Upload
lamduong
View
229
Download
3
Embed Size (px)
Citation preview
Telecommunication Services Engineering Lab
Roch H. Glitho1
Telecommunication Services Engineering Lab
Layering in next generation networks
Services ( value-addedservices) also calledapplication / services
Roch H. Glitho2
.
application / services
Services (Basic service) also called call/session
Transport (Below IP + IP + transport layer) also calledbearer
Telecommunication Services Engineering Lab
Layering in next generation networks
Services
Infrastructural, application, middleware and baseware services
NGN
Roch H. Glitho3
.
Resources
Servicecontrol functions
Transportcontrol functions
Servicemanagement functions
Transportmanagement functions
NGNservice
NGNtransport
Transfer functional area
Resources
Telecommunication Services Engineering Lab
Layering in UMTS
UMTS (Universal Mobile Telecommunication Systems)
- An example of 3G system:
- Evolution of GSM
- Use of WCDMA
- Largest footprint
- Another example of 3G system- Evolution of CDMA-One
Roch H. Glitho4
- Evolution of CDMA-One
- Use of WCDMA, but a version incompatible with UMTS
- Dwindling footprint
Telecommunication Services Engineering Lab
Layering in UMTS
UMTS (Universal Mobile Telecommunication Systems)
- UMTS transport:
- TCP
- IP
- Below IP
- WCDMA
- Bandwidth (Peak rate: single digit Mbits/s – usually lower than 2)
Roch H. Glitho5
Telecommunication Services Engineering Lab
Layering in UMTS
UMTS (Universal Mobile Telecommunication Systems)
- UMTS Service:
- IP Multimedia Subsystem (IMS)
- Basic service (call / session or control layer)
- Value added services (value added service or service layer)
- Focus of this lecture: IMS
Roch H. Glitho6
Telecommunication Services Engineering Lab
IMS
1. Overall view
2. Control layer
3. Service layer
Roch H. Glitho7
3. Service layer
Telecommunication Services Engineering Lab
Overall view
1. General picture
2. Simplified picture
Roch H. Glitho8
Telecommunication Services Engineering Lab
General picture
C x
I P M u l t im e d ia N e tw o r k s
P S T N
M m
M b
L e g a c y m o b i le
s ig n a l l in g N e tw o r k s
C S C F
M w
B G C FM j
M i
B G C F
M k M k
C , D ,
G c , G r
M b P S T N
P S T N
Roch H. Glitho9
P - C S C F
C S C FM G C F H S S
C x
I M S -
M G WM n
M b
M g
M R F P
M b
M r
G o
P D F
M w
G mU E
M b
M b
M R F C
S L F
D x
M p
I M S u b s y s te m
A S
I S C
D h S h ,S i
Telecommunication Services Engineering Lab
Simplified picture
Roch H. Glitho10
.
Telecommunication Services Engineering Lab
Another simplified picture
S - C S C F S - C S C F
S IP A p pli c a t io n S e rv e r
S IP A p pli c a t io n S e rv e r
H S S H S S O SA s erv ice
cap ab ilit y s erv er (SC S)
O SA s erv ice cap ab ilit y s erv er
(SC S)
O SA ap p licat io n
s erv er
O SA ap p licat io n
s erv er
IS C
C x IS C
S C IM
A S A S
S h
Roch H. Glitho11
(SC S) (SC S)
IM - S S F IM - S S F
C am el Serv i ce E n v iro n m en t
C am el Serv i ce E n v iro n m en t
s erv er s erv er C x IS C
IS C
C A P
M A P
O SA AP I S i
Telecommunication Services Engineering Lab
Control layer
1. Functional entities
2. Protocols
3. Call cases
Roch H. Glitho12
Telecommunication Services Engineering Lab
Functional entities
Data bases (just one)
Home Subscriber Server (HSS)
- Evolution of the HLR
- All user related subscription data (e.g. profile)
- A network may contain one or several
- Subscriber Location Function (SLF) maps users to specific HSS
Roch H. Glitho13
HSS
.
Telecommunication Services Engineering Lab
Functional entities
Control entities
Call Session Control Function (CSCF) “The switch”
Three types (May be collocated)
- Proxy CSCF
- Serving CSCF
- Interrogating CSCF
Roch H. Glitho14.
