Service Function Chaining J. Guichard
Internet-Draft Huawei
Intended status: Informational M. Smith
Expires: February 19, 2018 S. Kumar
Cisco Systems, Inc.
S. Majee
F5 Networks
P. Agarwal
Broadcom
K. Glavin
Riverbed
Y. Laribi
Citrix
T. Mizrahi
Marvell
August 18, 2017
Network Service Header (NSH) MD Type 1: Context Header Allocation (Data
Center)
draft-guichard-sfc-nsh-dc-allocation-07
Abstract
This document provides a recommended default allocation for the
Network Service Header (NSH) MD Type 1 fixed length context header
when NSH is used for Service Function Chaining within a data center.
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 February 19, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Definition Of Terms . . . . . . . . . . . . . . . . . . . . . 3
3. Recommended Data Center MD Type 1 Fixed Length Context
Allocation . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Data Center Allocation Specifics . . . . . . . . . . . . 3
4. Context Allocation and Control Plane Considerations . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Network Service Header (NSH) [I-D.ietf-sfc-nsh] provides a mechanism
to carry shared metadata between network devices and service
functions, and between service functions. When MD Type 1 is used,
such metadata is carried within a fixed length (16-bytes) context
header.
This document provides a recommended default allocation of the MD
Type 1 context header for Service Function Chaining [RFC7665] within
a data center. The context header may be used to support use cases
such as those described in [I-D.ietf-sfc-dc-use-cases].
The goal of this document is to provide a reference allocation that
may be used with or without a control plane. It also serves as a
guide to implementers and network operators.
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1.1. 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].
2. Definition Of Terms
This document uses the terms as defined in [RFC7498], [RFC7665], and
[I-D.ietf-sfc-nsh] .
3. Recommended Data Center MD Type 1 Fixed Length Context Allocation
The following context header allocation provides information used to
support SFC operation within a generic data center environment.
[I-D.ietf-sfc-dc-use-cases] provides an overview of data center use
cases to support the allocation.
The 16 bytes of Fixed Length Context Header is delivered to service
functions that may then use the metadata it carries for local policy
enforcement and other functionality.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|D| F |R| Source Node ID | Source Interface ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Tenant ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination Class / Reserved | Source Class |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Service Class |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: NSH DC Context Allocation
3.1. Data Center Allocation Specifics
The specific 16 byte allocation of the Fixed Length Context Header is
as follows:
Flag bits: Bits 0-3 are flag bits. Bits 0-2 are defined in this
document and the remaining bit is reserved.
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D bit: The D-bit is used to indicate whether the Destination Class
field in the 3rd word is used. If D-bit is not set then the field
is reserved.
F bits: Two-bit value that indicates the format of the Opaque
Service Class in the 4th word.
Source Node ID: An identifier indicating the source device where the
original traffic initially entered the Service Function Chain. This
identifier is unique within an SFC-enabled domain.
Source Interface ID: An identifier indicating the source interface
where the original traffic initially entered the Service Function
Chain. This identifier is scoped within the context of the Source
Node ID.
Tenant ID: The tenant identifier is used to represent the tenant that
the Service Function Chain is being applied to. The Tenant ID is a
unique value assigned by a control plane. The distribution of Tenant
ID's is outside the scope of this document. As an example
application of this field, hardware may insert a VRF ID, VLAN number
or VXLAN VNI.
Destination Class: The destination class represents the logical
classification of the destination of the traffic. This field is
optional and/or the Destination Class may not be known. The D-bit is
used to indicate that this field contains a valid Destination Class.
Source Class: represents the logical classification of the source of
the traffic. For example, this might represent a source application,
a group of like endpoints, or a set of users originating the traffic.
This grouping is done for the purposes of applying policy. Policy is
applied to groups rather than individual endpoints.
Opaque Service Class: A unique identifier that can carry metadata
specific to a Rendered Service Path, the format of which is specified
by the value of the F-bits as follows:
00: If the F-bits are not set, then the Opaque Service Class field
is not specified and can be used as determined by the control
plane.
01 (ServiceTag): a ServiceTag is used to identify a particular
flow, transaction or an application message unit. The ServiceTag
may be used to augment the source and/or destination class. A
ServiceTag is a unique identifier that can be used to enable
functionality such as classification bypass, slow path skipping
and flow programming. As part of the ServiceTag word, bit 0 is
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the A bit and is used, when needed, to indicate acknowledgement of
a ServiceTag by a Service Function.
