National Chung Cheng University 行動全網際網路電信

Microsoft PowerPoint - ITN_6_Mobile_All_IP_Telecom [] Mobile ALL IP Telecom.
(Wireless VoIP) Chiang, Wei-Kuo () Associate Professor Department of CSIE National Chung Cheng University Office : EA 311 Phone : 05-2720411~33126 Email : [email protected] URL : http://www.cs.ccu.edu.tw/~wkchiang/
National Chung Cheng University
Introduction to Telecom. Networks Mobile All IP Telecom (Wireless VoIP)2
Next Generation Network Internet Telecom & Wireless Communication
IP
MGCF
CSCF
Outline 3GPP All IP Network
Network Architecture
Network Entities
Message Flows
3GPP All IP Network
Packet (user traffic / signaling)

(circuit)RNCMS PSTN link (signaling)(packet) PS-domain VoIP (backward compatibility) legacy terminal
CSCF SIP proxy server HSS (Home Subscriber Server) HLR
3GPPRelease 4 & 5 Network Architecture Release 4Release 5 R99R4 - R4Soft-switch Signal
Media MSC (Mobile Station Center)MSC ServerSignalMedia GatewayMediaGMSC
Release 4 Circuit Switched DomainRelease 5 Packet Switched Domain3GGPRS 2.5G IPData AccessHSS (Home Subscriber Server)2G GSM HLR (Home Location Register)Services3G HSS
CSCF (Call Session Control Function) Call Control MRF (Multimedia Resource Function) Media Mixing, Play Announcement,Multi-party Conferencing H.323MCU Soft-switch Media Server
3GPP - All IP Core Network
Circuit-Switched Services

All IP MSC Server MSC MGCP/MEGACO All IP MSC (signaling) (media)MSC Server MGW (Media Gateway)MSC Server MGCP MEGACO MGW
Packet-Switched Services
Real-Time PS Services
Interworking with PSTN
Home Subscriber Server
HSS (1/2) HSS (Home Subscriber Server) is the master
database for a given user. Functionalities
The HLR functionality required by the PS-Domain
The circuit switched part of the HLR
User control functions required by the IP multimedia (IM) subsystem
HSS
D C Gr Gc Mh Cx

HSS (2/2) MAP termination Addressing protocol termination Authentication, Authorization protocol
termination IP multimedia control termination
MAP termination
Addressing Protocol
Media Gateway Control
MGCF & MGW Media Gateway Control Function
Being PSTN signaling termination point
Performing protocol conversion between the legacy (e.g., ISUP) and the All-IP network call control protocols
Media Gateway Being PSTN transport termination point
Interfacing UTRAN over Iu

MSC Server
MSC Server Mainly comprising the call control and mobility
control parts of a GSM/UMTS MSC Performing the connection control for media
channels in a MGW MSC server + MGW = MSC

MRF
RNC
MRF Multimedia Resource Function
The same function as an MCU in the H.323 network

T-SGW & R-SGW
T-SGW & R-SGW Transport Signaling Gateway Function
Mapping call related signaling (i.e., SS7/ISUP) from PSTN/PLMN on an IP bearer and sending it to the MGCF
Providing PSTN/PLMNIP transport level address mapping
Roaming Signaling Gateway Function Providing communication (i.e., SS7/MAP) with a 2G/R99 MSC/VLR

