Internet DRAFT - draft-beliveau-sfc-architecture
draft-beliveau-sfc-architecture
Network Working Group A. Beliveau
Internet-Draft Ericsson
Intended status: Standards Track October 16, 2013
Expires: April 19, 2014
Service Function Chaining Architecture
draft-beliveau-sfc-architecture-00
Abstract
This document describes an architecture for Service Function
Chaining. It addresses operational aspects of Service Function
Chaining such administration of Service Function Chains, network and
forwarding principles. It also covers architectural principles to
support scale-in and scale-out of Service Functions.
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.
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This Internet-Draft will expire on April 19, 2014.
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Copyright (c) 2013 IETF Trust and the persons identified as the
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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 . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Architecture principles . . . . . . . . . . . . . . . . . . . 4
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. Service Function Chain . . . . . . . . . . . . . . . . . . 4
3.3. Service Chaining Infrastructure . . . . . . . . . . . . . 5
3.4. Service Function scaling . . . . . . . . . . . . . . . . . 7
3.5. Service Function Classification . . . . . . . . . . . . . 7
3.6. Service Chaining Controller . . . . . . . . . . . . . . . 7
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
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1. Introduction
This document describes an architecture for Service Function Chaining
(SFC). It describes components and architecture principles to
provide Service Function Chaining in a network.
2. Terminology
This document makes use of the following terms:
Service Function(SF): An application or service which performs
specific treatments when packets traverses it. A non-exhaustive
list of Service Functions include: firewall (e.g.,[RFC6092]), DPI
(Deep Packet Inspection), NAT44 [RFC3022], NAT64 [RFC6146],
HOST_ID injection, HTTP Header Enrichment function, load-balancer,
etc. The exact definition of each Service Function is specifc to
each Service Function provider.
Service Function Identity(SF-ID): A unique identifier which
represents each SF in a network. SF-ID is unique within each SFC
network and does not need to be globally unique. Even if multiple
instances of the same Service Function are available in an SFC
network, the same SF-ID is used to identify the Service Function.
Service Function Locator(SF-Loc): A unique name or address which
identifies each Service Function. When multiple instances of the
same Service Function are available in an SFC network, each
instance has its own Service Function Locator.
Service Function Chain (SFC): An ordered list of SF which should be
traversed.
Service Function Chain Identity (SC-ID): A unique identifier which
represents each SFC in a network. SC-ID is unique within each SFC
network and does not need to be globally unique.
Service Function Chain Enforcement Point (SCEP): A node which is
able to guarantee that a list of SF will be traversed in a
specific order for flows which are associated with such SF chain.
Service Chaining Infrastructure Network (SC-IN): is formed by a one
or more SCEP nodes connected together.
Service Chaining Classification Function (SC-CL): A logical function
part of a SCEP node. SC-CL is mandatory to execute when packets
enter the SC-IN (ingress).
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Service Chaining Forwarding Function (SC-FWD): A logical function
part of a SCEP node. It is responsible for forwarding packets to
SF, forwarding packets to other SCEP nodes and to remove SC-IN
specific information from packets when exiting (egress) SC-IN.
SC-FWD is mandatory in all SCEP nodes.
Service Function Path: Specific path taken by packets through SC-IN.
Service Function Path includes specific SCEP nodes and SF nodes
traversed by an individual flow.
3. Architecture principles
3.1. Introduction
The concept of Service Function Chaining consists of applying a
number of Service Functions in a specific order. The proposed
architecture for Service Function Chaining ties together four
different mechanisms to guarantee the execution of Service Functions
in a specifc order.
Those four separate mechanisms are:
o A mechanism to specify a Service Function Chain (SFC) as an
ordered list of Service Functions.
o A mechanism to deliver packets between SF instances in the
specified order: Service Chaining Infrastructure (SC-IN).
o A mechanism to specify which packets should be associated with a
specific Service Function Chain: SFC classification.
o A mechanism to support scaling in/out the number of instances of
each SF.
