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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Miller 3 Internet-Draft The Jabber.org Project 4 Expires: December 14, 2000 June 15, 2000 6 Jabber 7 jabber 9 draft-miller-impp-jabber-00.txt 11 Status of this Memo 13 This document is an Internet-Draft and is in full conformance with 14 all provisions of Section 10 of RFC2026. 16 Internet-Drafts are working documents of the Internet Engineering 17 Task Force (IETF), its areas, and its working groups. Note that 18 other groups may also distribute working documents as 19 Internet-Drafts. 21 Internet-Drafts are draft documents valid for a maximum of six 22 months and may be updated, replaced, or obsoleted by other documents 23 at any time. It is inappropriate to use Internet-Drafts as reference 24 material or to cite them other than as "work in progress." 26 The list of current Internet-Drafts can be accessed at 27 http://www.ietf.org/ietf/1id-abstracts.txt. 29 The list of Internet-Draft Shadow Directories can be accessed at 30 http://www.ietf.org/shadow.html. 32 This Internet-Draft will expire on December 14, 2000. 34 Copyright Notice 36 Copyright (C) The Internet Society (2000). All Rights Reserved. 38 Abstract 40 This memo provides a comprehensive description of the Jabber 41 architecture, design principles, and protocol. 43 Table of Contents 45 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 46 1.1 What is Jabber? . . . . . . . . . . . . . . . . . . . . . . 4 47 1.2 Background and History . . . . . . . . . . . . . . . . . . . 4 48 1.3 Evolution . . . . . . . . . . . . . . . . . . . . . . . . . 4 49 1.4 Today . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 50 2. Architecture Overview . . . . . . . . . . . . . . . . . . . 6 51 2.1 Server . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 52 2.2 Client . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 53 2.3 Transport . . . . . . . . . . . . . . . . . . . . . . . . . 7 54 3. Entity Identification . . . . . . . . . . . . . . . . . . . 8 55 3.1 Three Tier . . . . . . . . . . . . . . . . . . . . . . . . . 8 56 3.1.1 Host (server) . . . . . . . . . . . . . . . . . . . . . . . 8 57 3.1.2 Node (user) . . . . . . . . . . . . . . . . . . . . . . . . 8 58 3.1.3 Resource . . . . . . . . . . . . . . . . . . . . . . . . . . 8 59 3.2 URI . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 60 4. XML . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 61 4.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 10 62 4.2 Namespaces . . . . . . . . . . . . . . . . . . . . . . . . . 10 63 4.3 Validation . . . . . . . . . . . . . . . . . . . . . . . . . 10 64 4.4 element . . . . . . . . . . . . . . . . . . . . . 10 65 4.4.1 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 10 66 4.4.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 11 67 4.4.3 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 11 68 4.5 element . . . . . . . . . . . . . . . . . . . . . 12 69 4.5.1 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 12 70 4.5.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 13 71 4.5.3 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 13 72 4.6 element . . . . . . . . . . . . . . . . . . . . . . . . 13 73 4.6.1 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 13 74 4.6.2 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 14 75 4.6.3 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 14 76 5. Client Access . . . . . . . . . . . . . . . . . . . . . . . 16 77 5.1 TCP Socket . . . . . . . . . . . . . . . . . . . . . . . . . 16 78 5.2 Transport Layer . . . . . . . . . . . . . . . . . . . . . . 16 79 5.3 Authentication . . . . . . . . . . . . . . . . . . . . . . . 16 80 5.4 Messages . . . . . . . . . . . . . . . . . . . . . . . . . . 16 81 5.5 Presence . . . . . . . . . . . . . . . . . . . . . . . . . . 16 82 5.6 Roster . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 83 5.7 Presence Subscriptions . . . . . . . . . . . . . . . . . . . 17 84 6. Servers . . . . . . . . . . . . . . . . . . . . . . . . . . 18 85 6.1 Connections . . . . . . . . . . . . . . . . . . . . . . . . 18 86 6.2 DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 87 7. Security Considerations . . . . . . . . . . . . . . . . . . 19 88 7.1 SSL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 89 7.2 Secure Identity and Encryption . . . . . . . . . . . . . . . 19 90 7.3 Client Connections . . . . . . . . . . . . . . . . . . . . . 19 91 7.4 Presence . . . . . . . . . . . . . . . . . . . . . . . . . . 19 92 8. Scaling Considerations . . . . . . . . . . . . . . . . . . . 20 93 8.1 TCP Sockets . . . . . . . . . . . . . . . . . . . . . . . . 20 94 8.2 Server Farms . . . . . . . . . . . . . . . . . . . . . . . . 20 95 8.3 Client Optimizations . . . . . . . . . . . . . . . . . . . . 20 96 8.4 Server Restrictions . . . . . . . . . . . . . . . . . . . . 20 97 9. Extended Functionality . . . . . . . . . . . . . . . . . . . 21 98 9.1 Services (Agents/Transports) . . . . . . . . . . . . . . . . 21 99 9.2 MIME Transfers . . . . . . . . . . . . . . . . . . . . . . . 21 100 9.3 XML Medium . . . . . . . . . . . . . . . . . . . . . . . . . 21 101 9.4 Session Initialization . . . . . . . . . . . . . . . . . . . 22 102 9.5 Client Access . . . . . . . . . . . . . . . . . . . . . . . 22 103 10. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 23 104 10.1 Minimal Client . . . . . . . . . . . . . . . . . . . . . . . 23 105 10.2 Basic Client . . . . . . . . . . . . . . . . . . . . . . . . 23 106 10.3 Extending . . . . . . . . . . . . . . . . . . . . . . . . . 25 107 11. IMPP and Interoperability Notes . . . . . . . . . . . . . . 28 108 11.1 Requirements Conformance . . . . . . . . . . . . . . . . . . 28 109 11.2 Interoperability . . . . . . . . . . . . . . . . . . . . . . 28 110 References . . . . . . . . . . . . . . . . . . . . . . . . . 29 111 Author's Address . . . . . . . . . . . . . . . . . . . . . . 30 112 A. The Jabber Protocol DTD . . . . . . . . . . . . . . . . . . 31 113 B. XML Streams DTD . . . . . . . . . . . . . . . . . . . . . . 33 114 C. element . . . . . . . . . . . . . . . . . . . . . . 34 115 C.1 Attributes . . . . . . . . . . . . . . . . . . . . . . . . . 