Internet DRAFT - draft-wei-sfc-mobile-consideration
draft-wei-sfc-mobile-consideration
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Interaction between SFC network and 3GPP network
draft-wei-sfc-mobile-consideration-00
Abstract
This document provides a discussion of how SFC (Service Function
Chain) domain could interact with carrier network to provide network
service for traffic. Here LTE (Long Term Evolution) network is used
as an example of carrier network for discussion.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Interaction between LTE network and SFC domain . . . . . . . . 4
2.1 Interaction model . . . . . . . . . . . . . . . . . . . . . 4
2.2 Information exchange . . . . . . . . . . . . . . . . . . . 6
3 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
4 Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 6
6 References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
6.1 Normative References . . . . . . . . . . . . . . . . . . . 6
6.2 Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1 Introduction
Different kinds of network Service Function (SF) have been deployed
in current network to provide network service for traffic. But
current SF deployments are tightly coupled to network topology and
physical resources, and this limits the ability of an operator to
introduce new services and/or service functions. To overcome the
disadvantages of current SF deployments, flexible SFC (Service
Function Chain) is under discussion in IETF [SFC PS].
Though SFC domain is typically deployed by the owner of carrier
network, here we treat SFC domain and carrier network as two separate
network domain. A typical relationship between carrier network and
SFC domain is shown in Figure 1. When network traffic goes through
SFC domain, the SFC domain needs to know how to steer the traffic,
i.e. which service chain the traffic should pass. The carrier network
and SFC domain should interact properly in order to provide network
service to traffic.
+---------------+ traffic +----------+ traffic--------+
|Carrier Network| <=======> |SFC domain| <=====>|Internet|
+---------------+ +----------+ +--------+
Figure 1 Relationship between carrier network and SFC domain
LTE (Long Term Evolution) network [TS23.401] is standardized by 3rd
Generation Partnership Project (3GPP), the basic architecture of LTE
network is shown in Figure 2, three network entities including
eNodeB, SGW and PDN-GW form the data path for user's traffic from UE
to IP service network, and MME (Mobility Management Entity) acts as a
central control point of the network.
+--------+
| IP |
S1-MME +-------+ S11 |Networks|
+----|----| MME |----|----+ +--------+
| | | | |SGi
| +-------+ | S5/ |
+----+ LTE-Uu +-------+ S1-U +-------+ S8 +-------+
|UE |----|---|eNodeB |---|-----------------| SGW |--|---|PDN-GW |
| |========|=======|=====================|=======|======| |
+----+ +-------+ +-------+ +-------+
Figure 2 Basic LTE network architecture
LTE network connects to IP service network through SGi interface
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[TS29.061].
Gi-LAN service area is presently used by mobile network operator to
differentiate their services to their subscribers; mobile network
operator could deploy any kinds of SFs, e.g. Firewall, video
optimizer, NAT (Network Address Translator), to provide network
service for user's traffic.
+-----------+ SGi +------+ +-----------+
|LTE network| <======> |Gi-LAN|<========>|IP Networks|
+-----------+ +------+ +-----------+
Figure 3 Gi-LAN for LTE network
This document use LTE network as an example to illustrate how carrier
network and SFC domain could cooperate to provide network service to
traffic.
1.1 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 RFC 2119 [RFC2119].
SFC domain: or SFC network, a network that implements SFC.
2. Interaction between LTE network and SFC domain
In this section, we will discuss how SFC domain could provide network
service for traffic in LTE network.
2.1 Interaction model
Before the discussion of interaction between LTE network and SFC
domain, we first introduce the concept of Logical Service Function
Chain (LSFC) and Physical Service Function Chain (PSFC). LSFC is a
service function chain which is consisted of a list of SF type, and
no specific SF instance is included in LSFC.
PSFC is a service function chain which is consisted of a list of SF
instance, so PSFC could be viewed as an instance of LSFC. Considering
of the requirements of load balance, there could be more than one
instance for one type of SF, so a LSFC could be mapped into one or
more PSFC.
LSFC stands for a requirement of service function chain for certain
traffic, and PSFC is a physical implementation that satisfies the
requirement.
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When we take LTE network and SFC domain as two separate domains, LTE
network plays the role of producing network service requirements and
SFC domain plays the role of providing network service for LTE
network's traffic.
An overview of interaction between LTE network and SFC domain is
depicted in Figure 4. LTE network creates LSFC for traffic and sends
the LSFC to SFC domain, and then SFC domain is in charge of
translating LSFC to PSFC.
Besides LSFC, additional information such as subscriber ID, that
might be used but could not be accessed directly by SFC domain, will
also be conveyed in service chain request procedure.
service chain request
+----------------------------+
| |
| |
+------|----+ traffic +----V-----+
|LTE Network| <==============> |SFC domain|
+-----------+ +----------+
Figure 4 Overview of Interaction between LTE network and SFC domain
There are sorts of information that could be used in creating of
LSFC:
- Mobile user's subscription information. For example, the network
operator could provide video optimization service for gold and silver
user's video traffic, but not for bronze user's traffic.
- Network status information. For example, the radio access type that
the mobile user currently attached to or the network congestion level
could affect the choice of video optimizer for video traffic.
- Agreement between content provider and network operator. Content
provider, e.g. YouTube, could rent TCP optimization or video
optimization function for its traffic, so for the traffic of content
provider that has service agreement with network operator certain
service function could be implemented.
- Application Characteristics. Application characteristics play very
important role in creating service chain for the traffic, different
kinds of application traffic, such as Web application and video
application, would definitely go through different service chain.
- QoS information of the service. QoS information of LTE network
traffic could affect the choice of specific SF.
Per operator's consideration, the combination of different
information can be used in creating LSFC for the traffic.
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2.2 Information exchange
This sub-section discusses what information elements should be
conveyed in service chain request procedure from LTE network to SFC
domain as depicted in Figure 4.
As discussed in sub-section 2.1, LSFC will be conveyed in service
chain request.
+-----------+---------------------------------------------------+
| Match rule| To identify which traffic the LSFC is specific to.|
+-----------+---------------------------------------------------+
| LSFC | To specify network service function chain that |
| | will act on the traffic. |
+-----------+---------------------------------------------------+
| Additional| SFC related auxiliary information such as User's |
| info | Subscriber ID. |
+-----------+---------------------------------------------------+
3 IANA Considerations
This document requires no requirement for IANA.
4 Security Considerations
Security related issues is not involved.
5 Acknowledgments
Many thanks to John Kaippallimalil and Chunshan Xiong (Sam) for their
valuable comments.
6 References
6.1 Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, June 2011.
[RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn,
Ed., "Diameter Base Protocol", RFC 6733, October 2012.
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6.2 Informative References
[Krishnan] R. Krishnan et al. "draft-krishnan-sfc-long-lived-flow-
use-cases", April 21, 2014
[SFC PS] P. Quinn et al. "draft-ietf-sfc-problem-statement-07",
June 24, 2014
Authors' Addresses
Xinpeng Wei
EMail: weixinpeng@huawei.com
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