Internet DRAFT - draft-ao-sfc-for-dc-interconnect
draft-ao-sfc-for-dc-interconnect
SFC WG Ting. Ao
Internet-Draft Bo. Wu
Intended status: Standards Track ZTE Corporation
Expires: April 17, 2016 October 15, 2015
Hierarchical SFC for DC Interconnection
draft-ao-sfc-for-dc-interconnect-01.txt
Abstract
In a SFC, sometimes some SFs are provided by several DC networks,
which means these SFs my locates in different DC network . How to
establish such SFC that is across several DCs is what the draft wants
to present. In this document, a hierarchical SFC method is proposed.
It covers data plane, control plane to archieve such hierarchical
SFC. And it includes requirements of the SFC Gateway for every DC
network that provide SF for SFC.
Status of This Memo
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This Internet-Draft will expire on April 17, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Architecture of Hierarchical SFC . . . . . . . . . . . . . . 3
3.1. SFC-GW . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Classifier for Complex SF . . . . . . . . . . . . . . . . 5
4. Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Overlap SFC encapsulation . . . . . . . . . . . . . . . . 6
4.2. Metadata SFC encapsulation . . . . . . . . . . . . . . . 6
4.3. Exchange SFC encapsulation . . . . . . . . . . . . . . . 7
5. Coordination . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Controllers . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Controller to Classifier . . . . . . . . . . . . . . . . 7
5.3. Controller to SFF . . . . . . . . . . . . . . . . . . . . 7
6. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7. Security Considerations . . . . . . . . . . . . . . . . . . . 8
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. Information References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction
Service Function Chain (SFC) is the chain with a series of ordered
Service Functions(SF). These SFs are distributed in a DC network or
some DC networks. So it's common that a SFC is across several DC
networks, which incurs the problem of DC network interconnection.
Every part of the SFC in one DC network is a SFC within DC network.
We call such SFC to be hierarchical SFC. And the part of such SFC
within a DC network is called to be Complex SF. Complex SF may
contain one or more SFs that are within one DC network, but is a
logical SF from the view of the hierarchical SFC.
This document is going to describe the architecture for such
scenario. And data plane and control plane will be provided to
specify how the hierarchical SFC works. Meantime, some concepts are
proposed.
2. Terminology
SFC(Service Function Chain): An ordered set of some abstract SFs.
H-SFC(Hierarchical SFC): A SFC that transfers one or more Data center
networks. Every Datacenter network provide a complex SF for H-SFC.
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Complex SF: A logical SF that is provided by a SFC in Datacenter
network. For H-SFC, the SFC in one Datacenter network is regarded as
a complex SF on the path of this H-SFC.
I-SFC( Internal-SFC): A Service Function Chain within the Datacenter
network which is corresponding to the complex SF in H-SFC.
SFC-GW: A gateway for SFC in a Datacenter network which is used to
interconnect with H-SFC.
3. Architecture of Hierarchical SFC
Hierarchical SFC is composed of an ordered of SFs or Complex SFs.
Complex SF is a logic SF that is composed of an ordered of SFs which
form a SFC in DC network. The Complex SF is managed by the operator
of the DC network. With H-SFC mechanism, we can interconnect every
SFC of every Datacenter network as a whole H-SFC.
For the architecture of the H-SFC, please see Figure 1 below. For
controller1, it set up a SFC which path is Complex SF#1->Complex
SF#2->Complex SF#3.Every Complex SF in such SFC is actually a SFC in
datacenter network, and such SFC is set up by the controller in the
DC network(Controller2). In the Figure 1, a Complex SF#2 is a SFC
which path is SF#21->SF#22. To setup a H-SFC, we need to:
1) To deteremin what kind of service the Complex SF should provide
has been determined by the Orchestration;
2) To establish the corresponding SFC in the Datacenter network of
the Complex SF has been established by the controller of the
Datacenter network;
3) Complex SF also has its SFID in H-SFC;
4) Complex SF as next hop of the H-SFC also has its locator, which
may be the address of the SFC-GW. This locator information has been
exchanged with Controller1.
