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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: March 27, 2015 Fluke Networks 6 H. Tschofenig 8 September 23, 2014 10 Diameter Applications Design Guidelines 11 draft-ietf-dime-app-design-guide-28 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. Furthermore, this document provides guidelines 20 to Diameter application designers reusing/defining Diameter 21 applications 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 March 27, 2015. 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 . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 4 72 4. Reusing Existing Diameter Applications . . . . . . . . . . . 6 73 4.1. Adding a New Command . . . . . . . . . . . . . . . . . . 6 74 4.2. Deleting an Existing Command . . . . . . . . . . . . . . 7 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 4.3.3. Changing the Flags Setting of AVP in existing 79 Commands . . . . . . . . . . . . . . . . . . . . . . 10 80 4.4. Reusing Existing AVPs . . . . . . . . . . . . . . . . . . 10 81 4.4.1. Setting of the AVP Flags . . . . . . . . . . . . . . 10 82 4.4.2. Reuse of AVP of Type Enumerated . . . . . . . . . . . 11 83 5. Defining New Diameter Applications . . . . . . . . . . . . . 11 84 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 11 85 5.2. Defining New Commands . . . . . . . . . . . . . . . . . . 11 86 5.3. Use of Application-Id in a Message . . . . . . . . . . . 12 87 5.4. Application-Specific Session State Machines . . . . . . . 13 88 5.5. Session-Id AVP and Session Management . . . . . . . . . . 13 89 5.6. Use of Enumerated Type AVPs . . . . . . . . . . . . . . . 14 90 5.7. Application-Specific Message Routing . . . . . . . . . . 16 91 5.8. Translation Agents . . . . . . . . . . . . . . . . . . . 17 92 5.9. End-to-End Application Capabilities Exchange . . . . . . 17 93 5.10. Diameter Accounting Support . . . . . . . . . . . . . . . 18 94 5.11. Diameter Security Mechanisms . . . . . . . . . . . . . . 20 95 6. Defining Generic Diameter Extensions . . . . . . . . . . . . 20 96 7. Guidelines for Registrations of Diameter Values . . . . . . . 21 97 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 98 9. Security Considerations . . . . . . . . . . . . . . . . . . . 23 99 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 24 100 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 24 101 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 102 12.1. Normative References . . . . . . . . . . . . . . . . . . 25 103 12.2. Informative References . . . . . . . . . . . . . . . . . 25 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 106 1. Introduction 108 The Diameter base protocol [RFC6733] is intended to provide an 109 Authentication, Authorization, and Accounting (AAA) framework for 110 applications such as network access or IP mobility in both local and 111 roaming situations. This protocol provides the ability for Diameter 112 peers to exchange messages carrying data in the form of Attribute- 113 Value Pairs (AVPs). 115 The Diameter base protocol provides facilities to extend Diameter 116 (see Section 1.3 of [RFC6733]) to support new functionality. In the 117 context of this document, extending Diameter means one of the 118 following: 120 1. Addition of new functionality to an existing Diameter application 121 without defining a new application. 123 2. Addition of new functionality to an existing Diameter application 124 that requires the definition of a new application. 126 3. The definition of an entirely new Diameter application to offer 127 functionality not supported by existing applications. 129 4. The definition of a new generic functionality that can be reused 130 across different applications. 132 All of these choices are design decisions that can be done by any 133 combination of reusing existing or defining new commands, AVPs or AVP 134 values. However, application designers do not have complete freedom 135 when making their design. A number of rules have been defined in 136 [RFC6733] that place constraints on when an extension requires the 137 allocation of a new Diameter application identifier or a new command 138 code value. The objective of this document is the following: 140 o Clarify the Diameter extensibility rules as defined in the 141 Diameter base protocol. 143 o Discuss design choices and provide guidelines when defining new 144 applications. 146 o Present trade-off choices. 148 2. Terminology 150 This document reuses the terminology defined in [RFC6733]. 151 Additionally, the following terms and acronyms are used in this 152 application: 154 Application Extension of the Diameter base protocol [RFC6733] via 155 the addition of new commands or AVPs. Each application is 156 uniquely identified by an IANA-allocated application identifier 157 value. 159 Command Diameter request or answer carrying AVPs between Diameter 160 endpoints. Each command is uniquely identified by a IANA- 161 allocated command code value and is described by a Command Code 162 Format (CCF) for an application. 164 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 165 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 166 document are to be interpreted as described in [RFC2119]. 168 3. Overview 170 As designed, the Diameter base protocol [RFC6733] can be seen as a 171 two-layer protocol. The lower layer is mainly responsible for 172 managing connections between neighboring peers and for message 173 routing. The upper layer is where the Diameter applications reside. 174 This model is in line with a Diameter node having an application 175 layer and a peer-to-peer delivery layer. The Diameter base protocol 176 document defines the architecture and behavior of the message 177 delivery layer and then provides the framework for designing Diameter 178 applications on the application layer. This framework includes 179 definitions of application sessions and accounting support (see 180 Section 8 and Section 9 of [RFC6733]). Accordingly, a Diameter node 181 is seen in this document as a single instance of a Diameter message 182 delivery layer and one or more Diameter applications using it. 184 The Diameter base protocol is designed to be extensible and the 185 principles are described in the Section 1.3 of [RFC6733]. As a 186 summary, Diameter can be extended by: 188 1. Defining new AVP values 190 2. Creating new AVPs 191 3. Creating new commands 193 4. Creating new applications 195 As a main guiding principle, application designers SHOULD follow the 196 following recommendation: "try to re-use as much as possible!". It 197 will reduce the time to finalize specification writing, and it will 198 lead to a smaller implementation effort as well as reduce the need 199 for testing. In general, it is clever to avoid duplicate effort when 200 possible. 202 However, re-use is not appropriate when the existing functionality 203 does not fit the new requirement and/or the re-use leads to 204 ambiguity. 206 The impact on extending existing applications can be categorized into 207 two groups: 209 Minor Extension: Enhancing the functional scope of an existing 210 application by the addition of optional features to support. Such 211 enhancement has no backward compatibility issue with the existing 212 application. 