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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group D. Fan 3 Internet-Draft L. Xia 4 Intended status: Standards Track Huawei 5 Expires: April 11, 2015 Z. Cao 6 China Mobile 7 N. Kim 8 KT 9 October 8, 2014 11 L2TP-VP: Layer Two Tunneling Protocol - Virtualization Profile 12 draft-fan-l2tp-vp-02 14 Abstract 16 This document describes Layer Two Tunneling Protocol (L2TP)'s 17 virtualization profile (L2TP-VP), which reuses session header of L2TP 18 data message to securely support overlay networks for multiple 19 tenants, and simplifies tunnel setup by disabling all kinds of L2TP 20 control messages. 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 http://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 April 11, 2015. 39 Copyright Notice 41 Copyright (c) 2014 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 (http://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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. L2TP-VP Frame Format . . . . . . . . . . . . . . . . . . . . 3 59 4. Control Plane Consideration . . . . . . . . . . . . . . . . . 6 60 5. Data Plane Consideration . . . . . . . . . . . . . . . . . . 6 61 5.1. Address Learning . . . . . . . . . . . . . . . . . . . . 6 62 5.2. Forwarding . . . . . . . . . . . . . . . . . . . . . . . 6 63 5.2.1. Unicast Traffic . . . . . . . . . . . . . . . . . . . 6 64 5.2.2. Broadcast/Unknown/Multicast(BUM) Traffic . . . . . . 6 65 5.3. MTU Configuration . . . . . . . . . . . . . . . . . . . . 7 66 5.4. Qos Consideration . . . . . . . . . . . . . . . . . . . . 7 67 5.5. ECMP . . . . . . . . . . . . . . . . . . . . . . . . . . 7 68 6. Management Plane Consideration . . . . . . . . . . . . . . . 7 69 7. Deployment Consideration . . . . . . . . . . . . . . . . . . 8 70 8. Security Considerations . . . . . . . . . . . . . . . . . . . 8 71 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 72 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 73 10.1. Normaative References . . . . . . . . . . . . . . . . . 8 74 10.2. Informative References . . . . . . . . . . . . . . . . . 8 75 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 77 1. Introduction 79 Traditional data centre network uses global VLAN ID to distinguish 80 different tenants. Usually, a tenant consumes several VLAN IDs, for 81 example, one for web server, one for application server and one for 82 database server. When the number of tenants increases, the number of 83 available VLAN IDs becomes insufficient. 85 When services provided by cloud via Internet becomes popular, a 86 tenant's local area network needs to securely and smoothly reach 87 anywhere via Internet if it wants. For example, a tenant can access 88 its office IT services hosted in cloud data centers consisting of 89 many geographically dispersed physical data centers. So, VPN access 90 to cloud data centers becomes very important. 92 Layer Two Tunneling Protocol - Version 3 (L2TPv3) [RFC3931] is a 93 mature and practical protocol that provides secure remote access 94 service and layer 2 over IP service, but L2TPv3 aslo uses complicated 95 control messages to setup tunnel. At the same time, L2TPv3 uses 96 dynamical session id that is controlled by signaling mechanism and 97 only has local significance. Currently, L2TPv3 is complex and does 98 not support multiple tenants though it provides basic overlay 99 functions. 101 This document will describe Layer Two Tunneling Protocol (L2TP)'s 102 virtualization profile (L2TP-VP), which reuses session header of L2TP 103 data message to securely support overlay networks for multiple 104 tenants, and simplifies tunnel setup by disabling all kinds of L2TP 105 control messages. Essentially, L2TP-VP defines a subset of L2TPv3 106 via fine and back-compatible reuse, and then extends L2TP's usage to 107 network virtualization. L2TP is widely deployed and used whatever 108 for operators' network or enterprises' network, L2TP-VP brings L2TP 109 to the entire cloud network by further covering data center network. 111 The motivation of this draft is to propose an altenative L3-based 112 overlay technology, besides the existed VxLAN [RFC7348] , NVGRE 113 [NVGRE], based on the following consideration: 115 o L2TPv3 is a mature IP-based tunnelling technology that is widely 116 supported and implemented on current operators' deployed networks. 117 Directly reusing it can help operators to save their costs; 119 o L2TPv3 inherent Cookie mechanism provides security protection 120 against network attacks for tenant service; 122 o L2TP-VP solution mainly focuses on the changing on network side, 123 i.e. router or switch, to be transparent to client/server for 124 alleviating their complexity and burden. 126 2. Terminology 128 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 129 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 130 document are to be interpreted as described in RFC-2119 [RFC2119]. 132 In this document, these words will appear with that interpretation 133 only when in ALL CAPS. Lower case uses of these words are not to be 134 interpreted as carrying RFC-2119 significance. 