736:: The URI originally indicated in the request-URI of a request generated by the calling user agent. When the request reaches the registrar (S-CSCF) of the called user, the registrar re-writes the request-URI on the first line of the request with the registered contact address (i.e. IP address) of the called user, and stores the replaced request-URI in this header field. In the IMS, a user may be identified by several SIP URIs (address-of-record), for instance, a SIP URI for work and another SIP URI for personal use, and when the registrar replaces the request-URI with the effective contact address, the original request-URI must be stored so that the called party knows to which address-of-record was the invitation sent.
665:
UPDATE requests are sent to inform about the reservation progress, and they are answered by 2XX response codes. In a typical offer/answer exchange, one UPDATE will be sent by the calling party when its reservation is completed, then the called party will respond and eventually finish allocating the resources. It is then, when all the resources for the call are in place, when the caller is alerted.
987:. To obtain transmission resources, the user agent must present an authorization token to the network (i.e. the policy enforcement point, or PEP) . This token will be obtained from its P-CSCF, which may be in charge of QoS policy control or have an interface with the policy control entity in the network (i.e. the policy decision function, or PDF) which originally provides the authorization token.
1135:(URN) that uniquely identifies that SIP instance, and the registrar (i.e. S-CSCF) builds the GRUU, associates it to the registered identity and SIP instance and sends it back to the user agent in the response. When the S-CSCF receives a request for that GRUU, it will be able to route the request to the registered SIP instance.
792:
to be used to query the user database (HSS) for a profile corresponding to the destination SIP URI of a particular SIP request. It is transmitted among proxies to perform faster database queries: the first proxy finds the key and the others query the database by directly using the key. This is useful
62:
The 3GPP, which is a collaboration between groups of telecommunications associations aimed at developing and maintaining the IMS, stated a series of requirements for SIP to be successfully used in the IMS. Some of them could be addressed by using existing capabilities and extensions in SIP while, in
830:
extension header. When a proxy server receives a request from an untrusted entity and authenticates the user (i.e. verifies that the user is who he or she says that he or she is), it then inserts this header with the identity that has been authenticated, and then forwards the request as usual. This
1130:
parameter to a SIP URI, either to the public SIP URI with a value that identifies the user agent instance, or to a specially created URI that does not reveal the relationship between the GRUU and the user's identity, for privacy purposes. They are commonly obtained during the registration process:
673:
In the IMS framework it is fundamental to handle user identities for authentication, authorization and accounting purposes. The IMS is meant to provide multimedia services over IP networks, but also needs a mechanism to charge users for it. All this functionality is supported by new special header
571:
The aim of the UPDATE method extension is to allow user agents to provide updated session description information within a dialog, before the final response to the initial INVITE request is generated. This can be used to negotiate and allocate the call resources before the called party is alerted.
277:
With the caller preferences extension, the calling party is able to indicate the kind of user agent they want to reach (e.g. whether it is fixed or mobile, a voicemail or a human, personal or for business, which services it is capable to provide, or which methods it supports) and how to search for
1049:
header field which accumulates and transmits the SIP URIs of the proxies that are situated between a user agent and its registrar as the REGISTER message traverses then. This way, the registrar is able to discover and record the sequence of proxies that must be transited to get back to the user
664:
The QoS negotiation is supported by the PRACK request, that starts resource reservation in the calling party network, and it is answered by a 2XX response code. Once this response has been sent, the called party has selected the codec too, and starts resource reservation on its side. Subsequent
423:
The event notification framework defines how a user agent can subscribe to events about the state of a resource, but it does not specify how that state can be published. The SIP extension for event state publication was defined to allow user agents to publish the state of an event to the entity
585:
before the phone rings. However, in the IMS, to reserve resources the network needs to know the callee's IP address, port and session parameters and therefore it is necessary that the initial offer/answer exchange to establish a session has started (INVITE request). In basic SIP, this exchange
532:
However, in such an scenario as the IMS framework, it is necessary to extend this reliability to provisional responses to INVITE requests (for session establishment, this is, to start a call). The reliability of provisional responses extension provides a mechanism to confirm that provisional
696:: A collection of charging information, such as the IMS Charging Identity (ICID) value, the address of the SIP proxy that creates the ICID value, and the Inter Operator Identifier (IOI). It may be filled during the establishment of a session or as a standalone transaction outside a dialog.
540:, that lets the caller know that the callee is being alerted, are successfully received. To do so, this extension defines a new method: PRACK, which is the request message used to tell the sender of a provisional response that his or her message has been received. This message includes a
484:
header field of the request message. A typical use of this mechanism is call transfer: during a call, the participant who sends the REFER message tells the recipient to contact to the user agent identified by the URI in the corresponding header field. The REFER message also implies an
918:
The security mechanisms agreement extension for SIP was then introduced to provide a secure mechanism for negotiating the security algorithms and parameters to be used by the P-CSCF and the terminal. This extension uses three new header fields to support the negotiation process:
1062:
header field in the REGISTER message, so that the S-CSCF receives and stores this information associated with the contact information of the user. This way, the S-CSCF will forward every request addressed to that user through the corresponding P-CSCF by listing its URI in the
702:: The addresses of the charging functions (functional entities that receive the charging records or events) in the user's home network. It also may be filled during the establishment of a dialog or as a standalone transaction, and informs each proxy involved in a transaction.
75:
by minimizing the exchange of signaling messages between the mobile terminal and the network, a minimum session setup time by performing tasks prior to session establishment instead of during session establishment, a minimum support required in the terminal, the support for
1166:
where all these words only appear once. In a first approach, this dictionary may be built for each message by the compressor and sent to the decompressor along with the message itself. However, as many words are repeated in different messages, the extended operations for
293:
By using the user agent capabilities extension, user agents (terminals) can describe themselves when they register so that others can search for them according to their caller preferences extension headers. For this purpose, they list their capabilities in the
814:
users, only within an administrative domain with previously agreed policies for generation, transport and usage of this identification information. These extensions also allow users to request privacy so that their identities are not spread outside the
235:. If these extensions are not listed in the client's message, the response from the server will be an error response. Likewise, if the server does not support any of the client's required extensions, it will send an error response with a list of its
580:
In the IMS framework, it is required that once the callee is alerted, the chances of a session failure are minimum. An important source of failure is the inability to reserve network resources to support the session, so these resources should be
876:
Access security in the IMS consists of first authenticating and authorizing the user, which is done by the S-CSCF, and then establishing secure connections between the P-CSCF and the user. There are several mechanisms to achieve this, such as:
1057:
or an equivalent mechanism when the user enters the IMS network, and all requests and responses from or to the user agent must traverse this proxy. When the user registers to the home registrar (S-CSCF), the P-CSCF adds its own SIP URI in a
742:: Additional URIs that are associated with a user that is registering. It is included in the 200 OK response to a REGISTER request to inform a user which other URIs the service provider has associated with an address-of-record (AOR) URI.
