Network Working Group M. Boucadair
Internet-Draft C. Jacquenet
Intended status: Informational France Telecom
Expires: February 23, 2014 Y. Jiang
H. Li
Huawei Technologies Co., Ltd.
R. Parker
Affirmed Networks
August 22, 2013
Requirements for Service Function Chaining
draft-boucadair-chaining-requirements-01
Abstract
This document identifies the requirements for the Service Function
Chaining.
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
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This Internet-Draft will expire on February 23, 2014.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Detailed Requirements List . . . . . . . . . . . . . . . . . 2
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5. Security Considerations . . . . . . . . . . . . . . . . . . . 7
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . 8
1. Introduction
This document identifies the requirements for the Service Function
Chaining (SFC).
The overall problem space is described in
[I-D.quinn-nsc-problem-statement]. The Service Chaining Framework is
documented in [I-D.boucadair-network-function-chaining].
2. Terminology
The reader should be familiar with the terms defined in
[I-D.boucadair-network-function-chaining].
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.
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REQ#2: The solution MUST NOT make any assumption on whether Service
Functions each reside on a separate addressable Network
Element, are co-resident on a single addressable Network
Element, or any combination thereof.
REQ#3: The solution MUST NOT require any IANA registry to store the
list of Service Functions.
REQ#4: The solution MUST NOT assume predefined chains of particular
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 a Service Function to be embedded in
multiple devices (e.g., servers).
a. This is used for load-balancing, load-sharing, prevent
from failures (e.g., hot or cold standby protection
mechanism), 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 be
involved in multiple Service Function Chains.
REQ#9: The solution MUST support multiple SFC-enabled domains be
deployed 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. In particular, unidirectional
Service Function Chains MUST be supported.
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 chains, the definition
of a new chain, the addition of new Service Functions
without having any impact on other existing Service
Functions or other Service Function Chains.
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REQ#12: Service Function Chaining logic and related policies SHOULD
NOT be exposed outside a given 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.
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 NOT make any assumption on the underlying
transport technologies used to interconnect involved Service
Functions.
a. 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.
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 (this is deployment-specific). An
administrative entity, grouping its Service Functions within
the same IP subnet, SHOULD be able to get rid of any
overhead (e.g., encapsulation).
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.
a. Service Function Chaining does not require new
classification capabilities compared to current
practices.
b. For instance, classification can rely on a subset of the
information carried in a received packet such as 5-tuple
classification.
REQ#19: The solution MUST support classifying traffic into Service
Function Chains.
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a. Preferably, a single classification of packets upon
their entry in the SFC domain SHOULD be supported, as
this will save computation resources consumed by
reclassification, and avoid the provisioning of
classification rules into multiple classifiers.
b. The solution MUST NOT require every Service Function be
co-located with a Classifier; this is a deployment-
specific decision.
REQ#20: A Classifier MAY be co-located with other Service Functions.
REQ#21: A Classifier MAY be considered as a Service Function in its
own.
REQ#22: The solution MAY allow reclassification at the Service
Functions (i.e., a Service Function can also be co-located
with a classifier).
a. Given the risk to jeopardize the overall consistency of
the Differentiated Forwarding policy enforced for a
specific traffic flow or a set thereof, the
administrative entity must configure coherent
classification rules.
b. The configuration of classification rules in such
context are the responsibility of the administrative
entity managing that SFC-enabled domain.
REQ#23: The solution MUST be able to forward the traffic between two
Service Functions (involved the same Service Function Chain)
without relying on the Destination Address.
REQ#24: The solution MUST support the ability to invoke
differentiated sets of policies for a Service Functions
(called Profiles). A profile denotes a set of policies
configured to a local Service 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. Finer-grained definition of policies belonging to a
Service Function should not be driven by the chaining
marking.
c. Finer-grained of policies should be configured directly
to each Service Function; no need to overload the design
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of Service Function chains with policies of low-level
granularity.
REQ#25: The solution MUST provide means to ensure the overall
consistency of the procedure. For example:
a. Ensure the completion of the forwarding actions derived
from the contents of the SFC Map until the border node
is reached.
b. Coherent classification rules are installed to all
classifiers.
c. The correlation between the classification policies and
forwarding actions should be verified.
REQ#26: The solution MUST prevent the same Service Function to be
invoked multiple times in the context of the same Service
Function Chain (at the risk of generating Service Function
Loop).
REQ#27: 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.
d. Because of the possible complications, load balancing
SHOULD NOT be handled at the classifier. This logic
should be embedded in the entity which is responsible
for ensuring the overall consistency of the solution
(i.e., Policy Decision Point).
REQ#28: The solution MUST separate provisioning-related aspects from
the actual handling of packets (including forwarding
decisions).
REQ#29: The solution MUST NOT exclude means to detect the liveliness
of involved Service Functions; nevertheless these means are
not considered as a mandatory component of the solution.
REQ#30: Means to dynamically discover Service Functions SHOULD be
supported. This feature is not required for the core
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chaining functionality, but its support is of high interest
for operators.
REQ#31: 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.
REQ#32: The solution MUST allow for gradual deployment in legacy
infrastructures, and therefore coexist with legacy
technologies that cannot support SFC-specific capabilities,
such as SFC Map 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#33: 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 traffic streams (e.g., configure
Classes of Service (CoSes)).
b. The solution MUST be compatible with Diffserv [RFC2475].
4. IANA Considerations
Authors of this document does not require any action from IANA.
5. Security Considerations
Below are listed some security-related requirements to be taken into
account when designing the Service Function Chaining solution:
SEC_REQ#1: The solution MUST offer at least the same security
protection level as the one provided using legacy service
engineering and delivery practices.
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SEC_REQ#2: The solution MUST provide means to prevent leaking any
information 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.).
SEC_REQ#3: The solution MUST support means to defend against denial-
of-service and theft of service (e.g., illegitimate
access to the service).
SEC_REQ#4: The solution MUST NOT interfere with IPsec [RFC4301] (in
particular IPsec integrity checks).
SEC_REQ#5: The solution MUST NOT lead to routing loops.
6. Acknowledgements
TBC.
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.
7.2. Informative References
[I-D.boucadair-connectivity-provisioning-profile]
Boucadair, M., Jacquenet, C., and N. Wang, "IP/MPLS
Connectivity Provisioning Profile", draft-boucadair-
connectivity-provisioning-profile-02 (work in progress),
September 2012.
[I-D.boucadair-network-function-chaining]
Boucadair, M., Jacquenet, C., Parker, R., Lopez, D.,
Yegani, P., Guichard, J., and P. Quinn, "Differentiated
Service Function Chaining Framework", draft-boucadair-
network-function-chaining-03 (work in progress), August
2013.
[I-D.quinn-nsc-problem-statement]
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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., and B.
McConnell, "Network Service Chaining Problem Statement",
draft-quinn-nsc-problem-statement-02 (work in progress),
July 2013.
[RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z.,
and W. Weiss, "An Architecture for Differentiated
Services", RFC 2475, December 1998.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
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
Hongyu Li
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129,
China
EMail: hongyu.lihongyu@huawei.com
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Ron Parker
Affirmed Networks
Acton, MA
USA
EMail: Ron_Parker@affirmednetworks.com
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