Tag-Archive for » cscf «

13
Apr
Entities and Function of IMS
uchan

In the IMS there are six categories

ims-entities
  1. CSCF ===> Session management and routing Server
  2. HSS   ===> Databases
  3. IW     ===> Interworking Element
  4. SE     ===> Support Entities
  5. CE     ===> Charging Entities
  6. AS     ===> Application Server

1.Proxy –call session control function

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the proxy call session control function is the first contact point for users within IMS, all SIP signaling traffic from or to UE go via the P-CSCF, it validates the request. forward to selected destinations and process and forward the response 

an operator network can be contain one or many P-CSCFs, furthermore P-CSCF provide IPsec or ESP (Encapsulation Security Payload) for SIP signaling and interacts with PDF (Policy Decision Function) for media policing purpose, finally it contributed to the charging process by sending accounting-related info to the CCF ( Charging Collection Functions)

2.Serving –Call Session Control Function

the S-CSCF have a functions ;

  • Handling of registration request and users de-registration when needed
  • Mutual authentication between user and Network
  • Download of user information and service related data from HSS
  • Routing of mobile termination traffic to the P-CSCF and mobile originated traffic to the I-CSCF, Breakout Gateway Control Function (BGCF) or the Application Server (AS)
  • Media Policing, a process that check the content of the user payload to find out whether it contains media type or codecs which are not allowed for a user
  • Accounting-related information to the CCF for offline charging purpose and to the online charging system  (OCS) for online charging purpose

the serving-cscf is the brain of IMS an operator can include multiple S-CSCF with different functionalities

3.Interrogation –Call Session Control Function

the functions of I-CSCF is :

  • contact the HSS to obtain the name of the S-CSCF that serving the user, and S-CSCF assignment
  • forwarding of SIP requests or response to the S-CSCF
  • provisioning of accounting-related information to the CCF
  • provisioning of a hiding functionality an optional integrated topology hiding internetwork Gateway (THIG) can be used to hide the configuration, capacity and topology of the network from outside an operator’s network

for scalability and redundancy reason an operator network may contain multiple I-CSCF

4.Home Subscriber Server

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the Home Subscriber Server (HSS) in the main data storage for all IMS subscriber and service –related data. the data stored in the HSS include user identities, registration information, access parameters and service triggering information

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user identities consist of two types: private and public user identities .. the private user identities is a user ID that assigned  by the home network operator and is used for purposes like registration and authorization. it can be compared to the international mobile subscriber identity (IMSI) in GSM network 

the public user identity is the ID that other users can use for requesting communication with the end user. it server a similar purpose as the TMSI, Temporary Mobile Subscriber Identity,in GSM

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A special mechanism called the Subscription Locator Function (SLF) is implemented within I-CSCF, S-CSCF and Application Server , when separately addressable HSSs have been installed within the network, it is used a resolution mechanism to find the proper address of the HSS that holds the subscriber data for a given user identity  

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IMS access parameters are used to set up sessions and include parameters like authentication, roaming authorization and allocated S-CSCF names, Serving-treggering information enables SIP service execution the also provides user specification requirement for S-CSCF capabilities ,this information is used by the I-CSCF to select the most suitable S-CSCF for user

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there can be more than one HSS in home network depending on the number of mobile subscribers, the equipment capacity and the organization of the network. communication between different HSS function is not standardized

5.Policy Decision Function (PDF)

The Decision Function (PDF) makes policy decisions base on session and media-related information obtain from the P-CSCF in Release 5 it is an integral part of the P-CSCF, it acts as a policy decisions point for service based local policy control

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Service based local policy (SBLP) provides parameters for :

  • session identification ex: IP address, port numbers,bandwidths,etc
  • session authorization to PDF and GGSN depending on the requested bearer ex: Packet data Protocol or PDP context
  • session maintenance (PDP context modification or re-establishment)
  • session charging by passing an IMS-charging identifier to the GGSN and a GPRS-charging identifier to the P-CSCF

image    to be continue …..(^^),\/

Category: IMS  Tags: , , , , , ,  One Comment
05
Feb
Pendahuluan IMS
uchan

Dalam wacana ini penulis coba membuat miniatur jaringan IMS supaya para pembaca lebih mudah dalam hal mengimplentasikan nya …

IMS (IP Multimedia Service) yaitu salah satu fungsinya memanage teknologi dan service yang telah ada atau pun yang akan datang dengan menggunakan basis IP sebagai domain teknologinya kelebihan dari OpenIMS lebih bermain disisi sofware sebagai pengganti hardware yang dapat di ganti dengan PC server dan juga bisa dimodifikasi sesuai kebutuhan dengan gratis, Pertama kali diperkenalkan oleh FOKUS (Fraunhofer Institute for Open Communication System) pada tahun 2006 di Jerman.


architecture dari jaringan IMS dapat di lihat pada gambar dibawah ini :


ims network

ims network

IMS tidak meberikan standar pada setiap service yang di berikan tapi hanya menyediakan layanan tersebut agar dapat berjalan dengan baik ,dan mendukung secara penuh turunan ayanan multimedia over IP,seperti VoIP,IM,Streaming,dll satu lagi yang menjadi keunggulan dari IMS bersifat modular dan open Interfacesehingga mudah di kembangkan secara terpisah

Sory gw lanjutin pake bahasa inggris .. Mohon maklum ya klo grammer rada2 nya ngacoo …

Lebih baik memulai sesuatu dengan berani dari pada gagal untuk berusaha memulai sesuatu..

At the present ,cellular network have already provide a wide range and the cellular user can access the internet using a data connection.. So way do we need IMS ?

As we know there are different domain in the 3G network they are the circuit switch (Iu-CS) and the package switch (Iu-PS), the Iu-CS carry the voice ,video and short message service (SMS), in the circuit network there are two different planes the signaling plane and the media plane

In the signaling plane include the protocol use to established the circuit switch path between terminal and the media plane include the data transmitted over the circuit switch path between the terminal

In the media plane include encode voice exchange between terminal

The 3GPP ( third generation partnership project) define the MSC (Mobile Switching Center) with two part MSC server and Media Gateway,

The MSC server will work for the signaling plane while the media gateway will handle the media plane beside of IMS has the signaling and media plane just as the circuit switch and the 3GPP

The first reason why we need the IMS ,it was to provide the service with QoS (Quality of Service), in the package switch domain provide best-effort service without the QoS, so the quality the VoIP conversation can change dramatically, example the person voice may sound perfectly clear but sometime that worse

The IMS allow the operator to control the Quality a user get, so that the operator can differentiated certain group of costumer from other

The second reason is to enable charge of multimedia session, the IMS provide the information about the service being invoked by the user and with this information the operator can decides whether used the flat rate for the service, apply traditional time base charging, package base charging, QoS base charging or perform any new type of charging

And the third reason for existence of IMS was to integrated service to user, service developer use the standard interface define the IMS so that the operator can integrated the service and create new service

The operator today want to provide more package switch services to users, that is the mobile internet needs to become more attractive to its users, if the IMS has been established so the aim is :

  1. Combine the latest trend technology
  2. Make the mobile internet paradigm come true
  3. Create a common platform to develop diverse multimedia service
  4. Create mechanism to boost margin due to extra usage of the mobile package switch network
Category: IMS  Tags: , , , , , ,  One Comment