1474:
63:
other cases, the 3GPP had to collaborate with the IETF to standardize new SIP extensions to meet the new requirements. The IETF develops SIP on a generic basis, so that the use of extensions is not restricted to the IMS framework.
1314:
Apart from all the explained extensions to SIP that make it possible for the IMS to work successfully, it is also necessary that the IMS framework interworks and exchanges services with existing network infrastructures, mainly the
846:
Finally, when privacy is requested, proxies must withhold asserted identity information outside the trusted domain by removing P-Asserted-Identity headers before forwarding user requests to untrusted identities (outside the
456:
This functionality is supported by the new MESSAGE method, which can be used to send an instant message to the resource stated in the request-URI, with the content carried in the message body. This content is defined as a
1122:
is: a URI that identifies a specific user agent instance (i.e. terminal or application instance) and it does it globally (i.e. it is valid to route messages to that user agent from any other user agent on the
Internet).
835:(i.e. the network of trusted entities with previously agreed security policies) can safely rely on the identity information carried in the P-Asserted-Identity header without the necessity of re-authenticating the user.
452:
is defined in the instant messaging extension. These messages are unrelated to each other (i.e. they do not originate a SIP dialog) and sent through the SIP signaling network, sharing resources with control messages.
520:
message arrives (i.e. the corresponding response code to a request, or the ACK request corresponding to a 2XX response code). This mechanism is necessary since SIP can run not only over reliable transport protocols
1186:
and is willing to receive compressed messages. When used in request-URIs, it indicates that the request is to be compressed, while in Via header fields it signals that the subsequent response is to be compressed.
842:
extension header is also defined, so that a user with several public identities is able to tell the proxy which public identity should be included in the P-Asserted-Identity header when the user is authenticated.
965:
header field cannot be altered as they are sent through the new established secure association, as long as this association is no breakable by the attacker in real time (i.e. before the P-CSCF discovers the
777:
at the edge of the administrative domain, this entity queries the SLF for the corresponding HSS and then, to prevent the S-CSCF from having to query the SLF again, sends the HSS address to the S-CSCF in the
332:
To this end, the specific event notification extension defines a framework for event notification in SIP, with two new methods: SUBSCRIBE and NOTIFY, new header fields and response codes and two roles: the
435:
The state publication framework defines a new method: PUBLISH, which is used to request the publication of the state of the resource specified in the request-URI, with reference to the event stated in the
934:
header field to the response that contains the same information as the client's but with reference to the P-CSCF. In case there are more than one mechanism, they are associated with a priority value.
990:
The private extensions for media authorization link session signaling to the QoS mechanisms applied to media in the network, by defining the mechanisms for obtaining authorization tokens and the
682:
The
Private Header Extensions to SIP, also known as P-Headers, are special header fields whose applicability is limited to private networks with a certain topology and characteristics of lower
602:
responds to the offer without establishing the session or alerting the user. This establishment will occur if and only if both the caller and the callee agree that the preconditions are met.
1294:
entries are properly configured to relay messages across both networks according to these recommendations, user agents will need to implement extensions so that they can directly exchange
1079:
header field that is used by the registrar in a 2XX response to a REGISTER request to inform the registering user of the entity that must forward every request originated by him or her.
1017:
header field, filled by the sender, supports this functionality by listing a set of proxies the message will visit. In the IMS context, there are certain network entities (i.e. certain
657:, that will carry the SDP list of supported codecs by both the caller and the callee. The corresponding PRACK to this provisional answer will be used to select a codec and initiate the
1542:
1118:) that are identified with the same public identity (i.e. SIP URI). Therefore, a mechanism is needed in order to route requests to the desired device or application. That is what a
649:
extensions, along with SDP in the body of the messages. The first offer, described by means of SDP, can be carried by the INVITE request and will deal with the caller's supported
403:
In order to make an efficient use of the signaling messages, it is also possible to establish a limited notification rate (not real-time notifications) through a mechanism called
1171:
define a way to use a shared dictionary among subsequent messages. Moreover, in order to speed up the process of building a dictionary along subsequent messages and provide high
136:
extensions. It must be also possible to present both the caller and the called party the identities of their counterparts, with the ability to hide this information if required.
321:
state, so that they know if they are reachable and what public identities they have registered. Moreover, event notification can be used to provide additional services such as
761:, that contains the profile of the user that generated a particular request. Although the HSS is a unique master database, it can be distributed into different nodes for
1374:
Moreover, the SIP INFO method extension is designed to carry user information between terminals without affecting the signaling dialog and can be used to transport the
1082:
In the IMS, the registrar is the home network's S-CSCF and it is also required that all requests are handled by this entity, so it will include its own SIP URI in the
290:
to specify how the request should be handled by servers in the network (i.e. whether or not to redirect and how to search for the user: sequentially or in parallel).
168:
so that these call session control functions (CSCFs) servers can properly provide their services. There can be special path requirements for certain messages as well.
1336:, that extends SIP and SDP for accessing classic telephone call services in the PSTN (e.g. basic telephone calls, fax service, receiving content over the telephone).
708:: Identification string of the visited network. It is used during registrations, to indicate to the user's home network which network is providing services to a
1240:
summarizes and unifies different methods to achieve this, such as symmetric response routing and client-initiated connections for SIP signaling, and the use of
1195:
In order to obtain even shorter SIP messages and make a very efficient use of the resources, the content indirection extension makes it possible to replace a
3435:
1203:
URI. This way the recipient of the message can decide whether or not to follow the reference to fetch the resource, depending on the bandwidth available.
3425:
782:
header. Then the S-CSCF will be able to directly query the HSS to get information about the user (e.g. authentication information during a registration).
726:
identity. It is used to inform service proxies and the home network, so that they can optimize services or simply so that they can locate the user in a
415:
to decide whether or not to send the complete NOTIFY message depending on if there is something new to notify since last subscription or there is not.
1568:
529:) that offer no delivery guarantees, and it is even possible that both kinds of protocols are present in different parts of the transport network.