34 116 C.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 35 117 D. Info/Query Namespaces . . . . . . . . . . . . . . . . . . . 36 118 D.1 Simple Client Authentication - jabber:iq:auth . . . . . . . 36 119 D.1.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 36 120 D.1.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 37 121 D.2 Roster (Contact List) Management - jabber:iq:roster . . . . 37 122 D.2.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 37 123 D.2.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 38 124 D.3 Registration Request - jabber:iq:register . . . . . . . . . 39 125 D.3.1 Children . . . . . . . . . . . . . . . . . . . . . . . . . . 39 126 D.3.2 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 40 127 E. X Namespaces . . . . . . . . . . . . . . . . . . . . . . . . 41 128 E.1 Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 41 129 F. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . 42 130 Full Copyright Statement . . . . . . . . . . . . . . . . . . 43 132 1. Introduction 134 1.1 What is Jabber? 136 At the core, Jabber is an API to provide instant messaging and 137 presence functionality independent of data exchanged between 138 entities. The primary use of Jabber is to give existing applications 139 instant connectivity through messaging and presence features, 140 contact list capabilities, and back-end services that transparently 141 enrich the available functionality. 143 Essentially, Jabber defines an abstraction layer utilizing XML[1] to 144 encode the common essential data types. This abstraction layer is 145 managed by an intelligent server which routes data between the 146 client APIs and the backend services that translate data from remote 147 networks or protocols. By using this compatible abstraction layer, 148 Jabber can provide many aspects of an Instant Messaging (IM) and/or 149 Presence service in a simplified and uniform way. 151 1.2 Background and History 153 Jabber began in early 1998 as an open source project to both enable 154 and ease the construction of compatible IM clients. The intention 155 was that a client would only have to understand simple standard XML 156 data types for messages and presence, and be able to focus on being 157 an IM client, not on the complexity of dealing with the various IM 158 networks. To avoid requiring the overhead of a typical "loadable 159 module" API, the XML abstraction layer was made available to the 160 client via a standard TCP[2] socket. 162 The chosen model is essentially that of a typical client-server, 163 where the clients utilizing the API access it as a server via TCP. 164 Certain server components have a very high frequency of upgrades, 165 based on the adapting protocols with which they translate. The 166 server was also then shared on a single host to a group of users to 167 reduce the maintenance requirements for the client API. This also 168 significantly reduces the deployment overhead for clients, since 169 they simply need a single TCP socket to the server. 171 1.3 Evolution 173 As Jabber was developed and the architecture evolved, it became 174 clear that a simple and flexible means of assigning identity to the 175 various components was required. This started with clients, which 176 are required to have a unique identity and be authorized to access 177 the server API. The server was also assigned a unique identity, as 178 were the individual components on the server side. 180 Due to the role that the server plays with respect to the clients, 181 and and due to the need to have a clear and established means of 182 identitfying individual entities, the natural evolution of the 183 server was to simply become an intelligent router. Not only does the 184 server manage and route the XML data between the client API and the 185 abstraction layer, but it also routes data directly between clients 186 acting as an independent IM server for all clients. By assigning 187 server identity as a hostname, servers are also able to route data 188 directly to each other and their connected clients, thereby creating 189 a new, inherently open IM network out of all the individual 190 installed servers and clients. 192 Additionally, to simplify clients as well as to add functionality to 193 the server, the server began to act as an XML repository by storing 194 XML for the client. This enables the server to store the contact 195 list (roster), offline messages, profile information such as a XML 196 vCard[3], or custom client preferences and data (bookmarks, 197 settings, etc.). 199 1.4 Today 201 After two years of full-time development by a large group of 202 individuals around the world: 204 o The abstraction layer and all APIs are fully implemented. 206 o The XML data types are well defined (Appendix A). 208 o Clients for all major platforms and environments are available or 209 being developed. See http://jabbercentral.com/clients/ for a 210 database of popular clients. 212 o The GPL[4]/LGPL[5] licensed Jabber Server[14] is fully functional. 214 o Numerous working server-side components (transports) exist or are 215 in public development for popular services such as ICQ, AOL IM, 216 Microsoft Messenger, Yahoo! Messenger, IRC, SMTP, RSS (news 217 headlines), and more. 219 See http://jabber.org/ for more information. 221 2. Architecture Overview 223 Connection Map 225 T1 = N1 = C3 226 / 227 C1 -- S1 - S2 = C4 228 / \ 229 C2 - T2 231 Above is a map of the typical connections within the Jabber 232 Architecture. 234 o "-" represents the Jabber XML Protocol. 236 o "=" represents any other protocol. 238 o C1, C2 - Jabber Clients. 240 o C3 - Client on another IM Network. 242 o C4 - Client using an alternate protocol to access the Jabber 243 Server. 245 o S1 - a Jabber Server. 247 o T1 - Transport, translating between the Jabber XML Protocol and 248 the protocol used on another IM Network. 250 o T2 - Transport providing other real-time data to Jabber, such as 251 log notifications or headline news feeds. 253 o N1 - third party IM Network. 