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+-------------+
| Controller1 |<-------------------------------------+
+-------------+ |
^ |
| |
+--------------+--------------------+----+-------------------+ |
| | | | |
| | .........|......... | |
| +--------------+ . +--------------+ . +--------------+ v
| | SFF1 | . | SFF2 | . | SFF3 | +-----------------+
| +--------------+ . +--------------+ . +--------------+ | |
| | . | . | | Orchestration |
| | . | . | | |
v v . v . v +-----------------+
+--------+ +---------------+ . +--------------+ . +--------------+ ^
--->| CF1 |--->| Complex SF#1 |--.-->| Complex SF#2 |--.--->| Complex SF#3 |-----> |
+--------+ +---------------+ . +--------------+ . +--------------+ |
. .................. |
|| |
|| |
|| |
\/ |
(-------------------) |
/ +-------------+ \ |
/ | Controller2 |<---\-------------------------------+
/ +-------------+ \
/ ^ )--------------------\
/--------( | \
/ +------------+----------------+---------------+ \
/ | | | \
/ v | | \
/ +------------------------------+ v v \
/ | +----------+ +--------+ | +---------+ +---------+ \
<=============>| | SFC-GW |---->| CF2 |-|----->| SN#21 |---->| SN#22 | \
| | +----------+ +--------+ | +---------+ +---------+ \
| +-------^----------------------+ | |
| | | |
| +--------------------------------------------------+ |
| DC Network |
(--------------------------------------------------------------------------)
Figure 1 H-SFC architecture
In the Figure 1, the Complex SF#1, Complex SF#2, Complex SF#3 which
is provided by a separate Datacenter network are an ordered set of a
Hierarchical SFC(H-SFC). For this H-SFC, they are logical SFs. But
for this datacenter network, it's actually a SFC within the
datacenter network.
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CF1 classifies the traffic and assign it a H-SFC. The traffic
traverses along the path according to this H-SFC. Whenever the
traffic enters into Complex SF#n, it actually enters into the
corresponding Datacenter network through SFC-GW to begin its SFC.
The setup of this SFC in the datacenter is invisible to H-SFC. The
path of the SFC in the datacenter network is also invisible to H-SFC.
3.1. SFC-GW
SFC-GW is the component that interconnect the DC networks, and
through which Complex SF#n communicate with H-SFC. For H-SFC, the
SFC-GW can be considered as a SFF for the corresponding Complex
SF#n,see Figure 2. And the SFC-GW's locator is regard as the next
hope address of the HSFC. Traffic enters into Complex SF#n arrives
the SFC-GW firstly, and then is forwarded to the Classifier in
Datacenter network by the SFC-GW .
When the traffic finishes this SFC in the Datacenter network, it
should be forwarded back to SFC-GW, and then be forwarded to next SF
or Complex SF by the SFC-GW.
+------------------------------+ +---------+
| SFC-GW | =======>| SFF |
+------------------------------+ +---------+
| |
| |
v |
................................... v
. +------+ +------+ +------+ . +---------+
. | CF |-->| SF1 |-->| SF2 | . ========>| SF |
. +------+ +------+ +------+ . +---------+
................................... ^
^ *
* *
* *
I-SFC view H-SFC view
Figure 2 View of the SFC-GW
3.2. Classifier for Complex SF
Classifier for Complex SF receives the traffic from SFC-GW. For the
traffic, the Classifier classifies the traffic and maps the traffic
into corresponding I-SFC in the Datacenter network according to the
H-SFC header information. The Classifier assigns the traffic the SFC
header and the traffic is forwarded alone the SFP specified by the
SFC header.
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4. Encapsulation
As description in section 3, SFC in Datacenter network is invisible
to H-SFC. So it's not feasible to use the forwarding method of SFC
that is in one Datacenter network. We need to assign a new SFC
header for the specific SFC in the Datacenter network.
Here is the analysis for the methods to handle the SFC in the
Datacenter network.
4.1. Overlap SFC encapsulation
When the packets with H-SFC header arrives the Classifier in the
Datacenter network, this Classifier would assign a new I-SFC header
based on the H-SFC header. An example is showed like the following
format, Figure 3.