3.2. Service Function Chain
A Service Function Chain (SFC) consists of an ordered list of Service
Function (SF). Each SF is defined by an identifier which is unique
within an administrative domain (SF-ID). No IANA registry is
required to store the identity of SFs.
Multiple Service Function Chains can exist in the same administrative
domain. Each Service Function Chain (SFC) is defined by an
identifier which is unique within an administrative domain (SC-ID).
No IANA registry is required to store the identity of Service
Function Chains.
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As no information about topology, SF classification or SF scaling is
represented in the SF chain definition therefore, Service Function
Chains are independent from changes in topology, classification or
scaling instances of a Service Function.
Here is a some examples of Service Function Chains:
+----------+ +----------+ +----------+ +----------+
| Load | | Web | | Fire | | |
SFC-ID=1 | Balancer |--| Proxy |--| wall |--| NAT44 |
| SF-ID=1 | | SF-ID=2 | | SF-ID=3 | | SF-ID=4 |
+----------+ +----------+ +----------+ +----------+
+----------+ +----------+ +----------+
| | | Header | | Fire |
SFC-ID=2 | DPI |--| enrichm. |--| wall |
| SF-ID=6 | | SF-ID=5 | | SF-ID=3 |
+----------+ +----------+ +----------+
Figure 1: Service Function Chain examples
3.3. Service Chaining Infrastructure
The Service Chaining Infrastructure (SC-IN) consists of Service
Chaining Enforcement Points (SCEP) and Service Functions
interconnected as a network. An SCEP node contains a forwarding
function (SC-FWD) and optionally a classification function (SC-CL).
Service Chaining Infrastructure (SC-IN) is illustrated in Figure 2.
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+..................................................................+
. +------------+ +------------+ +------------+ +------------+ .
. | Service | | Service | | Service | | Service | .
. |Function(SF)| |Function(SF)| |Function(SF)| |Function(SF)| .
. +------------+ +------------+ +------------+ +------------+ .
. \ / \ / .
. \ / \ / .
. \ / \ / .
. +------------+ +------------+ .
. | SCEP | | SCEP | .
. | (SC-FWD) | | (SC-FWD) | .
. +------------+ +------------+ .
. \ / .
. \ / .
. \ .--. / .
. +------------+ \ ( )-. / +------------+ .
. |SCEP-Ingress| .' ' | SCEP-Egress| .
. |(SC-CL,FWD) |-------( Network )------| (SC-FWD) | .
. +------------+ ( -' +------------+ .
. / '-( ) \ .
. / '---' \ .
. / Service Chaining Infrastructure \ .
+......../..............................................\..........+
/ \
.--. .--.
( )-. ( )-.
.' Ingress' .' Egress '
( Network ) ( Network )
( -' ( -'
'-( ) '-( )
'---' '---'
Figure 2: Service Chaining Infrastructure
SCEP can directly reach other SCEP nodes within the SC-IN. Service
Functions (SF) are directly connected to an SCEP. To enforce the
execution of SF in the specified order, Service Functions (SF) cannot
communicate directly between eachother without going through an SCEP.
One or many SFs can be attached to the same SCEP.
When entering an SC-IN, an ingress SCEP which contains an SC-CL will
map packets into a specific Service Function Path. Once this mapping
is done, the SC-FWD will determine the locator for the next SF on the
Service Function Path and forward the packet to the SF to be invoked.
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3.4. Service Function scaling
Multiple instances of the same Service Function can exist in the
SC-IN. Each new instances of a SF, when created, will be attached to
an SCEP in the SC-IN and a unique locator (SF-Loc) will be allocated
to it.
When instances of a Service Function needs to be removed, the Service
Function Controller will ensure that no packet can be forwarded to
the instance of Service Function to be removed. Once done, the
Service Function instance can be removed.