214 A typical example would be the definition of a new optional AVP 215 for use in an existing command. Diameter implementations 216 supporting the existing application but not the new AVP will 217 simply ignore it, without consequences for the Diameter message 218 handling, as described in [RFC6733]. The standardization effort 219 will be fairly small. 221 Major Extension: Enhancing an application that requires the 222 definition of a new Diameter application. Such enhancement causes 223 backward compatibility issue with existing implementations 224 supporting the application. 226 Typical examples would be the creation of a new command for 227 providing functionality not supported by existing applications or 228 the definition of a new AVP to be carried in an existing command 229 with the M-bit set in the AVP flags (see Section 4.1 of [RFC6733] 230 for definition of the "M-bit"). For such extension, a significant 231 specification effort is required and a careful approach is 232 recommended. 234 4. Reusing Existing Diameter Applications 236 An existing application may need to be enhanced to fulfill new 237 requirements and these modifications can be at the command level and/ 238 or at the AVP level. The following sections describe the possible 239 modifications that can be performed on existing applications and 240 their related impact. 242 4.1. Adding a New Command 244 Adding a new command to an existing application is considered as a 245 major extension and requires a new Diameter application to be 246 defined, as stated in the Section 1.3.4 of [RFC6733]. The need for a 247 new application is because a Diameter node that is not upgraded to 248 support the new command(s) within the (existing) application would 249 reject any unknown command with the protocol error 250 DIAMETER_COMMAND_UNSUPPORTED and cause the failure of the 251 transaction. The new application ensures that Diameter nodes only 252 receive commands within the context of applications they support. 254 Adding a new command means either defining a completely new command 255 or importing the command's Command Code Format (CCF) syntax from 256 another application whereby the new application inherits some or all 257 of the functionality of the application where the command came from. 258 In the former case, the decision to create a new application is 259 straightforward since this is typically a result of adding a new 260 functionality that does not exist yet. For the latter, the decision 261 to create a new application will depend on whether importing the 262 command in a new application is more suitable than simply using the 263 existing application as it is in conjunction with any other 264 application. 266 An example considers the Diameter EAP application [RFC4072] and the 267 Diameter Network Access Server application [RFC7155]. When network 268 access authentication using EAP is required, the Diameter EAP 269 commands (Diameter-EAP-Request/Diameter-EAP-Answer) are used; 270 otherwise the Diameter Network Access Server application will be 271 used. When the Diameter EAP application is used, the accounting 272 exchanges defined in the Diameter Network Access Server may be used. 274 However, in general, it is difficult to come to a hard guideline, and 275 so a case-by-case study of each application requirement should be 276 applied. Before adding or importing a command, application designers 277 should consider the following: 279 o Can the new functionality be fulfilled by creating a new command 280 independent from any existing command? In this case, the 281 resulting new application and the existing application can work 282 independent of, but cooperating with each other. 284 o Can the existing command be reused without major extensions and 285 therefore without the need for the definition of a new 286 application, e.g. new functionality introduced by the creation of 287 new optional AVPs. 289 It is important to note that importing commands too liberally could 290 result in a monolithic and hard to manage application supporting too 291 many different features. 293 4.2. Deleting an Existing Command 295 Although this process is not typical, removing a command from an 296 application requires a new Diameter application to be defined and 297 then it is considered as a major extension. This is due to the fact 298 that the reception of the deleted command would systematically result 299 in a protocol error (i.e., DIAMETER_COMMAND_UNSUPPORTED). 301 It is unusual to delete an existing command from an application for 302 the sake of deleting it or the functionality it represents. An 303 exception might be if the intent of the deletion is to create a newer 304 variance of the same application that is somehow simpler than the 305 application initially specified. 307 4.3. Reusing Existing Commands 309 This section discusses rules in adding and/or deleting AVPs from an 310 existing command of an existing application. The cases described in 311 this section may not necessarily result in the creation of new 312 applications. 314 From a historical point of view, it is worth to note that there was a 315 strong recommendation to re-use existing commands in the [RFC3588] to 316 prevent rapid depletion of code values available for vendor-specific 317 commands. However, [RFC6733] has relaxed the allocation policy and 318 enlarged the range of available code values for vendor-specific 319 applications. Although reuse of existing commands is still 320 RECOMMENDED, protocol designers can consider defining a new command 321 when it provides a solution more suitable than the twisting of an 322 existing command's use and applications. 324 4.3.1. Adding AVPs to a Command 326 Based on the rules in [RFC6733], AVPs that are added to an existing 327 command can be categorized into: 329 o Mandatory (to understand) AVPs. As defined in [RFC6733], these 330 are AVPs with the M-bit flag set in this command, which means that 331 a Diameter node receiving them is required to understand not only 332 their values but also their semantics. Failure to do so will 333 cause an message handling error: either a error message with the 334 result-code set to DIAMETER_AVP_UNSUPPORTED if the AVP not 335 understood in a request or a application specific error handling 336 if the given AVP is in an answer. 338 o Optional (to understand) AVPs. As defined in [RFC6733], these are 339 AVPs with the M-bit flag cleared in this command. A Diameter node 340 receiving these AVPs can simply ignore them if it does not support 341 them. 342 It is important to note that the definition given above are 343 independent of whether these AVPs are required or optional in the 344 command as specified by the command's Command Code Format (CCF) 345 syntax [RFC6733]. 347 NOTE: As stated in [RFC6733], the M-bit setting for a given AVP is 348 relevant to an application and each command within that 349 application that includes the AVP. 351 The rules are strict in the case where the AVPs to be added in an 352 exiting command are mandatory to understand, i.e., they have the 353 M-bit set. A mandatory AVP MUST NOT be added to an existing command 354 without defining a new Diameter application, as stated in [RFC6733]. 