Internet DRAFT - draft-fu-sfc-transport-network-usecase
draft-fu-sfc-transport-network-usecase
Internet Engineering Task Force Q. Fu, Ed.
Internet-Draft H. Deng
Intended status: Informational W. Cheng
Expires: September 6, 2015 China Mobile
March 5, 2015
Usecase of SFC for VCPE in the transport network
draft-fu-sfc-transport-network-usecase-00
Abstract
This document proposes a usecase of Service Function Chaining(SFC) to
realize Virtual Customer Premises Equipment (VCPE) in the transport
network. In this document, the concept of VCPE is introduced into
the transport network to provide value-added services for the
enterprise customers. The SFC is used to realize the VCPE and chains
different services according to the requirement of the customers.
Such architecture can provide value-added and self-defined services
to the customers. In the meantime, SDN controller is utilized in the
usecase to direct certain traffic flows to the VCPE. This usecase
provides a practical mechanism to offer value-added and self-defined
services in the transport network without complicating the CPE
devices or increase OPEX and CAPEX cost.
Status of This Memo
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Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Advantage of VCPE . . . . . . . . . . . . . . . . . . . . . . 3
4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Usecase in Current Transport Network . . . . . . . . . . . . 5
6. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 6
7. Informative References . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
This document proposes a usecase of Service Function Chaining (SFC)
to realize virtual CPE in the transport network. The traditional
transport network uses static allocation mechanism in general. In
order to provide network connection between different locations for
the enterprise customers, traditional transport network should
allocate dedicated lines between each pair of the locations. Such
architecture is not suitable when the enterprise customers require
LAN access, and moreover, L3-L7 functions among different locations.
In this draft, we will introduce Virtual Customer Premise Equipment
(VCPE) into the transport network. By utilizing SFC, the VCPE can
provide value-added services, such as virtual firewall (vFW), virtual
NAT (vNAT), and etc., to the traditional transport network customers.
In order to flexibly control the traffic flow, we also introduce SDN-
controller (Software Define Network Controller) into the transport
network. The SDN-controller is responsible for directing the traffic
of certain enterprise customer, who has paid for the VCPE services,
to the VCPE servers.
The concept of VCPE is to shift most of the networking and service
functionalities from the customer side to the network side. In this
way, the customer side's equipment, that is the CPE, can be
simplified. The VCPE refers to one or a set of equipments at the
network side to execute the networking and service functionalities
used to be executed at the CPE. In such architecture, the CPE can be
a simple L2 switch, which is only responsible for forwarding packets
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to a certain next hop. The VCPE can be realized by a SFC in the
physical network or the virtual network, in which the traffic of each
customer is directed to one or several Service Founctions (SF)
specified by the customer.
In this document, we will talk about the usecases of VCPE using SFC
in the transport network for enterprise customers.
2. Terminology
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 [RFC2119].
3. Advantage of VCPE
The benefit of introduting VCPE into the transport network can be
concluded as follows:
1) It will avoid complicating the CPE devices when providing value-
added L3-L7 services to the customers. Traditionally, CPEs at the
enterprise customer side are simple L2 devices in the transport
network. In order to meet the requirements for value-added L3-L7
services from the customers, the CPEs should be redesigned to become
L3 or even more complicated devices. Such devices will result in an
increase of manufacture and maintenance cost, and will also request
addtional efforts for frequent update to meet the constantly
increased requirements of the customers. Nevertheless, by utilizing
the VCPE achitecture, CPE can remain to be a simple L2 device, which
is only responsible for L2 forwarding. In this way, the manufacture
and maintenance cost of the complicated CPEs can be saved. In the
meantime, frequent update of these CPEs is not necessary, which will
greatly decrease both CAPEX and OPEX of the network operators.
2) It will greatly speed up the service launching period. Since most
of the complicated functions are located at the VCPE in the network
side, operators have more power over services. Benefitting from the
recent NFV (Network Function Virtualization) and cloud technologies,
VCPE can be accomplished using SFC in the virtual network, where
different services can act as different VNFs (Virtual Network
Functions). Operators only need to add new VNFs on the VCPE side to
launch new services to the customers. In this way, Operators can
provide a variety of services through the transport network.
3) It will provide user-define-network experience. By introducing
SFC concept into the VCPE, users can define his own service order and
sequence. Therefore, enterprise customers can enjoy the self-defined
services over the public transport network.
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4. Architecture
Figure 1 shows the architecture of the SFC usecase for VCPE in the
transport network. The solid lines indicate data traffic flows,
while the dash lines indicate control traffic flows. In this
architecture, the CPEs are located at different branches of the
enterprise customer, and act as L2 forwarding switches. The VCPE is
located at the core network.
All of the CPEs and the switches can be controlled by the SDN-
controller. When the enterprise customer selects a set of the value-
added services, the SDN-controller will inform the CPE of the
customer to direct the traffic flow to a certain switch connected to
the VCPE. And then this swich will forward the traffic to the VCPE
for further operations. After operations, the switch will forward
the traffic to the destination CPE. All these traffic flows are
directed under the control of the SDN controller.