136 3. L2TP-VP Frame Format 138 L2TPv3 message format is specified in [RFC3931]. In order to support 139 virtualization and reduce complexity from the control messages, two 140 key fields are added into L2TP header to carry the original payload 141 type and TNI (Tenant Network Identifier).The example of packet format 142 for Ethernet encapsulation in L2TP-VP is shown in Figure 1. 144 0 1 2 3 145 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 146 Outer Ethernet Header: 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | Outer Destination MAC Address | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 | Outer Destination MAC Address | Outer Source MAC Address | 151 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 152 | Outer Source MAC Address | 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 |Optional Ethertype=C-Tag 802.1Q| Outer VLAN Tag Information | 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | Ethertype 0x0800 | 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 158 Outer IPv4 Header: 159 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 160 |Version| IHL |Type of Service| Total Length | 161 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 162 | Identification |Flags| Fragment Offset | 163 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 164 | Time to Live | Protocol 115 | Header Checksum | 165 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 166 | Outer Source Address | 167 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 168 | Outer Destination Address | 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 L2TP-VP Header: 171 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 172 |M| Reserved#0 | Type | 173 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 174 | Tenant Network Identifier (TNI) | Reserved#1 | 175 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 176 | Cookie (optional) | 177 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 Inner Ethernet Header 179 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 180 | Inner Destination MAC Address | 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 | Inner Destination MAC Address | Inner Source MAC Address | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 | Inner Source MAC Address | 185 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 186 |Optional Ethertype=C-Tag 802.1Q| Inner VLAN Tag Information | 187 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 | Ethertype of Original Payload | 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 Original Ethernet Payload: 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 | | 193 | | 194 | Original Ethernet Payload | 195 | | 196 | | 197 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 199 Figure 1 L2TP-VP Encapsulation Frame Format 201 The original Ethernet frame is encapsulated with L2TP-VP Header, 202 Outer IP Header and Outer Ethernet Header. 204 L2TP-VP Header: 206 o M bit: Modified Identifier. The M bit MUST be set to 1 to 207 indicate the header is modified to L2TP-VP header format. If M=0 208 ,it indicates the header format following the L2TPv3 Session 209 Header Over IP format and should to refer to [RFC3931] (Session ID 210 is changed to a 31-bit field); 212 o Type field : A 16-bit field is used to carry original payload type 213 (e.g., frame type). Payload type can be Layer2 type such as ATM, 214 FR, Ethernet, etc. It also can be Layer3 type such as IPv4 , IPv6 215 ,etc. In Figure 1 the type of original packet is Ethernet; 217 o TNI field : A 24-bit field allows up to 16 million tenants in the 218 same management domain. The packets with different TNI will be 219 isolated logically; 221 o Cookie field : The optional Cookie field inherits all the 222 functions from cookie field in [RFC3931] . It is used to check the 223 association of a received data message with TNI. Only need to 224 change its length to be 32-bit. 226 Outer IP Header: Both IPv4 and IPv6 can be used as encapsulation IP 227 header. Figure 1 shows an example of IPv4. The source IP address is 228 filled with IP address of L2TP-VP endpoint which encapsulates the 229 original packet with L2TP-VP frame format. The destination IP 230 address is unicast address obtained by lookup of address table. Also 231 it may be a multicast address representing this packet may be used 232 for address learning. 234 Outer Ethernet Header: The destination MAC address in Figure 1 may be 235 the address of next hop device. The Optional Vlan Tag may be used to 236 limit the area of the broadcast. 238 4. Control Plane Consideration 240 In order to reduce complexity coming from control messages, there is 241 no separate control plane in L2TP-VP. All kinds of control messages 242 defined in [RFC3931] are disabled. All tunnel endpoints are expected 243 to be configured by management plane(e.g., OSS). 