255 2.1 Server 257 The Server acts as an intelligent abstraction layer, managing the 258 authorized client connections and connections to other Servers and 259 Transports. All of the XML data is routed to the appropriate 260 entities, or handled directly via internal modules on behalf of an 261 entity. Servers can also utilize their own protocol to provide 262 access to their clients. 264 2.2 Client 266 Clients may directly connect to the Server and use the XML Protocol 267 to take full advantage of the functionality available. A client may 268 also be customized to only operate with one server, or use an 269 alternate protocol to access a custom server. Clients of alternate 270 IM Networks are also part of the Architecture, made accessable via a 271 Transport to that IM Network. 273 2.3 Transport 275 A Tranport is a special-purpose Server. The primary function of a 276 Transport is to translate the Jabber XML protocol to the protocol of 277 a third party IM Network as well as translate the return data back 278 to XML. Transports may also function to provide access to additional 279 back-end functionality such as a real-time alert system, device 280 presence, pager delivery, language translation or other custom 281 needs. 283 3. Entity Identification 285 3.1 Three Tier 287 The basic concept behind all identity within Jabber is a three-tier 288 structure: the host, node, and resource. This allows a host to 289 manage its nodes, and allows each node to have independent 290 addressable resources. The most common use of this structure is as a 291 server, user, and connection identifier. 293 3.1.1 Host (server) 295 The basic required component of every ID is a Host. The Host is a 296 standard DNS hostname and not case sensitive. 298 3.1.2 Node (user) 300 Each Host can be addressed with individual Nodes, or users. Each 301 user is specific to the Host it is associated with, similar to 302 email. Usernames are restricted to 255 characters, and the following 303 ASCII characters are invalid: any character with a decimal value 304 less than 33 or in the following set [:@<>'"&]. Case is preserved, 305 but not used when comparing/matching. A Node address looks similar 306 to email: node@host. Node addresses are intended to be human 307 readable/usable in the same manner that email addresses are used 308 today. 310 3.1.3 Resource 312 Resources are specific to a Node. All characters are allowed and 313 there are no restrictions. Resource addresses are similar to the 314 path part of a URL. Resources are used to address specific 315 connections (since a Jabber server allows a user to be connected 316 from multiple resources simultaneously), devices, or inboxes. An 317 example Resource address: node@host/resource. Resource addresses are 318 intended to be hidden from a user and only used at the 319 software/protocol level. 321 3.2 URI 323 A Jabber identifier conforms to RFC 2396[6], "Uniform Resource 324 Identifiers (URI): Generic Syntax" by prepending a "jabber://" to 325 any address. When compared to other URIs, it acts like a hybrid 326 mailto: and http:// URI, offering both a user identity and an 327 optional path/resource specification. 329 Originally the abstraction layer used a Jabber URI within the 330 protocol, but this was dropped until that use could undergo further 331 review. Some of the reasoning was that the protocol was not capable 332 of handling any other URI, in the sense that SMTP does not directly 333 handle mailto: URIs within the protocol. Also, there was a tendency 334 to want to create proprietary custom URIs (such as 'icq:' or 335 'talk:') within the protocol. Enabling the abstraction layer to use 336 full URIs directly was deferred until such a use could be 337 standardized and agreed upon. 339 4. XML 341 4.1 Overview 343 XML[1] is used to define the common basic data types: message and 344 presence. Essentially, XML is the core enabling technology within 345 the abstraction layer, providing a common language with which 346 everything can communicate. XML allows for painless growth and 347 expansion of the basic data types and almost infinite customization 348 and extensibility anywhere within the data. Many solutions already 349 exist for handling and parsing XML, and the XML Industry has 350 invested significant time in understanding the technology and 351 ensuring full internationalization. 353 4.2 Namespaces 355 XML Namespaces[7] are used within all Jabber XML to create strict 356 boundaries of data ownership. The basic function of namespaces is to 357 separate different vocabularies of XML elements that are 358 structurally mixed together. By ensuring that Jabber's XML is 359 namespace-aware, it allows any XML defined by anyone to be 360 structurally mixed with any data element within the protocol. This 361 feature is relied upon frequently within the protocol to separate 362 the XML that is processed by different components. 364 4.3 Validation 366 Provided with this specification is a reference DTD for Jabber. It 367 is an important note that the Jabber server is not responsible for 368 validating the XML elements forwarded to a new user - an 369 implementation may choose to provide only validated data elements 370 but is not required to. 372 Clients should not rely on the ability to send data which does not 373 conform to the DTD, and should handle any non-conformant elements or 374 attributes on the incoming stream by ignoring them. 376 4.4 element 378 Messages are most similar in function to an email message. 380 4.4.1 Attributes 382 o to - Specifies to whom the message is intended to be delivered 383 to. 385 o from - Specifies the sender of the message. Server set to prevent 386 spoofing. 388 o type - Used to express the context as to what format the message 389 should be displayed in. If no type is set, clients default to a 390 type="normal". Values include: 392 * normal - Single message dialog, similar to original ICQ 393 messages. 395 * chat - Traditional two-way chat similar to AIM or IRC CTCP 396 Chat. 398 * groupchat - Group interface similar to an IRC channel with 399 multiple participants. 401 * headline - Ticker or active list of items (news, stock market). 403 * error - See the error element (Appendix C). 405 4.4.2 Children 407 o body - Contains the textual contents of the message for user 408 display. No attributes. 