In this architecture, the switch should be capable of bridging the L2
packets to the L3 packets. Such switch can be realized by updating
some existing L3 transport switch.
The VCPE is one or a set of devices following the SFC architecture,
in which the Service Classification Function (SCF) is responsible for
classifing traffic from different customer/network/service. The SCF
is controlled by the SDN-controller. When a packet arrives, the SCF
will ask the controller which Service Founction Path (SFP) this flow
should follow, and put corresponding SFC encapsulation into the
packet. The packet then goes into the service founction region, and
will be directed to different Service Founctions (SF) based on the
encapsulation. In the following architecture, the switch in front of
the VCPE can also act as the SCF to classify packet flows. Following
the SFC architecture, VCPE can be realized by physical devices or
virtual network functions as well.
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+-----------------------+
................+ SDN-Controller +................
: : +--+--------------------+ : :
: : : : :
: : : : :
: : : : :
: : +--------+--------------------------+ : :
: : | VCPE : +--------------+ | : :
: : | : |Service | | : :
: : | +------+-------+ |Function Path | | : :
: : | | Service | | +---+ +---+| | : :
: : +---+ +Classification+-+ |sf1|...|sf2|+ +---+ : :
: : | | | Function | | +---+ +---+| | | : :
: : | | +--------------+ +--------------+ | | : :
: : | +-----------------------------------+ | : :
: +-+-+--+ +--+-+-+ :
: |Switch| |Switch| :
: +-+----+ +----+-+ :
: |Transport Transport| :
: | Network Network | :
: | | :
+--+---+---+ +---+---+--+
| ++---++ | | ++---++ |
| | CPE | | | | CPE | |
| +-----+ | | +-----+ |
|Enterprise| |Enterprise|
| Branch | | Branch |
+----------+ +----------+
Figure 1: Architecture for SFC usecase for VCPE in the transport
network
5. Usecase in Current Transport Network
Based on the above architecture, some value-added functions and
services can be launched for the enterprise users using the transport
network. Examples may include VPN, FW, NAT and etc.. By utilizing
the NFV technologies, these services can be one or a set of VNFs on
the VCPE servers. Such architecture provides an agile mechanism for
operators to launch value-added services for the transport network.
Taking consideration that MPLS-TP is widely used in current transport
network, some extention for SFC to support MPLS-TP should be
considered.
In the MPLS-TP packet, the PW lable can be used to classify service
type. Such information can be used for Service Founction
Clasification. Extra label can also be added into the PW lable to
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indicate user/network specifics. Therefore, the SFC can do the
service clasification mapping based on the PW lable in the MPLS-TP
packets. In the meantime, L2 packets should also be bridged to L3
packets before entering the Service Function Region, and should be
re-encapsulated to the L2 packets after leaving the Service Function
Region.
In such case, the Service Founction Classifier (SFC) should have the
following capabilities:
1) Mapping PW lable to a certain Service Founction Path
2) Recording mapping between IP address and PW/LSP lable, so as to
re-encapsulate the L3 packets with a certain IP address.
3) Bridging L2 packets to L3 packets by taking off the MPLS-TP
header.
Therefore, the following table should be maintained by the SFC, in
which SFP indicates Service Function Path.
IP address | LSP label |PW label | SFP
-----------+-----------+---------+------
IP1 | LSP1 | PW1 | SFP1
IP2 | LSP2 | PW2 | SFP2
IP3 | LSP3 | PW3 | SFP3
Figure 2: Table in SFC
This proposed approach can reuse the existing MPLS-TP network, so
that operators can use the same transport network platform to support
both the traditional private line service and value added NFV
services.
6. Conclusion
In this document, a usecase of utilizing SFC in the transport network
is proposed. Such usecase provides an agile mechanism for launching
new value-added services in the transport network. In this document,
the concept of VCPE is introduced into the transport network to
provide an easy way to deploy these value-added services. SFC is
used in the VCPE to chain different SFs for different flows according
to the customers' specification. In the meantime, traffic flows are
directed with the help of the SDN-controller according to the
customers' specification.
The usecase proposed has the following advantages:
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1) It provides a practical way to launch value-added services, such
as NAT, VPN, FW, and etc., in the traditional transport network
without complicating the existing CPE devices.
2) Operators can use the solution in this usecase to provide
traditional private line service and value added NFV services using
the same transport network platform.
2) It provides more capabilities to the customers to define his own
network.
3) The SDN architecture utilized in this usecase provides flexibility
and intelligence to the traditional transport network.
7. Informative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
Authors' Addresses
Qiao Fu (editor)
China Mobile
Xuanwumenxi Ave. No.32
Beijing
China
Email: fuqiao1@outlook.com
Hui Deng
China Mobile
Xuanwumenxi Ave. No.32
Beijing
China
Email: denghui@chinamobile.com
Weiqiang Cheng
China Mobile
Xuanwumenxi Ave. No.32
Beijing
China
Email: Chengweiqiang@chinamobile.com
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