556:
number that identifies the corresponding INVITE request. To indicate that the user agent requests or supports reliable provisional responses, the
345:) sends a SUBSCRIBE message with the Uniform Resource Identifier (URI) of the resource in the request initial line, and the type of event in the
2190:
1249:
3377:
3349:
1518:
1484:
854:
There exist analogous extension headers for handling the identification of services of users, instead of the users themselves. In this case,
3470:
994:
header field to carry these tokens from the P-CSCF to the user agent. This extension is only applicable within administrative domains with
223:
in IMS) may use to specify the extensions they understand. When a client initiates a SIP dialog with a server, it states the extensions it
1322:
There are several standards that address this requirements, such as the following two for services interworking between the PSTN and the
937:
Finally, the user agent sends a new REGISTER request over the just created secure connection with the negotiated parameters, including a
1375:
1054:
1013:
is the mechanism that allows the sender of a message to specify partially or completely the route the message traverses. In SIP, the
1316:
762:
586:
eventually causes the callee to be alerted. To solve this problem, the concept of preconditions was introduced. In this concept the
317:
of a user (i.e. "online" or "offline") to others that may be waiting to contact them, or to notify a user and its P-CSCF of its own
172:
1340:
1218:, since it uses a private address that is mapped to a public one when packets originated by the terminal cross the NAT. Therefore,
2888:
The
Session Initiation Protocol (SIP) and Session Description Protocol (SDP) Static Dictionary for Signaling Compression (SigComp)
3460:
480:
The REFER method extension defines a mechanism to request a user agent to contact a resource which is identified by a URI in the
1175:
since the first INVITE message, SIP provides a static SIP/SDP dictionary which is already built with common SIP and SDP terms.
3297:
3252:
3207:
3162:
3117:
3072:
3027:
2982:
2937:
2892:
2847:
2802:
2757:
2712:
2667:
2622:
2577:
2532:
2487:
2442:
2397:
2352:
2307:
2233:
2151:
2106:
2061:
2016:
1968:
1923:
1878:
1833:
1788:
1743:
1698:
1653:
1608:
1432:
1263:
1233:
689:
These header fields are used for a variety of purposes including charging and information about the networks a call traverses:
517:
36:
1147:
or other low-bandwidth access, is essential in the IMS in order to provide the user with an acceptable experience in terms of
686:' protocols. They were designed specifically to meet the 3GPP requirements because a more general solution was not available.
109:
support with policy and charging control, as well as resource negotiation and allocation before alerting the destination user.
469:
164:
of SIP messages has its own requirements in the IMS as all terminal originated session setup attempts must transit both the
95:
to support new network functionality: requirement for registration, re-registration, de-registration, event notifications,
3430:
522:
489:
to the result of the operation, so that the sender will know whether or not the recipient could contact the third person.
357:
as well as the information about the status of the resource in the message body. Whenever the resource state changes, the
1508:
1331:
1299:
885:
770:
614:
80:
and non-roaming scenarios with terminal mobility management (supported by the access network, not SIP), and support for
396:
response codes to indicate if a subscription request has been preliminary accepted or has been turned down because the
1345:, that provides the opposite functionality to PINT, this is, supporting the access to Internet services from the PSTN.
1211:
244:
188:
129:
92:
17:
927:
header field containing the mechanisms, authentication and encryption algorithms it supports to the REGISTER request.
654:
537:
513:
1162:
Compression algorithms perform this operation by substituting repeated words in the message by its position in a
621:
initialization parameters, carried in the body of SIP messages. The new SDP attributes are meant to describe the
71:
The 3GPP has stated several general requirements for operation of the IMS. These include an efficient use of the
154:
Session release initiated by the network (e.g. in case the user terminal leaves coverage or runs out of credit).
3367:
1428:
Input 3rd-Generation
Partnership Project (3GPP) Release 5 Requirements on the Session Initiation Protocol (SIP)
998:
relationships. It was particularly designed for specialized SIP networks like the IMS, and not for the general
984:
967:
946:
890:
203:
There is a mechanism in SIP for extension negotiation between user agents (UA) or servers, consisting of three
3465:
3455:
3440:
1391:
1178:
There is a mechanism to indicate that a SIP message is desired to be compressed. This mechanism defines the
1018:
774:
758:
220:
165:
148:
125:
48:
29:
147:
Protection of SIP signaling with integrity and confidentiality support based on initial authentication and
1367:
1172:
526:
2348:
Private
Extensions to the Session Initiation Protocol (SIP) for Asserted Identity within Trusted Networks
1576:
3420:
3248:
Integrated
Services Digital Network (ISDN) User Part (ISUP) to Session Initiation Protocol (SIP) Mapping
2708:
Session
Initiation Protocol (SIP) Extension Header Field for Service Route Discovery During Registration
1148:
1132:
855:
712:
user, so that the home network is able to accept the registration according to their roaming agreements.
120:
between users and the network and among network nodes is a major issue to be addressed by using mutual
59:(RFC) protocol recommendations, have been added to the basic protocol for extending its functionality.
2753:
Obtaining and Using
Globally Routable User Agent URIs (GRUUs) in the Session Initiation Protocol (SIP)
3339:
3311:
3266:
3221:
3176:
3155:
Gurbani, V.; Ed., Brusilovsky; A., Faynberg; I., Gato; J., Lu; H., and; M., Unmehopa (October 2004).
3131:
3086:
3041:
2996:
2951:
2906:
2861:
2816:
2771:
2726:
2681:
2636:
2591:
2546:
2528:
Hypertext
Transfer Protocol (HTTP) Digest Authentication Using Authentication and Key Agreement (AKA)
2501:
2456:
2411:
2366:
2321:
2247:
2165:
2120:
2075:
2030:
1982:
1937:
1892:
1847:
1802:
1757:
1712:
1667:
1622:
1446:
1267:
1237:
1223:
719:
56:
2201:
3445:
995:
807:
582:
141:
2272:
274:
These two extensions allow users to specify their preferences about the service the IMS provides.
3450:
1227:
980:
794:
658:
595:
204:
106:
88:
1871:
Campbell, B.; Ed., Rosenberg; J., Schulzrinne; H., Huitema; C., and; D., Gurle (December 2002).
773:(SLF) is needed to find the HSS that handles a particular user. When a user request reaches the
718:: Information about the access technology (the network providing the connectivity), such as the
2840:
Hannu, H.; Christoffersson, J.; Forsgren, S.; Leung, K.-C.; Liu, Z.; Price, R. (January 2003).
2795:
Price, R.; Bormann, C.; Christoffersson, J.; Hannu, H.; Liu, Z.; Rosenberg, J. (January 2003).
3373:
3345:
2663:
Session
Initiation Protocol (SIP) Extension Header Field for Registering Non-Adjacent Contacts
1514:
1480:
1271:
1111:
683:
306:
The aim of event notification is to obtain the status of a given resource (e.g. a user, one's
117:
113:
96:
44:
40:
3400:
3113:
The PINT Service Protocol: Extensions to SIP and SDP for IP Access to Telephone Call Services
1090:
header field of all his or her requests, so that they are forwarded through the home S-CSCF.
