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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document seems to use 'NOT RECOMMENDED' as an RFC 2119 keyword, but does not include the phrase in its RFC 2119 key words list. == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: As a general recommendation, commands SHOULD not be defined from scratch. It is instead RECOMMENDED to re-use an existing command offering similar functionality and use it as a starting point. Code re-use lead to a smaller implementation effort as well as reduce the need for testing. == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD', or 'RECOMMENDED' is not an accepted usage according to RFC 2119. Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: Additionally, application designers using Vendor-Specific-Application-Id AVP SHOULD not use the Vendor-Id AVP to further dissect or differentiate the vendor-specification Application Id. Diameter routing is not based on the Vendor-Id. As such, the Vendor-Id SHOULD not be used as an additional input for routing or delivery of messages. The Vendor-Id AVP is an informational AVP only and kept for backward compatibility reasons. -- The document seems to contain a disclaimer for pre-RFC5378 work, and may have content which was first submitted before 10 November 2008. 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Diameter Maintenance and Extensions (DIME) L. Morand, Ed. 3 Internet-Draft Orange Labs 4 Intended status: Best Current Practice V. Fajardo 5 Expires: November 13, 2014 Independent 6 H. Tschofenig 7 Nokia Siemens Networks 8 May 12, 2014 10 Diameter Applications Design Guidelines 11 draft-ietf-dime-app-design-guide-23 13 Abstract 15 The Diameter base protocol provides facilities for protocol 16 extensibility enabling to define new Diameter applications or modify 17 existing applications. This document is a companion document to the 18 Diameter Base protocol that further explains and clarifies the rules 19 to extend Diameter. Futhermore, this document provides guidelines to 20 Diameter application designers reusing/defining Diameter applications 21 or creating generic Diameter extensions. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF). Note that other groups may also distribute 30 working documents as Internet-Drafts. The list of current Internet- 31 Drafts is at http://datatracker.ietf.org/drafts/current/. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 This Internet-Draft will expire on November 13, 2014. 40 Copyright Notice 42 Copyright (c) 2014 IETF Trust and the persons identified as the 43 document authors. All rights reserved. 45 This document is subject to BCP 78 and the IETF Trust's Legal 46 Provisions Relating to IETF Documents 47 (http://trustee.ietf.org/license-info) in effect on the date of 48 publication of this document. Please review these documents 49 carefully, as they describe your rights and restrictions with respect 50 to this document. Code Components extracted from this document must 51 include Simplified BSD License text as described in Section 4.e of 52 the Trust Legal Provisions and are provided without warranty as 53 described in the Simplified BSD License. 55 This document may contain material from IETF Documents or IETF 56 Contributions published or made publicly available before November 57 10, 2008. The person(s) controlling the copyright in some of this 58 material may not have granted the IETF Trust the right to allow 59 modifications of such material outside the IETF Standards Process. 60 Without obtaining an adequate license from the person(s) controlling 61 the copyright in such materials, this document may not be modified 62 outside the IETF Standards Process, and derivative works of it may 63 not be created outside the IETF Standards Process, except to format 64 it for publication as an RFC or to translate it into languages other 65 than English. 67 Table of Contents 69 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 70 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 71 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 4. Reusing Existing Diameter Applications . . . . . . . . . . . 5 73 4.1. Adding a New Command . . . . . . . . . . . . . . . . . . 5 74 4.2. Deleting an Existing Command . . . . . . . . . . . . . . 6 75 4.3. Reusing Existing Commands . . . . . . . . . . . . . . . . 7 76 4.3.1. Adding AVPs to a Command . . . . . . . . . . . . . . 7 77 4.3.2. Deleting AVPs from a Command . . . . . . . . . . . . 9 78 4.4. Reusing Existing AVPs . . . . . . . . . . . . . . . . . . 9 79 4.4.1. Setting of the AVP Flags . . . . . . . . . . . . . . 10 80 4.4.2. Reuse of AVP of Type Enumerated . . . . . . . . . . . 10 81 5. Defining New Diameter Applications . . . . . . . . . . . . . 10 82 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 10 83 5.2. Defining New Commands . . . . . . . . . . . . . . . . . . 11 84 5.3. Use of Application-Id in a Message . . . . . . . . . . . 11 85 5.4. Application-Specific Session State Machines . . . . . . . 12 86 5.5. Session-Id AVP and Session Management . . . . . . . . . . 12 87 5.6. Use of Enumerated Type AVPs . . . . . . . . . . . . . . . 13 88 5.7. Application-Specific Message Routing . . . . . . . . . . 15 89 5.8. Translation Agents . . . . . . . . . . . . . . . . . . . 15 90 5.9. End-to-End Application Capabilities Exchange . . . . . . 16 91 5.10. Diameter Accounting Support . . . . . . . . . . . . . . . 17 92 5.11. Diameter Security Mechanisms . . . . . . . . . . . . . . 18 93 6. Defining Generic Diameter Extensions . . . . . . . . . . . . 19 94 7. Guidelines for Registrations of Diameter Values . . . . . . . 20 95 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 96 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22 97 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22 98 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 23 99 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 100 12.1. Normative References . . . . . . . . . . . . . . . . . . 23 101 12.2. Informative References . . . . . . . . . . . . . . . . . 23 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 104 1. Introduction 106 The Diameter base protocol provides facilities to extend Diameter 107 (see Section 1.3 of [RFC6733]) to support new functionality. In the 108 context of this document, extending Diameter means one of the 109 following: 111 1. Addition of new functionality to an existing Diameter application 112 without defining a new application. 114 2. Addition of new functionality to an existing Diameter application 115 that requires the definition of a new application. 117 3. The definition of an entirely new Diameter application to offer 118 functionality not supported by existing applications. 120 4. The definition of a new generic functionality that can be reused 121 across different applications. 