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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-04) exists of draft-geng-coms-problem-statement-00 == Outdated reference: A later version (-20) exists of draft-ietf-i2rs-yang-network-topo-17 == Outdated reference: A later version (-02) exists of draft-qiang-coms-netslicing-information-model-01 Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 none X. de Foy 3 Internet-Draft A. Rahman 4 Intended status: Informational InterDigital Inc. 5 Expires: May 3, 2018 A. Galis 6 University College London 7 K. Makhijani 8 L. Qiang 9 Huawei Technologies 10 October 30, 2017 12 Interconnecting (or Stitching) Network Slice Subnets 13 draft-defoy-coms-subnet-interconnection-01 15 Abstract 17 This document aims to define a network slice subnet as a general 18 concept, and to augment a baseline network slice model with 19 attributes that describe interconnections between network slice 20 subnets. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on May 3, 2018. 39 Copyright Notice 41 Copyright (c) 2017 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. Interconnection Concepts . . . . . . . . . . . . . . . . . . 3 59 3. Information Model . . . . . . . . . . . . . . . . . . . . . . 5 60 3.1. Representing Interconnections . . . . . . . . . . . . . . 5 61 3.2. Relation to NS Information Model . . . . . . . . . . . . 5 62 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 64 6. Next Steps . . . . . . . . . . . . . . . . . . . . . . . . . 6 65 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 66 8. Informative References . . . . . . . . . . . . . . . . . . . 7 67 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 69 1. Introduction 71 Network Slicing enables deployment and management of services with 72 diverse requirements on end-to-end partitioned virtual networks, 73 including compute and storage resources, over the same 74 infrastructure. [I-D.geng-coms-problem-statement] describes a 75 problem statement for supervised heterogeneous network slicing, 76 enabling users to deploy network slices including connectivity, 77 computing and storage components. 79 Nevertheless, defining and managing a network slice (NS) end-to-end 80 does not always have to be done directly: it may be convenient to 81 define and manage subsets of NS components. The concept of network 82 slice subnet is defined originally in [NGMN_Network_Slicing], though 83 we only need to retain its definition in the most universal form: 84 network slice subnet instances are similar to slice instances in most 85 ways but cannot be operated in isolation as a complete network slice. 86 They can be interconnected with other NS subnets to form a complete, 87 end-to-end network slice (i.e. interconnection and/or stitching of NS 88 subnets). To summarize: a NS subnet can be seen as a network slice 89 with unconnected links. The term "network slice segment" has also 90 occasionally been used to designate a NS subnet. Use cases for using 91 NS subnets include managing multi-domain network slices, or even 92 within one domain, isolate management and maintenance of different 93 portions of a network slice. It includes also mapping services to an 94 ordered chain of network slice subnets instances. 96 A model for network slicing is currently being defined in 97 [I-D.qiang-coms-netslicing-information-model]. One question we would 98 like to address is how to augment this base model to describe 99 interconnections between NS subnets. The base model is not 100 technology specific, and therefore the description of 101 interconnections should not be either. Moreover, such an 102 augmentation should both enable describing the intent for 103 interconnection, as well as describing actual interconnections once 104 NS subnets have been stitched together. 106 1.1. Terminology 108 Network slicing related terminology used in this document should be 109 interpreted as described in [I-D.geng-coms-problem-statement]. 111 "Network slice subnet" is a term defined in this draft. It is 112 comprised of groups of connectivity, compute and storage resources, 113 possibly together with network functions and network management 114 entities, forming a complete instantiated logical/physical network in 115 support of certain network and service characteristics but cannot be 116 activated in isolation as an overall network slice. 118 2. Interconnection Concepts 120 The general goal of an interconnection between 2 NS subnets is to 121 have links established between nodes from both subnets. A secondary 122 goal is to keep NS subnet descriptions isolated from each other. 