355 This falls into the "Major Extensions" category. Despite the clarity 356 of the rule, ambiguity still arises when evaluating whether a new AVP 357 being added should be mandatory to begin with. Application designers 358 should consider the following questions when deciding about the M-bit 359 for a new AVP: 361 o Would it be required for the receiving side to be able to process 362 and understand the AVP and its content? 364 o Would the new AVPs change the state machine of the application? 366 o Would the presence of the new AVP lead to a different number of 367 round-trips, effectively changing the state machine of the 368 application? 370 o Would the new AVP be used to differentiate between old and new 371 variances of the same application whereby the two variances are 372 not backward compatible? 374 o Would the new AVP have duality in meaning, i.e., be used to carry 375 application-related information as well as to indicate that the 376 message is for a new application? 378 If the answer to at least one of the questions is "yes" then the 379 M-bit MUST be set for the new AVP and a new Diameter application MUST 380 be defined. This list of questions is non-exhaustive and other 381 criteria MAY be taken into account in the decision process. 383 If application designers are instead contemplating the use of 384 optional AVPs, i.e., with the M-bit cleared, there are still pitfalls 385 that will cause interoperability problems and therefore must be 386 avoided. Some examples of these pitfalls are : 388 o Use of optional AVPs with intersecting meaning. One AVP has 389 partially the same usage and meaning as another AVP. The presence 390 of both can lead to confusion. 392 o An optional AVPs with dual purpose, i.e., to carry application 393 data as well as to indicate support for one or more features. 394 This has a tendency to introduce interpretation issues. 396 o Adding one or more optional AVPs and indicating (usually within 397 descriptive text for the command) that at least one of them has to 398 be understood by the receiver of the command. This would be 399 equivalent to adding a mandatory AVP, i.e., an AVP with the M-bit 400 set, to the command. 402 4.3.2. Deleting AVPs from a Command 404 Application designers may want to reuse an existing command but some 405 of the AVP present in the command's CCF syntax specification may be 406 irrelevant for the functionality foreseen to be supported by this 407 command. It may be then tempting to delete those AVPs from the 408 command. 410 The impacts of deleting an AVP from a command depends on its command 411 code format specification and M-bit setting: 413 o Case 1: Deleting an AVP that is indicated as a required AVP (noted 414 as {AVP}) in the command's CCF syntax specification (regardless of 415 the M-bit setting). 417 In this case, a new command code and subsequently a new Diameter 418 application MUST be specified. 420 o Case 2: Deleting an AVP, which has the M-bit set, and is indicated 421 as optional AVP (noted as [AVP]) in the command CCF) in the 422 command's CCF syntax specification. 424 In this case, no new command code has to be specified but the 425 definition of a new Diameter application is REQUIRED. 427 o Case 3: Deleting an AVP, which has the M-bit cleared, and is 428 indicated as [AVP] in the command's CCF syntax specification. 430 In this case, the AVP can be deleted without consequences. 432 Application designers SHOULD attempt the reuse the command's CCF 433 syntax specification without modification and simply ignore (but not 434 delete) any optional AVP that will not be used. This is to maintain 435 compatibility with existing applications that will not know about the 436 new functionality as well as maintain the integrity of existing 437 dictionaries. 439 4.3.3. Changing the Flags Setting of AVP in existing Commands 441 Although unusual, implementors may want to change the setting of the 442 AVP flags a given AVP used in a command. 444 Into an existing command, a AVP that was initially defined as 445 mandatory AVP to understand, i.e., an AVP with the M-bit flag set in 446 the command, MAY be safely turned to an optional AVP, i.e., with the 447 M-bit cleared. Any node supporting the existing application will 448 still understand the AVP, whatever the setting of the M-bit. On the 449 contrary, an AVP initially defined as an optional AVP to understand, 450 i.e., an AVP with the M-bit flag cleared in the command, MUST NOT be 451 changed into a mandatory AVP with the M-bit flag set without defining 452 a new Diameter application. Setting the M-bit for an AVP that was 453 defined as an optional AVP is equivalent to adding a new mandatory 454 AVP to an existing command and the rules given in the section 4.3.1 455 apply. 457 All other AVP flags (V-bit, P-bit, reserved bits) MUST remain 458 unchanged. 460 4.4. Reusing Existing AVPs 462 This section discusses rules in reusing existing AVP when reusing an 463 existing command or defining a new command in a new application. 465 4.4.1. Setting of the AVP Flags 467 When reusing existing AVPs in a new application, application 468 designers MUST specify the setting of the M-bit flag for a new 469 Diameter application and, if necessary, for every command of the 470 application that can carry these AVPs. In general, for AVPs defined 471 outside of the Diameter base protocol, the characteristics of an AVP 472 are tied to its role within a given application and the commands used 473 in this application. 475 All other AVP flags (V-bit, P-bit, reserved bits) MUST remain 476 unchanged. 478 4.4.2. Reuse of AVP of Type Enumerated 480 When reusing an AVP of type Enumerated in a command for a new 481 application, it is RECOMMENDED to avoid modifying the set of valid 482 values defined for this AVP. Modifying the set of Enumerated values 483 includes adding a value or deprecating the use of a value defined 484 initially for the AVP. Modifying the set of values will impact the 485 application defining this AVP and all the applications using this 486 AVP, causing potential interoperability issues: a value used by a 487 peer that will not be recognized by all the nodes between the client 488 and the server will cause an error response with the Result-Code AVP 489 set to DIAMETER_INVALID_AVP_VALUE. When the full range of values 490 defined for this Enumerated AVP is not suitable for the new 491 application, it is RECOMMENDED to define a new AVP to avoid backwards 492 compatibility issues with existing implementations. 494 5. Defining New Diameter Applications 496 5.1. Introduction 498 This section discusses the case where new applications have 499 requirements that cannot be fulfilled by existing applications and 500 would require definition of completely new commands, AVPs and/or AVP 501 values. Typically, there is little ambiguity about the decision to 502 create these types of applications. Some examples are the interfaces 503 defined for the IP Multimedia Subsystem of 3GPP, e.g., Cx/Dx 504 ([TS29.228] and [TS29.229]), Sh ([TS29.328] and [TS29.329]) etc. 506 Application designers SHOULD try to import existing AVPs and AVP 507 values for any newly defined commands. In certain cases where 508 accounting will be used, the models described in Section 5.10 SHOULD 509 also be considered. 