410 o subject - Contains the subject of the message. Similar to an 411 email subject. No attributes. 413 o thread - A random string generated by the originating client and 414 copied back in replies. Used for tracking a conversation thread. 416 o error - See the error element (Appendix C). 418 4.4.3 Examples 420 The following examples have been server processed and contain the 421 'from' attribute. 423 A simple message: 425 426 Angels and Ministers of Grace, defend us! 427 428 Complete chat message: 430 431 Plotting 432 Here, sweet lord, at your service. 433 100052 434 436 4.5 element 438 Presence is used to express the current status from one entity to a 439 group of entities. The characteristics of presence are most similar 440 to that of a network game where the data travels from one host to 441 the server, and then broadcast to the other hosts participating in 442 that game. 444 4.5.1 Attributes 446 o to - Specifies for whom the presence is bound. If none is 447 specified, the server receives the presence. 449 o from - Whom the presence is from. Server set to prevent spoofing. 451 o id - A unique identifier for the presence. Sender of the presence 452 sets this attribute. 454 o type - Describes the type of presence. No 'type' attribute 455 implies "available" presence or current status. Allowable types 456 include: 458 * unavailable - Signals that the user is no longer available. 460 * subscribe - An attempt to subscribe to the recipient's 461 presence. 463 * subscribed - The sender has enabled the recipient to receive 464 their presence. 466 * unsubscribe - An unsubscription request. The server handles 467 the actual unsubscription, but clients receive a presence 468 element for notification reasons. 470 * unsubscribed - The subscription has been cancelled. 472 * probe - A server-to-server query to request an entity's 473 current presence. 475 4.5.2 Children 477 o show - Describes a user's exact availability. Must be one of: 479 * away - User is away from the client software temporarily. 481 * chat - User is free to chat. 483 * xa - User is away for an extended period (eXtended Away). 485 * dnd - User does not wish to be disturbed (Do Not Disturb). 487 o status - Custom availability message. Used in conjunction with 488 the show element to give a detailed description of availability. 490 4.5.3 Examples 492 Initial presence sent to server upon login to express default 493 availability: 495 497 Full-blown presence: 499 500 xa 501 Gone to England 502 504 4.6 element 506 Info/Query, or IQ, is a simple structured conversation wrapper. Just 507 as HTTP is a request-response medium, IQ enables an entity to make a 508 request and receive a response from another entity. The actual 509 content of the request and response is defined by another namespace 510 within the IQ. 512 4.6.1 Attributes 514 o to - Specifies for whom the IQ is bound. 516 o from - Specifies from whom the IQ is sent. Server set to prevent 517 spoofing. 519 o id - A unique identifier for the IQ for tracking the query 520 exchange. Sender of the IQ sets this attribute, which is returned 521 in the response. 523 o type - The 'type' attribute has several preset values. Each 524 indicates a distinct step within an IQ conversation. 526 * get - Indicates that the current query is a question or search 527 for information. 529 * set - This query contains data intended to set values or 530 replace existing values. 532 * result - This is a successful response to a get/set query. The 533 IQ usually contains no further information on a successful 534 result. 536 * error - The query failed. See the error element (Appendix C). 538 4.6.2 Children 540 In the strictest terms, the iq element contains no children since it 541 is a vessel for XML in another namespace. In operation, a query 542 element is usually contained within the iq element as defined by its 543 own separate namespace. See Appendix D. 545 4.6.3 Examples 547 The following examples are distinct parts of an IQ conversation for 548 registration with jabber:iq:register (Appendix D.3) namespace. 550 Client request for registration information to a server service 551 (service.denmark): 553 554 555 557 Server response with registration fields required: 559 560 561 Choose a username and password to register with this server. 562 563 564 565 106c0a7b5510f192a408a1d054150ed1065e255a 566 567 568 Client request to register for an account: 570 571 572 hamlet 573 hamlet@denmark 574 gertrude 575 106c0a7b5510f192a408a1d054150ed1065e255a 576 577 579 Successful registration: 581 583 Failed registration: 585 586 Not Acceptable 587 589 5. Client Access 591 5.1 TCP Socket 593 Clients connect to the server on TCP port 5222. The connection from 594 the client to the server is persistent and maintains the presence 595 state of the client after authentication. The server delivers all 596 data to the client via this socket. If it is broken because of a 597 network error, a client should reasonably attempt to reestablish the 598 link with the server. Clients are never required to accept an 599 incoming network connection, or establish a connection to any host 600 other than the server. 602 5.2 Transport Layer 604 An XML Stream (Appendix B) is simply the direct association of an 605 XML document with a single TCP socket, and is used as the default 606 transport layer to move data between clients and servers. When the 607 socket is opened, the first data sent is the opening root element of 608 the XML document representing that stream. All XML data within the 609 document is continually parsed as available via the socket. When a 610 top-level element is closed, it can then be further processed by the 611 application. This simple streaming transport layer reduces the 612 complexity of implementing applications that use Jabber, and 613 satisfies all the demands of the communication with the server. 