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Service Function Chaining                                       Qi Xu
Internet Draft                                           Huachun Zhou
Intended status: Informational                              Taixin Li
Expires: April 2019                                       Guanglei Li
Guanwen Li
Beijing Jiaotong University
A Method for Service Orchestration in hSFC
draft-xu-sfc-hierarchical-orchestration-03.txt
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Xu                     Expires April 27, 2019                 [Page 1]
Internet-Draft  draft-xu-sfc-hierarchical-orchestration September 2019
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Hierarchical SFC is a network architecture for implementing SFC the
chain with an ordered set of service functions which could be
deployed in multiple geographically dispersed networks. How to
forward traffic between networks in Hierarchical SFC is what the
draft wants to present.
This document proposes a mapping-based forwarding method with
coordinated orchestration by the translation of H-SFC and I-SFC to
forward traffic between networks in Hierarchical SFC.
1. Introduction ................................................ 2
1.1. Assumptions ............................................ 3
1.2. Requirements Language................................... 3
2. Terminology ................................................. 3
3. Hierarchical Service Orchestration........................... 3
3.1. East-west interface..................................... 4
3.1.1. C5: Interface between SFC Control Planes........... 4
3.1.2. Interface between SFC Control Planes and IBN....... 5
3.2. Hierarchical service orchestration...................... 5
4. Metadata Consideration....................................... 5
5. Security Considerations...................................... 5
6. IANA Considerations ......................................... 5
7. References .................................................. 5
7.1. Normative References.................................... 5
7.2. Informative References.................................. 6
Authors' Addresses ............................................. 7
Hierarchical SFC is a network architecture for supporting service
function chains across multiple geographically dispersed networks.
Hierarchical SFC is described in detail in [I.D. dolson-sfc-
hierarchical] and [I.D.ao-sfc-for-dc-interconnect], and is not
repeated here.
In hSFC, SFs in top-domain can be logical and composed of several
more refined SFs in sub-domain. Therefore, it is necessary to check
the availability of those logical SFs in the procedure of
orchestration.
This document proposes that adding an east-west interface for
coordination among different control planes of separate SFC-enabled
domains so to supporting hierarchical service orchestration.
1.1. Assumptions
The following assumptions are made:
o A Hierarchical SFC-enabled network has multiple level network
domains. Each domain has their own control plane and data plane.
o Control planes of different domain can work coordinately, but
they are independent or non-transparent to each other. For
example, Top-domain network domain just uses logical SFs, but
don't care how to construct a corresponding SFC for these logical
SFs in Lower-Level network domains.
1.2. Requirements Language
2. Terminology
The reader should be familiar with the terms contained in [RFC7665],
[I-D.ietf-sfc-control-plane], [I-D.dolson-sfc-hierarchical] and [I-
D.ao-sfc-for-dc-interconnect].
H-SFC: The SFC in the Top-domain network domain.
I-SFC: The SFC in the Lower-Level network domain.
3. Hierarchical Service Orchestration
When receiving a service request, the control plane should decide a
SFC for it, select appropriate SF instances and make a SFP for the
SFC. Furthermore, a classification policy which binds the flow with
the request to a given SFC should be told to classifiers so that the
flow can pass through relevant SFs along the SFP.
But in hierarchical SFC, SFs might be logical which means it can be
decomposed to several less abstract, more refined SFs. Besides,
logical SFs always represent SFCs in SFC-enabled sub-domains. So,
how to guarantee the availability of logical SFs and forward SFC
traffic among multiple SFC-enabled domains is an important problem.
3.1. East-west interface
+----------------------+    C5
|    SFC Control Plane +---->
|                      |
+---+----+----+----+---+
|    |    |    |
|    |    |    v
|    |    v    C4
|    v    C3
v    C2
Figure 1: Interfaces of SFC Control Plane
[I-D.ietf-sfc-control-plane] presents a reference architecture of
the SFC control plane, including 4 kinds of interfaces between the
SFC control plane and various SFC data plane elements.