793:
when Wildcarded Service Identities are used, this is, Public Service Identities that match a
3301:
3256:
3211:
3166:
3121:
3076:
3031:
2986:
2941:
2896:
2851:
2806:
2761:
2716:
2671:
2626:
2581:
2536:
2491:
2446:
2401:
2356:
2311:
2237:
2155:
2110:
2065:
2020:
1972:
1927:
1882:
1837:
1792:
1747:
1702:
1657:
1612:
1436:
1379:
1163:
1152:
1144:
903:
72:
953:
header field in order to force the terminal to choose weaker security algorithms, then the
810:
networks are designed to enable a network of trusted SIP servers to assert the identity of
552:
header field of the provisional response that is being acknowledged, and also contains the
1604:
Private Header (P-Header) Extensions to the Session Initiation Protocol (SIP) for the 3GPP
1295:
1275:
1253:
1215:
1107:
618:
545:
1270:
describes the necessary mechanisms to guarantee that SIP works successfully between both
1182:
parameter for SIP URIs, which signals that the SIP entity identified by the URI supports
1021:) that must be traversed by requests from or to a user, so they are to be listed in the
187:
are adapted to work with SIP, for instance for outbound proxy (P-CSCF) location and SIP
1363:
1010:
898:
811:
789:
449:
157:
121:
1053:
In the IMS every user agent is served by its P-CSCF, which is discovered by using the
3414:
1396:
1219:
587:
133:
858:
are used to identify a service (e.g. a voice call, an instant messaging session, an
516:) are transmitted reliably, this is, they are retransmitted by the sender until the
1099:
871:
599:
99:
or call control primitives with additional capabilities such as call transference.
28:(3GPP) to create and control multimedia sessions with multiple participants in the
3369:
The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds
2483:
Identification of Communications Services in the Session Initiation Protocol (SIP)
1476:
The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds
3338:
Poikselkä, Miikka; Mayer, Georg; Khartabil, Hisham; Niemi, Aki (March 10, 2006).
2978:
A Mechanism for Content Indirection in Session Initiation Protocol (SIP) Messages
1507:
Poikselkä, Miikka; Mayer, Georg; Khartabil, Hisham; Niemi, Aki (March 10, 2006).
3314:
3291:
3269:
3246:
3224:
3201:
3179:
3156:
3134:
3111:
3089:
3066:
3044:
3021:
2999:
2976:
2954:
2931:
2909:
2886:
2864:
2841:
2819:
2796:
2774:
2751:
2729:
2706:
2684:
2661:
2639:
2616:
2594:
2571:
2549:
2526:
2504:
2481:
2459:
2438:
A Session Initiation Protocol (SIP) Extension for the Identification of Services
2436:
2414:
2391:
2369:
2346:
2324:
2301:
2250:
2227:
2168:
2145:
2123:
2100:
2078:
2055:
2033:
2010:
1985:
1962:
1940:
1917:
1895:
1872:
1850:
1827:
1805:
1782:
1760:
1737:
1715:
1692:
1670:
1647:
1625:
1602:
1449:
1426:
983:(QoS) leads to another security issue: admission control and protection against
797:, because the first query has to resolve the regular expression to find the key.
766:
179:
Finally, it is also necessary that other protocols and network services such as
2885:
Garcia-Martin, M.; Bormann, C.; Ott, J.; Price, R.; Roach, A. (February 2003).
2229:
The Session Initiation Protocol (SIP) P-User-Database Private-Header (P-Header)
641:
In the IMS, the initial session parameter negotiation can be done by using the
428:) that is responsible for composing the event state and distributing it to the
349:. Then the entity in charge of keeping track of the state of the resource (the
2570:
Arkko, J.; Torvinen, V.; Camarillo, G.; Niemi, A.; Haukka, T. (January 2003).
1349:
And also for PSTN-SIP gateways to support calls with one end in each network:
1303:
1115:
907:
448:
The functionality of sending instant messages to provide a service similar to
231:), and the server will then send a response with a list of extensions that it
192:
3203:
Session Initiation Protocol for Telephones (SIP-T): Context and Architectures
2303:
The Session Initiation Protocol (SIP) P-Profile-Key Private Header (P-Header)
1302:
offer/answer initial exchange, that will be used to gather the IPv4 and IPv6
1025:
header field. To allow the sender to discover such entities and populate the
2618:
Private Session Initiation Protocol (SIP) Extensions for Media Authorization
1075:
The extension for service route discovery during registration consists of a
1045:
The extension header field for registering non-adjacent contacts provides a
723:
525:) that assure that the message is delivered, but also over unreliable ones (
512:
In the basic SIP specification, only requests and final responses (i.e. 2XX
322:
307:
137:
3401:
3rd Generation Partnership Project's page about the IP Multimedia Subsystem
1739:
Indicating User Agent Capabilities in the Session Initiation Protocol (SIP)
653:. This request will be answered by the provisional reliable response code
2057:
Reliability of Provisional Responses in Session Initiation Protocol (SIP)
1323:
1103:
999:
754:
727:
501:
468:
In order to have an instant messaging session with related messages, the
353:), receives the SUBSCRIBE request and sends back a NOTIFY message with a
313:
Event notification is necessary in the IMS framework to inform about the
2147:
Integration of Resource Management and Session Initiation Protocol (SIP)
1282:. While SIP signaling messages can be transmitted through heterogeneous
1214:(NAT) makes it impossible for a terminal to be reached from outside its
1098:
In the IMS it is possible for a user to have multiple terminals (e.g. a
257:
the use of a particular method in a particular dialog, they must use an
1829:
Session Initiation Protocol (SIP) Extension for Event State Publication
941:
header field that carries the same contents as the previously received
709:
365:. Each kind of event a subscriber can subscribe to is defined in a new
161:
77:
2573:
Security Mechanism Agreement for the Session Initiation Protocol (SIP)
492:
However, this mechanism is not restricted to call transfer, since the
3306:
3261:
3216:
3171:
3126:
3081:
3036:
2991:
2946:
2901:
2856:
2811:
2766:
2721:
2676:
2631:
2586:
2541:
2496:
2451:
2406:
2361:
2316:
2242:
2160:
2144:
Camarillo, G.; Ed., Marshall; W., Ed.; Rosenberg, J. (October 2002).
