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Korhonen 3 Management (NetLMM) Nokia Siemens Networks 4 Internet-Draft V. Devarapalli 5 Intended status: Informational WiChorus 6 Expires: November 26, 2009 May 25, 2009 8 LMA Discovery for Proxy Mobile IPv6 9 draft-ietf-netlmm-lma-discovery-00.txt 11 Status of this Memo 13 This Internet-Draft is submitted to IETF in full conformance with the 14 provisions of BCP 78 and BCP 79. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as Internet- 19 Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six months 22 and may be updated, replaced, or obsoleted by other documents at any 23 time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on November 26, 2009. 34 Copyright Notice 36 Copyright (c) 2009 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 in effect on the date of 41 publication of this document (http://trustee.ietf.org/license-info). 42 Please review these documents carefully, as they describe your rights 43 and restrictions with respect to this document. 45 Abstract 47 Large Proxy Mobile IPv6 deployments would benefit from a 48 functionality, where a Mobile Access Gateway could dynamically 49 discover a Local Mobility Anchor for a Mobile Node attaching to a 50 Proxy Mobile IPv6 domain. The purpose of the dynamic discovery 51 functionality is to reduce the amount of static configuration in the 52 Mobile Access Gateway. This specification describes a number of 53 possible dynamic Local Mobility Anchor discovery solutions. 55 Table of Contents 57 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 58 2. AAA-based Discovery Solutions . . . . . . . . . . . . . . . . . 3 59 2.1. Receiving LMA Address during the Network Access 60 Authentication . . . . . . . . . . . . . . . . . . . . . . 4 61 2.2. Receiving LMA FQDN during the Network Access 62 Authentication . . . . . . . . . . . . . . . . . . . . . . 4 63 3. Lower Layers based Discovery Solutions . . . . . . . . . . . . 5 64 3.1. Constructing the LMA FQDN from a mobile node Identity . . . 5 65 3.2. Receiving LMA FQDN or IP Address from Lower Layers . . . . 5 66 3.3. Constructing the LMA FQDN from a Service Name . . . . . . . 6 67 4. Domain Name System Considerations . . . . . . . . . . . . . . . 6 68 5. Handover Considerations . . . . . . . . . . . . . . . . . . . . 7 69 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 70 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 71 8. Informative References . . . . . . . . . . . . . . . . . . . . 8 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 74 1. Introduction 76 Large Proxy Mobile IPv6 (PMIPv6) [RFC5213] deployments would benefit 77 from a functionality, where a Mobile Access Gateway (MAG) could 78 dynamically discover a Local Mobility Anchor (LMA) for a Mobile Node 79 (MN) attaching to a PMIPv6 domain. The purpose of the dynamic 80 discovery functionality is to reduce the amount of static 81 configuration in the MAG. This specification describes a number of 82 possible dynamic LMA discovery solutions. 84 There are a number of different ways for dynamically discovering the 85 LMA at the MAG. The following list briefly introduces solutions that 86 will be discussed in this specification: 88 o LMA Address from AAA during the network access authentication 89 procedure when the MN attaches to the MAG. 91 o LMA FQDN from AAA during the network access authentication, 92 followed by a Domain Name System (DNS) lookup. 94 o LMA FQDN derived from the MN identity received from the lower 95 layers during the network attachment, followed by a DNS lookup. 97 o LMA FQDN or IP address received from the lower layers during the 98 network attachment followed by an optional DNS lookup. 100 o LMA FQDN derived from the service selection indication received 101 from lower layers during the network attachment, followed by a DNS 102 lookup. 104 When a MN performs a handover from one MAG to another, the new MAG 105 must use the same LMA that the old MAG was using. This is required 106 for session continuity. The LMA discovery mechanism used by the new 107 MAG should be able to return the information about the same LMA that 108 was being used by the old MAG. This document also discusses 109 solutions for LMA discovery during a handover. 