615 5.3 Authentication 617 The client initially sends an IQ packet over the XML Stream to the 618 server with the jabber:iq:auth namespace (Appendix D.1). This 619 provides the credentials to access the server, which are either 620 returned with an error or accepted. After accepting the credentials, 621 the connection is then authorized to send and receive data. 623 5.4 Messages 625 The client sends a message with a valid 'to' attribute. The server 626 processes the 'to' address and adds a 'from' address, then attempts 627 to deliver to the recipient. Messages that fail for any reason are 628 returned as an error. Messages may be delivered to the client from 629 the server at any time, with an appropriate 'from' attribute set. 631 5.5 Presence 633 The current presence for the client is updated by sending presence 634 to the server without a 'to' attribute. The server delivers this to 635 the authorized recipients based on the subscription status as stored 636 in the roster. The client will not receive presence from other 637 entities until it has provided some form of available presence to 638 the server. 640 5.6 Roster 642 The client can send an IQ get with the jabber:iq:roster namespace 643 (Appendix D.2) at any time, and will receive a result containing all 644 the items that the server has stored for that user. Changes to any 645 one item can be made by submitting that changed item via an IQ set 646 in the same namespace. 648 Since Jabber allows multiple connections for a single user, the 649 roster may change by one connection and that change needs to be 650 updated to the other connections. At any time, the server may do a 651 "Roster Push" by sending an IQ set to the client containing the 652 new/updated item[s]. 654 5.7 Presence Subscriptions 656 Presence information is made available only to approved entites. 657 This approval is managed by a simple subscription system, using the 658 presence element (Section 4.5). There are four distinct types of 659 subscription requests: 661 subscribe - A request to be approved for receiving all future 662 presence changes 664 unsubscribe - A request to no longer receive any presence changes 666 subscribed - A notice that a subscription has been created and 667 all future presence changes will be sent 669 unsubscribed - A notice that a subscription has been removed, and 670 no further presence changes will be sent 672 Request to subscribe to a user's presence: 674 676 Response to a subscribe request: 678 680 6. Servers 682 The abstraction layer that Jabber provides includes the ability to 683 individually address servers, and in fact relies on this ability for 684 all external sources of data and functionality. This model then 685 significantly expands the definition of a server to include 686 intelligent agents, transports, device gateways, or any interactive 687 data source. The additional expansion creates a need for flexibility 688 in how server-side entities communicate. 690 The server to server communication happens independent of the 691 client, and can use any protocol or communication means available. 692 The server may choose to implement a loadable module interface to 693 allow components (which might be addressed as a server) to interact 694 with clients, or two servers may choose to tunnel their data via an 695 alternate transport layer. In fact, the Jabber Server uses an 696 alternate communication library, libetherx, which manages 697 connections between the server and trusted transports in a more 698 efficient model. Although any protocol can be used between servers, 699 at least one common basic one must exist so that there can be some 700 guarantee of interoperability. 702 6.1 Connections 704 Servers interconnect on TCP port 5269. There is no required state 705 held between servers, so the connection is stateless and may be 706 dropped at any time, but it is recommended that the connection 707 persist based on the freqency of the interaction. Data is sent only 708 over a locally originated connection to another server. All data 709 from other servers is delivered via connections from those servers. 711 6.2 DNS 713 All connections are made directly to the IP address of the hostname 714 in the Entity Identifier (Section 3). If the connection to this host 715 fails, servers attempt an MX record lookup. A connection attempt is 716 made to each found MX record. In order to not conflict with SMTP and 717 be able to operate a Jabber server on a separate host, a list of MX 718 records is processed in reverse priority (highest number first). 720 7. Security Considerations 722 7.1 SSL 724 Servers can optionally support normal SSL[8] connections for added 725 security on port 5223 for client connections and 5270 for server 726 connections. 728 7.2 Secure Identity and Encryption 730 Clients may optionally support signing and encrypting messages and 731 presence by using PGP[15]/GnuPG[16]. 733 The Jabber model specifically does NOT require trust in the remote 734 servers or server-server trust. Although there may be benefits to a 735 trusted server model (this issue is hotly debated), the direct 736 client-client trust is already in use in email and allows those who 737 desire a higher level of security to use it without requiring the 738 significant increase in complexity throughout the architecture. 740 7.3 Client Connections 742 The IP address and method of access of clients is never made 743 available, nor are any connections other than the original server 744 connection required. This protects the client hosts from direct 745 attack or identification by third parties, and allows the service 746 provider to utilize an alternate protocol or provide another method 747 of access to its clients. 749 7.4 Presence 751 Presence subscriptions are enforced by the user's server. Only the 752 approved entities are able to discover a user's availability. 754 8. Scaling Considerations 756 8.1 TCP Sockets 758 A single, modern UNIX machine with proper tuning can handle 100,000 759 connections simultaneously. In c10k[10], Dan Kegel details how UNIX 760 machines can be properly configured to handle large numbers of TCP 761 connections. 763 8.2 Server Farms 765 By sending the 302 redirect error as response to an authorization 766 attempt, clients can be intelligently re-routed to a group of 767 servers. A large-scale Jabber Server deployment will function in a 768 manner very similar to that of a web server farm, with each server 769 handling a moderate load and adding server hardware as demand grows. 