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the (328), and (169), ims (94), sip (84), cscf (80), for (72), #network (70), user (50), used (45), are (39), service (36), services (35), that (34), control (33), with (32), information (32), from (31), function (31), media (31), this (29), can (29), also (28), multimedia (27), over (27), 3gpp (27), edit (27), between (27), networks (26), charging (26), hss (23), when (23), session (23), which (22), not (22), mrfc (20), gateway (20), based (19), agcf (19), application (18), call (17), identity (17), access (16), interfaces (16), subscriber (16), server (16), bgcf (16), may (15), other (15), diameter (15), mgw (15), domain (15), interconnection (15), use (14), messages (14), interface (14), exchange (14), using (13), voice (13), signalling (13), message (13), public (13), impu (13), has (12), terminal (12), subsystem (11), mobile (11), architecture (11), lte (11), release (11), different (11), added (11), registration (11), resources (11), 248 (11), plane (11), pstn (11), policy (10), 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Text of the page (random words):
res wildcarded public user identity a wildcarded public user identity expresses a set of impu grouped together the hss subscriber database contains the impu impi imsi msisdn subscriber service profiles service triggers and other information call session control function cscf edit several roles of sip servers or proxies collectively called call session control function cscf are used to process sip signaling packets in the ims a proxy cscf p cscf is a sip proxy that is the first point of contact for the ims terminal it can be located either in the visited network in full ims networks or in the home network when the visited network is not ims compliant yet some networks may use a session border controller sbc for this function the p cscf is at its core a specialized sbc for the user network interface which not only protects the network but also the ims terminal the use of an additional sbc between the ims terminal and the p cscf is unnecessary and infeasible due to the signaling being encrypted on this leg the terminal discovers its p cscf with either dhcp or it may be configured e g during initial provisioning or via a 3gpp ims management object mo or in the isim or assigned in the pdp context in general packet radio service gprs it is assigned to an ims terminal before registration and does not change for the duration of the registration it sits on the path of all signaling and can inspect every signal the ims terminal must ignore any other unencrypted signaling it provides subscriber authentication and may establish an ipsec or tls security association with the ims terminal this prevents spoofing attacks and replay attacks and protects the privacy of the subscriber it inspects the signaling and ensures that the ims terminals do not misbehave e g change normal signaling routes disobey home network s routing policy it can compress and decompress sip messages using sigcomp which reduces the round trip over slow radio links it may include a policy decision function pdf which authorizes media plane resources e g quality of service qos over the media plane it is used for policy control bandwidth management etc the pdf can also be a separate function it also generates charging records an interrogating cscf i cscf is another sip function located at the edge of an administrative domain its ip address is published in the domain name system dns of the domain using naptr and srv type of dns records so that remote servers can find it and use it as a forwarding point e g registering for sip packets to this domain it queries the hss to retrieve the address of the s cscf and assign it to a user performing sip registration it also forwards sip request or response to the s cscf up to release 6 it can also be used to hide the internal network from the outside world encrypting parts of the sip message in which case it s called a topology hiding inter network gateway thig from release 7 onwards this entry point function is removed from the i cscf and is now part of the interconnection border control function ibcf the ibcf is used as gateway to external networks and provides nat and firewall functions pinholing the ibcf is a session border controller specialized for the network to network interface nni a serving cscf s cscf is the central node of the signaling plane it is a sip server but performs session control too it is always located in the home network it uses diameter cx and dx interfaces to the hss to download user profiles and upload user to s cscf associations the user profile is only cached locally for processing reasons and is not changed all necessary subscriber profile information is loaded from the hss it handles sip registrations which allows it to bind the user location e g the ip address of the terminal and the sip address it sits on the path of all signaling messages of the locally registered users and can inspect every message it decides to which application server s the sip message will be forwarded in order to provide their services it provides routing services typically using electronic numbering enum lookups it enforces the policy of the network operator there can be multiple s cscfs in the network for load distribution and high availability reasons it s the hss