Internet DRAFT - draft-xuan-sfc-chain-high-availability
draft-xuan-sfc-chain-high-availability
<Service Function Chaining> Truong-Xuan Do
Internet Draft Younghan Kim
Intended status: Informational Soongsil University, Korea
Expires: April 2016 Oct 20, 2015
High Availability mechanism for Service Function Chains
draft-xuan-sfc-chain-high-availability-01
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Abstract
This document describes mechanisms to achieve the high
availability of the service function chains. This document
considers the high availability in the perspective of entire chain.
This means the SFC control plane needs to take into account some
metrics related service chain in addition to individual service
functions. This document covers both stateless and stateful service
functions as well.
Table of Contents
1. Introduction...................................................3
2. Conventions used in this document..............................3
3. High availability architecture of SFC..........................4
3.1. Metrics for back-up SFPs..................................5
3.2 SFP with all stateless service functions...................6
3.3 SFP with stateful service funtions.........................7
4. Security Considerations........................................8
5. IANA Considerations............................................8
6. References.....................................................8
6.1. Normative References......................................8
6.2. Informative References....................................8
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1. Introduction
Service function chaining currently is redesigned with the support
of the software-defined network (SDN) and network function
virtualization (NFV) which provide more flexible and dynamical
end-to-end services.
In order to ensure the high availability of service function
chains, some traditional mechanisms for individual service function
are reused (e.g. Active/Standby or Active/Active). These mechanisms
are based on the deployment of the backup or redundant service
functions. The recovery of whole service chain relies on the
recovery of individual service function.
This document describe a mechanism which ensure the high
availability of service chain based on some metrics of whole chain.
The mechanism also considers both stateless and stateful service
functions in the chain.
2. Conventions used in this document
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].
The terms about SFC are defined in [RFC7498] and
[I-D.ietf-sfc-architecture]
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3. High availability architecture of SFC
Figure 1. shows the architecture for achieving the high
availability of the SFC. We make assumptions that each service
function has several instances which are connected to different
service function forwarders (SFF). Each service function path (SFP)
is created by the combination of different service instances of
different service functions. We propose a new entity called SFC
HA manager which is responsible for monitoring metrics which belong
not only to the individual service functions, such as fail-over,
load condition, but also the whole service chain, such as, latency,
total load, and traffic engineering. The SFC HA Manager takes
responsibilities of making the backup SFPs. SFC HA manager should
be located in the control plane part [I-D.ietf-sfc-control-plane]
of SFC architecture
[SFC HA Manager]
+****************+********+***>> back-up SFP
+|.......+........|........|.........+.....>> current SFP
|| | | | |
SFI1 SFI2 SFI2 SFI3 SFI3
| | | | |
+---+----+ +----+---+ |
| | |
SFFI1 SFFI2 SFFI3
Figure 1. High availability architecture of SFC
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3.1. Metrics for back-up SFPs
Some metrics for whole service function chain are listed below:
Fail-over: a back-up SFP with the replacement of failed service
functions
Total latency: a back-up SFP with better latency
Total bandwidth: a back-up SFP with highest bandwidth
Total path: a back-up SFP with shortest path
Total load: a back-up SFP with the lowest load
Traffic engineering: a back-up SFP with the pre-defined traffic
engineering goals
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3.2 SFP with all stateless service functions
Procedures for making a back-up service function path
+ Gather and monitor the states of current service function paths
+ Evaluate the current SFPs based on collected data and above
metrics
+ HA manager makes back-up SFPs for current SFP
+ When a critical event occurs, the back-up SFP can be invoked and
replace the current SFP.
+ The information about new SFP (back-up) is updated to all
corresponding SFFs.
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3.3 SFP with stateful service funtions
Procedures for making a back-up service function path
+ Gather and monitor the states of current service function paths
+ Evaluate the current SFPs based on collected data and above
metrics
+ HA manager makes back-up SFPs for current SFP
- For stateful service functions in the SFP, internal state
management for each service function is required and
synchronized with the same kind of service function when
creating a back-up SFP
- State synchronization can be handled by the direct
communication between two same kind service functions
+ When a critical event occurs, the back-up SFP can be invoked and
replace the current SFP.
+ The information about new SFP (back-up) is updated to all
corresponding SFFs.
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4. Security Considerations
TBD.
5. IANA Considerations
TBD.
6. References
6.1. Normative References
[RFC7498]
Quinn, P. and T. Nadeau, "Problem Statement for Service
Function Chaining", RFC 7498, April 2015.
6.2. Informative 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-control-plane]
H. Li, Q. Wu, O. Huang, etc. al., "Service Function
Chaining (SFC) Control Plane Components & Requirements",
draft-ietf-sfc-control-plane-00, Aug 2015
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Authors' Addresses
Truong-Xuan Do
Soongsil University
4F Hyungnam Engineering Bldg. 424,
(156-743) 511 Sangdo-Dong, Dongjak-Gu, Seoul, Korea
Phone: +82 10 4473 6869
Email: xuan@dcn.ssu.ac.kr
Younghan Kim
Soongsil University
4F Hyungnam Engineering Bldg. 424,
(156-743) 511 Sangdo-Dong, Dongjak-Gu, Seoul, Korea
Phone: +82-2-820-0904
Email: younghak@ssu.ac.kr
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