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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 service function chain W. Meng 3 Internet-Draft C. Wang 4 Intended status: Standards Track ZTE Corporation 5 Expires: April 10, 2016 October 8, 2015 7 Redundancy Mechanism for Service Function Chains 8 draft-meng-sfc-chain-redundancy-02 10 Abstract 12 This document discusses about hot standby analysis of service 13 function instances (SFIs) under different scenarios. The document 14 provides requirement and use cases and also describes the suitable 15 scenarios that each solution may be deployed in. 17 Status of this Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at http://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on April 10, 2016. 34 Copyright Notice 36 Copyright (c) 2015 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (http://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 52 2. Convention and Terminology . . . . . . . . . . . . . . . . . . 4 53 3. Redundancy Mechanisms . . . . . . . . . . . . . . . . . . . . 5 54 3.1. Homogeneous Backup . . . . . . . . . . . . . . . . . . . . 5 55 3.2. Heterogeneous Backup . . . . . . . . . . . . . . . . . . . 5 56 3.3. Internal Backup . . . . . . . . . . . . . . . . . . . . . 6 57 3.4. External Backup . . . . . . . . . . . . . . . . . . . . . 6 58 4. Redirect Service Function Paths . . . . . . . . . . . . . . . 8 59 5. Control Plane Considerations . . . . . . . . . . . . . . . . . 9 60 6. Data Plane Considerations . . . . . . . . . . . . . . . . . . 10 61 7. Load Balancing Considerations . . . . . . . . . . . . . . . . 11 62 8. Normative References . . . . . . . . . . . . . . . . . . . . . 12 63 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 65 1. Introduction 67 The object of Service Function Chains (SFC) is trying to unload 68 services from nodes in traditional network and deal with such 69 services through service function chains. As a result of this, 70 redundancy of service function instances needs to be standardize, 71 rather than maintain as an internal mechanism in a traditional 72 network device. 74 Many SFs might be located in large-scale networks, such as ISP 75 networks or enterprise ones, where exist a large number of customers. 76 In each service function, these customers which is served by a single 77 service function instance (SFI) may experience service degradation in 78 case of the presence of the single point of exceptional failure. 79 Therefore, redundancy of the SFI will be strongly desired in order to 80 deliver highly available services. 82 This memo describes some use cases of redundancy among SFIs under 83 typical scenarios. 85 2. Convention and Terminology 87 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 88 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 89 document are to be interpreted as described in [RFC2119]. 91 The terms about SFC are defined in [I-D.ietf-sfc-problem-statement] 92 and [I-D.ietf-sfc-architecture]. 94 3. Redundancy Mechanisms 96 As illustrated in Figure 1, two SFIs (SFI1 and SFI1') are deployed 97 for redundancy purposes. This is the reference architecture for the 98 mechanisms we describe in this memo. 100 ,---. 101 / \ 102 --------( SFI1 |- 103 \ / \ 104 `-^-' \ ,---. 105 | \-- / \-------> Master Service Function Path 106 Backup --> | ( SFI2 ) 107 ,-v-. .... \ /.......> Backup Service Function Path 108 / \ . `---' 109 ........( SFI1' ). 110 \ / 111 `---' 113 Figure 1: Reference Model 115 3.1. Homogeneous Backup 117 Figure 2 illustrates a homogeneous backup cases. In this scenario, 118 each of those master SFIs will have a corresponding backup SFI. 120 ,---. ,---. ,---. 121 / \ / \ / \ 122 ( SFI1 | ( SFI2 | ( SFI3 | 123 \ / \ / \ / 124 `-^-' `-^-' `-^-' 125 | | | 126 | | | 127 | | | 128 ,-v-. ,-v-. ,-v-. 129 / \ / \ / \ 130 ( SFI1' ) ( SFI2' ) ( SFI3' ) 131 \ / \ / \ / 132 `---' `---' `---' 134 Figure 2: Homogeneous Backup Model 136 3.2. Heterogeneous Backup 138 Figure 3 illustrates a heterogeneous backup cases. In this scenario, 139 each of those master SFIs might have more than one corresponding 140 backup SFIs. 142 ,---. ,---. 143 / \ / \ 144 ( SFI1 | ( SFI2 | 145 \ / / \ / \ 146 `-^-' / `---' \ 147 | | | 148 | | | 149 | | | 150 ,-v-. ,-v-. ,-v-. 151 / \ / \ / \ 152 ( SFI1' ) ( SFI2' ) ( SFI2'') 153 \ / \ / \ / 154 `---' `---' `---' 156 Figure 3: Heterogeneous Backup Model 158 3.3. Internal Backup 160 Figure 4 illustrates a internal backup cases. In this scenario, both 161 sides of backup are located in a same Service Function Node. 163 +----------------------------------------+ 164 | ,---. ,---. ,---. | 165 | / \ / \ / \ | 166 | ( SFI1 <---> SFI1' | ( SFI2 | | <-- Service Function Node 167 | \ / \ / \ / | 168 | `---' `---' `---' | 169 +----------------------------------------+ 171 Figure 4: Internal Backup Model 173 3.4. External Backup 175 Figure 5 illustrates a external backup cases. In this scenario, each 176 side of backup is located in its own Service Function Node. 178 +---------------------------------------+ 179 | ,---. ,---. ,---. | 180 | / \ / \ / \ | 181 | ( SFI1 | ( SFI2 | ( SFI3 | | <-- Service Function Node 1 182 | \ / \ / \ / | 183 | `-^-' `-^-' `-^-' | 184 +-------|-----------|-----------|-------+ 185 | | | <------- Network 186 +-------|-----------|-----------|-------+ 187 | ,-v-. ,-v-. ,-v-. | 188 | / \ / \ / \ | 189 | ( SFI1' | ( SFI2' | ( SFI3' | | <-- Service Function Node 2 190 | \ / \ / \ / | 191 | `---' `---' `---' | 192 +---------------------------------------+ 194 Figure 5: External Backup Model 196 4. Redirect Service Function Paths 198 As described in [ietf-sfc-architecture], a Service Function Path is 199 the instantiation of the defined SFC. 201 In case of planned maintenance operations or exceptional failure of 202 Service Function Node, The SFP MUST be changed to prevent disrupting 203 the normal traffic. 205 5. Control Plane Considerations 207 TBD 209 6. Data Plane Considerations 211 TBD 213 7. Load Balancing Considerations 215 TBD 217 8. Normative References 219 [I-D.ietf-sfc-architecture] 220 Halpern, J. and C. Pignataro, "Service Function Chaining 221 (SFC) Architecture", draft-ietf-sfc-architecture-11 (work 222 in progress), July 2015. 224 [I-D.ietf-sfc-problem-statement] 225 Quinn, P. and T. Nadeau, "Service Function Chaining 226 Problem Statement", draft-ietf-sfc-problem-statement-13 227 (work in progress), February 2015. 229 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 230 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ 231 RFC2119, March 1997, 232 . 234 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 235 "Remote Authentication Dial In User Service (RADIUS)", 236 RFC 2865, DOI 10.17487/RFC2865, June 2000, 237 . 239 Authors' Addresses 241 Wei Meng 242 ZTE Corporation 243 No.50 Software Avenue, Yuhuatai District 244 Nanjing 245 China 247 Email: meng.wei2@zte.com.cn,vally.meng@gmail.com 249 Cui Wang 250 ZTE Corporation 251 No.50 Software Avenue, Yuhuatai District 252 Nanjing 253 China 255 Email: wang.cui1@zte.com.cn