Requirements for Service Function Chaining (SFC)
draft-boucadair-sfc-requirements-04
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Mohamed Boucadair , Christian Jacquenet , Yuanlong Jiang , Ron Parker , Carlos Pignataro , Kengo | ||
| Last updated | 2014-04-04 | ||
| Replaces | draft-boucadair-chaining-requirements | ||
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| Stream | Stream state | (No stream defined) | |
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| Send notices to | (None) |
draft-boucadair-sfc-requirements-04
SFC M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Informational France Telecom
Expires: October 6, 2014 Y. Jiang
Huawei Technologies Co., Ltd.
R. Parker
Affirmed Networks
C. Pignataro
Cisco Systems, Inc.
K. Naito
NTT
April 04, 2014
Requirements for Service Function Chaining (SFC)
draft-boucadair-sfc-requirements-04
Abstract
This document identifies the requirements for the Service Function
Chaining (SFC).
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 http://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 October 6, 2014.
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Copyright Notice
Copyright (c) 2014 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
(http://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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Detailed Requirements List . . . . . . . . . . . . . . . . . 3
4. SFC Diagnosis & Troubleshooting . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
9.1. Normative References . . . . . . . . . . . . . . . . . . 11
9.2. Informative References . . . . . . . . . . . . . . . . . 11
1. Introduction
This document identifies the requirements for the Service Function
Chaining (SFC). In particular:
1. Generic requirements are listed in Section 3.
2. SFC diagnostic requirements are discussed in Section 4.
3. Security-specific requirements are listed in Section 6.
The overall problem space is described in
[I-D.ietf-sfc-problem-statement].
2. Terminology
The reader should be familiar with the terms defined in
[I-D.ietf-sfc-problem-statement].
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The document makes use of the following terms:
o SFC-enabled domain: denotes a network (or a region thereof) that
implements SFC.
o Service Function Loop: If a Service Function Chain is structured
to not invoke Service Functions multiple times, a loop is the
error that occurs when the same Service Function is invoked
several times when handling data bound to that Service Function
Chain. In other words, a loop denotes an error that occurs when a
packet handled by a Service Function, forwarded onwards, and
arrives once again at that Service Function while this is not
allowed by the Service Function Chain it is bound to.
o Service Function Spiral: denotes a Service Function Chain in which
data is handled by a Service Function, forwarded onwards, and
arrives once again at that Service Function.
* Note that some Service Functions support built-in functions to
accommodate spirals; these service-specific functions may
require that the data received in a spiral should differ in a
way that will result in a different processing decision than
the original data. This document does not make such
assumption.
* A Service Function Chain may involve one or more Service
Function Spirals.
* Unlike Service Function loop, spirals are not considered as
errors.
3. Detailed Requirements List
The following set of functional requirements should be considered for
the design of the Service Function Chaining solution:
REQ#1: The solution MUST NOT make any assumption on whether Service
Functions (SF) are deployed directly on physical hardware,
as one or more Virtual Machines, or any combination thereof.
REQ#2: The solution MUST NOT make any assumption on whether Service
Functions each reside on a separate addressable Network
Element, or as a horizontal scaling of Service Functions, or
are co-resident in a single addressable Network Element, or
any combination thereof.
Note: Communications between co-located Service Functions
are considered implementation-specific. These
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considerations are therefore out of scope of the SFC
specification effort.
REQ#3: The solution MUST NOT require any IANA registry for Service
Functions.
REQ#4: The solution MUST NOT assume any predefined order of Service
Functions. In particular, the solution MUST NOT require any
IANA registry to store typical Service Function Chains.
REQ#5: The identification of instantiated Service Function Chains
is local to each administrative domain; it is policy-based
and deployment-specific.
REQ#6: The solution MUST allow multiple instances of a given
Service Function ( i.e., a Service Function can be embedded
in multiple Network Elements).
A. This is used for load-balancing, load-sharing, to
minimize the impact of failures (e.g., by means of a hot
or cold standby protection design), to accommodate
planned maintenance operations, etc.