123 This relative isolation will contribute to simplify and decentralize 124 management, as well as enabling operations such as substituting a 125 subnet with another, composing slice subnets of different domains, 126 etc. 128 As described in Figure 1, we can represent a network slice subnet as 129 a network slice that also has one or more logical nodes, which 130 terminate (at logical termination points) links that need to be 131 interconnected with external nodes (cross-subnet links). 133 During a stitching operation, logical termination points from both NS 134 subnets can be paired together into an interconnection point. When 135 implemented at the infrastructure layer, this interconnection point 136 may be either implemented as a gateway, or abstracted away, in which 137 case nodes from both NS subnets end up being directly interconnected 138 between each other. In any cases, interconnected links will need to 139 have compatible QoS attributes. 141 Slice Provider 142 | 143 +---------------------------------v---------------------------------+ 144 | Slice Manager | 145 | | 146 | +---------------------------------------------------------------+ | 147 | | Data model: network slice composed of NS subnet 1 and 2 | | 148 | | | | 149 | | Network Slice Subnet 1 Network Slice Subnet 2 | | 150 | | +---------------------------+ +----------------------------+ | | 151 | | | cross-subnet link | | cross-subnet | | | 152 | | | +----------------+ | | link +------+ | | | 153 | | | | | | | +--------o node | | | | 154 | | | | |Interconnection| +---o--+ | | | 155 | | |+---o--+ +-------|-----+--+------|------+ | | | | 156 | | || node | | | | | | | | | | | 157 | | |+---o--+ | +-----|---+ | | +----|----+ | | | | | 158 | | | | | | | | | | | | | | | | | | 159 | | | | | | o - - - - - - - o | | | | | | 160 | | | | | | | | | | | | | | | | 161 | | | | | | logical | | | | logical | | | | | | 162 | | | | | | node | | | | node | | | | | | 163 | | | | | | | | | | | | +---+ | | | 164 | | | | | | o - - - - - - - o | | | | | | 165 | | | | | | | | | | | | | | | | | | 166 | | | | | +-----|---+ | | +----|----+ | +---o--+ | | | 167 | | | | | | | | | | | node | | | | 168 | | | | +-------|-----+--+------|------+ +---o--+ | | | 169 | | | | +------+ | | | | | | | | 170 | | | +-o node o-------+ | | +----------------+ | | | 171 | | | +------+ cross-subnet| | cross-subnet | | | 172 | | | link | | link | | | 173 | | +---------------------------+ +----------------------------+ | | 174 | +---------------------------------------------------------------+ | 175 +--------------------------------+----------------------------------+ 176 | 177 v 178 Network Infrastructure 180 Figure 1: Network Slice Subnets Interconnection 182 Network slice interconnection information in data models can be used 183 for different related purposes: 185 o Anchoring interconnections at logical termination points: a NS 186 subnet model should specify which link termination points are the 187 "network slice subnet boundaries" that need to be interconnected. 189 o Programming interconnections: a NS provider may set attributes in 190 a NS subnet model to configure the interconnection with another NS 191 subnet. For example, constraints on the interconnection (on 192 throughput, latency, etc.) may be programmed to trigger an alarm 193 that may be lead the NS operator to disable NS subnets, replace NS 194 subnets by others, etc. to maintain overall service performance. 196 o Describing the state of interconnection (once NS subnets are 197 interconnected). 199 3. Information Model 201 3.1. Representing Interconnections 203 A fairly minimal way to represent an interconnection is: 205 o To represent an interconnection anchor in a subnet: a "logical 206 termination point" in this subnet. 208 o To program or represent an interconnection between subnets: a pair 209 of logical termination points, one in each subnet. 211 Some form of grouping of logical termination points (for example, in 212 logical nodes) may tell the NS manager to treat those termination 213 points as a single unit for placement, implementation, etc. 215 Additional information may be useful to complement the description of 216 an interconnections. Some attributes may be useful to describe an 217 interconnection point anchor, while others may be useful to program 218 or represent the state of an interconnection. For example, logical 219 termination points may be associated with information that 220 facilitates placement or stitching operations. Future work should 221 determine what type of information would be useful to specify or 222 represent a NS interconnection. 