123 All of these choices are design decisions that can be done by any 124 combination of reusing existing or defining new commands, AVPs or AVP 125 values. However, application designers do not have complete freedom 126 when making their design. A number of rules have been defined in 127 [RFC6733] that place constraints on when an extension requires the 128 allocation of a new Diameter application identifier or a new command 129 code value. The objective of this document is the following: 131 o Clarify the Diameter extensibility rules as defined in the 132 Diameter base protocol. 134 o Discuss design choices and provide guidelines when defining new 135 applications. 137 o Present trade-off choices. 139 2. Terminology 141 This document reuses the terminology defined in [RFC6733]. 142 Additionally, the following terms and acronyms are used in this 143 application: 145 Application Extension of the Diameter base protocol [RFC6733] via 146 the addition of new commands or AVPs. Each application is 147 uniquely identified by an IANA-allocated application identifier 148 value. 150 Command Diameter request or answer carrying AVPs between Diameter 151 endpoints. Each command is uniquely identified by a IANA- 152 allocated command code value and is described by a Command Code 153 Format (CCF) for an application. 155 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 156 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 157 document are to be interpreted as described in [RFC2119]. 159 3. Overview 161 As designed, the Diameter base protocol [RFC6733] can be seen as a 162 two-layer protocol. The lower layer is mainly responsible for 163 managing connections between neighboring peers and for message 164 routing. The upper layer is where the Diameter applications reside. 165 This model is in line with a Diameter node having an application 166 layer and a peer-to-peer delivery layer. The Diameter base protocol 167 document defines the architecture and behavior of the message 168 delivery layer and then provides the framework for designing Diameter 169 applications on the application layer. This framework includes 170 definitions of application sessions and accounting support (see 171 Section 8 and Section 9 of [RFC6733]). Accordingly, a Diameter node 172 is seen in this document as a single instance of a Diameter message 173 delivery layer and one or more Diameter applications using it. 175 The Diameter base protocol is designed to be extensible and the 176 principles are described in the Section 1.3 of [RFC6733]. As a 177 summary, Diameter can be extended by: 179 1. Defining new AVP values 181 2. Creating new AVPs 183 3. Creating new commands 185 4. Creating new applications 187 As a main guiding principle, application designers SHOULD follow the 188 following recommendation: "try to re-use as much as possible!". It 189 will reduce the time to finalize specification writing, and it will 190 lead to a smaller implementation effort as well as reduce the need 191 for testing. In general, it is clever to avoid duplicate effort when 192 possible. 194 However, re-use is not appropriate when the existing functionality 195 does not fit the new requirement and/or the re-use leads to 196 ambiguity. 198 The impact on extending existing applications can be categorized into 199 two groups: 201 Minor Extension: Enhancing the functional scope of an existing 202 application by the addition of optional features to support. Such 203 enhancement has no backward compatibility issue with the existing 204 application. 206 A typical example would be the definition of a new optional AVP 207 for use in an existing command. Diameter implementations 208 supporting the existing application but not the new AVP will 209 simply ignore it, without consequences for the Diameter message 210 handling, as described in [RFC6733]. The standardization effort 211 will be fairly small. 213 Major Extension: Enhancing an application that requires the 214 definition of a new Diameter application. Such enhancement causes 215 backward compatibility issue with existing implementations 216 supporting the application. 218 Typical examples would be the creation of a new command for 219 providing functionality not supported by existing applications or 220 the definition of a new AVP to be carried in an existing command 221 with the M-bit set in the AVP flags (see Section 4.1 of [RFC6733] 222 for definition of the "M-bit"). For such extension, a significant 223 specification effort is required and a careful approach is 224 recommended. 226 4. Reusing Existing Diameter Applications 228 An existing application may need to be enhanced to fulfill new 229 requirements and these modifications can be at the command level and/ 230 or at the AVP level. The following sections describe the possible 231 modifications that can be performed on existing applications and 232 their related impact. 234 4.1. Adding a New Command 236 Adding a new command to an existing application is considered as a 237 major extension and requires a new Diameter application to be 238 defined, as stated in the Section 1.3.4 of [RFC6733]. Adding a new 239 command means either defining a completely new command or importing 240 the command's Command Code Format (CCF) syntax from another 241 application whereby the new application inherits some or all of the 242 functionality of the application where the command came from. In the 243 former case, the decision to create a new application is 244 straightforward since this is typically a result of adding a new 245 functionality that does not exist yet. For the latter, the decision 246 to create a new application will depend on whether importing the 247 command in a new application is more suitable than simply using the 248 existing application as it is in conjunction with any other 249 application. Therefore, a case by case study of each application 250 requirement SHOULD be applied. 252 An example considers the Diameter EAP application [RFC4072] and the 253 Diameter Network Access Server application [RFC7155]. When network 254 access authentication using EAP is required, the Diameter EAP 255 commands (Diameter-EAP-Request/Diameter-EAP-Answer) are used; 256 otherwise the Diameter Network Access Server application will be 257 used. When the Diameter EAP application is used, the accounting 258 exchanges defined in the Diameter Network Access Server may be used. 260 However, in general, it is difficult to come to a hard guideline, and 261 so a case-by-case study of each application requirement should be 262 applied. Before adding or importing a command, application designers 263 should consider the following: 265 o Can the new functionality be fulfilled by creating a new command 266 independent from any existing command? In this case, the 267 resulting new application and the existing application can work 268 independent of, but cooperating with each other. 270 o Can the existing command be reused without major extensions and 271 therefore without the need for the definition of a new 272 application, e.g. new functionality introduced by the creation of 273 new optional AVPs. 275 Note: Importing commands too liberally could result in a monolithic 276 and hard to manage application supporting too many different 277 features. 