that assigns the s cscf to a user when it s queried by the i cscf there are multiple options for this purpose including a mandatory optional capabilities to be matched between subscribers and s cscfs application servers edit see also next generation network services sip application servers as host and execute services and interface with the s cscf using sip an example of an application server that is being developed in 3gpp is the voice call continuity function vcc server depending on the actual service the as can operate in sip proxy mode sip ua user agent mode or sip b2bua mode an as can be located in the home network or in an external third party network if located in the home network it can query the hss with the diameter sh or si interfaces for a sip as sip as host and execute ims specific services ip multimedia service switching function im ssf interfaces sip to cap to communicate with camel application servers osa service capability server osa scs interfaces sip to the osa framework functional model edit the as ilcm application server incoming leg control model and as olcm application server outgoing leg control model store transaction state and may optionally store session state depending on the specific service being executed the as ilcm interfaces to the s cscf ilcm for an incoming leg and the as olcm interfaces to the s cscf olcm for an outgoing leg application logic provides the service s and interacts between the as ilcm and as olcm public service identity edit public service identities psi are identities that identify services which are hosted by application servers as user identities psi takes the form of either a sip or tel uri psis are stored in the hss either as a distinct psi or as a wildcarded psi a distinct psi contains the psi that is used in routing a wildcarded psi represents a collection of psis media servers edit the media resource function mrf provides media related functions such as media manipulation e g voice stream mixing and playing of tones and announcements each mrf is further divided into a media resource function controller mrfc and a media resource function processor mrfp the mrfc is a signalling plane node that interprets information coming from an as and s cscf to control the mrfp the mrfp is a media plane node used to mix source or process media streams it can also manage access right to shared resources the media resource broker mrb is a functional entity that is responsible for both collection of appropriate published mrf information and supplying of appropriate mrf information to consuming entities such as the as mrb can be used in two modes query mode as queries the mrb for media and sets up the call using the response of mrb in line mode as sends a sip invite to the mrb the mrb sets up the call breakout gateway edit a breakout gateway control function bgcf is a sip proxy which processes requests for routing from an s cscf when the s cscf has determined that the session cannot be routed using dns or enum dns it includes routing functionality based on telephone numbers pstn gateways edit a pstn cs gateway interfaces with pstn circuit switched cs networks for signalling cs networks use isdn user part isup or bicc over message transfer part mtp while ims uses sip over ip for media cs networks use pulse code modulation pcm while ims uses real time transport protocol rtp a signalling gateway sgw interfaces with the signalling plane of the cs it transforms lower layer protocols as stream control transmission protocol sctp an ip protocol into message transfer part mtp a signalling system 7 ss7 protocol to pass isdn user part isup from the mgcf to the cs network the sgw does call control protocol conversion between sip and isup bicc under the control of the mgcf a media gateway controller function mgcf is a sip endpoint that interfaces with the sgw over sctp it also controls the resources in a media gateway mgw across an h 248 interface a media gateway mgw interfaces with the media plane of the cs network by converting between rtp and pcm it can also transcode when the codecs don t match e g ims might use amr pstn might use g 711 media resources edit media resources are those components that operate on the media plane and are under the control of ims core functions specifically media server ms and media gateway mgw ngn interconnection edit there are two types of next generation networking interconnection service oriented interconnection soix the physical and logical linking of ngn domains that allows carriers and service providers to offer services over ngn i e ims and pes platforms with control signalling i e session based which provides defined levels of interoperability for instance this is the case of carrier grade voice and or multimedia services over ip interconnection defined levels of interoperability are dependent upon the service or the qos or the security etc connectivity oriented interconnection coix the physical and logical linking of carriers and service providers based on simple ip connectivity irrespective of the levels of interoperability for example an ip interconnection of this type is not aware of the specific end to end service and as a consequence service specific network performance qos and security requirements are not necessarily assured this definition does not exclude that some services may provide a defined level of