111 2. AAA-based Discovery Solutions 113 This section presents a LMA discovery solution that requires a MAG to 114 be connected to an AAA infrastructure. The AAA infrastructure is 115 also assumed to be aware of and support PMIPv6 functionality. A MN 116 attaching to a PMIPv6 domain is typically required to authenticate to 117 the network access and to be authorized for the mobility services 118 before the MN is allowed to send or receive any IP packets or even 119 complete its IP level configuration. 121 The AAA-based LMA discovery solution hooks into the network access 122 authentication and authorization procedure. The MAG has also the 123 role of a Network Access Server (NAS) at this step. While the MN is 124 attaching to the network, the PMIPv6 related parameters are 125 bootstrapped at the same time the MN is authenticated for the network 126 access and authorized for the mobility services using the AAA 127 infrastructure. The PMIPv6 parameters bootstrapping involves the 128 Policy Profile download over the AAA infrastructure to the MAG. The 129 procedure for the Policy Profile download resembles largely the 130 client Mobile IPv6 Integrated Scenario bootstrapping [RFC5447]. 132 2.1. Receiving LMA Address during the Network Access Authentication 134 After the MN has successfully authenticated for the network access 135 and authorized for the mobility service, the MAG receives the LMA IP 136 address(es) from the AAA server over the AAA infrastructure. The LMA 137 IP address information would be part of the AAA message(s) that ends 138 the successful authentication and authorization AAA exchange. 140 Once the MAG receives the LMA IP address(es), it sends Proxy Binding 141 Update (PBU) message for the newly authenticated and authorized MN. 142 The MAG trusts that the LMA returned by the AAA server is able to 143 provide mobility session continuity for the MN, i.e. after a handover 144 the LMA would be the same the MN already has a mobility session set 145 up with. 147 2.2. Receiving LMA FQDN during the Network Access Authentication 149 This solution is identical to the procedure described in Section 2.1. 150 The difference is that the MAG receives a Fully Qualified Domain Name 151 (FQDN) of the LMA instead of the IP address(es). The MAG has to 152 query the DNS infrastructure in order to resolve the FQDN to the LMA 153 IP address(es). 155 The LMA FQDN might be a generic to a PMIPv6 domain resolving to one 156 or more LMAs in the said domain. Alternatively the LMA FQDN might 157 resolve to exactly one LMA within the PMIPv6 domain. The latter 158 approach would obviously be useful if a new target MAG after a 159 handover should resolve the LMA FQDN to the LMA IP address where the 160 MN mobility session is already located. 162 The procedures described in this section and in Section 2.1 may also 163 be used together. For example, the AAA server might return a generic 164 LMA FQDN during the MN initial attach and once the LMA gets selected, 165 return the LMA IP address during the subsequent attachments to other 166 MAGs in the PMIPv6 domain. In order for this to work, the resolved 167 and selected LMA IP address must be updated to the remote Policy 168 Store. For example, the LMA could perform the update once it 169 receives the initial PBU from the MAG for the new mobility session. 171 3. Lower Layers based Discovery Solutions 173 The following section discusses solutions, where the MAG receives 174 information from lower layers below the IP layer when the MN attaches 175 to the MAG. Based on this information, the MAG is then able to 176 determine which LMA to contact. These solution could essentially 177 allow large PMIPv6 deployments without the AAA infrastructure. The 178 lower layers discussed here are not explicitly defined but could 179 include different radio access technologies and tunneling solutions 180 such as IKEv2 [RFC4306] IPsec tunnel [RFC4303]. 182 3.1. Constructing the LMA FQDN from a mobile node Identity 184 Depending on the actual network access technology, the MAG may be 185 able to receive a MN identity (or actually the subscription identity 186 but from now on we assume that the MN identity equals to the 187 subscription identity, which is a rather broad simplification) as a 188 result of the network access attachment procedure. The MN may signal 189 its identity as part of the attachment signaling or alternatively the 190 MAG receives the MN identity from a remote policy store. 