02 (Application ID): contains an application identification as
described in [RFC6759], and [I-D.penno-sfc-appid]
03 (Timestamp): indicates the time at which the packet was
received by the Classifier.
The Timestamp has two possible formats:
* A 32-bit nanosecond field (Figure 2), which uses the 32 least
significant bits of the IEEE 1588 [IEEE1588] timestamp format.
* The NTP [RFC5905] 32-bit Timestamp format (Figure 3), which is
one of the recommended timestamp formats in
[I-D.mizrahi-intarea-packet-timestamps].
It is assumed that in a given administrative domain only one of
the formats will be used, and that the control plane determines
which timestamp format is used.
The two timestamp formats are illustrated in the following
figures.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Nanoseconds |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: 32-bit Timestamp Format based on PTP [IEEE1588]
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Seconds | Fraction |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: NTP [RFC5905] 32-bit Timestamp Format
4. Context Allocation and Control Plane Considerations
The context header allocations specified in this document are one of
many possible allocation schemes and should be used as a guideline
only; that is to say these allocations may vary based upon deployment
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specifics and use cases. The suggested allocation is valid with or
without a control plane but the semantics of context values MUST be
shared amongst participating nodes via some mechanism. The actual
method of defining and distributing the allocation scheme is outside
of the scope of this document.
5. Security Considerations
This document describes an allocation scheme for the metadata carried
within the NSH Fixed Length Context Header. This allocation includes
a number of identifiers that must be distributed to participating
network elements. While the control plane protocols for distributing
these identifiers is outside the scope of this document, any control
plane protocol should ensure that these identifiers are securely
distributed to the network elements participating in the SFC.
Additionally, many of the fields such as Source and Destination Class
described in the metadata directly impact the network policy applied
to the traffic flowing through the SFC. There is a risk that these
identifiers may be spoofed and proper precautions should be put in
place to ensure that these fields can only be updated by trusted
entities. Due to the importance of these fields, confidentiality may
also be required to ensure that traffic cannot be targeted for attack
based on the policy identifiers. This document does not directly
address these threats but provides input to the NSH specification as
requirements to be considered in securing the contents of the
metadata.
6. Acknowledgments
The authors would like to thank Mohamed Boucadair for his helpful
review and comments.
7. IANA Considerations
This document includes no request to IANA.
8. References
8.1. Normative References
[I-D.ietf-sfc-nsh]
Quinn, P., Elzur, U., and C. Pignataro, "Network Service
Header (NSH)", draft-ietf-sfc-nsh-19 (work in progress),
August 2017.
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[I-D.penno-sfc-appid]
Penno, R., Claise, B., Pignataro, C., and C. Fontaine,
"Using Application Identification in Services Function
Chaining Metadata", draft-penno-sfc-appid-05 (work in
progress), August 2016.
[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>.
[RFC6759] Claise, B., Aitken, P., and N. Ben-Dvora, "Cisco Systems
Export of Application Information in IP Flow Information
Export (IPFIX)", RFC 6759, DOI 10.17487/RFC6759, November
2012, <https://www.rfc-editor.org/info/rfc6759>.
[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>.
8.2. Informative References
[I-D.ietf-sfc-dc-use-cases]
Kumar, S., Tufail, M., Majee, S., Captari, C., and S.
Homma, "Service Function Chaining Use Cases In Data
Centers", draft-ietf-sfc-dc-use-cases-06 (work in
progress), February 2017.
[I-D.mizrahi-intarea-packet-timestamps]
Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for
Defining Packet Timestamps", draft-mizrahi-intarea-packet-
timestamps-00 (work in progress), June 2017.
[IEEE1588]
IEEE, "IEEE 1588 Standard for a Precision Clock
Synchronization Protocol for Networked Measurement and
Control Systems Version 2", 2008.
[RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
"Network Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010,
<https://www.rfc-editor.org/info/rfc5905>.
[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>.
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Authors' Addresses
Jim Guichard
Huawei
Email: james.n.guichard@huawei.com
Michael Smith
Cisco Systems, Inc.
Email: michsmit@cisco.com
Surendra Kumar
Cisco Systems, Inc.
Email: smkumar@cisco.com
Sumandra Majee
F5 Networks
90 Rio Robles
San Jose, CA 95134
Email: S.Majee@f5.com
Puneet Agarwal
Broadcom
Email: pagarwal@broadcom.com
Kevin Glavin
Riverbed
Email: Kevin.Glavin@riverbed.com
Youcef Laribi
Citrix
Email: Youcef.Laribi@citrix.com
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Tal Mizrahi
Marvell
Email: talmi@marvell.com
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