279 4.2. Deleting an Existing Command 281 Although this process is not typical, removing a command from an 282 application requires a new Diameter application to be defined and 283 then it is considered as a major extension. This is due to the fact 284 that the reception of the deleted command would systematically result 285 in a protocol error (i.e., DIAMETER_COMMAND_UNSUPPORTED). 287 It is unusual to delete an existing command from an application for 288 the sake of deleting it or the functionality it represents. This 289 normally indicates of a flawed design. An exception might be if the 290 intent of the deletion is to create a newer variance of the same 291 application that is somehow simpler than the application initially 292 specified. 294 4.3. Reusing Existing Commands 296 This section discusses rules in adding and/or deleting AVPs from an 297 existing command of an existing application. The cases described in 298 this section may not necessarily result in the creation of new 299 applications. 301 From a historical point of view, it is worth to note that there was a 302 strong recommendation to re-use existing commands in the [RFC3588] to 303 prevent rapid depletion of code values available for vendor-specific 304 commands. However, [RFC6733] has relaxed the allocation policy and 305 enlarged the range of available code values for vendor-specific 306 applications. Although reuse of existing commands is still 307 RECOMMENDED, protocol designers MAY consider defining a new command 308 when it provides a solution more suitable than the twisting of an 309 existing command's use and applications. 311 4.3.1. Adding AVPs to a Command 313 Based on the rules in [RFC6733], AVPs that are added to an existing 314 command can be categorized into: 316 o Mandatory (to understand) AVPs. As defined in [RFC6733], these 317 are AVPs with the M-bit flag set in this command, which means that 318 a Diameter node receiving them is required to understand not only 319 their values but also their semantics. Failure to do so will 320 cause an message handling error. 322 o Optional (to understand) AVPs. As defined in [RFC6733], these are 323 AVPs with the M-bit flag cleared in this command. A Diameter node 324 receiving these AVPs can simply ignore them if it does not support 325 them. 326 It is important to note that the definition given above are 327 independent of whether these AVPs are required or optional in the 328 command as specified by the command's Command Code Format (CCF) 329 syntax [RFC6733]. 331 NOTE: As stated in [RFC6733], the M-bit setting for a given AVP is 332 relevant to an application and each command within that 333 application that includes the AVP. 335 The rules are strict in the case where the AVPs to be added in an 336 exiting command are mandatory to understand, i.e., they have the 337 M-bit set. A mandatory AVP MUST NOT be added to an existing command 338 without defining a new Diameter application, as stated in [RFC6733]. 339 This falls into the "Major Extensions" category. Despite the clarity 340 of the rule, ambiguity still arises when evaluating whether a new AVP 341 being added should be mandatory to begin with. Application designers 342 SHOULD consider the following questions when deciding about the M-bit 343 for a new AVP: 345 o Would it be required for the receiving side to be able to process 346 and understand the AVP and its content? 348 o Would the new AVPs change the state machine of the application? 350 o Would the presence of the new AVP lead to a different number of 351 round-trips, effectively changing the state machine of the 352 application? 354 o Would the new AVP be used to differentiate between old and new 355 variances of the same application whereby the two variances are 356 not backward compatible? 358 o Would the new AVP have duality in meaning, i.e., be used to carry 359 application-related information as well as to indicate that the 360 message is for a new application? 362 If the answer to at least one of the questions is "yes" then the 363 M-bit MUST be set for the new AVP. This list of questions is non- 364 exhaustive and other criteria MAY be taken into account in the 365 decision process. 367 If application designers are instead contemplating the use of 368 optional AVPs, i.e., with the M-bit cleared, then the following are 369 some of the pitfalls that SHOULD be avoided: 371 o Use of optional AVPs with intersecting meaning. One AVP has 372 partially the same usage and meaning as another AVP. The presence 373 of both can lead to confusion. 375 o An optional AVPs with dual purpose, i.e., to carry application 376 data as well as to indicate support for one or more features. 377 This has a tendency to introduce interpretation issues. 379 o Adding one or more optional AVPs and indicating (usually within 380 descriptive text for the command) that at least one of them has to 381 be present in the command. This essentially circumventing the 382 ABNF and is equivalent to adding a mandatory AVP to the command. 384 These practices generally result in interoperability issues and 385 SHOULD be avoided. 387 4.3.2. Deleting AVPs from a Command 389 Application designers may want to reuse an existing command but some 390 of the AVP present in the command's CCF syntax specification may be 391 irrelevant for the functionality foreseen to be supported by this 392 command. It may be then tempting to delete those AVPs from the 393 command. 395 The impacts of deleting an AVP from a command depends on its command 396 code format specification and M-bit setting: 398 o Deleting an AVP that is indicated as a required AVP (noted as 399 {AVP}) in the command's CCF syntax specification (regardless of 400 the M-bit setting). 402 In this case, a new command code and subsequently a new Diameter 403 application MUST be specified. 405 o Deleting an AVP, which has the M-bit set, and is indicated as 406 optional AVP (noted as [AVP]) in the command CCF) in the command's 407 CCF syntax specification. 409 No new command code has to be specified but the definition of a 410 new Diameter application is REQUIRED. 412 o Deleting an AVP, which has the M-bit cleared, and is indicated as 413 [ AVP ] in the command's CCF syntax specification. 415 In this case, the AVP can be deleted without consequences. 417 Application designers SHOULD attempt the reuse the command's CCF 418 syntax specification without modification and simply ignore (but not 419 delete) any optional AVP that will not be used. This is to maintain 420 compatibility with existing applications that will not know about the 421 new functionality as well as maintain the integrity of existing 422 dictionaries. 424 4.4. Reusing Existing AVPs 426 This section discusses rules in reusing existing AVP when reusing an 427 existing command or defining a new command in a new application. 