511 Additional considerations are described in the following sections. 513 5.2. Defining New Commands 515 As a general recommendation, commands SHOULD NOT be defined from 516 scratch. It is instead RECOMMENDED to re-use an existing command 517 offering similar functionality and use it as a starting point. Code 518 re-use lead to a smaller implementation effort as well as reduce the 519 need for testing. 521 Moreover, the new command's CCF syntax specification SHOULD be 522 carefully defined when considering applicability and extensibility of 523 the application. If most of the AVPs contained in the command are 524 indicated as fixed or required, it might be difficult to reuse the 525 same command and therefore the same application in a slightly changed 526 environment. Defining a command with most of the AVPs indicated as 527 optional is considered as a good design choice in many cases, despite 528 the flexibility it introduces in the protocol. Protocol designers 529 MUST clearly state the reasons why these optional AVPs might or might 530 not be present and properly define the corresponding behavior of the 531 Diameter nodes when these AVPs are absent from the command. 533 NOTE: As a hint for protocol designers, it is not sufficient to just 534 look at the command's CCF syntax specification. It is also 535 necessary to carefully read through the accompanying text in the 536 specification. 538 In the same way, the CCF syntax specification SHOULD be defined such 539 that it will be possible to add any arbitrary optional AVPs with the 540 M-bit cleared (including vendor-specific AVPs) without modifying the 541 application. For this purpose, "* [AVP]" SHOULD be added in the 542 command's CCF, which allows the addition of any arbitrary number of 543 optional AVPs as described in [RFC6733]. 545 5.3. Use of Application-Id in a Message 547 When designing new applications, application designers SHOULD specify 548 that the Application Id carried in all session-level messages is the 549 Application Id of the application using those messages. This 550 includes the session-level messages defined in Diameter base 551 protocol, i.e., RAR/RAA, STR/STA, ASR/ASA and possibly ACR/ACA in the 552 coupled accounting model, see Section 5.10. Some existing 553 specifications do not adhere to this rule for historical reasons. 554 However, this guidance SHOULD be followed by new applications to 555 avoid routing problems. 557 When a new application has been allocated with a new Application Id 558 and it also reuses existing commands with or without modifications, 559 the commands SHOULD use the newly allocated Application Id in the 560 header and in all relevant Application Id AVPs (Auth-Application-Id 561 or Acct-Application-Id) present in the commands message body. 563 Additionally, application designers using Vendor-Specific- 564 Application-Id AVP SHOULD NOT use the Vendor-Id AVP to further 565 dissect or differentiate the vendor-specification Application Id. 566 Diameter routing is not based on the Vendor-Id. As such, the Vendor- 567 Id SHOULD NOT be used as an additional input for routing or delivery 568 of messages. The Vendor-Id AVP is an informational AVP only and kept 569 for backward compatibility reasons. 571 5.4. Application-Specific Session State Machines 573 Section 8 of [RFC6733] provides session state machines for 574 authentication, authorization and accounting (AAA) services and these 575 session state machines are not intended to cover behavior outside of 576 AAA. If a new application cannot clearly be categorized into any of 577 these AAA services, it is RECOMMENDED that the application defines 578 its own session state machine. Support for server-initiated request 579 is a clear example where an application-specific session state 580 machine would be needed, for example, the Rw interface for ITU-T push 581 model (cf.[Q.3303.3]). 583 5.5. Session-Id AVP and Session Management 585 Diameter applications are usually designed with the aim of managing 586 user sessions (e.g., Diameter network access session (NASREQ) 587 application [RFC4005]) or specific service access session (e.g., 588 Diameter SIP application [RFC4740]). In the Diameter base protocol, 589 session state is referenced using the Session-Id AVP. All Diameter 590 messages that use the same Session-Id will be bound to the same 591 session. Diameter-based session management also implies that both 592 Diameter client and server (and potentially proxy agents along the 593 path) maintain session state information. 595 However, some applications may not need to rely on the Session-Id to 596 identify and manage sessions because other information can be used 597 instead to correlate Diameter messages. Indeed, the User-Name AVP or 598 any other specific AVP can be present in every Diameter message and 599 used therefore for message correlation. Some applications might not 600 require the notion of Diameter session concept at all. For such 601 applications, the Auth-Session-State AVP is usually set to 602 NO_STATE_MAINTAINED in all Diameter messages and these applications 603 are therefore designed as a set of stand-alone transactions. Even if 604 an explicit access session termination is required, application- 605 specific commands are defined and used instead of the Session- 606 Termination-Request/Answer (STR/STA) or Abort-Session-Request/Answer 607 (ASR/ASA) defined in the Diameter base protocol [RFC6733]. In such a 608 case, the Session-Id is not significant. 610 Based on these considerations, protocol designers should carefully 611 appraise whether the Diameter application being defined relies on the 612 session management specified in the Diameter base protocol: 614 o If it is, the Diameter command defined for the new application 615 MUST include the Session-Id AVP defined in the Diameter base 616 protocol [RFC6733] and the Session-Id AVP MUST be used for 617 correlation of messages related to the same session. Guidance on 618 the use of the Auth-Session-State AVP is given in the Diameter 619 base protocol [RFC6733]. 621 o Otherwise, because session management is not required or the 622 application relies on its own session management mechanism, 623 Diameter commands for the application need not include the 624 Session-Id AVP. If any specific session management concept is 625 supported by the application, the application documentation MUST 626 clearly specify how the session is handled between client and 627 server (and possibly Diameter agents in the path). Moreover, 628 because the application is not maintaining session state at the 629 Diameter base protocol level, the Auth-Session-State AVP MUST be 630 included in all Diameter commands for the application and MUST be 631 set to NO_STATE_MAINTAINED. 633 5.6. Use of Enumerated Type AVPs 635 The type Enumerated was initially defined to provide a list of valid 636 values for an AVP with their respective interpretation described in 637 the specification. For instance, AVPs of type Enumerated can be used 638 to provide further information on the reason for the termination of a 639 session or a specific action to perform upon the reception of the 640 request. 