2115:
2070:
2025:
1977:
1932:
1887:
1842:
1797:
1752:
1707:
1662:
1617:
1441:
1401:
945:
header field. This procedure protects the negotiation mechanism from
591:
3158:
The SPIRITS (Services in PSTN requesting Internet Services) Protocol
949:: if an attacker removed the strongest security mechanisms from the
746:
More private headers have been defined for user database accessing:
341:. The entity interested in the state information of a resource (the
3293:
Session Initiation Protocol (SIP) INFO Method and Package Framework
1362:, which makes it possible to translate SIP signaling messages into
39:
as a standard for controlling multimedia communication sessions in
3020:
Boulton, C.; Rosenberg, J.; Camarillo, G.; Audet, F. (July 2011).
1360:
ISDN User Part (ISUP) to Session Initiation Protocol (SIP) Mapping
1199:
body part of the message with an external reference, typically an
911:
831:
way, other proxy servers that receive this SIP request within the
650:
629:
of the reservation to proceed with session establishment, and the
326:
3405:
3366:
Camarillo, Gonzalo; GarcĂa-MartĂn, Miguel A. (November 4, 2008).
3245:
Camarillo, G.; Roach, A.; Peterson, J.; Ong, L. (December 2002).
1916:
Campbell, B.; Ed., Mahy; R., Ed.; Jennings, C. (September 2007).
1874:
Session Initiation Protocol (SIP) Extension for Instant Messaging
1473:
Camarillo, Gonzalo; GarcĂa-MartĂn, Miguel A. (November 4, 2008).
381:
type to carry the event state information in the NOTIFY message.
1306:
of both ends so that they can establish a direct communication.
1287:
1283:
1279:
1245:
1241:
1200:
1196:
882:
859:
497:
458:
378:
310:
service) and to receive updates of that status when it changes.
180:
81:
25:
889:, which is part of the basic SIP specification and leads to a
633:, to indicate when the reservation status should be confirmed.
1291:
184:
3065:
Camarillo, G.; El, Malki; K., and; V., Gurbani (April 2011).
2393:
A Privacy Mechanism for the Session Initiation Protocol (SIP)
1784:
Session Initiation Protocol (SIP)-Specific Event Notification
1086:
header field. The user will then include this SIP URI in the
605:
The preconditions SIP extension affects both SIP, with a new
1694:
Caller Preferences for the Session Initiation Protocol (SIP)
1143:
The efficient use of network resources, which may include a
1029:
header field, there are mainly two extension header fields:
388:
header to indicate event notification capabilities, and the
87:
Other requirements involve protocol extensions, such as SIP
1736:
Rosenberg, J.; Schulzrinne, H.; Kyzivat, P. (August 2004).
1691:
Rosenberg, J.; Schulzrinne, H.; Kyzivat, P. (August 2004).
979:
The necessity in the IMS of reserving resources to provide
325:(i.e. to notify that they have new voice messages in their
32:(IMS). It is therefore a key element in the IMS framework.
1356:, that describes the practices and uses of these gateways.
914:
security associations between the P-CSCF and the terminal.
637:
The SDP offer/answer model using PRACK and UPDATE requests
227:
to be used and also other extensions that are understood (
43:(IP) networks. It is characterized by its position in the
642:
3068:
IPv6 Transition in the Session Initiation Protocol (SIP)
2345:
Jennings, C.; Peterson, J.; Watson, M. (November 2002).
440:, and with the information carried in the message body.
1649:
Session Initiation Protocol (SIP): Locating SIP Servers
1513:(2 ed.). John Wiley & Sons. pp. 320–331.
1479:(3 ed.). John Wiley & Sons. pp. 55–336.
902:, a more secure version of the previous mechanism for
496:
header field can be any kind of URI, for instance, an
3290:
Holmberg, C.; Burger, E.; Kaplan, H. (January 2011).
2843:
Signaling Compression (SigComp) - Extended Operations
2525:
Niemi, A.; Arkko, J.; Torvinen, V. (September 2002).
819:. To indicate so, they must insert the privacy token
806:
The private extensions for asserted identity within
606:
590:
states a set of constraints about the session (i.e.
560:
2102:
The Session Initiation Protocol (SIP) UPDATE Method
961:header fields would not match. The contents of the
1964:The Session Initiation Protocol (SIP) Refer Method
1354:Session Initiation Protocol for Telephones (SIP-T)
151:; error recovery and verification are also needed.
2933:Compressing the Session Initiation Protocol (SIP)
1601:Jesske, R.; Drage, K.; Holmberg, C. (July 2014).
646:
400:does not understand the kind of event requested.
282:to describe the desired destination user agents,
1370:(SS7) which is used in the PSTN, and vice versa.
253:header to state which methods they support. To
249:. In that case, user agents or servers use the
239:extensions. This kind of extensions are called
219:, which UAs or servers (i.e. user terminals or
270:Caller preferences and user agent capabilities
3023:NAT Traversal Practices for Client-Server SIP
1341:Services in PSTN requesting Internet Services
8:
3341:The IMS: IP multimedia concepts and services
2054:Rosenberg, J.; Schulzrinne, H. (June 2002).
1646:Rosenberg, J.; Schulzrinne, H. (June 2002).
1510:The IMS: IP multimedia concepts and services
1151:. To achieve this goal, SIP messages can be
114:authentication, authorization and accounting
91:to exchange user or server information, and
24:) is the signaling protocol selected by the
3200:Vemuri, A.; Peterson, J. (September 2002).
2660:Willis, D.; Hoeneisen, B. (December 2002).
1468:
1466:
826:The main functionality is supported by the
2705:Willis, D.; Hoeneisen, B. (October 2003).
2004:
2002:
906:that uses the information from the user's
893:connection between the user and the proxy.
617:(SDP), which is a format used to describe
613:) and defined offer/answer exchanges, and
407:. Moreover, there is also a mechanism for
3305:
3260:
3215:
3170:
3125:
3080:
3035:
2990:
2945:
2900:
2855:
2810:
2765:
2720:
2675:
2630:
2585:
2540:
2495:
2450:
2405:
2360:
2315:
2300:Camarillo, G.; Blanco, G. (August 2007).
2241:
2159:
2114:
2069:
2024:
1976:
1931:
1919:The Message Session Relay Protocol (MSRP)
1886:
1841:
1796:
1751:
1706:
1661:
1616:
1596:
1594:
1440:
1420:
1418:
1416:
1259:Internet Protocol version 6 compatibility
1252:, which combines both previous ones, for
1126:These URIs are constructed by adding the
500:URI, to require the recipient to visit a
2226:Camarillo, G.; Blanco, G. (April 2006).
2009:Rosenberg, J.; et al. (June 2002).
