ietf-sfc-multi-layer-oam, RFC 9516 | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-ao-sfc-oam-path-consistency-03
SFC WG T. Ao
Internet-Draft ZTE Corporation
Intended status: Standards Track G. Mirsky
Expires: April 19, 2019 ZTE Corp.
Z. Chen
China Telecom
Oct 16, 2018
SFC OAM for path consistency
draft-ao-sfc-oam-path-consistency-03
Abstract
Service Function Chain (SFC) defines an ordered set of service
functions (SFs) to be applied to packets and/or frames and/or flows
selected as a result of classification. SFC Operation,
Administration and Maintenance can monitor the continuity of the SFC,
i.e., that all elements of the SFC are reachable to each other in the
downstream direction. But SFC OAM must support verification that the
order of traversing these SFs corresponds to the state defined by the
SFC control plane or orchestrator, the metric referred in this
document as the path consistency of the SFC. This document defines a
new SFC OAM method to support SFC consistency, i.e. verification that
all elements of the given SFC are being traversed in the expected
order.
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 April 19, 2019.
Ao, et al. Expires April 19, 2019 [Page 1]
Internet-Draft SFC OAM for path consistency Oct 2018
Copyright Notice
Copyright (c) 2018 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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Consistency OAM: Theory of Operation . . . . . . . . . . . . 3
3.1. COAM packet . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. SF information Sub-TLV . . . . . . . . . . . . . . . . . 4
3.3. SF information Sub-TLV construction . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
5.1. COAM Message Types . . . . . . . . . . . . . . . . . . . 7
5.2. SFF Information Record TLV Type . . . . . . . . . . . . . 7
5.3. SF Information Sub-TLV Type . . . . . . . . . . . . . . . 7
5.4. SF Identifier Types . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informational References . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
Service Function Chain (SFC) is a chain with a series of ordered
Service Functions (SFs). Service Function Path (SFP) is a path of a
SFC. SFC is described in detail in the SFC architecture document
[RFC7665]. The SFs in the SFC are ordered and only when traffic is
processed by one SF then it should be processed by the next SF,
otherwise errors may occur. Sometimes, a SF needs to use the
metadata from its upstream SF process. That's why it's very
important for the operator to make sure that the order of traversing
the SFs is exactly as defined by the control plane or the
Ao, et al. Expires April 19, 2019 [Page 2]
Internet-Draft SFC OAM for path consistency Oct 2018
orchestrator. This document refers to the correspondence between the
state of control plane and the SFP itself as the SFP consistency.
This document defines the method to check the path consistency of the
SFP. It is an extension of the SFC Echo-request/Echo-reply specified
in the [I-D.wang-sfc-multi-layer-oam].
2. Conventions used in this document
2.1. Terminology
SFC(Service Function Chain): An ordered set of some abstract SFs.
SFF: Service Function Forwarder
SF: Service Function
OAM: Operation, Administration and Maintenance
SFP: Service Function Path
COAM(Consistency OAM): OAM that can be used to check path
consistency.
2.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Consistency OAM: Theory of Operation
Consistency OAM uses two functions: COAM Request and COAM Reply. The
SFF, that is ingress of the SFP, transmits COAM Request packet.
Every intermediate SFF that receives the COAM Request MUST perform
the following actions:
collect information of traversed by the COAM Request packet SFs
and send it to the ingress SFF as COAM Reply packet over IP
network [I-D.wang-sfc-multi-layer-oam];
forward the COAM Request to next downstream SFF if the one exists.
As result, the ingress SFF collects information about all traversed
SFFs and SFs, information of the actual path the COAM packet has
traveled, so that we can verify the path consistency of the SFC. The
Ao, et al. Expires April 19, 2019 [Page 3]
Internet-Draft SFC OAM for path consistency Oct 2018
mechanism for the SFP consistency verification is outside the scope
of this document.