+------------------+
| Overlay Header |
+------------------+
| I-SFC Header |
+------------------+
| H-SFC Header |
+------------------+
| Original Packet |
+------------------+
Figure 3 View of the SFC-GW
The traffic with the above 2 layer-SFC header would be forwarded
according to the I-SFC header in the Datacenter network. H-SFC
header is just preserved in the packets. At the last SFF of the
Service Function Chain of the network, the I-SFC header is removed
from the packet and then the packet is forwarded to the SFC-GW of the
Datacenter network for further forwarding based on the H-SFC header.
With such encapsulation, H-SFC information is carried along the the
whole H-SFC life without modification, so that the last SFF in the
Datacenter center of the I-SFC is not required to be aware of the
H-SFC. This forwarding method eliminates the last SFF's awareness of
the H-SFC.
4.2. Metadata SFC encapsulation
In this method, H-SFC header is transferred as a metadata that is
stored in the I-SFC header. And at the last SFF of the I-SFC, the
SFF need to restore metadata information into H-SFC header, then pass
such traffic to SFC-GW.
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This method requires that the last SFF must transfer I-SFC header to
H-SFC header before forward the traffic to SFC-GW.
4.3. Exchange SFC encapsulation
In this kind of encapsulation, there is 1 layer SFC header with the
packet all the time. The Classifier in the Datacenter network maps
the H-SFC header to the I-SFC header. And the last SFF of the I-SFC
maps the I-SFC header back to H-SFC header.
This method requires the last SFF in Datacenter networknot only map
the I-SFC header back to H-SFC, but also must learn the mapping
information from controller.
5. Coordination
5.1. Controllers
To make sure that the H-SFC and I-SFC can work coordinately,
Controller1 in Figure 1 and Controller2 should communicate each
other.
a. Controller2 setup Internal Service Function Chain(I-SFC)
corresponding to Complex SF provided to H-SFC. The service the
Complex SF provides is communicated between Controller1 and
Controller2.
b. Once Controller1 get the information of Complex SF, Controller1
setup the Hierarchical SFC. Furthermore, Controller1 need to get
SFC-GW locator as next hop address of the H-SFC.
c. The relationship between H-SFC and I-SFC, especially SPFID,
Index, etc information.
5.2. Controller to Classifier
d. Sometimes, the classifier policy in DC network may also take
considerate of SFPID in H-SFC.
5.3. Controller to SFF
e. For each Complex SF, controller2 should tell the last SFF of the
I-SFC that the next hop is SFC-GW, so that the traffic can be
forwarded to such SFF after the process of the complex SF.
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6. Summary
As we discuss above, H-SFC is very useful in the Service Function
Chain across several Datacenter networks so that the SFC is more
scalability. With the overlap SFC encapsulation, we keep the
principle that the two level SFC decouple as possible as it can. And
we can use the existing SFC in Datacenter to be a Complex SF without
modification and with no new requirement for SFF.
7. Security Considerations
To be added later
8. IANA Considerations
N/A
9. Information References
[I-D.ietf-sfc-architecture]
Halpern, J. and C. Pignataro, "Service Function Chaining
(SFC) Architecture", draft-ietf-sfc-architecture-11 (work
in progress), July 2015.
[I-D.ietf-sfc-dc-use-cases]
Surendra, S., Tufail, M., Majee, S., Captari, C., and S.
Homma, "Service Function Chaining Use Cases In Data
Centers", draft-ietf-sfc-dc-use-cases-03 (work in
progress), July 2015.
[I-D.ietf-sfc-nsh]
Quinn, P. and U. Elzur, "Network Service Header", draft-
ietf-sfc-nsh-01 (work in progress), July 2015.
[RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for
Service Function Chaining", RFC 7498,
DOI 10.17487/RFC7498, April 2015,
<http://www.rfc-editor.org/info/rfc7498>.
Authors' Addresses
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Ting Ao
ZTE Corporation
No.50, Ruanjian Road
Nanjing 210012
China
Phone: +86 25 88016576
Email: ao.ting@zte.com.cn
Bo Wu
ZTE Corporation
No.50, Ruanjian Road
Nanjing 210012
China
Email: wu.bo@zte.com.cn
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