3.5. Service Function Classification
In order to direct specific packets to follow a certain Service
Function Path, SC-CL will analyse the packet headers and determine
which Service Function Path should be followed. A Service Function
Path is a list of Service Function locators (SF-Loc) for the specific
instances of SF which constitutes a SFC.
Once the Service Function Path is determined, the Service Chaining
Forwarding function (SC-FWD) will determine the next Service Function
and forward the traffic to it.
3.6. Service Chaining Controller
The Service Function Chaining Controller is responsible to configure
SCEP nodes in the Service Chaining Infrastructure. It is the
controller which ties together Service Function Chains/Paths, the
topology of the Service Chaining Infrastructure, the locating
information of SF instances as they are being scaled in/out and
Service Chaining Classification rules.
It is responsible to guarantee the consistency of the configuration
of SCEP across the SC-IN. Service Chaining Controller is illustrated
in Figure 3.
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+-----------------+
| Service |
| Chaining |.....................
| Controller | .
+-----------------+ .
. . .
+..................................................................+
. . . . .
. . +------------+ . .
. . | SCEP | . .
. . | (SC-FWD) | . .
. . +------------+ . .
. . \ . .
. . \ . .
. . \ .--. . .
. +------------+ \ ( )-. +------------+ .
. |SCEP-Ingress| .' ' | SCEP-Egress| .
. |(SC-CL,FWD) |-------( Network )------| (SC-FWD) | .
. +------------+ ( -' +------------+ .
. '-( ) .
. '---' .
. Service Chaining Infrastructure .
+..................................................................+
Figure 3: Service Chaining Controller
4. Acknowledgements
This template was derived from an initial version written by Pekka
Savola and contributed by him to the xml2rfc project.
5. IANA Considerations
This document has no IANA actions.
6. Security Considerations
SFC must address at least the following security considerations:
o Secure and authenticate communication between controller and SCEP
nodes
o Authenticate communication between SF and SCEP node.
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o Isolate SC-IN network when infrastructure is shared with nodes
which are not SCEP nodes.
o Protect interface at border of SC-IN (ingress/egress SCEP) against
fraudulent usage.
o Protect SFC specific protocol/metadata information against
fraudulent usage.
o When an SCEP participate in multiple networks, isolation between
them.
o Protect interface between SF and SCEP node against fraudulent
usage.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3022] Srisuresh, P. and K. Egevang, "Traditional IP Network
Address Translator (Traditional NAT)", RFC 3022,
January 2001.
[RFC6092] Woodyatt, J., "Recommended Simple Security Capabilities in
Customer Premises Equipment (CPE) for Providing
Residential IPv6 Internet Service", RFC 6092,
January 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
7.2. Informative References
[I-D.boucadair-sfc-framework]
Boucadair, M., Jacquenet, C., Parker, R., Lopez, D.,
Guichard, J., and C. Pignataro, "Service Function
Chaining: Framework & Architecture",
draft-boucadair-sfc-framework-00 (work in progress),
October 2013.
[I-D.boucadair-sfc-requirements]
Boucadair, M., Jacquenet, C., Jiang, Y., Parker, R., and
C. Pignataro, "Requirements for Service Function
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Chaining", draft-boucadair-sfc-requirements-00 (work in
progress), October 2013.
[I-D.quinn-sfc-problem-statement]
Quinn, P., Guichard, J., Surendra, S., Agarwal, P., Manur,
R., Chauhan, A., Leymann, N., Boucadair, M., Jacquenet,
C., Smith, M., Yadav, N., Nadeau, T., Gray, K., McConnell,
B., and K. Kevin, "Service Function Chaining Problem
Statement", draft-quinn-sfc-problem-statement-00 (work in
progress), October 2013.
Author's Address
Andre Beliveau
Ericsson
8400 Decarie Blvd.
Town of Mount Royal, QC
Canada
Phone: +1 514 345 2708
Email: andre.beliveau@ericsson.com
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