B. How these multiple devices are involved in the service
delivery is deployment-specific.
REQ#7: The solution MUST allow for multiple Service Chains to be
simultaneously enforced within an administrative domain.
REQ#8: The solution MUST allow the same Service Function to belong
to multiple Service Function Chains.
REQ#9: The solution MUST support the ability to deploy multiple
SFC-enabled domains within the same administrative domain.
REQ#10: The solution MUST be able to associate the same or distinct
Service Function Chains for each direction (inbound/
outbound) of the traffic pertaining to a specific service.
In particular, unidirectional Service Function Chains, bi-
directional Service Function Chains, or any combination
thereof MUST be supported.
Note, the solution must allow to involve distinct SFC
Boundary Nodes for upstream and downstream. Multiple SFC
Boundary Nodes may be deployed within an administrative
domain.
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REQ#11: The solution MUST be able to dynamically enforce Service
Function Chains. In particular, the solution MUST allow the
update or the withdrawal of existing Service Function
Chains, the definition of a new Service Function Chain, the
addition of new Service Functions without having any impact
on other existing Service Functions or other Service
Function Chains.
REQ#12: The solution MUST provide means to control the SF-inferred
information to be leaked outside an SFC-enabled domain. In
particular, an administrative entity MUST be able to prevent
the exposure of the Service Function Chaining logic and its
related policies outside the administrative domain.
REQ#13: The solution SHOULD minimize fragmentation; in particular, a
minimal set of SFC-specific information should be conveyed
in the data packet.
A. Traffic forwarding on a SFC basis MUST be undertaken
without relying on dedicated resources to treat
fragments. In particular, Out of order fragments MUST
be forwarded on a per-SFC basis without relying on any
state.
B. Of course, some SFs (e.g., NAT) may require dedicated
resources (e.g., resources to store fragmented packets)
or they may adopt a specific behavior (e.g, limit the
time interval to accept fragments). The solution MUST
NOT interfere with such practices.
REQ#14: The solution MUST NOT make any assumption on how RIBs
(Routing Information Bases) and FIBs (Forwarding Information
Bases) are populated. Particularly, the solution does not
make any assumption on protocols and mechanisms used to
build these tables.
REQ#15: The solution MUST be transport independent.
A. The Service Function Chaining should operate regardless
of the network transport used by the administrative
entity. In particular, the solution can be used
whatever the switching technologies deployed in the
underlying transport infrastructure.
B. Techniques such as MPLS are neither required nor
excluded.
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REQ#16: The solution MUST allow for chaining logics where involved
Service Functions are not within the same layer 3 subnet.
REQ#17: The solution MUST NOT exclude Service Functions to be within
the same IP subnet (because this is deployment-specific).
REQ#18: The solution MUST NOT make any assumption on how the traffic
is to be bound to a given chaining policy. In other words,
classification rules are deployment-specific and policy-
based. For instance, classification can rely on a subset of
the information carried in a received packet such as 5-tuple
classification, be subscriber-aware, be driven by traffic
engineering considerations, or any combination thereof.
A. The solution SHOULD accommodate a large number of
classification policy entries.
B. In order to reduce classification look-up time, means to
optimize the size of the classification table (e.g.,
aggregation) SHOULD be supported by the Classifier.
REQ#19: The solution MUST support traffic classification
capabilities according to the Service Function Chains
supported within the SFC domain.
REQ#20: The solution MUST NOT require every Service Function to be
co-located with a SFC Classifier; this is a deployment-
specific decision.
A. The solution MAY allow traffic re-classification at the
level of Service Functions (i.e., a Service Function can
also be co-located with a classifier). The
configuration of classification rules in such context
are the responsibility of the administrative entity that
operates the SFC-enabled domain.
REQ#21: The solution MUST be able to forward traffic between two
Service Functions (involved in the same Service Function
Chain) without relying upon the destination address field of
the a data packet.