642 As described in the section 4.4.2 above, defining an AVP of type 643 Enumerated presents some limitations in term of extensibility and 644 reusability. Indeed, the finite set of valid values defined at the 645 definition of the AVP of type Enumerated cannot be modified in 646 practice without causing backward compatibility issues with existing 647 implementations. As a consequence, AVPs of Type Enumerated MUST NOT 648 be extended by adding new values to support new capabilities. 649 Diameter protocol designers SHOULD carefully consider before defining 650 an Enumerated AVP whether the set of values will remain unchanged or 651 new values may be required in a near future. If such extension is 652 foreseen or cannot be avoided, it is RECOMMENED to rather define AVPs 653 of type Unsigned32 or Unsigned64 in which the data field would 654 contain an address space representing "values" that would have the 655 same use of Enumerated values. Whereas only the initial values 656 defined at the definition of the AVP of type Enumerated are valid as 657 described in section 4.4.2, any value from the address space from 0 658 to 2^32 - 1 for AVPs of type Unsigned32 or from 0 to 2^64 - 1 for 659 AVPs of type Unsigned64 is valid at the Diameter base protocol level 660 and will not interoperability issues for intermediary nodes between 661 clients and servers. Only clients and servers will be able to 662 process the values at the application layer. 664 For illustration, an AVP describing possible access networks would be 665 defined as follow: 667 Access-Network-Type AVP (XXX) is of type Unsigned32 and contains a 668 32-bit address space representing types of access networks. This 669 application defines the following classes of access networks, all 670 identified by the thousands digit in the decimal notation: 672 o 1xxx (Mobile Access Networks) 674 o 2xxx (Fixed Access Network) 676 o 3xxx (Wireless Access Networks) 678 Values that fall within the Mobile Access Networks category are used 679 to inform a peer that a request has been sent for a user attached to 680 a mobile access network. The following values are defined in this 681 application: 683 1001: 3GPP-GERAN 685 The user is attached to a GSM EDGE Radio Access Network. 687 1002: 3GPP-UTRAN-FDD 689 The user is attached to a UMTS access network that uses 690 frequency-division duplexing for duplexing. 692 Unlike Enumerated AVP, any new value can be added in the address 693 space defined by this Unsigned32 AVP without modifying the definition 694 of the AVP. There is therefore no risk of backward compatibility 695 issue, especially when intermediate nodes may be present between 696 Diameter endpoints. 698 In the same line, AVPs of type Enumerated are too often used as a 699 simple Boolean flag, indicating for instance a specific permission or 700 capability, and therefore only two values are defined, e.g., TRUE/ 701 FALSE, AUTORIZED/UNAUTHORIZED or SUPPORTED/UNSUPPORTED. This is a 702 sub-optimal design since it limits the extensibility of the 703 application: any new capability/permission would have to be supported 704 by a new AVP or new Enumerated value of the already defined AVP, with 705 the backward compatibility issues described above. Instead of using 706 an Enumerated AVP for a Boolean flag, protocol designers SHOULD use 707 AVPs of type Unsigned32 or Unsigned64 AVP in which the data field 708 would be defined as bit mask whose bit settings are described in the 709 relevant Diameter application specification. Such AVPs can be reused 710 and extended without major impact on the Diameter application. The 711 bit mask SHOULD leave room for future additions. Examples of AVPs 712 that use bit masks are the Session-Binding AVP defined in [RFC6733] 713 and the MIP6-Feature-Vector AVP defined in [RFC5447]. 715 5.7. Application-Specific Message Routing 717 As described in [RFC6733], a Diameter request that needs to be sent 718 to a home server serving a specific realm, but not to a specific 719 server (such as the first request of a series of round trips), will 720 contain a Destination-Realm AVP and no Destination-Host AVP. 722 For such a request, the message routing usually relies only on the 723 Destination-Realm AVP and the Application Id present in the request 724 message header. However, some applications may need to rely on the 725 User-Name AVP or any other application-specific AVP present in the 726 request to determine the final destination of a request, e.g., to 727 find the target AAA server hosting the authorization information for 728 a given user when multiple AAA servers are addressable in the realm. 730 In such a context, basic routing mechanisms described in [RFC6733] 731 are not fully suitable, and additional application-level routing 732 mechanisms MUST be described in the application documentation to 733 provide such specific AVP-based routing. Such functionality will be 734 basically hosted by an application-specific proxy agent that will be 735 responsible for routing decisions based on the received specific 736 AVPs. 738 Examples of such application-specific routing functions can be found 739 in the Cx/Dx applications ([TS29.228] and [TS29.229]) of the 3GPP IP 740 Multimedia Subsystem, in which the proxy agent (Subscriber Location 741 Function aka SLF) uses specific application-level identities found in 742 the request to determine the final destination of the message. 744 Whatever the criteria used to establish the routing path of the 745 request, the routing of the answer MUST follow the reverse path of 746 the request, as described in [RFC6733], with the answer being sent to 747 the source of the received request, using transaction states and hop- 748 by-hop identifier matching. This ensures that the Diameter Relay or 749 Proxy agents in the request routing path will be able to release the 750 transaction state upon receipt of the corresponding answer, avoiding 751 unnecessary failover. Moreover, especially in roaming cases, proxy 752 agents in the path must be able to apply local policies when 753 receiving the answer from the server during authentication/ 754 authorization and/or accounting procedures, and maintain up-to-date 755 session state information by keeping track of all authorized active 756 sessions. Therefore, application designers MUST NOT modify the 757 answer-routing principles described in [RFC6733] when defining a new 758 application. 760 5.8. Translation Agents 762 As defined in [RFC6733], a translation agent is a device that 763 provides interworking between Diameter and another AAA protocol, such 764 as RADIUS . 766 In the case of RADIUS, it was initially thought that defining the 767 translation function would be straightforward by adopting few basic 768 principles, e.g., by the use of a shared range of code values for 769 RADIUS attributes and Diameter AVPs. Guidelines for implementing a 770 RADIUS-Diameter translation agent were put into the Diameter NASREQ 771 Application ([RFC4005]). 