3.1. COAM packet
Consistency OAM introduces two new types of messages to the SFC Echo
request/reply operation [I-D.wang-sfc-multi-layer-oam] with the
following values Section 5.1:
o TBA1 - COAM Request
o TBA2 - COAM Reply
An SFF, upon receiving the Consistency OAM Request, MUST include the
corresponding SFs information, Section 3.2, into the Value field of
the COAM Reply packet.
The COAM packet is displayed in Figure 1.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Message Type | Reply mode | Return Code | Return S.code |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sender's Handle |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sequence Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Value ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: COAM Packet Header
3.2. SF information Sub-TLV
Every SFF receiving COAM Request packet MUST include the SF
characteristic data into the COAM Reply packet. The per SF data
included in COAM Reply packet as SF Information sub-TLV that is
displayed in Figure 2.
After the COAM traversed the SFP, all the information of the SFs on
the SFP are collected in the TLVs with COAM Reply.
Ao, et al. Expires April 19, 2019 [Page 4]
Internet-Draft SFC OAM for path consistency Oct 2018
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SF sub-TLV Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Service Path Identifier(SPI) | Service Index |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SF Type | Reserved | SF ID Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SF Identifiers |
~ ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Service Function information sub-TLV
Service Path Identifier(SPI): The identifier of SFP to which all the
SFs in this TLV belong.
Service Index: indicates the SF's position on the SFP.
SF sub-TLV Type: is two octets long field. It indicates that the TLV
is a SF TLV which contains the information of one SF.
Length: is two octets long field. The value of the field is the
length of the data following the Length field counted in octets.
SF Type: is two octets long field. It is defined in
[I-D.ietf-bess-nsh-bgp-control-plane] and indicates the type of SF,
e.g., Firewall, Deep Packet Inspection, WAN optimization controller,
etc.
Reserved: For future use. MUST be zeroed on transmission and MUST be
ignored on receipt.
SF ID Type: is one octet long field with values defined as
Section 5.4.
SF Identifier: An identifier of the SF. The length of the SF
Identifier depends on the type of the SF ID Type. For example, if
the SF Identifier is its IPv4 address, the SF Identifier should be 32
bits.
3.3. SF information Sub-TLV construction
For each SFF in the SFP, it should send one COAM Reply corresponding
to each one COAM Request. If there is only one SF attached to the
SFF in such SFP, only one SF information sub-TLV is included in the
Ao, et al. Expires April 19, 2019 [Page 5]
Internet-Draft SFC OAM for path consistency Oct 2018
on COAM Reply. If there are several SFs attached to the SFF in the
SFP, SF information sub-TLV is constructed as the following two
cases.
1. Multiple SFs as hops of SFP:
Multiple SFs attached to one SFF are the several hops of the SFP, the
service indexes of these SFs are different. Service function types
of these SFs could be different or be same. All these SFs
information are included in one COAM Reply message, every SF
information should be listed as separate SF information sub-TLVs in
COAM Reply message.
2. Multiple SFs for load balance:
Multiple SFs are attached to one SFF for load balance, that means
only one SF will be transmitted for one traffic flow. These SFs have
the same Service Function Type, Service Index. For this case, the SF
identifiers of all these SFs will be listed in the SF Identifiers
field in a single SF information sub-TLV of COAM Reply message. The
number of these SFs can be calculated according to SF ID Type and the
value of Length field of the sub-TLV.
In the draft [I-D.ietf-sfc-nsh-tlv], a Flow ID is introduced which
can be used for load balance. SFF will distribute the SFC traffic
flow to a given SF according to the Flow ID. So for a NSH COAM
message carrying a Flow ID TLV, the SFF along the SFC could detect
the COAM message and then send back the COAM Reply message with the
corresponding SF information according to the Flow ID in the COAM.
4. Security Considerations
Security considerations discussed in [RFC8300] apply to this
document.
In addition, since Service Function sub-TLV discloses information
about the RSP the spoofed COAM Request packet may be used to obtain
network information, it is RECOMMENDED that implementations provide a
means of checking the source addresses of COAM Request messages,
specified in SFC Source TLV [I-D.wang-sfc-multi-layer-oam], against
an access list before accepting the message.