897:HTTP digest access authentication using
373:describes a new value for the SUBSCRIBE
243:, but SIP can also be extended with new
1412:
486:
286:to state the user agents to avoid, and
1298:. These extensions are related to the
1290:networks as long as proxy servers and
1120:Globally Routable User Agent URI (GRU)
298:header field of the REGISTER message.
37:Internet Engineering Task Force (IETF)
3372:(3 ed.). John Wiley & Sons.
3344:(2 ed.). John Wiley & Sons.
3110:Petrack, S.; Conroy, L. (June 2000).
7:
1310:Interworking with other technologies
598:requirements) in the offer, and the
508:Reliability of provisional responses
221:call session control function (CSCF)
3436:Mobile telecommunications standards
1376:dual-tone multi-frequency signaling
1222:mechanisms are needed for both the
1131:the registering user agent sends a
1055:Dynamic Host Configuration Protocol
171:Interoperation between IMS and the
3406:IP Multimedia Subsystem call flows
1332:PSTN Interworking Service Protocol
361:sends a new NOTIFY message to the
26:3rd Generation Partnership Project
14:
3426:Telecommunications infrastructure
1567:Systems & Networks Training.
1317:Public switched telephone network
1106:) or application instances (e.g.
1094:Globally routable user agent URIs
625:of the resource reservation, the
189:Uniform Resource Identifier (URI)
173:public switched telephone network
102:Other specific requirements are:
2012:SIP: Session Initiation Protocol
2930:Camarillo, G. (February 2003).
2798:Signaling Compression (SigComp)
1264:Internet Engineering Task Force
1234:Internet Engineering Task Force
823:into the Privacy header field.
199:Extension negotiation mechanism
2750:Rosenberg, J. (October 2009).
2390:Peterson, J. (November 2002).
2099:Rosenberg, J. (October 2002).
1425:Garcia-Martin, M. (May 2005).
470:Message Session Relay Protocol
409:conditional event notification
278:it, with three header fields:
1:
2615:Marshall, W. (January 2003).
1543:"8.6. SIP AND IMS EXTENSIONS"
1155:using the mechanism known as
140:in session establishment and
1300:Session Description Protocol
886:digest access authentication
771:Subscriber location function
759:Home Subscriber Server (HSS)
647:session description updating
615:Session Description Protocol
567:Session description updating
149:symmetric cryptographic keys
112:Identification of users for
3471:Application layer protocols
2480:Rosenberg, J. (June 2010).
2435:Drage, K. (November 2010).
1212:Network address translation
923:First, the terminal adds a
700:P-Charging-Function-Address
669:Identification and charging
261:associated to that method.
18:Session Initiation Protocol
3487:
1826:Niemi, A. (October 2004).
869:
753:: The address of the user
195:resolution, respectively.
1961:Sparks, R. (April 2003).
1159:(signaling compression).
1006:Source-routing mechanisms
985:denial-of-service attacks
947:Man-in-the-middle attacks
910:and commonly creates two
769:reasons. In this case, a
355:subscription-state header
158:Source-routing mechanisms
67:3GPP requirements for SIP
35:SIP was developed by the
1326:(i.e. the IMS network):
968:Man-in-the-middle attack
930:Then, the P-CSCF adds a
891:Transport Layer Security
544:header field which is a
3461:Audio network protocols
2975:Burger, E. (May 2006).
1781:Roach, A. (June 2002).
1392:Next-generation network
720:radio access technology
126:private and public keys
49:Internet Protocol Suite
30:IP Multimedia Subsystem
1368:Signaling System No. 7
856:Uniform Resource Names
533:responses such as the
1139:Signaling compression
1133:Uniform Resource Name
992:P-Media-Authorization
716:P-Access-Network-Info
643:provisional responses
472:(MSRP) is available.
465:the most common one.
166:P-CSCF and the S-CSCF
3431:Network architecture
1382:function for users.
1274:versions during the
840:P-Preferred-Identity
706:P-Visited-Network-ID
655:183 Session Progress
57:Request for Comments
1191:Content Indirection
975:Media authorization
866:Security mechanisms
828:P-Asserted-Identity
631:confirmation status
288:Request-Disposition
144:are also important.
132:, as well as media
124:mechanisms such as
2273:"IMS registration"
2207:on 22 January 2015
1173:compression ratios
981:quality of service
795:regular expression
487:event subscription
302:Event notification
107:Quality of service
3379:978-0-470-51662-1
3351:978-0-470-01906-1
2191:"IMS to IMS call"
1520:978-0-470-01906-1
1486:978-0-470-51662-1
1272:Internet Protocol
1112:instant messaging
904:cellular networks
802:Asserted identity
734:P-Called-Party-ID
694:P-Charging-Vector
548:that matches the
444:Instant messaging
419:State publication
384:There is also an
97:instant messaging
45:application layer
41:Internet Protocol
3478:
3390:
3388:
3386:
3362:
3360:
3358:
3326:
3325:
3323:
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3309:
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3262:10.17487/RFC3398
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3217:10.17487/RFC3372
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3172:10.17487/RFC3910
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3129:
3127:10.17487/RFC2848
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3084:
3082:10.17487/RFC6157
3062:
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3039:
3037:10.17487/RFC6314
3017:
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2992:10.17487/RFC4483
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2857:10.17487/RFC3321
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2812:10.17487/RFC3320
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2769:
2767:10.17487/RFC5627
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2724:
2722:10.17487/RFC3608
2702:
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2677:10.17487/RFC3327
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2632:10.17487/RFC3313
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2587:10.17487/RFC3329
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2497:10.17487/RFC5897
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2259:
2257:
2245:
2243:10.17487/RFC4457
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2214:
2212:
2206:
2200:. Archived from
2195:
2186:
2180:
2179:
2177:
2175:
2163:
2161:10.17487/RFC3312
2141:
2135:
2134:
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2006:
1997:
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1978:10.17487/RFC3515
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1753:10.17487/RFC3840
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1727:
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1708:10.17487/RFC3841
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1682:
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1665:
1663:10.17487/RFC3263
1643:
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1634:
1632:
1620:
1618:10.17487/RFC7315
1598:
1589:
1588:
1586:
1584:
1579:on 28 March 2015
1575:. Archived from
1564:
1558:
1557:
1555:
1553:
1538:
1532:
1531:
1529:
1527:
1504:
1498:
1497:
1495:
1493:
1470:
1461:
1460:
1458:
1456:
1444:
1442:10.17487/RFC4083
1422:
1380:telephone keypad
1366:messages of the
740:P-Associated-URI
411:that allows the
405:event throttling