771 8.3 Client Optimizations 773 Custom clients can also make additional optimizations to reduce 774 server load, such as idle auto-disconnect or local caching of server 775 data that changes infrequently. These changes would be specific to 776 the service requiring them and the clients supporting that service. 778 8.4 Server Restrictions 780 The server can apply limits to various aspects of the client 781 functionality: roster size, offline message sizes, simultaneous 782 session restrictions, rate limits, etc. These limits require no 783 changes to clients and can be enforced on any server. 785 9. Extended Functionality 787 9.1 Services (Agents/Transports) 789 The Jabber Architecture is designed to transparently provide access 790 to independent data sources, so it is inherently geared to be 791 extended in this way. Any server-side entity can easily participate 792 in the real-time generation and delivery of XML. These entities can 793 expose simple data sources such as instant calendaring events or log 794 notifications, or enable access to an existing group of individuals 795 by translating to an alternate protocol. All the new functionality 796 is immediately available to any application utilizing Jabber or any 797 entity available via the abstraction layer. 799 9.2 MIME Transfers 801 All MIME objects, such as files, are transferred externally to the 802 Jabber XML. MIME[11] is the dominant and successful method for 803 transferring such data, and accessible in almost every environment. 804 The Jabber XML Protocol is used to exchange http:// URLs between 805 entities needing to exchange a MIME object. The jabber:x:oob can be 806 inserted into messages and presence to express a MIME attachment. 807 The jabber:iq:oob can be sent directly to another entity to express 808 a single immediate MIME transfer. Recipient entities are then able 809 to make the judgment whether they are able to handle the MIME 810 objects, before incurring the cost of retreiving them. 812 9.3 XML Medium 814 As mentioned, the use of XML Namespaces allows any entity to insert 815 any custom XML in an alternate namespace anywhere within the 816 protocol. This flexibiliy is used frequently within clients and 817 servers, and enables custom applications to utilize the access 818 Jabber provides to instantly exchange structured data with each 819 other. 821 Because Jabber is an XML medium, many of the new XML data formats 822 can be immediately deployed on top of Jabber. This includes vCard 823 XML[3], SyncML[17], XML/EDI[18], VoiceXML[19], and many more. 825 The server can also act as an XML repository. The Jabber Server 826 supports this via the jabber:iq:private namespace, which can contain 827 any other XML that is stored on the server for the client. This can 828 be used to store client preferences, bookmarks, game states, address 829 books, notes, and any other structured data. 831 A message with some custom XML included 833 834 Angels and Ministers of Grace, defend us! 835 836 abcd 837 838 840 9.4 Session Initialization 842 Users often use the existing presence and contact list to manually 843 initiate other interactive software (e.g., "Hamlet, ready to start 844 the game? I'm on and ready!"). By including custom XML or sending a 845 URI, this could be automated within the client or application. 846 Common uses are voice and video conferencing, games, collaborative 847 tools, calendaring, and more. 849 9.5 Client Access 851 By utilizing the XML abstraction layer available as a client, 852 additional gateways can be built to provide access to Jabber 853 functionality for existing devices and software. Already, HTTP and 854 IRC client gateways exist, with telnet and WAP[20] gateways under 855 construction. In the future, devices with limited functionality or 856 restricted access could use a custom gateway to access the messaging 857 and presence features available on the server. 859 10. Examples 861 All data is sent over the TCP socket to denmark:5222. 863 SEND: indicates that the stream is going to the server while RECV: 864 indicates that the stream is coming from the server to the client. 866 10.1 Minimal Client 868 A simple example: 870 SEND: 875 RECV: 881 SEND: 882 SEND: 883 SEND: hamlet 884 SEND: gertrude 885 SEND: Castle 886 SEND: 887 SEND: 889 RECV: 891 SEND: 892 SEND: The air bites shrewdly; it is very cold. 893 SEND: 895 RECV: 911 RECV: 917 SEND: 918 SEND: 919 SEND: hamlet 920 SEND: gertrude 921 SEND: Castle 922 SEND: 923 SEND: 925 RECV: 927 SEND: 928 SEND: 929 SEND: 931 RECV: 932 RECV: 934 RECV: 935 RECV: 936 RECV: Friends 937 RECV: 938 RECV: 939 RECV: 941 SEND: 943 RECV: 944 RECV: chat 945 RECV: 947 RECV: 948 RECV: How does my good Lord Hamlet? 949 RECV: 951 SEND: 952 SEND: Well, God-a-mercy. 953 SEND: 955 RECV: 956 RECV: Do you know me, my lord? 957 RECV: 959 SEND: 960 RECV: 962 Note that only polonius@denmark is online at this time, thus no 963 presence was received from other roster items. 965 10.3 Extending 967 A more advanced example that includes adding users to the roster, 968 two new users coming online, a user changing status, and a client 969 version request. 971 SEND: 976 RECV: 982 SEND: 983 SEND: 984 SEND: hamlet 985 SEND: gertrude 986 SEND: Courtyard 987 SEND: 988 SEND: 990 RECV: 992 SEND: 993 SEND: 994 SEND: 996 RECV: 997 RECV: 999 RECV: 1000 RECV: 1001 RECV: Friends 1002 RECV: 1003 RECV: 1004 RECV: 1005 SEND: 1007 RECV: 1008 RECV: chat 1009 RECV: 1011 RECV: 1012 RECV: away 1013 RECV: Busy with project. 1014 RECV: 1016 RECV: 1017 RECV: 1019 SEND: 1020 SEND: 1022 RECV: 1023 RECV: 1024 RECV: 1025 RECV: 1026 RECV: 1028 RECV: 1029 RECV: 1030 RECV: 1031 RECV: 1032 RECV: 1034 RECV: 1035 RECV: 1037 SEND: 1038 SEND: Well, God-a-mercy. 