5. IANA Considerations
Ao, et al. Expires April 19, 2019 [Page 6]
Internet-Draft SFC OAM for path consistency Oct 2018
5.1. COAM Message Types
IANA is requested to assign values from its Message Types sub-
registry in SFC Echo Request/Echo Reply Message Types registry as
follows:
+-------+------------------------------+---------------+
| Value | Description | Reference |
+-------+------------------------------+---------------+
| TBA1 | SFP Consistency Echo Request | This document |
| TBA2 | SFP Consistency Echo Reply | This document |
+-------+------------------------------+---------------+
Table 1: SFP Consistency Echo Request/Echo Reply Message Types
5.2. SFF Information Record TLV Type
IANA is requested to assign new type value from SFC OAM TLV Type
registry as follows:
+-------+-----------------------------+---------------+
| Value | Description | Reference |
+-------+-----------------------------+---------------+
| TBA3 | SFF Information Record Type | This document |
+-------+-----------------------------+---------------+
Table 2: SFF-Information Record
5.3. SF Information Sub-TLV Type
IANA is requested to assign new type value from SFC OAM TLV Type
registry as follows:
+-------+----------------+---------------+
| Value | Description | Reference |
+-------+----------------+---------------+
| TBA4 | SF Information | This document |
+-------+----------------+---------------+
Table 3: SF-Information Sub-TLV Type
5.4. SF Identifier Types
IANA is requested create in the registry SF Types the new sub-
registry SF Identifier Types. All code points in the range 1 through
191 in this registry shall be allocated according to the "IETF
Review" procedure as specified in [RFC8126] and assign values as
follows:
Ao, et al. Expires April 19, 2019 [Page 7]
Internet-Draft SFC OAM for path consistency Oct 2018
+------------+-------------+-------------------------+
| Value | Description | Reference |
+------------+-------------+-------------------------+
| 0 | Reserved | This document |
| TBA6 | IPv4 | This document |
| TBA7 | IPv6 | This document |
| TBA8 | MAC | This document |
| TBA8+1-191 | Unassigned | IETF Review |
| 192-251 | Unassigned | First Come First Served |
| 252-254 | Unassigned | Private Use |
| 255 | Reserved | This document |
+------------+-------------+-------------------------+
Table 4: SF Identifier Type
6. Acknowledgements
Thanks to John Drake for his review and the reference to the work on
BGP Control Plane for NSH SFC.
7. References
7.1. Normative References
[I-D.ietf-bess-nsh-bgp-control-plane]
Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L.
Jalil, "BGP Control Plane for NSH SFC", draft-ietf-bess-
nsh-bgp-control-plane-04 (work in progress), July 2018.
[I-D.ietf-sfc-nsh-tlv]
Quinn, P., Elzur, U., and S. Majee, "Network Service
Header TLVs", draft-ietf-sfc-nsh-tlv-00 (work in
progress), January 2018.
[I-D.wang-sfc-multi-layer-oam]
Mirsky, G., Meng, W., Khasnabish, B., and C. Wang, "Active
OAM for Service Function Chains in Networks", draft-wang-
sfc-multi-layer-oam-12 (work in progress), October 2018.
[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>.
[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>.
Ao, et al. Expires April 19, 2019 [Page 8]
Internet-Draft SFC OAM for path consistency Oct 2018
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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. Informational 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
Ting Ao
ZTE Corporation
No.889, BiBo Road
Shanghai 201203
China
Phone: +86 21 68897642
Email: ao.ting@zte.com.cn
Greg Mirsky
ZTE Corp.
1900 McCarthy Blvd. #205
Milpitas, CA 95035
USA
Email: gregimirsky@gmail.com
Zhonghua Chen
China Telecom
No.1835, South PuDong Road
Shanghai 201203
China
Phone: +86 18918588897
Email: 18918588897@189.cn
Ao, et al. Expires April 19, 2019 [Page 9]