429 4.4.1. Setting of the AVP Flags 431 When reusing AVPs in a new application, the M-bit flag setting MUST 432 be re-evaluated for a new Diameter application and, if necessary, 433 even for every command within the application. In general, for AVPs 434 defined outside of the Diameter base protocol, the characteristics of 435 an AVP are tied to its role within a given application and the 436 commands used in this application. 438 All other AVP flags (V-bit, P-bit, reserved bits) MUST remain 439 unchanged. 441 4.4.2. Reuse of AVP of Type Enumerated 443 When reusing an AVP of type Enumerated in a command for a new 444 application, it is RECOMMENDED to avoid modifying the set of valid 445 values defined for this AVP. Modifying the set of Enumerated values 446 includes adding a value or deprecating the use of a value defined 447 initially for the AVP. Modifying the set of values will impact the 448 application defining this AVP and all the applications using this 449 AVP, causing potential interoperability issues. When the full range 450 of values defined for this Enumerated AVP is not suitable for the new 451 application, it is RECOMMENDED to define a new AVP to avoid backwards 452 compatibility issues with existing implementations. 454 5. Defining New Diameter Applications 456 5.1. Introduction 458 This section discusses the case where new applications have 459 requirements that cannot be fulfilled by existing applications and 460 would require definition of completely new commands, AVPs and/or AVP 461 values. Typically, there is little ambiguity about the decision to 462 create these types of applications. Some examples are the interfaces 463 defined for the IP Multimedia Subsystem of 3GPP, e.g., Cx/Dx 464 ([TS29.228] and [TS29.229]), Sh ([TS29.328] and [TS29.329]) etc. 466 Application designers SHOULD try to import existing AVPs and AVP 467 values for any newly defined commands. In certain cases where 468 accounting will be used, the models described in Section 5.10 SHOULD 469 also be considered. 471 Additional considerations are described in the following sections. 473 5.2. Defining New Commands 475 As a general recommendation, commands SHOULD not be defined from 476 scratch. It is instead RECOMMENDED to re-use an existing command 477 offering similar functionality and use it as a starting point. Code 478 re-use lead to a smaller implementation effort as well as reduce the 479 need for testing. 481 Moreover, the new command's CCF syntax specification SHOULD be 482 carefully defined when considering applicability and extensibility of 483 the application. If most of the AVPs contained in the command are 484 indicated as fixed or required, it might be difficult to reuse the 485 same command and therefore the same application in a slightly changed 486 environment. Defining a command with most of the AVPs indicated as 487 optional MUST NOT be seen as a sub-optimal design introducing too 488 much flexibility in the protocol. The protocol designers SHOULD only 489 clearly state the condition of presence of these AVPs and properly 490 define the corresponding behaviour of the Diameter nodes when these 491 AVPs are absent from the command. 493 NOTE: As a hint for protocol designers, it is not sufficient to just 494 look at the command's CCF syntax specification. It is also 495 necessary to carefully read through the accompanying text in the 496 specification. 498 In the same way, the CCF syntax specification SHOULD be defined such 499 that it will be possible to add any arbitrary optional AVPs with the 500 M-bit cleared (including vendor-specific AVPs) without modifying the 501 application. For this purpose, "* [AVP]" SHOULD be added in the 502 command's CCF, which allows the addition of any arbitrary number of 503 optional AVPs as described in [RFC6733]. 505 5.3. Use of Application-Id in a Message 507 When designing new applications, application designers SHOULD specify 508 that the Application Id carried in all session-level messages is the 509 Application Id of the application using those messages. This 510 includes the session-level messages defined in Diameter base 511 protocol, i.e., RAR/RAA, STR/STA, ASR/ASA and possibly ACR/ACA in the 512 coupled accounting model, see Section 5.10. Some existing 513 specifications do not adhere to this rule for historical reasons. 514 However, this guidance SHOULD be followed by new applications to 515 avoid routing problems. 517 When a new application has been allocated with a new Application Id 518 and it also reuses existing commands with or without modifications, 519 the commands SHOULD use the newly allocated Application Id in the 520 header and in all relevant Application Id AVPs (Auth-Application-Id 521 or Acct-Application-Id) present in the commands message body. 523 Additionally, application designers using Vendor-Specific- 524 Application-Id AVP SHOULD not use the Vendor-Id AVP to further 525 dissect or differentiate the vendor-specification Application Id. 526 Diameter routing is not based on the Vendor-Id. As such, the Vendor- 527 Id SHOULD not be used as an additional input for routing or delivery 528 of messages. The Vendor-Id AVP is an informational AVP only and kept 529 for backward compatibility reasons. 531 5.4. Application-Specific Session State Machines 533 Section 8 of [RFC6733] provides session state machines for 534 authentication, authorization and accounting (AAA) services and these 535 session state machines are not intended to cover behavior outside of 536 AAA. If a new application cannot clearly be categorized into any of 537 these AAA services, it is RECOMMENDED that the application defines 538 its own session state machine. Support for server-initiated request 539 is a clear example where an application-specific session state 540 machine would be needed, for example, the Rw interface for ITU-T push 541 model (cf.[Q.3303.3]). 543 5.5. Session-Id AVP and Session Management 545 Diameter applications are usually designed with the aim of managing 546 user sessions (e.g., Diameter network access session (NASREQ) 547 application [RFC4005]) or specific service access session (e.g., 548 Diameter SIP application [RFC4740]). In the Diameter base protocol, 549 session state is referenced using the Session-Id AVP. All Diameter 550 messages that use the same Session-Id will be bound to the same 551 session. Diameter-based session management also implies that both 552 Diameter client and server (and potentially proxy agents along the 553 path) maintain session state information. 555 However, some applications may not need to rely on the Session-Id to 556 identify and manage sessions because other information can be used 557 instead to correlate Diameter messages. Indeed, the User-Name AVP or 558 any other specific AVP can be present in every Diameter message and 559 used therefore for message correlation. Some applications might not 560 require the notion of Diameter session concept at all. For such 561 applications, the Auth-Session-State AVP is usually set to 562 NO_STATE_MAINTAINED in all Diameter messages and these applications 563 are therefore designed as a set of stand-alone transactions. Even if 564 an explicit access session termination is required, application- 565 specific commands are defined and used instead of the Session- 566 Termination-Request/Answer (STR/STA) or Abort-Session-Request/Answer 567 (ASR/ASA) defined in the Diameter base protocol [RFC6733]. In such a 568 case, the Session-Id is not significant. 