Telecommunication Services Engineering Lab
Functional entities
Control entities
Proxy-CSCF:
- Location
Either visited network or home network
- First contact point in the IM network
- Outbound / In-bound SIP proxy (All requests from/to IMS terminals go through it)
Roch H. Glitho15
terminals go through it)
- Forward SIP requests in the appropriate direction (Terminals or IMS network)
- Several functions
- Security
- Generation of charging information
- Compression and un-compression of messages
Telecommunication Services Engineering Lab
Functional entities
Control entities
Interrogating CSCF (I-CSCF):
SIP proxy located at the edge of an admnistrative domain
- Listed in the domain name server (DNS)
- There may be several in the same network for scalability reasons
Roch H. Glitho16
.
Telecommunication Services Engineering Lab
Functional entities
Control entities
Serving CSCF (S-CSCF):
Always located in home domain
SIP proxy + SIP registrar with possibility of performing session control
- Binding between IP address (terminal location) and user SIP address
- Interacts with application servers for value added service
Roch H. Glitho17
- Interacts with application servers for value added service purpose
- Translation services (Telephone number / Sip URIs)
- Routing
Telecommunication Services Engineering Lab
Functional entities
Control entities
Media Resource Function (MRF)
- Source of media (media mixing, announcement playing)
- Two parts
Control part: MRFC
Media Part: MRFP
Roch H. Glitho18
.
Telecommunication Services Engineering Lab
Functional entities
Control entities
Media Gateway Function (MGF):Signaling conversion between PSTN/2G and IMS
Media Gateway (MG)Media conversion between PSTN/2G and IMS
Roch H. Glitho19
.
Telecommunication Services Engineering Lab
Protocols
Signalling
SIP with extensions
Interactions with HSS
AAA
Roch H. Glitho20
.
Telecommunication Services Engineering Lab
Protocols
Example of SIP extension for IMS
Reliability of Provisional Responses for SIP
PRACK Method
Roch H. Glitho21
.
Telecommunication Services Engineering Lab
Example of SIP extension for IMS
PRACK
- Bring more reliability by enabling the acknowledgement of provisional responses:
- Only final responses are acknowledged in standard SIP
- ACK for OK
- PRACK plays the same role as OK, but for provisional responses (e.g. 180 - ringing) except (100 – trying)
Roch H. Glitho22
Telecommunication Services Engineering Lab
Example of SIP extension for IMS
PRACK
- Essential features
- Normal SIP request with its own response (i.e. OK)
- Each provisional response is given a sequence number Rseq
- PRACK contains a header Rack to indicate the sequence of the provisional response being acknowledged
- Caller indicates if it supports or not PRACK
Roch H. Glitho23
- Both parties can indicates if it is required or not
Telecommunication Services Engineering Lab
Example of SIP extension for IMS
PRACK
Roch H. Glitho24
• http://www.dialogic.com/webhelp/IMG1010/10.5.1/WebHelp/Description/SIP/SIP_PRACK_Call_Flows.htm
.
Telecommunication Services Engineering Lab
Example of SIP extension for IMS
PRACK
Roch H. Glitho25
• http://www.dialogic.com/webhelp/IMG1010/10.5.1/WebHelp/Description/SIP/SIP_PRACK_Call_Flows.htm
.
Telecommunication Services Engineering Lab
Example of SIP extension for IMS
PRACK
Roch H. Glitho26
• http://www.dialogic.com/webhelp/IMG1010/10.5.1/WebHelp/Description/SIP/SIP_PRACK_Call_Flows.htm
.
Telecommunication Services Engineering Lab
Authentication, Authorization and Accounting
1. Informal definitions
2. AAA in Internet
3. AAA in IMS
Roch H. Glitho27
4. Call cses
Telecommunication Services Engineering Lab
Informal definitions
• Authentication– Means of verifying that an entity is really what it claims to be
• Authorization
– Means of ensuring that en entity does only what it is allowed to do
Accounting
Roch H. Glitho28
• Accounting
– Means of keeping track of what an entity does for auditing, billing and other purposes
Telecommunication Services Engineering Lab
AAA in Internet
Remote Authentication Dial In User Service (RADIUS) protocol– RFC 2058, then 2138, 1997
– RFC 2865, 2000
• Possibility for a Network Access Server (NAS) to get authentication, authorization and accounting (AAA) services from a RADIUS server
• Client/server
Roch H. Glitho29
• Client/server
• Runs on top of UDP
• Example: Computer with a modem, connected to a NAS and NAS connected to a RADIUS server
» Very useful when there are several NAS
.
Telecommunication Services Engineering Lab
AAA in Internet
Remote Authentication Dial In User Service (RADIUS) protocol
• Issues
– Lack of scalability
– Lack of functionality (e.g. no possibility for unsolicited messages from RADIUS server to NAS)
Roch H. Glitho30
.