interoperability however only soix fully satisfies ngn interoperability requirements an ngn interconnection mode can be direct or indirect direct interconnection refers to the interconnection between two network domains without any intermediate network domain indirect interconnection at one layer refers to the interconnection between two network domains with one or more intermediate network domain s acting as transit networks the intermediate network domain s provide s transit functionality to the two other network domains different interconnection modes may be used for carrying service layer signalling and media traffic charging edit offline charging is applied to users who pay for their services periodically e g at the end of the month online charging also known as credit based charging is used for prepaid services or real time credit control of postpaid services both may be applied to the same session charging function addresses are addresses distributed to each ims entities and provide a common location for each entity to send charging information charging data function cdf addresses are used for offline billing and online charging function ocf for online billing offline charging all the sip network entities p cscf i cscf s cscf bgcf mrfc mgcf as involved in the session use the diameter rf interface to send accounting information to a cdf located in the same domain the cdf will collect all this information and build a call detail record cdr which is sent to the billing system of the domain each session carries an ims charging identifier icid as a unique identifier generated by the first ims entity involved in a sip transaction and used for the correlation with cdrs inter operator identifier ioi is a globally unique identifier shared between sending and receiving networks each domain has its own charging network billing systems in different domains will also exchange information so that roaming charges can be applied online charging the s cscf talks to a ims gateway function ims gwf which looks like a regular sip application server the ims gwf can signal the s cscf to terminate the session when the user runs out of credits during a session the as and mrfc use the diameter ro interface towards an ocf when immediate event charging iec is used a number of credit units is immediately deducted from the user s account by the ecf and the mrfc or as is then authorized to provide the service the service is not authorized when not enough credit units are available when event charging with unit reservation ecur is used the ecf event charging function first reserves a number of credit units in the user s account and then authorizes the mrfc or the as after the service is over the number of spent credit units is reported and deducted from the account the reserved credit units are then cleared ims based pes architecture edit ims based pes pstn emulation system provides ip networks services to analog devices ims based pes allows non ims devices to appear to ims as normal sip users analog terminal using standard analog interfaces can connect to ims based pes in two ways via a mgw access media gateway that is linked and controlled by agcf agcf is placed within the operators network and controls multiple a mgw a mgw and agcf communicate using h 248 1 megaco over the p1 reference point pots phone connect to a mgw over the z interface the signalling is converted to h 248 in the a mgw and passed to agcf agcf interprets the h 248 signal and other inputs from the a mgw to format h 248 messages into appropriate sip messages agcf presents itself as p cscf to the s cscf and passes generated sip messages to s cscf or to ip border via ibcf interconnection border control function service presented to s cscf in sip messages trigger pes as agcf has also certain service independent logic for example on receipt of off hook event from a mgw the agcf requests the a mgw to play dial tone via vgw voip gateway or sip gateway adapter on customer premises pots phones via voip gateway connect to p cscf directly operators mostly use session border controllers between voip gateways and p cscfs for security and to hide network topology voip gateway link to ims using sip over gm reference point the conversion from pots service over the z interface to sip occurs in the customer premises voip gateway pots signaling is converted to sip and passed on to p cscf vgw acts as sip user agent and appears to p cscf as sip terminal both a mgw and vgw are unaware of the services they only relay call control signalling to and from the pstn terminal session control and handling is done by ims components interfaces description edit tispan ims architecture with interfaces interface name ims entities description protocol technical specification cr mrfc as used by mrfc to fetch documents e g scripts announcement files and other resources from an as also used for media control related commands tcp sctp channels cx i cscf s cscf hss used to send subscriber data to the s cscf including filter criteria and their priority also used to furnish cdf and or ocf addresses diameter ts29 229 ts29 212 dh as sip as osa im ssf slf used by as to find the hss holding the user profile information in a multi hss environment dh_slf_query indicates an impu and dx_slf_resp return the hss name diameter dx i cscf or s cscf slf used by i cscf or s cscf to find a...