570 Based on these considerations, protocol designers SHOULD carefully 571 appraise whether the application currently defined relies on its own 572 session management concept or whether the Session-Id defined in the 573 Diameter base protocol would be used for correlation of messages 574 related to the same session. If not, the protocol designers MAY 575 decide to define application commands without the Session-Id AVP. If 576 any session management concept is supported by the application, the 577 application documentation MUST clearly specify how the session is 578 handled between client and server (as possibly Diameter agents in the 579 path). 581 5.6. Use of Enumerated Type AVPs 583 The type Enumerated was initially defined to provide a list of valid 584 values for an AVP with their respective interpretation described in 585 the specification. For instance, AVPs of type Enumerated can be used 586 to provide further information on the reason for the termination of a 587 session or a specific action to perform upon the reception of the 588 request. 590 As described in the section 4.4.2 above, defining an AVP of type 591 Enumerated presents some limitations in term of extensibility and 592 reusability. Indeed, the finite set of valid values defined at the 593 definition of the AVP of type Enumerated cannot be modified in 594 practice without causing backward compatibility issues with existing 595 implementations. As a consequence, AVPs of Type Enumerated MUST NOT 596 be extended by adding new values to support new capabilities. 597 Diameter protocol designers SHOULD carefully consider before defining 598 an Enumerated AVP whether the set of values will remain unchanged or 599 new values may be required in a near future. If such extension is 600 foreseen or cannot be avoided, it is RECOMMENED to rather define AVPs 601 of type Unsigned32 or Unsigned64 in which the data field would 602 contain an address space representing "values" that would have the 603 same use of Enumerated values. 605 For illustration, an AVP describing possible access networks would be 606 defined as follow: 608 Access-Network-Type AVP (XXX) is of type Unsigned32 and contains an 609 32-bit address space representing types of access networks. This 610 application defines the following classes of access networks, all 611 identified by the thousands digit in the decimal notation: 613 o 1xxx (Mobile Access Networks) 615 o 2xxx (Fixed Access Network) 617 o 3xxx (Wireless Access Networks) 619 Values that fall within the Mobile Access Networks category are used 620 to inform a peer that a request has been sent for a user attached to 621 a mobile access networks. The following values are defined in this 622 application: 624 1001: 3GPP-GERAN 626 TBD. 628 1002: 3GPP-UTRAN-FDD 630 TBD. 632 Unlike Enumerated AVP, any new value can be added in the address 633 space defined by this Unsigned32 AVP without modifying the definition 634 of the AVP. There is therefore no risk of backward compatibility 635 issue, especially when intermediate nodes may be present between 636 Diameter endpoints. 638 In the same line, AVPs of type Enumerated are too often used as a 639 simple Boolean flag, indicating for instance a specific permission or 640 capability, and therefore only two values are defined, e.g., TRUE/ 641 FALSE, AUTORIZED/UNAUTHORIZED or SUPPORTED/UNSUPPORTED. This is a 642 sub-optimal design since it limits the extensibility of the 643 application: any new capability/permission would have to be supported 644 by a new AVP or new Enumerated value of the already defined AVP, with 645 the backward compatibility issues described above. Instead of using 646 an Enumerated AVP for a Boolean flag, protocol designers SHOULD use 647 AVPs of type Unsigned32 or Unsigned64 AVP in which the data field 648 would be defined as bit mask whose bit settings are described in the 649 relevant Diameter application specification. Such AVPs can be reused 650 and extended without major impact on the Diameter application. The 651 bit mask SHOULD leave room for future additions. Examples of AVPs 652 that use bit masks are the Session-Binding AVP defined in [RFC6733] 653 and the MIP6-Feature-Vector AVP defined in [RFC5447]. 655 5.7. Application-Specific Message Routing 657 As described in [RFC6733], a Diameter request that needs to be sent 658 to a home server serving a specific realm, but not to a specific 659 server (such as the first request of a series of round trips), will 660 contain a Destination-Realm AVP and no Destination-Host AVP. 662 For such a request, the message routing usually relies only on the 663 Destination-Realm AVP and the Application Id present in the request 664 message header. However, some applications may need to rely on the 665 User-Name AVP or any other application-specific AVP present in the 666 request to determine the final destination of a request, e.g., to 667 find the target AAA server hosting the authorization information for 668 a given user when multiple AAA servers are addressable in the realm. 670 In such a context, basic routing mechanisms described in [RFC6733] 671 are not fully suitable, and additional application-level routing 672 mechanisms MUST be described in the application documentation to 673 provide such specific AVP-based routing. Such functionality will be 674 basically hosted by an application-specific proxy agent that will be 675 responsible for routing decisions based on the received specific 676 AVPs. 678 Examples of such application-specific routing functions can be found 679 in the Cx/Dx applications ([TS29.228] and [TS29.229]) of the 3GPP IP 680 Multimedia Subsystem, in which the proxy agent (Subscriber Location 681 Function aka SLF) uses specific application-level identities found in 682 the request to determine the final destination of the message. 684 Whatever the criteria used to establish the routing path of the 685 request, the routing of the answer MUST follow the reverse path of 686 the request, as described in [RFC6733], with the answer being sent to 687 the source of the received request, using transaction states and hop- 688 by-hop identifier matching. In particular, this ensures that the 689 Diameter Relay or Proxy agents in the request routing path will be 690 able to release the transaction state upon receipt of the 691 corresponding answer, avoiding unnecessary failover. Application 692 designers SHOULD NOT modify the answer-routing principles described 693 in [RFC6733] when defining a new application. 695 5.8. Translation Agents 697 As defined in [RFC6733], a translation agent is a device that 698 provides interworking between Diameter and another AAA protocol, such 699 as RADIUS . 