REQ#22: The solution MUST allow for the association of a context
with the data packets. In particular:
A. The solution MUST support the ability to invoke
differentiated sets of policies for a Service Function
(such sets of policies are called Profiles). A profile
denotes a set of policies configured to a local Service
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Function (e.g., content-filter-child, content-filter-
adult).
a. Few profiles should be assumed per Service Function
to accommodate the need for scalable solutions.
b. A finer granularity of profiles may be configured
directly to each Service Function; there is indeed
no need to overload the design of Service Function
Chains with policies of low-level granularity.
REQ#23: The solution MUST allow for Operations, Administration, and
Maintenance (OAM) features [RFC6291]. In particular, the
solution MUST:
A. Support means to verify the completion of the forwarding
actions until the SFC Border Node is reached (see
Section 3.4.1 of [RFC5706]).
B. Support means to ensure coherent classification rules
are installed in and enforced by all the Classifiers of
the SFC domain.
C. Support means to correlate classification policies with
observed forwarding actions.
D. Support in-band liveliness and functionality checking
mechanisms for the instantiated Service Function Chains
and the Service Functions that belong to these chains.
REQ#24: The solution MUST prevent infinite Service Function Loops.
A. Service Functions MAY be invoked multiple times in the
same Service Function Chain (denoted as SF Spiral), but
the solution MUST prevent infinite forwarding loops.
REQ#25: The solution MUST allow for load-balancing.
A. Load-balancing may be provided by legacy technologies or
protocols (e.g., make use of load-balancers)
B. Load-balancing may be part of the Service Function
itself.
C. Load-balancer may be considered as a Service Function
element.
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D. Because of the possible complications, load balancing
SHOULD NOT be driven by the SFC Classifier.
REQ#26: The solution MUST separate SF-specific policy provisioning-
related aspects from the actual handling of packets
(including forwarding decisions).
REQ#27: The solution MUST support means to detect the liveliness of
Service Functions of an SFC-enabled domain. In particular,
the solution MUST support means to (dynamically) detect that
a Service Function instance is out of service and notify the
relevant elements accordingly (PDP and Classifiers, for
one).
REQ#28: Service Functions may be reachable using IPv4 and/or IPv6.
The administrative domain entity MUST be able to define and
enforce policies with regards to the address family to be
used when invoking a Service Function.
A. A Service Function Chain may be composed of IPv4
addresses, IPv6 addresses, or a mix of both IPv4 and
IPv6 addresses.
B. Multiple Service Functions can be reachable using the
same IP address. Each of these Service Functions is
unambiguously identified with a Service Function
Identifier.
REQ#29: The solution MUST allow for gradual deployment in legacy
infrastructures, and therefore coexist with legacy
technologies that cannot support SFC-specific capabilities,
such as Service Function Chain interpretation and
processing. The solution MUST be able to work in a domain
that may be partly composed of opaque elements, i.e.,
elements that do not support SFC-specific capabilities.
REQ#30: The solution MUST be able to provide different SLAs (Service
Level Agreements,
[I-D.boucadair-connectivity-provisioning-profile]). In
particular,
A. The solution MUST allow for different levels of service
to be provided for different traffic streams (e.g.,
configure Classes of Service (CoSes)).
B. The solution MUST be able to work properly within a
Diffserv domain [RFC2475].
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C. The solution SHOULD support the two modes defined in
[RFC2983].
REQ#31: ECN re-marking, when required, MUST be performed according
to [RFC6040].
4. SFC Diagnosis & Troubleshooting
This section lists the set of requirements for the SFC Diagnosis &
Troubleshooting procedure (denoted hereafter as "the solution").
DIAG_REQ#1: The solution MUST allow to assess the status of the
serviceability of a Service Function (i.e., the
Service Function that provides the service(s) it is
configured for).
DIAG_REQ#2: The solution MUST NOT rely only on IP reachability to
assess whether a Service Function is up and running.
DIAG_REQ#3: The solution MUST allow to diagnose the availability of
a Service Function Chain.
DIAG_REQ#4: The solution MUST support the correlation between a
Service Function Chain and the actual forwarding path
followed by a packet matching that SFC.