T-SGW (Transport Signaling Gateway Function) ISUP, SS7 (mapping) PSTN/PLMN IP
R-SGW (Roaming Signaling Gateway Function) query GSM/GPRS VLR
T-SGW R-SGW Signaling gateway T-SGW (: ISUP)R-SGW2G/Release 99 MSC/VLR
Outline 3GPP All IP Network
Network Architecture
Network Entities
Message Flows
IP Multimedia Subsystem (1/2)
IP Multimedia (IM) CN subsystem Comprising all CN elements for provision of multimedia services.
The IM subsystem (IMS) utilizes the PS domain to transport multimedia signaling and bearer traffic.
The IMS attempts to be conformant to IETF “Internet standards”. SIP (Session Initiation Protocol) has been selected as the interfaces between the IM CN elements.
IP Multimedia Subsystem (2/2)
UE presence in IMS Home Network IM Subsystem
Visited Network IM Subsystem
Gi
Virtual presence of UE in visited network IM subsystem (UE’s IP-address is here)
UE shall acquire the necessary IP address(es) as part of the PDP context activation procedure(s)
Identification of IM Users Private user identities
Assigned by the home network operator
Stored on USIM (UMTS Subscriber Identity Module)
Stored within the HSS (use for registration)
Contained in all registration requests passed from UE to home network (for authentication)
Not used for routing of SIP messages
Public user identities Every IM subscriber shall have one or more public
user identities.
The public user identity shall take the form of SIP URL or E.164 number. (SIP URL for routing of SIP)
Call Session Control Function The main function entity in 3G IM Subsystem Behaves as SIP Proxy server CSCFs may have different capabilities Terminal and node behaviours should be
consistent, regardless of whether the user is roaming
Three kinds of CSCFs defined Proxy CSCF (P-CSCF)
Interrogating CSCF (I-CSCF)
Serving CSCF (S-CSCF)
Proxy CSCF P-CSCF is the first contact point for the handset
Its address is discovered by UEs following PDP context activation procedure.
Behaving like a Proxy server Also behaving as a User Agent in abnormal conditions
Functions Forward SIP register request from the UE to I-CSCF determined using the home domain name.
Forward SIP messages from the UE to the SIP server (e.g. S-CSCF) whose name the P-CSCF has received as a result of registration procedure.
Detect an emergency session and select a S-CSCF to handle emergency sessions.
Authorization of bearer resources & QoS management.
Interrogating CSCF I-CSCF is the contact point within an operator’s
network for all connections destined to a subscriber of that network operator. That is,I-CSCF is the first contact point within an
operator’s network for incoming call signaling.
Registration Assigning a Serving CSCF to a user performing SIP
registration
Session Flow Routing a SIP request received from the S-CSCF(Serving
Originating UE) towards the S-CSCF(Serving Terminating UE)
Obtaining the S-CSCF address from HSS
I-CSCF(THIG) Topology Hiding Inter-network Gateway
In the I-CSCF, the operator may use a Topology Hiding Inter-network Gateway (THIG) function to hide the configuration, capacity, and topology of the network from the outside.
When an I-CSCF(THIG) is chosen to meet the hiding requirement then for sessions traversing across different operators domains, the I- CSCF(THIG) may forward the SIP request or response to another I-CSCF(THIG) allowing the operators to maintain configuration independence.
Serving CSCF S-CSCF performs session control services for the UE
Maintaining a session state as needed by the network operator for support of the services
Registration As a Registrar, it accepts registration requests and makes its information available through the location server (e.g., HSS).
Session-related/-unrelated Flows As a Proxy Server, it accepts requests & services them internally or forwards them on.
As a User Agent, it may terminate & independently generate SIP transactions.
Interaction with Service Platforms for support of services
ENUM DNS Translation The S-CSCF shall support the ability to
translate the E.164 address contained in a request-URI in the non-SIP URL to SIP URL Using ENUM DNS translation mechanism
RFC 2916 If the translation fails, then the session may be routed to the PSTN or appropriate notification shall be sent to the mobile.
Database aspects of ENUM are outside the scope of 3GPP.
Registration Diagram
GGSNGGSN SGSNSGSN
I-CSCF
HSS
1. P-CSCF & GPRS within the same network. 2. Forward to I-CSCF by “home domain name. 3. User can register in the P-CSCF network ? 5. Request info about required S-CSCF cap. ? 4,6. Responses & Information. 7. Select S-CSCF. 8,9. Send S-CSCF to HSS for the subscriber. 10,11. Download user profile to access service. 12. Send Register info to Service Platform.
3,5 4,6
Application Level Registration
5. Cx-Select-Pull 6. Cx-Select-Pull Resp.
7. Register
8. Cx-Put
9. Cx-Put-Resp.
10. Cx-Pull
11. Cx-Pull-Resp.
15. 200 OK
12. Service Control
Request info about required S-CSCF cap. ?
Send S-CSCF name to HSS for the subscriber