701 In the case of RADIUS, it was initially thought that defining the 702 translation function would be straightforward by adopting few basic 703 principles, e.g., by the use of a shared range of code values for 704 RADIUS attributes and Diameter AVPs. Guidelines for implementing a 705 RADIUS-Diameter translation agent were put into the Diameter NASREQ 706 Application ([RFC4005]). 708 However, it was acknowledged that such translation mechanism was not 709 so obvious and deeper protocol analysis was required to ensure 710 efficient interworking between RADIUS and Diameter. Moreover, the 711 interworking requirements depend on the functionalities provided by 712 the Diameter application under specification, and a case-by-case 713 analysis is required. As a consequence, all the material related to 714 RADIUS-to-Diameter translation is removed from the new version of the 715 Diameter NASREQ application specification [RFC4005bis], (see 716 [RFC7155]) which deprecates the RFC4005 ([RFC4005]). 718 Therefore, protocol designers SHOULD NOT assume the availability of a 719 "standard" Diameter-to-RADIUS gateways agent when planning to 720 interoperate with the RADIUS infrastructure. They SHOULD specify the 721 required translation mechanism along with the Diameter application, 722 if needed. This recommendation applies for any kind of translation. 724 5.9. End-to-End Application Capabilities Exchange 726 Diameter applications can rely on optional AVPs to exchange 727 application-specific capabilities and features. These AVPs can be 728 exchanged on an end-to-end basis at the application layer. Examples 729 of this can be found with the MIP6-Feature-Vector AVP in [RFC5447] 730 and the QoS-Capability AVP in [RFC5777]. 732 End-to-end capabilities AVPs can be added as optional AVPs with the 733 M-bit cleared to existing applications to announce support of new 734 functionality. Receivers that do not understand these AVPs or the 735 AVP values can simply ignore them, as stated in [RFC6733]. When 736 supported, receivers of these AVPs can discover the additional 737 functionality supported by the Diameter end-point originating the 738 request and behave accordingly when processing the request. Senders 739 of these AVPs can safely assume the receiving end-point does not 740 support any functionality carried by the AVP if it is not present in 741 corresponding response. This is useful in cases where deployment 742 choices are offered, and the generic design can be made available for 743 a number of applications. 745 When used in a new application, these end-to-end capabilities AVPs 746 SHOULD be added as optional AVP into the CCF of the commands used by 747 the new application. Protocol designers SHOULD clearly specify this 748 end-to-end capabilities exchange and the corresponding behaviour of 749 the Diameter nodes supporting the application. 751 It is also important to note that this end-to-end capabilities 752 exchange relying on the use of optional AVPs is not meant as a 753 generic mechanism to support extensibility of Diameter applications 754 with arbitrary functionality. When the added features drastically 755 change the Diameter application or when Diameter agents must be 756 upgraded to support the new features, a new application SHOULD be 757 defined, as recommended in [RFC6733]. 759 5.10. Diameter Accounting Support 761 Accounting can be treated as an auxiliary application that is used in 762 support of other applications. In most cases, accounting support is 763 required when defining new applications. This document provides two 764 possible models for using accounting: 766 Split Accounting Model: 768 In this model, the accounting messages will use the Diameter base 769 accounting Application Id (value of 3). The design implication 770 for this is that the accounting is treated as an independent 771 application, especially for Diameter routing. This means that 772 accounting commands emanating from an application may be routed 773 separately from the rest of the other application messages. This 774 may also imply that the messages end up in a central accounting 775 server. A split accounting model is a good design choice when: 777 * The application itself does not define its own accounting 778 commands. 780 * The overall system architecture permits the use of centralized 781 accounting for one or more Diameter applications. 783 Centralizing accounting may have advantages but there are also 784 drawbacks. The model assumes that the accounting server can 785 differentiate received accounting messages. Since the received 786 accounting messages can be for any application and/or service, the 787 accounting server MUST have a method to match accounting messages 788 with applications and/or services being accounted for. This may 789 mean defining new AVPs, checking the presence, absence or contents 790 of existing AVPs, or checking the contents of the accounting 791 record itself. One of these means could be to insert into the 792 request sent to the accounting server an Auth-Application-Id AVP 793 containing the identifier of the application for which the 794 accounting request is sent. But in general, there is no clean and 795 generic scheme for sorting these messages. Therefore, the use of 796 this model is NOT RECOMMENDED when all received accounting 797 messages cannot be clearly identified and sorted. For most cases, 798 the use of Coupled Accounting Model is RECOMMENDED. 800 Coupled Accounting Model: 802 In this model, the accounting messages will use the Application Id 803 of the application using the accounting service. The design 804 implication for this is that the accounting messages are tightly 805 coupled with the application itself; meaning that accounting 806 messages will be routed like the other application messages. It 807 would then be the responsibility of the application server 808 (application entity receiving the ACR message) to send the 809 accounting records carried by the accounting messages to the 810 proper accounting server. The application server is also 811 responsible for formulating a proper response (ACA). A coupled 812 accounting model is a good design choice when: 814 * The system architecture or deployment does not provide an 815 accounting server that supports Diameter. Consequently, the 816 application server MUST be provisioned to use a different 817 protocol to access the accounting server, e.g., via LDAP, SOAP 818 etc. This case includes the support of older accounting 819 systems that are not Diameter aware. 821 * The system architecture or deployment requires that the 822 accounting service for the specific application should be 823 handled by the application itself. 825 In all cases above, there will generally be no direct Diameter 826 access to the accounting server. 828 These models provide a basis for using accounting messages. 