Telecommunication Services Engineering Lab
Roch H. Glitho, PhD
Concordia University, Montreal
Canada
http://users.encs.concordia.ca/~glitho/
1
Roch H. Glitho
Telecommunication Services Engineering Lab
ITU-T Next Generation Networks: A vision
More a vision than a reality
• 2003 – 2004: Background work
– Requirements (or Wish list / desired characteristics)
– Architectural framework (e.g. overall principles, reference
model)
• 2004 – 2005: Focus group
– More detailed requirements
– Technical studies
• Since 2006: Global Standards Initiative
– Attempt to produce interface specifications and
implementation guidelines (or backing of existing
specifications / implementation guidelines)
2
Roch H. Glitho
Telecommunication Services Engineering Lab
3GPP/3GPP2 Next Generation Networks: A
Reality
More a reality than a vision
• Groups of telecommunications associations
– 3GPP (Third Generation Partnership Project)
– 3GPP 2 (Third Generation Partnership Project 2)
• Aiming at evolving the current telecommunication
infrastructure (i.e. 2G/2.5G) to 3G
– Work initiated much earlier than ITU-T (late 1990s)
– Much more momentum
• 3GPP perspective: system specification for evolving GSM
infrastructure to 3G
• 3GPP2 perspective: : system specification for evolving
CDMAone infrastructure to 3G
3
Roch H. Glitho
Telecommunication Services Engineering Lab
A bit of History: Standards Standpoint
First generation cellular networks (70s – 80s)
• Analog systems, circuit switching based
– Total Access Communications Systems (TACS) – UK
– Advanced Mobile Phone Systems (AMPS) – USA/Canada
– Nordic Mobile Telephone System (NMT) – Scandinavia
Second Generation (80s – early 90s)
• Digital systems, circuit switching based
–
–
–
–
GSM – Europe mainly – However, gaining ground in North America
D-AMPS (Digital version of AMPS)
PDC (Japan)
CDMA one (Korea, US)
4
Roch H. Glitho
Telecommunication Services Engineering Lab
A bit of History: Standards Perspective
Third (or Next) Generation (early 00s – )
• 3G / 3G and Beyond
– Still digital, but more capacity
– Packet switching based
– Two main standards
• UMTS (GSM evolution)
• CDMA 2000 (CDMA one evolution)
.
5
Roch H. Glitho
Telecommunication Services Engineering Lab
Telephony services
Sessions oriented / conversational services
• Two party main components
– Signalling
• Establishment, modification and tear down
– Media handling
• Transportation, mixing and other
• Examples
– Multimedia multiparty conferencing (e.g. multiparty
multimedia games)
• and many others
Examples of non sessions oriented / non conversational
end-user services
• Internet access, email, file transfer
6
Roch H. Glitho
Telecommunication Services Engineering Lab
Agenda
1. ITU-T Vision for Next Generation
Networks
2. Technologies for realizing the vision
(e.g. SIP, H.323, Megaco/H.248)
3. Soft-switches
4. 3GPP UMTS
7
Roch H. Glitho
Telecommunication Services Engineering Lab
The ITU-T Vision of Next Generation Networks
-
Desired characteristics
-
Architectural framework
.
8
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Categorization scheme used in this speech
•
•
•
•
•
•
Business model
En-user services and their provision
Separation of concerns
Network capacities
Regulatory issues
Inter-working with legacy
.
9
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Business model
• Unrestricted access to different service providers
– Has huge implications
• Plug and play by end – users when it comes to subscriptions
–
–
–
–
Last mile from provider A
Internet access from provider B
Telephony services running on the last mile from provider C
Streaming services running on last mile from provider D
.
10
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
End-user services and their provision
• Support of a wide range of services, applications and
mechanisms based on building blocks
• Generalized mobility (terminal, end-user and services)
• Variety of identification schemes
• Unified characteristics for the same service as perceived by
the user
• Converged services between fixed and mobile
.