773 However, it was acknowledged that such translation mechanism was not 774 so obvious and deeper protocol analysis was required to ensure 775 efficient interworking between RADIUS and Diameter. Moreover, the 776 interworking requirements depend on the functionalities provided by 777 the Diameter application under specification, and a case-by-case 778 analysis is required. As a consequence, all the material related to 779 RADIUS-to-Diameter translation is removed from the new version of the 780 Diameter NASREQ application specification [RFC7155], which deprecates 781 the RFC4005 ([RFC4005]). 783 Therefore, protocol designers SHOULD NOT assume the availability of a 784 "standard" Diameter-to-RADIUS gateways agent when planning to 785 interoperate with the RADIUS infrastructure. They SHOULD specify the 786 required translation mechanism along with the Diameter application, 787 if needed. This recommendation applies for any kind of translation. 789 5.9. End-to-End Application Capabilities Exchange 791 Diameter applications can rely on optional AVPs to exchange 792 application-specific capabilities and features. These AVPs can be 793 exchanged on an end-to-end basis at the application layer. Examples 794 of this can be found with the MIP6-Feature-Vector AVP in [RFC5447] 795 and the QoS-Capability AVP in [RFC5777]. 797 End-to-end capabilities AVPs can be added as optional AVPs with the 798 M-bit cleared to existing applications to announce support of new 799 functionality. Receivers that do not understand these AVPs or the 800 AVP values can simply ignore them, as stated in [RFC6733]. When 801 supported, receivers of these AVPs can discover the additional 802 functionality supported by the Diameter end-point originating the 803 request and behave accordingly when processing the request. Senders 804 of these AVPs can safely assume the receiving end-point does not 805 support any functionality carried by the AVP if it is not present in 806 corresponding response. This is useful in cases where deployment 807 choices are offered, and the generic design can be made available for 808 a number of applications. 810 When used in a new application, these end-to-end capabilities AVPs 811 SHOULD be added as optional AVP into the CCF of the commands used by 812 the new application. Protocol designers SHOULD clearly specify this 813 end-to-end capabilities exchange and the corresponding behaviour of 814 the Diameter nodes supporting the application. 816 It is also important to note that this end-to-end capabilities 817 exchange relying on the use of optional AVPs is not meant as a 818 generic mechanism to support extensibility of Diameter applications 819 with arbitrary functionality. When the added features drastically 820 change the Diameter application or when Diameter agents must be 821 upgraded to support the new features, a new application SHOULD be 822 defined, as recommended in [RFC6733]. 824 5.10. Diameter Accounting Support 826 Accounting can be treated as an auxiliary application that is used in 827 support of other applications. In most cases, accounting support is 828 required when defining new applications. This document provides two 829 possible models for using accounting: 831 Split Accounting Model: 833 In this model, the accounting messages will use the Diameter base 834 accounting Application Id (value of 3). The design implication 835 for this is that the accounting is treated as an independent 836 application, especially for Diameter routing. This means that 837 accounting commands emanating from an application may be routed 838 separately from the rest of the other application messages. This 839 may also imply that the messages end up in a central accounting 840 server. A split accounting model is a good design choice when: 842 * The application itself does not define its own accounting 843 commands. 845 * The overall system architecture permits the use of centralized 846 accounting for one or more Diameter applications. 848 Centralizing accounting may have advantages but there are also 849 drawbacks. The model assumes that the accounting server can 850 differentiate received accounting messages. Since the received 851 accounting messages can be for any application and/or service, the 852 accounting server MUST have a method to match accounting messages 853 with applications and/or services being accounted for. This may 854 mean defining new AVPs, checking the presence, absence or contents 855 of existing AVPs, or checking the contents of the accounting 856 record itself. One of these means could be to insert into the 857 request sent to the accounting server an Auth-Application-Id AVP 858 containing the identifier of the application for which the 859 accounting request is sent. But in general, there is no clean and 860 generic scheme for sorting these messages. Therefore, this model 861 SHOULD NOT be used when all received accounting messages cannot be 862 clearly identified and sorted. For most cases, the use of Coupled 863 Accounting Model is RECOMMENDED. 865 Coupled Accounting Model: 867 In this model, the accounting messages will use the Application Id 868 of the application using the accounting service. The design 869 implication for this is that the accounting messages are tightly 870 coupled with the application itself; meaning that accounting 871 messages will be routed like the other application messages. It 872 would then be the responsibility of the application server 873 (application entity receiving the ACR message) to send the 874 accounting records carried by the accounting messages to the 875 proper accounting server. The application server is also 876 responsible for formulating a proper response (ACA). A coupled 877 accounting model is a good design choice when: 879 * The system architecture or deployment does not provide an 880 accounting server that supports Diameter. Consequently, the 881 application server MUST be provisioned to use a different 882 protocol to access the accounting server, e.g., via LDAP, SOAP 883 etc. This case includes the support of older accounting 884 systems that are not Diameter aware. 886 * The system architecture or deployment requires that the 887 accounting service for the specific application should be 888 handled by the application itself. 890 In all cases above, there will generally be no direct Diameter 891 access to the accounting server. 893 These models provide a basis for using accounting messages. 894 Application designers may obviously deviate from these models 895 provided that the factors being addressed here have also been taken 896 into account. As a general recommendation, application designers 897 SHOULD NOT define a new set of commands to carry application-specific 898 accounting records. 900 5.11. Diameter Security Mechanisms 902 As specified in [RFC6733], the Diameter message exchange SHOULD be 903 secured between neighboring Diameter peers using TLS/TCP or DTLS/ 904 SCTP. However, IPsec MAY also be deployed to secure communication 905 between Diameter peers. When IPsec is used instead of TLS or DTLS, 906 the following recommendations apply. 