DIAG_REQ#5: The solution MUST allow to diagnose the availability of
a segment of a Service Function Chain, i.e., a subset
of service functions that belong to the said chain.
DIAG_REQ#6: The solution MUST support the unsolicited notification
of signals as a means to notify the PDPs whenever some
events occur (for example, a malfunctioning service
function instance).
DIAG_REQ#7: The solution MUST allow for local diagnostic procedures
specific to each Service Function.
* In particular, the solution MUST allow to make use
of local diagnostic procedures (e.g., regular
checks using SF built-in diagnostic procedures) for
SFC diagnosis purposes.
DIAG_REQ#8: The solution MUST allow for customized service
diagnostic.
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* For example, the solution should be able to
generate a test packet as per a customer's request
who may have observed some service degradation.
5. IANA Considerations
This document does not require any action from IANA.
6. Security Considerations
Below are listed some security-related requirements to be taken into
account when designing the Service Function Chaining solution. This
version does not cover the provisioning interface used to enforce
policies into the Classifier and Service Functions.
SEC_REQ#1: The solution MUST provide means to prevent any
information leaking that would be used as a hint to guess
internal engineering practices (e.g., network topology,
service infrastructure topology, hints on the enabled
mechanisms to protect internal service infrastructures,
etc.).
The solution MUST support means to protect the SFC
domain as a whole against attacks that would lead to
the discovery of Service Functions enabled in a SFC
domain.
In particular, topology hiding means MUST be supported
to avoid the exposure of the SFC-enabled domain
topology (including the set of the service function
chains supported within the domain and the
corresponding Service Functions that belong to these
chains).
SEC_REQ#2: The solution MUST support means to protect the SFC-
enabled domain against any kind of denial-of-service and
theft of service (e.g., illegitimate access to the
service) attack.
For example, a user should not be granted access to
connectivity services he/she didn't subscribe to
(including direct access to some SFs), at the risk of
providing illegitimate access to network resources.
SEC_REQ#3: The solution MUST NOT interfere with IPsec [RFC4301] (in
particular IPsec integrity checks).
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7. Contributors
The following individuals contributed text to the document:
Hongyu Li
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129,
China
EMail: hongyu.lihongyu@huawei.com
Jim Guichard
Cisco Systems, Inc.
USA
EMail: jguichar@cisco.com
Paul Quinn
Cisco Systems, Inc.
USA
Email: paulq@cisco.com
8. Acknowledgements
Many thanks to K. Gray, N. Takaya, H. Kitada, H. Kojima, D. Dolson,
B. Wright, and J. Halpern for their comments.
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
9.2. Informative References
[I-D.boucadair-connectivity-provisioning-profile]
Boucadair, M., Jacquenet, C., and N. Wang, "Connectivity
Provisioning Profile (CPP)", draft-boucadair-connectivity-
provisioning-profile-03 (work in progress), March 2014.
[I-D.ietf-sfc-problem-statement]
Quinn, P. and T. Nadeau, "Service Function Chaining
Problem Statement", draft-ietf-sfc-problem-statement-03
(work in progress), April 2014.
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[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, December 1998.
[RFC2983] Black, D., "Differentiated Services and Tunnels", RFC
2983, October 2000.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions", RFC
5706, November 2009.
[RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion
Notification", RFC 6040, November 2010.
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291, June 2011.
Authors' Addresses
Mohamed Boucadair
France Telecom
Rennes 35000
France
EMail: mohamed.boucadair@orange.com
Christian Jacquenet
France Telecom
Rennes 35000
France
EMail: christian.jacquenet@orange.com
Yuanlong Jiang
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129,
China
EMail: jiangyuanlong@huawei.com
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Ron Parker
Affirmed Networks
Acton, MA
USA
EMail: Ron_Parker@affirmednetworks.com
Carlos Pignataro
Cisco Systems, Inc.
USA
EMail: cpignata@cisco.com
Kengo Naito
NTT
Midori-Cho 3-9-11
Musashino-shi, Tokyo 180-8585
Japan
EMail: naito.kengo@lab.ntt.co.jp
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