Telecommunication Services Engineering Lab
AAA in Internet
Diameter– Addresses RADIUS shortcomings
• Scales
• More functionality
– Much more complex
• Base protocol, RFC 33588, 2003
– Basic commands (e.g. Re-Auth-Request, Re-Auth-Answer, Accounting-Request)
Roch H. Glitho31
Accounting-Request)
• Application protocols
– Extend the basic commands
.
Telecommunication Services Engineering Lab
AAA in IMS
• Interfaces
– Cx: I-CSCF / HSS and S-CSCF/HSS
– Dx: I-CSCF / SLF and S-CSCF / SLF
– Sh: HSS/SIP AS and HSS/OSA SCS
• Protocol
Roch H. Glitho32
• Protocol
– Diameter with IMS specific applications
.
Telecommunication Services Engineering Lab
IP Multimedia portion – Registration
.
P - C S C F H S SI - C S C F
1 . R e g i s t e r
2 . R e g i s t e r
3 . C x - Q u e r y
U E
V i s i t e d N e t w o r k H o m e N e t w o r k
4 . C x - Q u e r y R e s p
5 . C x - S e l e c t - p u l l
6 . C x - S e l e c t - p u l l R e s p
7 . R e g i s t e r
8 . C x - p u t
S - C S C F
Roch H. Glitho33
1 0 . C x - P u l l
1 1 . C x - P u l l R e s p
1 3 . 2 0 0 O K
1 4 . 2 0 0 O K1 5 . 2 0 0 O K
9 . C x - p u t R e s p
1 2 . S e r v i c e C o n t r o l
Telecommunication Services Engineering Lab
IP Multimedia portion – Un-Registration
.
P-CSCF HSSI-CSCFUE
Visited Network Home Network
1. REGISTER
2. REGISTER
3. Cx-Query
S-CSCF
Roch H. Glitho34
4. Cx-Query-Resp
5. REGISTER
9. 200 OK
10. 200 OK
11. 200 OK
7. Cx -Put
8. Cx -Put Resp
6. Service Control
Telecommunication Services Engineering Lab
Use of Megaco / H.248
– Interworking 3G/2G
• MGF
• MG
– Conferencing
• MRFC
• MRFP
Roch H. Glitho35
.
Telecommunication Services Engineering Lab
Service layer
1. Functional entities
2. Protocols
Roch H. Glitho36
Telecommunication Services Engineering Lab
Functional entities
Application server (AS)
Host services and execute services
Communicate with control layer using SIP (i.e. ISC interface)
Two types
SIP AS:
Open Service Architecture – Service Capability Server
Roch H. Glitho37
Open Service Architecture – Service Capability Server (OSA/SCS)
Telecommunication Services Engineering Lab
Functional entities
S - C S C F S - C S C F
S IP A p pli c a t io n S e rv e r
S IP A p pli c a t io n S e rv e r
H S S H S S O SA s erv ice
cap ab ilit y s erv er (SC S)
O SA s erv ice cap ab ilit y s erv er
(SC S)
O SA ap p licat io n
s erv er
O SA ap p licat io n
s erv er
IS C
C x IS C
S C IM
A S A S
S h
Roch H. Glitho38
(SC S) (SC S)
IM - S S F IM - S S F
C am el Serv i ce E n v iro n m en t
C am el Serv i ce E n v iro n m en t
s erv er s erv er C x IS C
IS C
C A P
M A P
O SA AP I S i
Telecommunication Services Engineering Lab
Functional entities
SIP AS
SIP servlets technology
Open Service Architecture – Service Capability Server (OSA/SCS)
Parlay / OSA technology
Roch H. Glitho39
Parlay / OSA technology
Telecommunication Services Engineering Lab
Protocols
ISC
SIP + extensions
Roch H. Glitho40
.
Telecommunication Services Engineering Lab
References
3GPP• K. Knightson, N. Morita and T. Towle, NGN Architecture: General Principles, Functional
Architecture and Implementation, IEEE Communications Magazine , October 2005, Vol.43, No10
• G. Camarillo and M. Garcia-Martin, The 3G IP Multimedia Subsystem, Wiley, 2004 , Part II
• M. Toy, H. Stuttgen and M. Ulema, guest editors, IP Multimedia Subsystems (IMS), IEEE Communications Magazine special issue, March 2007
• M. Toy, H. Stuttgen and M. Ulema, guest editors, IP Multimedia Subsystems (IMS), IEEE Communications Magazine special issue, July 2007
Roch H. Glitho41
Communications Magazine special issue, July 2007
.