192 Once the MAG has acquired the MN identity, the MAG can use the 193 information embedded in the identity to construct a generic LMA FQDN 194 (based on some pre-configured formatting rules) and then proceed to 195 resolve the LMA IP address(es) using the DNS. Obviously, the MN 196 identity must embed information elements that can be extracted and at 197 minimum used to determine the entity hosting and operating the LMA 198 for the MN. Thus the MN identity in this solution cannot be a "flat" 199 identity without any structure and "clear text" parts containing the 200 hosting entity information. Examples of such identities are the 201 International Mobile Subscriber Identity (IMSI) or Globally Unique 202 Temporary User Equipment Identity (GUTI) [3GPP.23.003] that both 203 contain information of the operator owning the given subscription. 205 The solution discussed in this section has issues if MN's identity 206 does not embed enough information. In a case the MN identity does 207 not embed any LMA hosting entity information, the MAG might use a 208 local database to map MN identities to corresponding LMAs. However, 209 this solution is unlikely to scale outside a limited PMIPv6 domain. 211 3.2. Receiving LMA FQDN or IP Address from Lower Layers 213 The solution described in this section is similar to the solution 214 discussed in Section 3.1. Instead of deriving the LMA FQDN from the 215 MN identity, the MAG receives explicit LMA FQDN or IP address 216 information from lower layers. This usually means the MN is the 217 originator of the LMA information and explicitly participates to the 218 mobility management signaling (even if that only means providing LMA 219 discovery assisting information). 221 3.3. Constructing the LMA FQDN from a Service Name 223 Some network access technologies (including tunneling solutions) 224 allow the MN to signal the service name that identifies a particular 225 service or the external network it wants to access. If the MN 226 originated service name also embeds the information of the entity 227 hosting the service or the external network, then the MAG can 228 construct a generic LMA FQDN (e.g., based on some pre-configured 229 formatting rules) providing an access to the service or the external 230 network. Once the MAG has the FQDN it can proceed to resolve the LMA 231 IP address(es) using the DNS. Example of such service or external 232 network name is the Access Point Name (APN) [3GPP.23.003] that 233 contain information of the operator providing the access to the given 234 service or the external network. 236 4. Domain Name System Considerations 238 A number of LMA discovery solutions described in Section 2 and 239 Section 3 eventually depend on the DNS. This section discusses 240 impacts of the DNS response caching and issues related to the Dynamic 241 DNS [RFC2136] updates. 243 The caching (positive or negative) properties of the DNS [RFC2308] 244 and the fact that updates to the DNS take time to propagate globally, 245 need to be considered when applying DNS-based solutions to the PMIPv6 246 domain. First, the caching of DNS responses effectively delay the 247 propagation of up to date FQDN to IP address mappings (after both 248 addition and deletion). Hosts in the PMIPv6 domain keep using the 249 stale cached DNS response (positive or negative) until they give up 250 or the caching times out. The delay can be in order of hours in the 251 worst case. On the other hand, DNS administrators can lower the 252 resource record caching time (the Time To Live (TTL) value). 253 Obviously, too low TTL values increase the number of DNS queries 254 considerably. Second, the secondary DNS servers do not get 255 immediately updated when the masters do. These updates are also 256 periodic, usually in order of several hours, and may cause 257 considerable delay on global propagation of the updated naming 258 information. 260 The above considerations are valid when, for example, the PMIPv6 261 domain LMA availability or load information is dynamically updated 262 into the DNS. There are incentives for doing so, however, the 263 concerns described above need to be understood clearly in that case. 265 5. Handover Considerations 267 Whenever a MN moves and attaches to a new MAG in a PMIPv6 domain, all 268 the MAGs that the MN attaches to, should use the same LMA. If there 269 is only one LMA per PMIPv6 domain, then there is no issue. If there 270 is a context transfer mechanism available between the MAGs, then the 271 new MAG knows the LMA information from the old MAG. Such a mechanism 272 is described in [I-D.ietf-mipshop-pfmipv6]. If the MN related 273 context is not transferred between the MAGs, then a mechanism to 274 deliver the current LMA information to the new MAG is required. 