Download user profile to access service. Store P-CSCF addressIf I-CSCF(THIG),
Encrypt S-CSCF
Proxy-CSCF Discovery
1. Activate PDP Context Request
3. Activate PDP Context Accept
1. Create PDP Context Request
3. Create PDP Context Response
DHCP server DNS serverUE GGSN
UE SGSN GGSN
Use of DHCP (Dynamic Host Configuration Protocol)
Transfer the P-CSCF address with the PDP Context Activation signaling to the UE
GGSN acts as a DHCP Relay Agent 1.Create PDP context bearer ( TS 23.060) 2.UE requests a DHCP server
2a. P-CSCF domain name 2b. IP addresses of DNS servers
3. UE performs a DNS query to retrieve P-CSCF(s) IP addresses
During PDP Context Activation signalling 1. UE indicates the request of P-CSCF
IP address(es) in PDP context request 1a. the indication forwarded to GGSN
2. GGSN gets IP-CSCF IP addresses (internal configure, implement choice)
3. P-CSCF IP forwarded to UE
Call Setup Diagram
I-CSCF
8
7
Session Flow Procedures(1/2)
UE#1 S-CSCF#1 S-CSCF#2 UE#2
One of the S-CSCF to S-CSCF Invite sequence information flows inserted
here
flows inserted here
flows inserted here
MO: Mobile Origination
MT: Mobile Termination
UE#1 S-CSCF#1 S-CSCF#2 UE#2
INVITE
Ringing
CSCF Roles & Features CSCF
P-CSCF (Proxy)
I-CSCF (Interrogating)
S-CSCF (Serving)
Behaving like Features/Functions Register Forward SIP register to I-CSCF by home domain name. Session Flow Forward SIP messages from UE to SIP server (S-CSCF)
as a result of registration procedure. Detect an emergency session and select a S-CSCF to
handle emergency sessions. Authorization of bearer resources & QoS management.
Proxy server User Agent
(register reject)
Register Assigning a Serving CSCF to the subscriber. Session Flow Routing a SIP request from another network towards
the S-CSCF(Serving Terminating UE) Obtaining the S-CSCF address from HSS
Registrar Proxy Server User Agent
Register As a Registrar, store registration info to HSS. Session-related/unrelated Flow S-CSCF performs session control services for the UE. Interaction with Service Platforms. Maintaining a session state as needed by the network
operator for support of the services.
IP Version Interworking
Signaling
Bearer
Note that the standardisation and functional requirements of Mx & Ix reference points are FFS.
IMS ALG & TrGW IMS Application Level Gateway (ALG)
The IMS ALG needs to modify the SIP message bodies and headers that have IP address association indicated.
The IMS ALG will request NA(P)T-PT to provide the bindings data between the different IP addresses (IPv6 to IPv4 and vice versa) upon session initiation, and will release the bindings at session release.
The TrGW is a NA(P)T-PT NAT-PT binds addresses in IPv6 network with addresses in
IPv4 network and vice versa to provide transparent routing between the two IP domain
without requiring any changes to end points, like the UE.
IP-Connectivity Access Network: that provides the underlying IP transport connectivity
between the UE and the IMS entities. An example of an "IP-Connectivity Access Network" is GPRS.
Originating towards IPv4 UE(A) IP-CAN P-CSCF(A) S-CSCF(A) IMS-ALG TrGW User side(B)
2. S- CSCF determines via DNS query that the domain of the terminating end supports IPv4 only
1. Session Initiation
3. Link in the IMS-ALG and get TrGW IPv4 addr/port information for user (A)
.4.Session Initiation continues
Terminating from IPv4 UE(A) IP-CAN P-CSCF(A) S-CSCF(A)
I-CSCF/ IMS-ALG
TrGW User side(B)
2. IMS-ALG determines (via DNS or preconfigured) the terminating I-CSCF and gets the IPv6 addr/port for user (A) from TrGW & forwards request to ICSCF so I-CSCF sees User (B) as IPv6
5.5.5.Session signalling path established
1. Session Initiation
Useful Web Sites International Packet Comm. Consortium
(IPCC) http://www.packetcomm.org/ International Softswitch Consortium(ISC)
IETF SIP & SIPPING Working Groups http://www.cs.columbia.edu/~hgs/sip/ http://www.ietf.org/html.charters/sip-charter.html http://www.sipcenter.com/
3GPP-Third Generation Partnership Project http://www.3gpp.org/
3GPP All IP Network TS 23.002 “Network architecture”
TS 23.221 “Architectural requirements”
IP Multimedia Subsystem (IMS); Stage 2(Release 7)
TS 23.228 “IP multimedia subsystem (IMS)”
TS 23.218 “IP multimedia (IM) call model”
TS 24.228 “Signaling flows based on SIP & SDP”
TS 24.229 “Call control based on SIP and SDP”
3GPP Specifications (1/2)
QoS related specs (P-CSCF) TS 23.107 “QoS concept and architecture” TS 23.207 “End-to-End QoS concept & architecture” TS 29.208 “End-to-End QoS signaling flows”
Security related specs (P-CSCF) TS 33.102 “Security architecture” TS 33.203 “Access security for IP-based services” TS 33.210 “IP network layer security”
Cx Interface specs (S-CSCF, I-CSCF) TS 29.228 “IP Multimedia (IM) Subsystem Cx Interface; Signaling flows and message contents”
TS 29.229 “Cx Interface based on the Diameter protocol; Protocol details”
3GPP Specifications (2/2)
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