3486:
3485:
3481:
3480:
3479:
3477:
3476:
3475:
3411:
3410:
3397:
3384:
3382:
3380:
3365:
3356:
3354:
3352:
3337:
3334:
3329:
3319:
3317:
3289:
3288:
3284:
3274:
3272:
3244:
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3239:
3229:
3227:
3199:
3198:
3194:
3184:
3182:
3154:
3153:
3149:
3139:
3137:
3109:
3108:
3104:
3094:
3092:
3064:
3063:
3059:
3049:
3047:
3019:
3018:
3014:
3004:
3002:
2974:
2973:
2969:
2959:
2957:
2929:
2928:
2924:
2914:
2912:
2884:
2883:
2879:
2869:
2867:
2839:
2838:
2834:
2824:
2822:
2794:
2793:
2789:
2779:
2777:
2749:
2748:
2744:
2734:
2732:
2704:
2703:
2699:
2689:
2687:
2659:
2658:
2654:
2644:
2642:
2614:
2613:
2609:
2599:
2597:
2569:
2568:
2564:
2554:
2552:
2524:
2523:
2519:
2509:
2507:
2479:
2478:
2474:
2464:
2462:
2434:
2433:
2429:
2419:
2417:
2389:
2388:
2384:
2374:
2372:
2344:
2343:
2339:
2329:
2327:
2299:
2298:
2294:
2284:
2282:
2280:eventhelix.com/
2275:
2270:
2269:
2265:
2255:
2253:
2225:
2224:
2220:
2210:
2208:
2204:
2198:eventhelix.com/
2193:
2188:
2187:
2183:
2173:
2171:
2143:
2142:
2138:
2128:
2126:
2098:
2097:
2093:
2083:
2081:
2053:
2052:
2048:
2038:
2036:
2008:
2007:
2000:
1990:
1988:
1960:
1959:
1955:
1945:
1943:
1915:
1914:
1910:
1900:
1898:
1870:
1869:
1865:
1855:
1853:
1825:
1824:
1820:
1810:
1808:
1780:
1779:
1775:
1765:
1763:
1735:
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1690:
1689:
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1675:
1673:
1645:
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1640:
1630:
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1600:
1599:
1592:
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1566:
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1540:
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1525:
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1506:
1505:
1501:
1491:
1489:
1487:
1472:
1471:
1464:
1454:
1452:
1424:
1423:
1414:
1410:
1388:
1312:
1261:
1224:signaling plane
1216:private network
1209:
1193:
1145:radio interface
1141:
1108:video telephony
1096:
1073:
1043:
1008:
977:
963:Security-Verify
959:Security-Server
955:Security-Verify
951:Security-Server
943:security-server
939:security-verify
932:security-server
925:security–client
874:
868:
804:
780:P-User-Database
757:, this is, the
751:P-User-Database
680:
671:
639:
619:streaming media
578:
569:
546:sequence number
510:
478:
446:
421:
377:, as well as a
304:
272:
267:
201:
73:radio interface
69:
12:
11:
5:
3484:
3482:
3474:
3473:
3468:
3466:VoIP protocols
3463:
3458:
3456:Videotelephony
3453:
3448:
3443:
3441:3GPP standards
3438:
3433:
3428:
3423:
3413:
3412:
3409:
3408:
3403:
3396:
3395:External links
3393:
3392:
3391:
3378:
3363:
3350:
3333:
3330:
3328:
3327:
3282:
3237:
3192:
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1998:
1953:
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1067:header field.
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1011:Source routing
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860:IPTV streaming
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638:
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627:desired status
623:current status
577:
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563:will be used.
514:response codes
509:
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477:
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450:text messaging
445:
442:
420:
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303:
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284:Reject-Contact
280:Accept-Contact
271:
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265:SIP extensions
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200:
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122:authentication
110:
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1397:Voice over IP
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1254:media streams
1251:
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1221:
1220:NAT traversal
1217:
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1207:NAT traversal
1206:
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1084:service-route
1080:
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1077:Service-Route
1071:Service route
1070:
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1035:service-route
1032:
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812:authenticated
809:
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786:P-Profile-Key
784:
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661:negotiation.
660:
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624:
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616:
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608:
603:
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593:
589:
584:
576:Preconditions
575:
573:
566:
564:
562:
559:
555:
551:
547:
543:
539:
538:response code
536:
530:
528:
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476:Call transfer
475:
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394:489 bad event
391:
387:
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372:
371:event package
368:
367:event package
364:
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134:authorization
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85:
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55:published in
54:
50:
46:
42:
38:
33:
31:
27:
23:
19:
3421:IMS services
3383:. Retrieved
3368:
3355:. Retrieved
3340:
3318:. Retrieved
3292:
3285:
3273:. Retrieved
3247:
3240:
3228:. Retrieved
3202:
3195:
3183:. Retrieved
3157:
3150:
3138:. Retrieved
3112:
3105:
3093:. Retrieved
3067:
3060:
3048:. Retrieved
3022:
3015:
3003:. Retrieved
2977:
2970:
2958:. Retrieved
2932:
2925:
2913:. Retrieved
2887:
2880:
2868:. Retrieved
2842:
2835:
2823:. Retrieved
2797:
2790:
2778:. Retrieved
2752:
2745:
2733:. Retrieved
2707:
2700:
2688:. Retrieved
2662:
2655:
2643:. Retrieved
2617:
2610:
2598:. Retrieved
2572:
2565:
2553:. Retrieved
2527:
2520:
2508:. Retrieved
2482:
2475:
2463:. Retrieved
2437:
2430:
2418:. Retrieved
2392:
2385:
2373:. Retrieved
2347:
2340:
2328:. Retrieved
2302:
2295:
2283:. Retrieved
2279:
2266:
2254:. Retrieved
2228:
2221:
2209:. Retrieved
2202:the original
2197:
2184:
2172:. Retrieved
2146:
2139:
2127:. Retrieved
2101:
2094:
2082:. Retrieved
2056:
2049:
2039:November 15,
2037:. Retrieved
2011:
1989:. Retrieved
1963:
1956:
1944:. Retrieved
1918:
1911:
1899:. Retrieved
1873:
1866:
1854:. Retrieved
1828:
1821:
1809:. Retrieved
1783:
1776:
1764:. Retrieved
1738:
1731:
1719:. Retrieved
1693:
1686:
1674:. Retrieved
1648:
1641:
1631:November 15,
1629:. Retrieved
1603:
1581:. Retrieved
1577:the original
1572:
1569:"SIP in IMS"
1562:
1550:. Retrieved
1546:
1536:
1524:. Retrieved
1509:
1502:
1490:. Retrieved
1475:
1455:November 29,
1453:. Retrieved
1427:
1373:
1359:
1353:
1348:
1339:
1330:
1321:
1313:
1262:
1232:
1210:
1194:
1183:
1180:comp=sigcomp
1179:
1177:
1168:
1161:
1156:
1142:
1127:
1125:
1119:
1100:mobile phone
1097:
1087:
1083:
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1076:
1074:
1064:
1059:
1052:
1046:
1044:
1034:
1030:
1026:
1022:
1014:
1009:
991:
989:
978:
970:in progress.