224 3.2. Relation to NS Information Model 226 The network slice information model defined in 227 [I-D.qiang-coms-netslicing-information-model] will be used as a base. 228 This model is itself based on the "ietf-network" model defined in 229 [I-D.ietf-i2rs-yang-network-topo] 231 Individual network slice data model instances ("network" attributes 232 of the "ietf-network" model) can represent network slice subnets. If 233 there is a need to tie multiple subnets together, a parent network 234 slice may be added to the model if necessary, but this is out of 235 scope of the present draft. A "network" attribute may also represent 236 a full, end-to-end slice, in which case it does not need be 237 interconnected using the mechanisms described in the present draft. 239 Interconnection anchors are logical termination points (TP) included 240 in logical nodes. The base model can be augmented as described 241 below. Those new logical node and logical TP attributes will 242 typically be used only for nodes and termination points used as 243 interconnection anchors. Logical nodes should be as simple as 244 possible (e.g. should not include any compute or storage unit), so 245 that they can be abstracted away in underlying networks during the 246 interconnection operation, if needed. 248 module: ietf-network 249 +--rw networks 250 +--rw network* [network-id] 251 +--rw network-id 252 +--rw network-types 253 +--rw supporting-network* [network-ref] 254 | +--rw network-ref 255 +--rw node* [node-id] 256 | +--... (augmented with new attributes of logical nodes) 257 | +--rw nt:termination-point* [tp-id] 258 | | ... (augmented with new attributes of logical TP) 259 ... 261 4. Operations 263 Stitching may occur when network slice subnets are initially 264 instantiated, or later after instantiation. 266 5. Security Considerations 268 Access control mechanisms for managing network slices can likely be 269 reused for network slice subnets, since their models should be 270 similar to each other. 272 Stitching 2 NS subnets together may be subject to some form of 273 authorization by a NS tenant. 275 6. Next Steps 277 The present draft investigates one aspect of a non-technology 278 specific representation of a network slice. It may therefore be part 279 of the larger discussion on the need for such a representation. 281 Beyond this, next steps can include the following: 283 o Discussing the definition and need for NS subnets. Is "NS with 284 unconnected links" an adequate simple definition? Is there an 285 agreement on the use cases? Should NS subnet interconnection be 286 standardized? 288 o Assuming there is some interest in this, further work is needed to 289 better understand what attributes and operations are needed, and 290 how to integrate them in a baseline NS model. 292 o Additionally, we can also further study NS composition mechanisms, 293 beyond the simple connect/disconnect mechanism in the present 294 draft. 296 7. IANA Considerations 298 This document has no actions for IANA. 300 8. Informative References 302 [I-D.geng-coms-problem-statement] 303 67, 4., Slawomir, S., Qiang, L., Matsushima, S., Galis, 304 A., and L. Contreras, "Problem Statement of Supervised 305 Heterogeneous Network Slicing", draft-geng-coms-problem- 306 statement-00 (work in progress), September 2017. 308 [I-D.ietf-i2rs-yang-network-topo] 309 Clemm, A., Medved, J., Varga, R., Bahadur, N., 310 Ananthakrishnan, H., and X. Liu, "A Data Model for Network 311 Topologies", draft-ietf-i2rs-yang-network-topo-17 (work in 312 progress), October 2017. 314 [I-D.qiang-coms-netslicing-information-model] 315 Qiang, L., Galis, A., 67, 4., kiran.makhijani@huawei.com, 316 k., Martinez-Julia, P., Flinck, H., and X. Foy, 317 "Technology Independent Information Model for Network 318 Slicing", draft-qiang-coms-netslicing-information-model-01 319 (work in progress), October 2017. 321 [NGMN_Network_Slicing] 322 NGMN, "Description of Network Slicing Concept", 10 2016, 323 . 326 Authors' Addresses 327 Xavier de Foy 328 InterDigital Inc. 329 1000 Sherbrooke West 330 Montreal 331 Canada 333 Email: Xavier.Defoy@InterDigital.com 335 Akbar Rahman 336 InterDigital Inc. 337 1000 Sherbrooke West 338 Montreal 339 Canada 341 Email: Akbar.Rahman@InterDigital.com 343 Alex Galis 344 University College London 346 Email: a.galis@ucl.ac.uk 348 Kiran Makhijani 349 Huawei Technologies 350 2890 Central Expressway 351 Santa Clara CA 95050 352 USA 354 Email: kiran.makhijani@huawei.com 356 Li Qiang 357 Huawei Technologies 358 Huawei Campus, No. 156 Beiqing Rd. 359 Beijing 100095 361 Email: qiangli3@huawei.com