908 IPsec ESP [RFC4301] in transport mode with non-null encryption and 909 authentication algorithms MUST be used to provide per-packet 910 authentication, integrity protection and confidentiality, and support 911 the replay protection mechanisms of IPsec. IKEv2 [RFC5996] SHOULD be 912 used for performing mutual authentication and for establishing and 913 maintaining security associations (SAs). 915 IKEv1 [RFC2409] was used with RFC 3588 [RFC3588] and for easier 916 migration from IKEv1 based implementations both RSA digital 917 signatures and pre-shared keys SHOULD be supported in IKEv2. 918 However, if IKEv1 is used, implementers SHOULD follow the guidelines 919 given in Section 13.1 of RFC 3588 [RFC3588]. 921 6. Defining Generic Diameter Extensions 923 Generic Diameter extensions are AVPs, commands or applications that 924 are designed to support other Diameter applications. They are 925 auxiliary applications meant to improve or enhance the Diameter 926 protocol itself or Diameter applications/functionality. Some 927 examples include the extensions to support realm-based redirection of 928 Diameter requests (see [RFC7075]), convey a specific set of priority 929 parameters influencing the distribution of resources (see [RFC6735]), 930 and the support for QoS AVPs (see [RFC5777]). 932 Since generic extensions may cover many aspects of Diameter and 933 Diameter applications, it is not possible to enumerate all scenarios. 934 However, some of the most common considerations are as follows: 936 Backward Compatibility: 938 When defining generic extensions designed to be supported by 939 existing Diameter applications, protocol designers MUST consider 940 the potential impacts of the introduction of the new extension on 941 the behavior of node that would not be yet upgraded to support/ 942 understand this new extension. Designers MUST also ensure that 943 new extensions do not break expected message delivery layer 944 behavior. 946 Forward Compatibility: 948 Protocol designers MUST ensure that their design will not 949 introduce undue restrictions for future applications. 951 Trade-off in Signaling: 953 Designers may have to choose between the use of optional AVPs 954 piggybacked onto existing commands versus defining new commands 955 and applications. Optional AVPs are simpler to implement and may 956 not need changes to existing applications. However, this ties the 957 sending of extension data to the application's transmission of a 958 message. This has consequences if the application and the 959 extensions have different timing requirements. The use of 960 commands and applications solves this issue, but the trade-off is 961 the additional complexity of defining and deploying a new 962 application. It is left up to the designer to find a good balance 963 among these trade-offs based on the requirements of the extension. 965 In practice, generic extensions often use optional AVPs because they 966 are simple and non-intrusive to the application that would carry 967 them. Peers that do not support the generic extensions need not 968 understand nor recognize these optional AVPs. However, it is 969 RECOMMENDED that the authors of the extension specify the context or 970 usage of the optional AVPs. As an example, in the case that the AVP 971 can be used only by a specific set of applications then the 972 specification MUST enumerate these applications and the scenarios 973 when the optional AVPs will be used. In the case where the optional 974 AVPs can be carried by any application, it should be sufficient to 975 specify such a use case and perhaps provide specific examples of 976 applications using them. 978 In most cases, these optional AVPs piggybacked by applications would 979 be defined as a Grouped AVP and it would encapsulate all the 980 functionality of the generic extension. In practice, it is not 981 uncommon that the Grouped AVP will encapsulate an existing AVP that 982 has previously been defined as mandatory ('M'-bit set) e.g., 3GPP IMS 983 Cx/Dx interfaces ([TS29.228] and [TS29.229]). 985 7. Guidelines for Registrations of Diameter Values 987 As summarized in the Section 3 of this document and further described 988 in the Section 1.3 of [RFC6733], there are four main ways to extend 989 Diameter. The process for defining new functionality slightly varies 990 based on the different extensions. This section provides protocol 991 designers with some guidance regarding the definition of values for 992 possible Diameter extensions and the necessary interaction with IANA 993 to register the new functionality. 995 a. Defining new AVP values 996 The specifications defining AVPs and AVP values MUST provide 997 guidance for defining new values and the corresponding policy for 998 adding these values. For example, the RFC 5777 [RFC5777] defines 999 the Treatment-Action AVP which contains a list of valid values 1000 corresponding to pre-defined actions (drop, shape, mark, permit). 1001 This set of values can be extended following the Specification 1002 Required policy defined in [RFC5226]. As a second example, the 1003 Diameter base specification [RFC6733] defines the Result-Code AVP 1004 that contains a 32-bit address space used to identity possible 1005 errors. According to the Section 11.3.2 of [RFC6733], new values 1006 can be assigned by IANA via an IETF Review process [RFC5226]. 1008 b. Creating new AVPs 1010 Two different types of AVP Codes namespaces can be used to create 1011 a new AVPs: 1013 * IETF AVP Codes namespace; 1015 * Vendor-specific AVP Codes namespace. 1017 In the latter case, a vendor needs to be first assigned by IANA 1018 with a private enterprise number, which can be used within the 1019 Vendor-Id field of the vendor-specific AVP. This enterprise 1020 number delimits a private namespace in which the vendor is 1021 responsible for vendor-specific AVP code value assignment. The 1022 absence of a Vendor-Id or a Vendor-Id value of zero (0) in the AVP 1023 header identifies standard AVPs from the IETF AVP Codes namespace 1024 managed by IANA. The allocation of code values from the IANA- 1025 managed namespace is conditioned by an Expert Review of the 1026 specification defining the AVPs or an IETF review if a block of 1027 AVPs needs to be assigned. Moreover, the remaining bits of the 1028 AVP Flags field of the AVP header are also assigned via Standard 1029 Action if the creation of new AVP Flags is desired. 1031 c. Creating new commands 1033 Unlike the AVP Code namespace, the Command Code namespace is flat 1034 but the range of values is subdivided into three chunks with 1035 distinct IANA registration policies: 1037 * A range of standard Command Code values that are allocated via 1038 IETF review; 1040 * A range of vendor-specific Command Code values that are 1041 allocated on a First-Come/First-Served basis; 1043 * A range of values reserved only for experimental and testing 1044 purposes. 1046 As for AVP Flags, the remaining bits of the Command Flags field of 1047 the Diameter header are also assigned via a Standards Action to 1048 create new Command Flags if required. 1050 d. Creating new applications 1052 Similarly to the Command Code namespace, the Application-Id 1053 namespace is flat but divided into two distinct ranges: 1055 * A range of values reserved for standard Application-Ids 1056 allocated after Expert Review of the specification defining the 1057 standard application; 1059 * A range for values for vendor specific applications, allocated 1060 by IANA on a First-Come/First-Serve basis. 