245 5. Data Plane Consideration 247 5.1. Address Learning 249 For the E2E link and tunnel setup of L2TP-VP overlay network, the 250 forwarding information including tenant systems' address, and its 251 associated L2TP-VP endpoint address and TNI should be populated in 252 the network. There are several options to support address learning: 254 o Through the management plane, L2TP-VP endpoints will be configured 255 part or all of the address table; 257 o L2TP-VP endpoints directly acquire the forwarding information 258 through data plane by flooding mechanism; 260 o L2TP-VP endpoints join the multicast group and populate the 261 forwarding information to the other endpoints in the same virtual 262 network by the multicast tree. 264 5.2. Forwarding 266 5.2.1. Unicast Traffic 268 Ingress L2TP-VP endpoint firstly gets the destination address from 269 the unicast traffic, then obtains IP address of the egress endpoint 270 and the TNI by lookup of address table, at last encapsulates the 271 original packet in L2TP-VP frame format. The source IP address in 272 outer IP header is filled with its own IP address and the destination 273 IP address is filled with egress endpoint's IP address. 275 5.2.2. Broadcast/Unknown/Multicast(BUM) Traffic 277 There are several proven methods to process BUM traffic. 279 One method needs the multicast support of underlay network. All BUM 280 traffic originating from within a TNI is terminated by the L2TP-VP 281 endpoint, then encapsulated and sent to the assigned multicast 282 address. The binding relation of the TNI and the multicast address 283 of underlay network can be configured by the management plane. 285 Another method is ingress replication. One BUM frame in a TNI can be 286 replicated to multiple unicast frames which will be sent to all the 287 egress L2TP-VP endpoints in the same TNI. 289 5.3. MTU Configuration 291 L2TP-VP overlay header can cause the MTU of the path to the egress 292 tunnel endpoint to be exceeded. Here lists some solutions: 294 o Modifying the MTU support configuration in the network devices, 295 including L2TP-VP endpoints and other network devices which will 296 transmit the encapsulation packets; 298 o Classical ICMP-based MTU Path Discovery [RFC1191] [RFC1981] or 299 Extended MTU Path Discovery techniques such as defined in 300 [RFC4821]. 302 5.4. Qos Consideration 304 QoS of underlay network can be provided without problem due to the 305 fact that it's an IP network. 307 QoS of the overlay network may need to support the mapping of CoS 308 marking between different network layers (e.g., Tenant Systems, 309 Overlays, and/or Underlay) in L2TP-VP endpoints, for enabling each 310 networking layer to independently enforce its own CoS policies. 312 TS's QoS fields (e.g. IP DSCP and/or Ethernet 802.1p) and policies 313 can be defined to indicate application level CoS requirements. L2TP- 314 VP endpoint can use the new service CoS fields in the overlay header 315 to indicate the proper service CoS to be applied across the overlay 316 network. This field can be mapped from the TS's QoS fields or other 317 mechanism (e.g. DPI). 319 5.5. ECMP 321 Because the outer header is standard IP header, the L2TP-VP endpoint 322 SHOULD provide ECMP. Basically the L2TP-VP endpoint uses a hash of 323 various fields of the outer Ethernet header and outer IP header, 324 furthermore it can uses the fields of L2TP-VP header or even inner 325 original packet. And the endpoint can select different fields for 326 hash according to the requirement. 328 6. Management Plane Consideration 330 Management plane is needed to configure access type, TNI, QoS, 331 Cookie, etc. In some scenarios, management plane should support to 332 configure the forwarding information or policies for data plane and 333 control plane , such as routing table, address table, etc. 334 Management plane can be OSS or SDN controller. 336 7. Deployment Consideration 338 TBD. 340 8. Security Considerations 342 Like L2TPv3, L2TP-VP continues to adopt Cookie Field as an additional 343 check to the received packet. A 32-bit random field is difficult to 344 be cracked so that it can afford protection against brute-force, 345 blind and insertion attacks. 347 When the network is open network and someone can sniff the whole 348 traffic through the network , it will need other security measures. 349 Traditional security mechanisms based on IP technique will provide 350 authentication/encryption function ,such as IPSec. 352 9. IANA Considerations 354 TBD. 356 10. References 358 10.1. Normaative References 360 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 361 Requirement Levels", March 1997. 363 [RFC3931] Lau, J., "Layer Two Tunneling Protocol - Version 3 364 (L2TPv3)", March 2005. 366 [RFC7348] Mahalingam , M., "Virtual eXtensible Local Area Network 367 (VXLAN): A Framework for Overlaying Virtualized Layer 2 368 Networks over Layer 3 Networks", August 2014. 370 10.2. Informative References 372 [NVGRE] Sridharan , M., "NVGRE: Network Virtualization using 373 Generic Routing Encapsulation", ID draft-sridharan- 374 virtualization-nvgre-06, October 2014. 376 Authors' Addresses 377 Duoliang Fan 378 Huawei 379 101 Software Avenue, Yuhua District 380 Nanjing, Jiangsu 210012 381 China 383 Email: fanduoliang@huawei.com 385 Liang Xia 386 Huawei 387 101 Software Avenue, Yuhua District 388 Nanjing, Jiangsu 210012 389 China 391 Email: frank.xialiang@huawei.com 393 Zhen Cao 394 China Mobile 395 Xuanwumenxi Ave. No.32 , Xicheng District 396 Beijing 100053 397 China 399 Email: zehn.cao@gmail.com, caozhen@chinamobile.com 401 Namgon Kim 402 KT 403 463-1 Jeonmin-Dong, Yuseoung-Gu Daejeon, 305-811 404 Korea 406 Email: ng.kim@kt.com