1039 SEND: 1041 RECV: 1042 RECV: My honoured lord! 1043 RECV: 1045 RECV: 1046 RECV: My most dear lord! 1047 RECV: 1049 SEND: 1050 SEND: 1051 SEND: 1053 RECV: 1054 RECV: 1055 RECV: Gabber 1056 RECV: 0.6.1 1057 RECV: Debian GNU/Linux 2.2.16 1058 RECV: 1059 RECV: 1061 SEND: 1062 RECV: 1064 11. IMPP and Interoperability Notes 1066 11.1 Requirements Conformance 1068 The implemented protocol presented in this memo is in near 1069 conformance to RFC 2778[12], "A Model for Presence and Instant 1070 Messaging" and RFC 2779[13], "Instant Messaging / Presence Protocol 1071 Requirements." Notable differences are outlined in the following 1072 section. It should be noted that the Jabber protocol has been in 1073 evolution for approximately two years as of the date of this memo, 1074 thus this protocol has not been designed in response to RFCs 2778 1075 and 2779. 1077 o RFC 2779, section 2.5 - Complete conformance with these 1078 requirements can be obtained by using a standard public key 1079 infrastructure such as GnuPG or PGP. 1081 o RFC 2779, section 4.1, paragraph 10 - all MIME data is delivered 1082 via HTTP. 1084 11.2 Interoperability 1086 Jabber already provides complete interoperability, but at the cost 1087 of reverse engineering a 3rd party IM network protocol and operating 1088 a local translator to that protocol. The form of interoperability 1089 that Jabber offers is also restricted to the clients and requires 1090 the user to have a valid account on each IM network. It is the goal 1091 and desire of the Jabber development effort to increase the reach of 1092 the XML abstraction layer to overcome these limitations and reduce 1093 the reliance on local transports. The Jabber Development Team is 1094 ready and eager to interoperate directly at the server level with 1095 any other IM network and also willing to do much of the work to 1096 assist with this effort, as it reduces the complexity of the 1097 transport and adds significant new functionality to both sides. 1099 Using MSN Messenger as a example, full interoperability can be 1100 achieved with a relatively simple addition to their IM network. The 1101 MSN Messenger service would directly translate the Jabber XML to and 1102 from the native format at the server level, as well as ensuring that 1103 the MSN Messenger client software would be able to address 1104 non-native users (it already utilizes a user@host based format, 1105 which may enable interoperability without any changes to client 1106 software). The actual details of the translation depend on the 1107 native data format and accessibility within the network of servers, 1108 but the XML is well defined and functionality across both networks 1109 is similiar enough for an almost direct mapping. This level of 1110 interoperability enables all Jabber and MSN Messenger users to 1111 communicate instantly and transparently without modifying parts of 1112 either network. 1114 References 1116 [1] World Wide Web Consortium, "Extensible Markup Language (XML) 1117 1.0", W3C xml, February 1998, 1118 . 1120 [2] University of Southern California, "Transmission Control 1121 Protocol", RFC 793, September 1981, 1122 . 1124 [3] The Jabber.org Project, "vCard XML", March 2000, 1125 . 1127 [4] Free Software Foundation, "GNU General Public License", June 1128 1991, . 1130 [5] Free Software Foundation, "GNU Library General Public 1131 License", June 1991, . 1133 [6] Berners-Lee, T., Fielding, R.T. and L. Masinter, "Uniform 1134 Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1135 1998, . 1137 [7] World Wide Web Consortium, "Namespaces in XML", W3C xml-names, 1138 January 1999, 1139 . 1141 [8] Freier, A., Karlton, P. and P. Kocher, "The SSL Protocol - 1142 Version 3.0", November 1996, 1143 . 1145 [9] Fielding, R., Gettys, J., Mogul, J., Frystyk, H. and T. 1146 Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 1147 2068, January 1997, . 1149 [10] Kegel, D., "The C10K Problem", June 2000, 1150 . 1152 [11] Borenstein, N. and N. Freed, "MIME (Multipurpose Internet Mail 1153 Extensions) Part One: Mechanisms for Specifying and Describing 1154 the Format of Internet Message Bodies", RFC 1521, September 1155 1993, . 1157 [12] Day, M., Rosenberg, J. and H. Sugano, "A Model for Presence 1158 and Instant Messaging", RFC 2778, February 2000, 1159 . 1161 [13] Day, M., Aggarwal, S., Mohr, G. and J. Vincent, "A Model for 1162 Presence and Instant Messaging", RFC 2779, February 2000, 1163 . 1165 [14] http://jabber.org 1167 [15] http://www.pgp.com 1169 [16] http://www.gnupg.org 1171 [17] http://www.syncml.org 1173 [18] http://www.xmledi-group.org/ 1175 [19] http://www.voicexml.org/ 1177 [20] http://www.wapforum.org/ 1179 Author's Address 1181 Jeremie Miller 1182 The Jabber.org Project 1183 414 DeLong St. 1184 Cascade, IA 52033 1185 US 1187 Phone: 319-852-3464 1188 EMail: jeremie@jabber.org 1190 Appendix A. The Jabber Protocol DTD 1192 1198 1200 1201 1202 1204 1206 1207 1213 1215 1217 1219 1221 1222 1229 1231 1233 1237 1238 1240 1242 1244 1245 1252 Appendix B. XML Streams DTD 1254 1255 1262 1264 Appendix C. element 1266 A standard error element is used for failed processing of messages 1267 and iq. This element is a child of the failed element. 1269 C.1 Attributes 1271 o code - a numerical error code corresponding to a specific error 1272 description. The numerical codes used are nearly synchronous with 1273 HTTP error codes: 1275 * 302 - Redirect 1277 * 400 - Bad Request 1279 * 401 - Unauthorized 1281 * 402 - Payment Required 1283 * 403 - Forbidden 1285 * 404 - Not Found 1287 * 405 - Not Allowed 1289 * 406 - Not Acceptable 1291 * 407 - Registration Required 1293 * 408 - Request Timeout 1295 * 500 - Internal Server Error 1297 * 501 - Not Implemented 1299 * 502 - Remote Server Error 1301 * 503 - Service Unavailable 1303 * 504 - Remote Server Timeout 1305 C.2 Examples 1307 Message error: 1309 1310 Angels and Ministers of Grace, defend us! 1311 Not Found 1312 1314 IQ Error: 1316 1317 1318 hamlet 1319 hamlet@denmark 1320 gertrude 1321 106c0a7b5510f192a408a1d054150ed1065e255a 1322 1323 Remote Server Error 1324 1326 Appendix D. Info/Query Namespaces 1328 Numerous Info/Query (Section 4.6) namespaces have been implemented 1329 to faciliate exchange of information between Jabber entities. 1330 Namespaces currently implemented within the Jabber server include: 1332 o Simple Client Authentication (jabber:iq:auth) 1334 o Agent Properties (jabber:iq:agent) 1336 o Registration Requests (jabber:iq:register) 1338 o Roster (Contact List) Management (jabber:iq:roster) 1340 o Available Agents List (jabber:iq:agents) 1342 o Out Of Band Data (jabber:iq:oob) 1344 o Client Time (jabber:iq:time) 1346 o Client Version (jabber:iq:version) 1348 o Temporary vCard (vcard-temp) 1350 Note that the Temporary vCard namespace is being used until the 1351 vCard XML standard has been finalized. 