In hierarchical SFC that SFs are distributed over multiple SFC-
enabled domains that the SFC needs to pass through, the control
plane also should be hierarchical. As we know, each control plane is
responsible for managing a single SFC-enabled domain. Then, each SFC
control plane should gather and update information of local domain
real-timely. Due to there is no formal control hierarchy scheme,
this document attempts to propose a simple Hierarchical Control
Plane Scheme for Hierarchical SFC architecture.
Figure 1 shows the interface reference points of the SFC control
plane architecture. C1 is the interface between SFC Control Plane
and SFC Classifier; C2 is the interface between SFC Control Plane
and SFF; C3 is the interface between SFC Control Plane and SFC-aware
SFs; C4 is the interface between SFC Control Plane and SFC Proxy; C5
this document proposes is the east-west interface between SFC
Control Planes for supporting coordination among those control
planes of separate domains.
3.1.1. C5: Interface between SFC Control Planes
As [I-D.ietf-sfc-hierarchical] said the IBN acts as a SFC-aware SF
in the Top-Level domain and as a classifier in the Lower-Level
At the Top-domain, the SFs that compose an SFC might be logical
which means they are actually SFCs composed by more refined SFs in
the Lower-Levels. To setup these logical SFs, it needs coordinated
orchestration between the control planes of Top-domain and Lower-
domains.
3.1.2. Interface between SFC Control Planes and IBN
Due to IBN behaves as an SF to Top-domain, it is controlled by
interface C3 or C4. Besides, IBN acts as a classifier and a SFF of
end-of-chains to Lower-Level domain, it exchanges information with
control plane of Lower-Level domain through interface C1 and C2.
3.2. Hierarchical service orchestration
During the orchestration for logical SFs of service chains in the
Top-domain, the control plane of the Top-domain should send an
instruction to control plane of the corresponding Lower-domain. When
the latter receives this instruction, it is likely that the Top-
domain receives service requests from users. Then Lower-Level would
construct or assign an I-SFC for this "service request", and make a
classification rule for the classifier of the IBN.
4. Metadata Consideration
Because the IBN is regarded as a Service Function to the Top-domain
domain, it should provide the ability to handle the metadata in the
NSH header if necessary.
For example, it is common that checking the liveness of the service
function of a service function path before the traffic selected by a
Classifier traverse the network along a SFC which has been describe
in [I-D.penno-sfc-trace-03]. Therefore, the IBN must be able to add
its identifying information at the end of the existing NSH headers
as a Service Function.
7.1. Normative References
[RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
Chaining (SFC) Architecture", RFC 7665, DOI
10.17487/RFC7665, October 2015, <http://www.rfc-
editor.org/info/rfc7665>.
7.2. Informative References
[I-D.ietf-sfc-hierarchical]
Dolson, D., Homma, S., Lopez, D., and Boucadair, M.,
"Hierarchical Service Function Chaining", draft- ietf-sfc-
hierarchical-07 (work in progress), February 2018.
[I-D.ao-sfc-for-dc-interconnect]
Ao, T. and W. Bo, "Hierarchical SFC for DC
Interconnection", draft-ao-sfc-for-dc-interconnect-
01(expired), October 2015.
[I-D.ietf-sfc-dc-use-cases]
Komma, 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.ietf-sfc-control-plane]
Boucadair, M., Ed., "Service Function Chaining (SFC)
Control Plane Components & Requirements", draft-ietf-sfc-
control-plane-06 (work in progress), May 2016.
[I-D.unify-sfc-control-plane-exp]
Szabo, R., Sonkoly, B., "A Multi-Domain Multi-Technology
SFC Control Plane Experiment: A UNIFYed", draft-unify-sfc-
control-plane-exp-00 (work in progress), March 2016.
[1]       Sahhaf, Sahel, et al. "Network service chaining with
optimized network function embedding supporting service
decompositions." Computer Networks (2015): 492-505.
Xu                    Expires April 27, 2019                [Page 6]
Qi Xu
Beijing 100044 P.R. China
Email: 15111046@bjtu.edu.cn
Huachun Zhou
Email: hchzhou@bjtu.edu.cn
Taixin Li
Guanglei Li