829 Application designers may obviously deviate from these models 830 provided that the factors being addressed here have also been taken 831 into account. An application MAY define a new set of commands to 832 carry application-specific accounting records but it is NOT 833 RECOMMENDED to do so. 835 5.11. Diameter Security Mechanisms 837 As specified in [RFC6733], the Diameter message exchange SHOULD be 838 secured between neighboring Diameter peers using TLS/TCP or DTLS/ 839 SCTP. However, IPsec MAY also be deployed to secure communication 840 between Diameter peers. When IPsec is used instead of TLS or DTLS, 841 the following recommendations apply. 843 IPsec ESP [RFC4301] in transport mode with non-null encryption and 844 authentication algorithms MUST be used to provide per-packet 845 authentication, integrity protection and confidentiality, and support 846 the replay protection mechanisms of IPsec. IKEv2 [RFC5996] SHOULD be 847 used for performing mutual authentication and for establishing and 848 maintaining security associations (SAs). 850 IKEv1 [RFC2409] was used with RFC 3588 [RFC3588] and for easier 851 migration from IKEv1 based implementations both RSA digital 852 signatures and pre-shared keys SHOULD be supported in IKEv2. 853 However, if IKEv1 is used, implementers SHOULD follow the guidelines 854 given in Section 13.1 of RFC 3588 [RFC3588]. 856 6. Defining Generic Diameter Extensions 858 Generic Diameter extensions are AVPs, commands or applications that 859 are designed to support other Diameter applications. They are 860 auxiliary applications meant to improve or enhance the Diameter 861 protocol itself or Diameter applications/functionality. Some 862 examples include the extensions to support realm-based redirection of 863 Diameter requests (see [RFC7075]), convey a specific set of priority 864 parameters influencing the distribution of resources (see [RFC6735]), 865 and the support for QoS AVPs (see [RFC5777]). 867 Since generic extensions may cover many aspects of Diameter and 868 Diameter applications, it is not possible to enumerate all scenarios. 869 However, some of the most common considerations are as follows: 871 Backward Compatibility: 873 When defining generic extensions designed to be supported by 874 existing Diameter applications, protocol designers MUST consider 875 the potential impacts of the introduction of the new extension on 876 the behavior of node that would not be yet upgraded to support/ 877 understand this new extension. Designers MUST also ensure that 878 new extensions do not break expected message delivery layer 879 behavior. 881 Forward Compatibility: 883 Protocol designers MUST ensure that their design will not 884 introduce undue restrictions for future applications. 886 Trade-off in Signaling: 888 Designers may have to choose between the use of optional AVPs 889 piggybacked onto existing commands versus defining new commands 890 and applications. Optional AVPs are simpler to implement and may 891 not need changes to existing applications. However, this ties the 892 sending of extension data to the application's transmission of a 893 message. This has consequences if the application and the 894 extensions have different timing requirements. The use of 895 commands and applications solves this issue, but the trade-off is 896 the additional complexity of defining and deploying a new 897 application. It is left up to the designer to find a good balance 898 among these trade-offs based on the requirements of the extension. 900 In practice, generic extensions often use optional AVPs because they 901 are simple and non-intrusive to the application that would carry 902 them. Peers that do not support the generic extensions need not 903 understand nor recognize these optional AVPs. However, it is 904 RECOMMENDED that the authors of the extension specify the context or 905 usage of the optional AVPs. As an example, in the case that the AVP 906 can be used only by a specific set of applications then the 907 specification MUST enumerate these applications and the scenarios 908 when the optional AVPs will be used. In the case where the optional 909 AVPs can be carried by any application, it SHOULD be sufficient to 910 specify such a use case and perhaps provide specific examples of 911 applications using them. 913 In most cases, these optional AVPs piggybacked by applications would 914 be defined as a Grouped AVP and it would encapsulate all the 915 functionality of the generic extension. In practice, it is not 916 uncommon that the Grouped AVP will encapsulate an existing AVP that 917 has previously been defined as mandatory ('M'-bit set) e.g., 3GPP IMS 918 Cx/Dx interfaces ([TS29.228] and [TS29.229]). 920 7. Guidelines for Registrations of Diameter Values 922 As summarized in the Section 3 of this document and further described 923 in the Section 1.3 of [RFC6733], there are four main ways to extend 924 Diameter. The process for defining new functionality slightly varies 925 based on the different extensions. This section provides protocol 926 designers with some guidance regarding the definition of values for 927 possible Diameter extensions and the necessary interaction with IANA 928 to register the new functionality. 930 a. Defining new AVP values 932 The specifications defining AVPs and AVP values MUST provide 933 guidance for defining new values and the corresponding policy for 934 adding these values. For example, the RFC 5777 [RFC5777] defines 935 the Treatment-Action AVP which contains a list of valid values 936 corresponding to pre-defined actions (drop, shape, mark, permit). 937 This set of values can be extended following the Specification 938 Required policy defined in [RFC5226]. As a second example, the 939 Diameter base specification [RFC6733] defines the Result-Code AVP 940 that contains a 32-bit address space used to identity possible 941 errors. According to the Section 11.3.2 of [RFC6733], new values 942 can be assigned by IANA via an IETF Review process [RFC5226]. 944 b. Creating new AVPs 946 Two different types of AVP Codes namespaces can be used to create 947 a new AVPs: 949 * IETF AVP Codes namespace; 951 * Vendor-specific AVP Codes namespace. 953 In the latter case, a vendor needs to be first assigned by IANA 954 with a private enterprise number, which can be used within the 955 Vendor-Id field of the vendor-specific AVP. This enterprise 956 number delimits a private namespace in which the vendor is 957 responsible for vendor-specific AVP code value assignment. The 958 absence of a Vendor-Id or a Vendor-Id value of zero (0) in the AVP 959 header identifies standard AVPs from the IETF AVP Codes namespace 960 managed by IANA. The allocation of code values from the IANA- 961 managed namespace is conditioned by an Expert Review of the 962 specification defining the AVPs or an IETF review if a block of 963 AVPs needs to be assigned. Moreover, the remaining bits of the 964 AVP Flags field of the AVP header are also assigned via Standard 965 Action if the creation of new AVP Flags is desired. 967 c. Creating new commands 969 Unlike the AVP Code namespace, the Command Code namespace is flat 970 but the range of values is subdivided into three chunks with 971 distinct IANA registration policies: 973 * A range of standard Command Code values that are allocated via 974 IETF review; 976 * A range of vendor-specific Command Code values that are 977 allocated on a First-Come/First-Served basis; 979 * A range of values reserved only for experimental and testing 980 purposes. 