1353 The following subsections describe the three most fundamental 1354 extensions. 1356 D.1 Simple Client Authentication - jabber:iq:auth 1358 The jabber:iq:auth namespaces provides a simple mechanism for 1359 clients to authenticate and create a resource representing their 1360 connection to the server. 1362 D.1.1 Children 1364 o username - the unique user name for this user. 1366 o password - the secret key or passphrase for the user account. 1368 o digest - send a password in a SHA1 hash instead of clear text 1369 password. 1371 o resource - unique value to represent current connection. 1373 D.1.2 Examples 1375 The following is a complete example of how a client authenticates 1376 with the server. 1378 Client sends user information: 1380 1381 1382 hamlet 1383 gertrude 1384 Castle 1385 1386 1388 Server confirms login: 1390 1392 D.2 Roster (Contact List) Management - jabber:iq:roster 1394 Provides a simple method for server-side contact list management. 1395 Upon connecting to the server, clients should request for the roster 1396 using jabber:iq:roster. Since the roster may not be desirable for 1397 all clients (e.g., cellular phone client), the client request of the 1398 roster is optional. 1400 D.2.1 Children 1402 o item - a specific roster item (contact) has the following 1403 attributes: 1405 * jid - the complete JID (Jabber ID) of the user that this item 1406 represents 1408 * subscription - the current status of the subscription related 1409 to this item. May have a value of: 1411 + none - no subscription. 1413 + from - this entity has a subscription to the user. 1415 + to - the user has a subscription to this entity. 1417 + both - subscription is both to and from. 1419 + remove - item is to be removed. 1421 * ask - the current status of a request to this item. May be one 1422 of: 1424 + subscription - the user is asking this item for a 1425 subscription. 1427 + unsubscription - the user is asking this item for an 1428 unsubscription. 1430 This element may contain one or more instances of the following 1431 element: 1433 * group - contains a user-specified user group name. 1435 D.2.2 Examples 1437 Client request for current roster: 1439 1440 1441 1443 Server response to client query: 1445 1446 1447 1448 Family 1449 1450 1451 Friends 1452 1453 1454 1455 1456 Client adding new items and modifying an entry: 1458 1459 1460 1461 Visitors 1462 1463 1464 Visitors 1465 1466 1467 Family 1468 Royalty 1469 1470 1471 1473 The server would then respond with the new roster information, plus 1474 an IQ result: 1476 1477 1478 1479 Visitors 1480 1481 1482 Visitors 1483 1484 1485 Family 1486 Royalty 1487 1488 1489 1490 1492 D.3 Registration Request - jabber:iq:register 1494 Through jabber:iq:register, clients can register with the Jabber 1495 server itself or with new services. 1497 D.3.1 Children 1499 Note that while numerous fields are available, only the ones 1500 returned by the server are required for registration. 1502 o username 1504 o password 1505 o name 1507 o email 1509 o address 1511 o city 1513 o state 1515 o zip 1517 o phone 1519 o url 1521 o date 1523 o misc 1525 o text 1527 o instructions - contains server provided instructions for 1528 registration. 1530 o key - a unique key provided by the server, required for the 1531 entire registration process. 1533 D.3.2 Examples 1535 A complete example is provided in the IQ examples (Section 4.6.3). 1537 Appendix E. X Namespaces 1539 For sending information that does not require the IQ structure, the 1540 X namespace series has been implemented. Clients can use this type 1541 of namespace to send URLs, Roster (Contact List) items, Offline 1542 Options and other information. The following X namespaces have been 1543 implemented so far in the Jabber server: 1545 o Delay Logging (jabber:x:delay) 1547 o Out Of Band Data (File Transfers) (jabber:x:oob) 1549 o Embedded Roster Items (jabber:x:roster) 1551 E.1 Examples 1553 Sending an embedded roster item to a user: 1555 1556 Visitors 1557 This message contains roster items. 1558 1559 Visitors 1560 Visitors 1561 1562 1564 Appendix F. Acknowledgments 1566 While the entire Jabber.org team has been actively involved in the 1567 development of this protocol, the following individuals have 1568 significantly contributed: 1570 Eliot Landrum 1572 Thomas Muldowney 1574 Thomas Charron 1576 Julian Missig 1578 Peter Millard 1580 Full Copyright Statement 1582 Copyright (C) The Internet Society (2000). All Rights Reserved. 1584 This document and translations of it may be copied and furnished to 1585 others, and derivative works that comment on or otherwise explain it 1586 or assist in its implementation may be prepared, copied, published 1587 and distributed, in whole or in part, without restriction of any 1588 kind, provided that the above copyright notice and this paragraph 1589 are included on all such copies and derivative works. However, this 1590 document itself may not be modified in any way, such as by removing 1591 the copyright notice or references to the Internet Society or other 1592 Internet organizations, except as needed for the purpose of 1593 developing Internet standards in which case the procedures for 1594 copyrights defined in the Internet Standards process must be 1595 followed, or as required to translate it into languages other than 1596 English. 1598 The limited permissions granted above are perpetual and will not be 1599 revoked by the Internet Society or its successors or assigns. 1601 This document and the information contained herein is provided on an 1602 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING 1603 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING 1604 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION 1605 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF 1606 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. 1608 Acknowledgement 1610 Funding for the RFC editor function is currently provided by the 1611 Internet Society.