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service function chain W. Meng
Internet-Draft C. Wang
Intended status: Standards Track ZTE Corporation
Expires: April 10, 2016 October 8, 2015


Redundancy Mechanism for Service Function Chains
draft-meng-sfc-chain-redundancy-02

Abstract

This document discusses about hot standby analysis of service
function instances (SFIs) under different scenarios. The document
provides requirement and use cases and also describes the suitable
scenarios that each solution may be deployed in.

Status of this Memo

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provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on April 10, 2016.

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Convention and Terminology . . . . . . . . . . . . . . . . . . 4
3. Redundancy Mechanisms . . . . . . . . . . . . . . . . . . . . 5
3.1. Homogeneous Backup . . . . . . . . . . . . . . . . . . . . 5
3.2. Heterogeneous Backup . . . . . . . . . . . . . . . . . . . 5
3.3. Internal Backup . . . . . . . . . . . . . . . . . . . . . 6
3.4. External Backup . . . . . . . . . . . . . . . . . . . . . 6
4. Redirect Service Function Paths . . . . . . . . . . . . . . . 8
5. Control Plane Considerations . . . . . . . . . . . . . . . . . 9
6. Data Plane Considerations . . . . . . . . . . . . . . . . . . 10
7. Load Balancing Considerations . . . . . . . . . . . . . . . . 11
8. Normative References . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13




































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1. Introduction

The object of Service Function Chains (SFC) is trying to unload
services from nodes in traditional network and deal with such
services through service function chains. As a result of this,
redundancy of service function instances needs to be standardize,
rather than maintain as an internal mechanism in a traditional
network device.

Many SFs might be located in large-scale networks, such as ISP
networks or enterprise ones, where exist a large number of customers.
In each service function, these customers which is served by a single
service function instance (SFI) may experience service degradation in
case of the presence of the single point of exceptional failure.
Therefore, redundancy of the SFI will be strongly desired in order to
deliver highly available services.

This memo describes some use cases of redundancy among SFIs under
typical scenarios.
































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2. Convention and 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].

The terms about SFC are defined in [I-D.ietf-sfc-problem-statement]
and [I-D.ietf-sfc-architecture].











































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3. Redundancy Mechanisms

As illustrated in Figure 1, two SFIs (SFI1 and SFI1') are deployed
for redundancy purposes. This is the reference architecture for the
mechanisms we describe in this memo.

,---.
/ \
--------( SFI1 |-
\ / \
`-^-' \ ,---.
| \-- / \-------> Master Service Function Path
Backup --> | ( SFI2 )
,-v-. .... \ /.......> Backup Service Function Path
/ \ . `---'
........( SFI1' ).
\ /
`---'


Figure 1: Reference Model

3.1. Homogeneous Backup

Figure 2 illustrates a homogeneous backup cases. In this scenario,
each of those master SFIs will have a corresponding backup SFI.

,---. ,---. ,---.
/ \ / \ / \
( SFI1 | ( SFI2 | ( SFI3 |
\ / \ / \ /
`-^-' `-^-' `-^-'
| | |
| | |
| | |
,-v-. ,-v-. ,-v-.
/ \ / \ / \
( SFI1' ) ( SFI2' ) ( SFI3' )
\ / \ / \ /
`---' `---' `---'

Figure 2: Homogeneous Backup Model

3.2. Heterogeneous Backup

Figure 3 illustrates a heterogeneous backup cases. In this scenario,
each of those master SFIs might have more than one corresponding
backup SFIs.



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,---. ,---.
/ \ / \
( SFI1 | ( SFI2 |
\ / / \ / \
`-^-' / `---' \
| | |
| | |
| | |
,-v-. ,-v-. ,-v-.
/ \ / \ / \
( SFI1' ) ( SFI2' ) ( SFI2'')
\ / \ / \ /
`---' `---' `---'

Figure 3: Heterogeneous Backup Model

3.3. Internal Backup

Figure 4 illustrates a internal backup cases. In this scenario, both
sides of backup are located in a same Service Function Node.

+----------------------------------------+
| ,---. ,---. ,---. |
| / \ / \ / \ |
| ( SFI1 <---> SFI1' | ( SFI2 | | <-- Service Function Node
| \ / \ / \ / |
| `---' `---' `---' |
+----------------------------------------+

Figure 4: Internal Backup Model

3.4. External Backup

Figure 5 illustrates a external backup cases. In this scenario, each
side of backup is located in its own Service Function Node.
















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+---------------------------------------+
| ,---. ,---. ,---. |
| / \ / \ / \ |
| ( SFI1 | ( SFI2 | ( SFI3 | | <-- Service Function Node 1
| \ / \ / \ / |
| `-^-' `-^-' `-^-' |
+-------|-----------|-----------|-------+
| | | <------- Network
+-------|-----------|-----------|-------+
| ,-v-. ,-v-. ,-v-. |
| / \ / \ / \ |
| ( SFI1' | ( SFI2' | ( SFI3' | | <-- Service Function Node 2
| \ / \ / \ / |
| `---' `---' `---' |
+---------------------------------------+

Figure 5: External Backup Model


































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4. Redirect Service Function Paths

As described in [ietf-sfc-architecture], a Service Function Path is
the instantiation of the defined SFC.

In case of planned maintenance operations or exceptional failure of
Service Function Node, The SFP MUST be changed to prevent disrupting
the normal traffic.











































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5. Control Plane Considerations

TBD
















































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6. Data Plane Considerations

TBD
















































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7. Load Balancing Considerations

TBD
















































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8. Normative 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-problem-statement]
Quinn, P. and T. Nadeau, "Service Function Chaining
Problem Statement", draft-ietf-sfc-problem-statement-13
(work in progress), February 2015.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
.

[RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson,
"Remote Authentication Dial In User Service (RADIUS)",
RFC 2865, DOI 10.17487/RFC2865, June 2000,
.






























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Authors' Addresses

Wei Meng
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China

Email: meng.wei2@zte.com.cn,vally.meng@gmail.com


Cui Wang
ZTE Corporation
No.50 Software Avenue, Yuhuatai District
Nanjing
China

Email: wang.cui1@zte.com.cn

































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