982 As for AVP Flags, the remaining bits of the Command Flags field of 983 the Diameter header are also assigned via a Standards Action to 984 create new Command Flags if required. 986 d. Creating new applications 987 Similarly to the Command Code namespace, the Application-Id 988 namespace is flat but divided into two distinct ranges: 990 * A range of values reserved for standard Application-Ids 991 allocated after Expert Review of the specification defining the 992 standard application; 994 * A range for values for vendor specific applications, allocated 995 by IANA on a First-Come/First-Serve basis. 997 The IANA AAA parameters page can be found at http://www.iana.org/ 998 assignments/aaa-parameters/aaa-parameters.xml and the enterprise 999 number IANA page is available at http://www.iana.org/assignments/ 1000 enterprise-numbers. More details on the policies followed by IANA 1001 for namespace management (e.g. First-Come/First-Served, Expert 1002 Review, IETF Review, etc.) can be found in [RFC5226]. 1004 NOTE: 1005 When the same functionality/extension is used by more than one 1006 vendor, it is RECOMMENDED to define a standard extension. 1007 Moreover, a vendor-specific extension SHOULD be registered to 1008 avoid interoperability issues in the same network. With this aim, 1009 the registration policy of vendor-specific extension has been 1010 simplified with the publication of [RFC6733] and the namespace 1011 reserved for vendor-specific extensions is large enough to avoid 1012 exhaustion. 1014 8. IANA Considerations 1016 This document does not require actions by IANA. 1018 9. Security Considerations 1020 This document provides guidelines and considerations for extending 1021 Diameter and Diameter applications. Although such an extension may 1022 be related to a security functionality, the document does not 1023 explicitly give guidance on enhancing Diameter with respect to 1024 security. 1026 10. Contributors 1028 The content of this document was influenced by a design team created 1029 to revisit the Diameter extensibility rules. The team was formed in 1030 February 2008 and finished its work in June 2008. Except the 1031 authors, the design team members were: 1033 o Avi Lior 1034 o Glen Zorn 1036 o Jari Arkko 1038 o Jouni Korhonen 1040 o Mark Jones 1042 o Tolga Asveren 1044 o Glenn McGregor 1046 o Dave Frascone 1048 We would like to thank Tolga Asveren, Glenn McGregor, and John 1049 Loughney for their contributions as co-authors to earlier versions of 1050 this document. 1052 11. Acknowledgments 1054 We greatly appreciate the insight provided by Diameter implementers 1055 who have highlighted the issues and concerns being addressed by this 1056 document. The authors would also like to thank Jean Mahoney, Ben 1057 Campbell, Sebastien Decugis and Benoit Claise for their invaluable 1058 detailed reviews and comments on this document. 1060 12. References 1062 12.1. Normative References 1064 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1065 Requirement Levels", BCP 14, RFC 2119, March 1997. 1067 [RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, 1068 "Diameter Base Protocol", RFC 6733, October 2012. 1070 12.2. Informative References 1072 [Q.3303.3] 1073 3rd Generation Partnership Project, "ITU-T Recommendation 1074 Q.3303.3, "Resource control protocol no. 3 (rcp3): 1075 Protocol at the Rw interface between the Policy Decision 1076 Physical Entity (PD-PE) and the Policy Enforcement 1077 Physical Entity (PE-PE): Diameter"", 2008. 1079 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange 1080 (IKE)", RFC 2409, November 1998. 1082 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 1083 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 1085 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 1086 "Diameter Network Access Server Application", RFC 4005, 1087 August 2005. 1089 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 1090 Authentication Protocol (EAP) Application", RFC 4072, 1091 August 2005. 1093 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1094 Internet Protocol", RFC 4301, December 2005. 1096 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 1097 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 1098 Initiation Protocol (SIP) Application", RFC 4740, November 1099 2006. 1101 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1102 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1103 May 2008. 1105 [RFC5447] Korhonen, J., Bournelle, J., Tschofenig, H., Perkins, C., 1106 and K. Chowdhury, "Diameter Mobile IPv6: Support for 1107 Network Access Server to Diameter Server Interaction", RFC 1108 5447, February 2009. 1110 [RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M., 1111 and A. Lior, "Traffic Classification and Quality of 1112 Service (QoS) Attributes for Diameter", RFC 5777, February 1113 2010. 1115 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 1116 "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 1117 5996, September 2010. 1119 [RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, 1120 "Diameter Base Protocol", RFC 6733, October 2012. 1122 [RFC6735] Carlberg, K. and T. Taylor, "Diameter Priority Attribute- 1123 Value Pairs", RFC 6735, October 2012. 1125 [RFC7075] Tsou, T., Hao, R., and T. Taylor, "Realm-Based Redirection 1126 In Diameter", RFC 7075, November 2013. 1128 [RFC7155] Zorn, G., "Diameter Network Access Server Application", 1129 RFC 7155, April 2014. 1131 [TS29.228] 1132 3rd Generation Partnership Project, "3GPP TS 29.228; 1133 Technical Specification Group Core Network and Terminals; 1134 IP Multimedia (IM) Subsystem Cx and Dx Interfaces; 1135 Signalling flows and message contents", 1136 . 1138 [TS29.229] 1139 3rd Generation Partnership Project, "3GPP TS 29.229; 1140 Technical Specification Group Core Network and Terminals; 1141 Cx and Dx interfaces based on the Diameter protocol; 1142 Protocol details", 1143 . 1145 [TS29.328] 1146 3rd Generation Partnership Project, "3GPP TS 29.328; 1147 Technical Specification Group Core Network and Terminals; 1148 IP Multimedia (IM) Subsystem Sh interface; signalling 1149 flows and message content", 1150 . 1152 [TS29.329] 1153 3rd Generation Partnership Project, "3GPP TS 29.329; 1154 Technical Specification Group Core Network and Terminals; 1155 Sh Interface based on the Diameter protocol; Protocol 1156 details", 1157 . 1159 Authors' Addresses 1161 Lionel Morand (editor) 1162 Orange Labs 1163 38/40 rue du General Leclerc 1164 Issy-Les-Moulineaux Cedex 9 92794 1165 France 1167 Phone: +33145296257 1168 Email: lionel.morand@orange.com 1170 Victor Fajardo 1171 Independent 1173 Email: vf0213@gmail.com 1174 Hannes Tschofenig 1175 Nokia Siemens Networks 1176 Linnoitustie 6 1177 Espoo 02600 1178 Finland 1180 Phone: +358 (50) 4871445 1181 Email: Hannes.Tschofenig@gmx.net 1182 URI: http://www.tschofenig.priv.at