962:
958:
954:
950:
942:
938:
931:
924:
917:
896:
881:
875:
872:IMS security
853:
849:Trust Domain
848:
845:
839:
837:
833:Trust Domain
832:
827:
825:
820:
817:trust domain
816:
805:
785:
779:
750:
745:
739:
733:
715:
705:
699:
693:
688:
681:
672:
663:
640:
630:
626:
622:
611:precondition
610:
604:
579:
570:
557:
553:
549:
541:
534:
531:
511:
493:
491:
481:
479:
467:
462:
461:type, being
455:
447:
438:Event header
437:
434:
429:
425:
422:
412:
408:
404:
402:
397:
393:
390:202 accepted
389:
386:allow-events
385:
383:
375:Event header
374:
370:
366:
362:
358:
354:
350:
347:Event header
346:
342:
338:
334:
331:
319:registration
318:
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305:
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283:
279:
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258:
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228:
224:
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212:
208:
202:
178:
101:
86:
84:addressing.
70:
61:
52:
34:
21:
15:
3385:15 November
3357:15 November
3320:December 5,
3275:December 5,
3230:December 5,
3185:December 5,
3140:December 5,
3095:December 5,
3050:December 5,
3005:December 4,
2960:December 4,
2915:December 4,
2870:December 4,
2825:December 4,
2780:December 5,
2735:December 5,
2690:December 5,
2645:December 5,
2600:December 5,
2555:December 5,
2510:December 5,
2465:December 5,
2420:December 3,
2375:December 3,
2330:December 5,
2271:EvenHelix.
2256:December 5,
2189:EvenHelix.
2174:December 3,
2129:December 2,
2084:December 2,
1991:December 2,
1946:December 2,
1901:December 2,
1856:December 2,
1811:December 1,
1766:December 1,
1721:December 1,
1676:December 1,
1583:15 November
1552:15 November
1526:15 November
1492:15 November
1378:to provide
1228:media plane
767:scalability
763:reliability
535:180 Ringing
518:acknowledge
430:subscribers
241:option tags
237:unsupported
217:unsupported
93:SIP methods
3446:Multimedia
3415:Categories
2285:5 December
2211:3 December
1547:redhat.com
1408:References
1276:transition
1164:dictionary
1153:compressed
1116:voice mail
908:smart card
870:See also:
607:option tag
561:option tag
463:text/plain
363:subscriber
343:subscriber
335:subscriber
259:option tag
193:IP address
116:purposes.
51:. Several
3451:Telephony
1573:snt.co.uk
1541:Red Hat.
1343:(SPIRITS)
1304:addresses
678:P-headers
583:allocated
323:voicemail
308:voicemail
229:supported
209:supported
138:Anonymity
1386:See also
1324:Internet
1319:(PSTN).
1268:RFC 6157
1238:RFC 6314
1226:and the
1104:computer
1000:Internet
755:database
728:wireless
674:fields.
502:web page
494:Refer-To
482:Refer-To
426:notifier
413:notifier
398:notifier
359:notifier
351:notifier
339:notifier
337:and the
315:presence
233:requires
225:requires
207:fields:
118:Security
1184:SigComp
1169:SigComp
1157:SigComp
1149:latency
1050:agent.
808:trusted
730:network
710:roaming
296:Contact
255:require
246:methods
213:require
175:(PSTN).
162:routing
142:privacy
130:digests
78:roaming
47:of the
3376:
3348:
1517:
1483:
1402:TISPAN
1334:(PINT)
788:: The
775:I-CSCF
684:layers
651:codecs
600:callee
592:codecs
588:caller
558:100rel
205:header
160:. The
3332:Books
2276:(PDF)
2205:(PDF)
2194:(PDF)
1088:Route
1065:route
1027:route
1023:Route
1019:CSCFs
1015:route
996:trust
912:IPsec
369:. An
327:inbox
251:Allow
3387:2014
3374:ISBN
3359:2014
3346:ISBN
3322:2014
3315:6086
3298:IETF
3277:2014
3270:3398
3253:IETF
3232:2014
3225:3372
3208:IETF
3187:2014
3180:3910
3163:IETF
3142:2014
3135:2848
3118:IETF
3097:2014
3090:6157
3073:IETF
3052:2014
3045:6314
3028:IETF
3007:2014
3000:4483
2983:IETF
2962:2014
2955:3486
2938:IETF
2917:2014
2910:3485
2893:IETF
2872:2014
2865:3321
2848:IETF
2827:2014
2820:3320
2803:IETF
2782:2014
2775:5627
2758:IETF
2737:2014
2730:3608
2713:IETF
2692:2014
2685:3327
2668:IETF
2647:2014
2640:3313
2623:IETF
2602:2014
2595:3329
2578:IETF
2557:2014
2550:3310
2533:IETF
2512:2014
2505:5897
2488:IETF
2467:2014
2460:6050
2443:IETF
2422:2014
2415:3323
2398:IETF
2377:2014
2370:3325
2353:IETF
2332:2014
2325:5002
2308:IETF
2287:2014
2258:2014
2251:4457
2234:IETF
2213:2014
2176:2014
2169:3312
2152:IETF
2131:2014
2124:3311
2107:IETF
2086:2014
2079:3262
2062:IETF
2041:2014
2034:3261
2017:IETF
1993:2014
1986:3515
1969:IETF
1948:2014
1941:4975
1924:IETF
1903:2014
1896:3428
1879:IETF
1858:2014
1851:3903
1834:IETF
1813:2014
1806:3265
1789:IETF
1768:2014
1761:3840
1744:IETF
1723:2014
1716:3841
1699:IETF
1678:2014
1671:3263
1654:IETF
1633:2014
1626:7315
1609:IETF
1585:2014
1554:2014
1528:2014
1515:ISBN
1494:2014
1481:ISBN
1457:2014
1450:4083
1433:IETF
1364:ISUP
1288:IPv6
1284:IPv4
1280:IPv6
1248:and
1246:TURN
1242:STUN
1201:HTTP
1197:MIME
1102:, a
1060:Path
1047:Path
1041:Path
1033:and
1031:path
957:and
883:HTTP
838:The
765:and
724:cell
722:and
645:and
594:and
554:CSeq
550:RSeq
542:RACK
498:HTTP
459:MIME
392:and
379:MIME
215:and
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