275 Obviously, relying on DNS during handovers is not a working solution 276 if the PMIPv6 domain has more than one LMA. In most cases described 277 in Section 3, where the MAG derives the LMA FQDN, there is no prior 278 knowledge whether the LMA FQDN resolves to one or more LMA IP 279 address(es) in the PMIPv6 domain. 281 Once the MN completes its initial attachment to a PMIPv6 domain, the 282 information about the LMA that is selected to serve the MN is stored 283 in the Policy Store (or the AAA server). The LMA information is 284 conveyed to the policy store by the LMA after the initial attachment 285 is completed [I-D.ietf-dime-pmip6]. 287 When the MN moves and attaches to another MAG in the PMIPv6 domain, 288 then the AAA servers delivers the existing LMA information to the new 289 MAG as part of the authentication and authorization procedure as 290 described in Section 2.1 292 6. Security Considerations 294 The use of DNS for obtaining the IP address of a mobility agent 295 carries certain security risks. These are explained in detail in 296 Section 9.1 of RFC 5026 [RFC5026]. However, the risks described in 297 RFC 5026 are mitigated to a large extent in this document, since the 298 MAG and the LMA belong belong to the same PMIPv6 domain. The DNS 299 server that the MAG queries is also part of the same PMIPv6 domain. 300 Even if the MAG obtains the IP address of a bogus LMA from a bogus 301 DNS server, further harm is prevented since the MAG and the LMA 302 should authenticate each other before exchanging PMIPv6 signaling 303 messages. RFC 5213 [RFC5213] specifies the use of IKEv2 [RFC4306] 304 between the MAG and the LMA to authenticate each other and setup 305 IPsec security associations for protecting the PMIPv6 signaling 306 messages. 308 The AAA infrastructure may be used to transport the LMA discovery 309 related information between the MAG and the AAA server via one or 310 more AAA brokers and/or AAA proxies. In this case the MAG to the AAA 311 server communication relies on the security properties of the 312 intermediate AAA brokers and AAA proxies. 314 7. IANA Considerations 316 This specification has no actions for IANA. 318 8. Informative References 320 [3GPP.23.003] 321 3GPP, "Numbering, addressing and identification", 3GPP 322 TS 23.003 8.2.0, September 2008. 324 [I-D.ietf-dime-pmip6] 325 Korhonen, J., Bournelle, J., Chowdhury, K., Muhanna, A., 326 and U. Meyer, "Diameter Proxy Mobile IPv6: Mobile Access 327 Gateway and Local Mobility Anchor Interaction with 328 Diameter Server", draft-ietf-dime-pmip6-02 (work in 329 progress), April 2009. 331 [I-D.ietf-mipshop-pfmipv6] 332 Yokota, H., Chowdhury, K., Koodli, R., Patil, B., and F. 333 Xia, "Fast Handovers for Proxy Mobile IPv6", 334 draft-ietf-mipshop-pfmipv6-04 (work in progress), 335 May 2009. 337 [RFC2136] Vixie, P., Thomson, S., Rekhter, Y., and J. Bound, 338 "Dynamic Updates in the Domain Name System (DNS UPDATE)", 339 RFC 2136, April 1997. 341 [RFC2308] Andrews, M., "Negative Caching of DNS Queries (DNS 342 NCACHE)", RFC 2308, March 1998. 344 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", 345 RFC 4303, December 2005. 347 [RFC4306] Kaufman, C., "Internet Key Exchange (IKEv2) Protocol", 348 RFC 4306, December 2005. 350 [RFC5026] Giaretta, G., Kempf, J., and V. Devarapalli, "Mobile IPv6 351 Bootstrapping in Split Scenario", RFC 5026, October 2007. 353 [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., 354 and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. 356 [RFC5447] Korhonen, J., Bournelle, J., Tschofenig, H., Perkins, C., 357 and K. Chowdhury, "Diameter Mobile IPv6: Support for 358 Network Access Server to Diameter Server Interaction", 359 RFC 5447, February 2009. 361 Authors' Addresses 363 Jouni Korhonen 364 Nokia Siemens Networks 365 Linnoitustie 6 366 FIN-02600 Espoo 367 Finland 369 Email: jouni.nospam@gmail.com 371 Vijay Devarapalli 372 WiChorus 373 3950 North First Street 374 San Jose, CA 95134 375 USA 377 Email: vijay@wichorus.com