1062 The IANA AAA parameters page can be found at 1063 http://www.iana.org/assignments/aaa-parameters and the enterprise 1064 number IANA page is available at http://www.iana.org/assignments/ 1065 enterprise-numbers. More details on the policies followed by IANA 1066 for namespace management (e.g. First-Come/First-Served, Expert 1067 Review, IETF Review, etc.) can be found in [RFC5226]. 1069 NOTE: 1070 When the same functionality/extension is used by more than one 1071 vendor, it is RECOMMENDED to define a standard extension. 1072 Moreover, a vendor-specific extension SHOULD be registered to 1073 avoid interoperability issues in the same network. With this aim, 1074 the registration policy of vendor-specific extension has been 1075 simplified with the publication of [RFC6733] and the namespace 1076 reserved for vendor-specific extensions is large enough to avoid 1077 exhaustion. 1079 8. IANA Considerations 1081 This document does not require actions by IANA. 1083 9. Security Considerations 1085 This document provides guidelines and considerations for extending 1086 Diameter and Diameter applications. Although such an extension may 1087 be related to a security functionality, the document does not 1088 explicitly give additional guidance on enhancing Diameter with 1089 respect to security. However, as a general guideline, it is 1090 recommended that any Diameter extension SHOULD NOT break the security 1091 concept given in the [RFC6733]. In particular, it is reminded here 1092 that any command defined or reused in a new Diameter application 1093 SHOULD be secured by using TLS [RFC5246] or DTLS/SCTP [RFC6083] and 1094 MUST NOT be used without one of TLS, DTLS, or IPsec [RFC4301]. When 1095 defining a new Diameter extension, any possible impact of the 1096 existing security principles described in the [RFC6733] MUST be 1097 carefully appraised and documented in the Diameter application 1098 specification. 1100 10. Contributors 1102 The content of this document was influenced by a design team created 1103 to revisit the Diameter extensibility rules. The team was formed in 1104 February 2008 and finished its work in June 2008. Except the 1105 authors, the design team members were: 1107 o Avi Lior 1109 o Glen Zorn 1111 o Jari Arkko 1113 o Jouni Korhonen 1115 o Mark Jones 1117 o Tolga Asveren 1119 o Glenn McGregor 1121 o Dave Frascone 1123 We would like to thank Tolga Asveren, Glenn McGregor, and John 1124 Loughney for their contributions as co-authors to earlier versions of 1125 this document. 1127 11. Acknowledgments 1129 We greatly appreciate the insight provided by Diameter implementers 1130 who have highlighted the issues and concerns being addressed by this 1131 document. The authors would also like to thank Jean Mahoney, Ben 1132 Campbell, Sebastien Decugis and Benoit Claise for their invaluable 1133 detailed reviews and comments on this document. 1135 12. References 1137 12.1. Normative References 1139 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1140 Requirement Levels", BCP 14, RFC 2119, March 1997. 1142 [RFC6733] Fajardo, V., Arkko, J., Loughney, J., and G. Zorn, 1143 "Diameter Base Protocol", RFC 6733, October 2012. 1145 12.2. Informative References 1147 [Q.3303.3] 1148 3rd Generation Partnership Project, "ITU-T Recommendation 1149 Q.3303.3, "Resource control protocol no. 3 (rcp3): 1150 Protocol at the Rw interface between the Policy Decision 1151 Physical Entity (PD-PE) and the Policy Enforcement 1152 Physical Entity (PE-PE): Diameter"", 2008. 1154 [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange 1155 (IKE)", RFC 2409, November 1998. 1157 [RFC3588] Calhoun, P., Loughney, J., Guttman, E., Zorn, G., and J. 1158 Arkko, "Diameter Base Protocol", RFC 3588, September 2003. 1160 [RFC4005] Calhoun, P., Zorn, G., Spence, D., and D. Mitton, 1161 "Diameter Network Access Server Application", RFC 4005, 1162 August 2005. 1164 [RFC4072] Eronen, P., Hiller, T., and G. Zorn, "Diameter Extensible 1165 Authentication Protocol (EAP) Application", RFC 4072, 1166 August 2005. 1168 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 1169 Internet Protocol", RFC 4301, December 2005. 1171 [RFC4740] Garcia-Martin, M., Belinchon, M., Pallares-Lopez, M., 1172 Canales-Valenzuela, C., and K. Tammi, "Diameter Session 1173 Initiation Protocol (SIP) Application", RFC 4740, November 1174 2006. 1176 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 1177 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 1178 May 2008. 1180 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1181 (TLS) Protocol Version 1.2", RFC 5246, August 2008. 1183 [RFC5447] Korhonen, J., Bournelle, J., Tschofenig, H., Perkins, C., 1184 and K. Chowdhury, "Diameter Mobile IPv6: Support for 1185 Network Access Server to Diameter Server Interaction", RFC 1186 5447, February 2009. 1188 [RFC5777] Korhonen, J., Tschofenig, H., Arumaithurai, M., Jones, M., 1189 and A. Lior, "Traffic Classification and Quality of 1190 Service (QoS) Attributes for Diameter", RFC 5777, February 1191 2010. 1193 [RFC5996] Kaufman, C., Hoffman, P., Nir, Y., and P. Eronen, 1194 "Internet Key Exchange Protocol Version 2 (IKEv2)", RFC 1195 5996, September 2010. 1197 [RFC6083] Tuexen, M., Seggelmann, R., and E. Rescorla, "Datagram 1198 Transport Layer Security (DTLS) for Stream Control 1199 Transmission Protocol (SCTP)", RFC 6083, January 2011. 1201 [RFC6735] Carlberg, K. and T. Taylor, "Diameter Priority Attribute- 1202 Value Pairs", RFC 6735, October 2012. 1204 [RFC7075] Tsou, T., Hao, R., and T. Taylor, "Realm-Based Redirection 1205 In Diameter", RFC 7075, November 2013. 1207 [RFC7155] Zorn, G., "Diameter Network Access Server Application", 1208 RFC 7155, April 2014. 1210 [TS29.228] 1211 3rd Generation Partnership Project, "3GPP TS 29.228; 1212 Technical Specification Group Core Network and Terminals; 1213 IP Multimedia (IM) Subsystem Cx and Dx Interfaces; 1214 Signalling flows and message contents", 1215 . 1217 [TS29.229] 1218 3rd Generation Partnership Project, "3GPP TS 29.229; 1219 Technical Specification Group Core Network and Terminals; 1220 Cx and Dx interfaces based on the Diameter protocol; 1221 Protocol details", 1222 . 1224 [TS29.328] 1225 3rd Generation Partnership Project, "3GPP TS 29.328; 1226 Technical Specification Group Core Network and Terminals; 1227 IP Multimedia (IM) Subsystem Sh interface; signalling 1228 flows and message content", 1229 . 1231 [TS29.329] 1232 3rd Generation Partnership Project, "3GPP TS 29.329; 1233 Technical Specification Group Core Network and Terminals; 1234 Sh Interface based on the Diameter protocol; Protocol 1235 details", 1236 . 1238 Authors' Addresses 1240 Lionel Morand (editor) 1241 Orange Labs 1242 38/40 rue du General Leclerc 1243 Issy-Les-Moulineaux Cedex 9 92794 1244 France 1246 Phone: +33145296257 1247 Email: lionel.morand@orange.com 1249 Victor Fajardo 1250 Fluke Networks 1252 Email: vf0213@gmail.com 1254 Hannes Tschofenig 1255 Hall in Tirol 6060 1256 Austria 1258 Email: Hannes.Tschofenig@gmx.net 1259 URI: http://www.tschofenig.priv.at