11
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Separation of concerns
• Separation of control functions between bearer, call/session
and application / service
• Decoupling of service provision from transport and provision
of open interfaces
• Independence of service related functions from underlying
transport technologies
.
12
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Capacities
• Broadband
• Multiple last mile technologies
• Packet based transfer
.
13
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Regulatory issues
• Compliance with all regulatory issues
– Emergency communications
– Lawful interception
– Security
.
14
Roch H. Glitho
Telecommunication Services Engineering Lab
Desired characteristics
Inter-working with legacy
• Through open interfaces
.
15
Roch H. Glitho
Telecommunication Services Engineering Lab
Architectural framework
e.g., Video services (TV, movie, etc.)
e.g., Data services (WWW, e-mail, etc.)
e.g., voice telephony services (audio, fax, etc.)
G services
.
CO-CS, CO-PS and CLPS layer technologies
G transport
16
Roch H. Glitho
Telecommunication Services Engineering Lab
Architectural framework
Infrastructural, application, middleware and
baseware services
Services
NGN
service
Service
management functions
Service
control functions
Transport
management functions
Transport
control functions
NGN
transport
Resources
.
Resources
Transfer functional area
17
Roch H. Glitho
Telecommunication Services Engineering Lab
Architectural framework
……
Other NGNs
IWF
IWF
NGN
.
IWF
IWF
IWF
Internet
PLMN
PSTN
18
Roch H. Glitho
Telecommunication Services Engineering Lab
Standard technologies that may be used to
realize the vision
-
At the service control functions level
(IP Telephony)
-
Session Initiation Protocol (SIP)
-
H.323
- At the inter-working level
-
H.248 / Megaco
19
Roch H. Glitho
Telecommunication Services Engineering Lab
SIP
SIP: A set of IETF specifications including:
– SIP core signalling:
• RFC 2543, March 1999
• RFC 3261, June 2002 (Obsoletes RFC 2543)
– SIP extensions (e.g. RFC 3265, June 2002 - Event notification)
• May have nothing to do with signalling
– Used in conjunction with other IETF protocols
• QOS related protocol (e.g. RSVP)
• Media transportation related protocol (e.g. RTP - RFC 1889)
• Others (e.g. SDP - RFC 2327)
20
Roch H. Glitho
Telecommunication Services Engineering Lab
SIP
SIP core Signaling
– A signalling protocol for the establishment, modification and tear down
of multimedia sessions
– Based on HTTP
A few key features
– Text based protocol
– Client/server protocol (request/response protocol)
21
Roch H. Glitho
Telecommunication Services Engineering Lab
SIP: A simplified call case
•
CALLER
PROXY A
PROXY B
CALLEE
INVITE (1)
INVITE (2)
100 TRYING (3)
.
INVITE (4)
100 TRYING (5)
180 RINGING (6)
180 RINGING (7)
180 RINGING (8)
200 OK (9)
200 OK (10)
200 OK (11)
ACK (12)
MEDIA SESSION
BYE (13)
200 OK (14)
22
Roch H. Glitho
Telecommunication Services Engineering Lab
H.323: Introduction
An umbrella ITU-T standard including
– signalling standards:
• H.225.0: Registration – Admission - Status
• Q.931: Call Signalling
• H.245: Media Signalling
– Others (e.g. H.324 Terminal for low bit rate multimedia
communications)
23
.
Roch H. Glitho
Telecommunication Services Engineering Lab
H.323: Introduction
An umbrella ITU-T standard including
– signalling standards:
• H.225.0: RAS Signalling
• Q.931: Call Signalling
• H.245: Media Signalling
– Others (e.g. H.324 Terminal for low bit rate multimedia
communications)
24
.
Roch H. Glitho
Telecommunication Services Engineering Lab
H.323 signaling: Putting it together - A Call
Scenario
Gatekeeper Cloud
1 ARQ
2 ACF/ARJ
3 Setup
4 Setup
5 ARQ
6 ACF/ARJ
7 Connect
8 Connect
9 H.245 Channel
10 H.245 Channel
1
2
3
8
4
9
5
6
7
10
Endpoint 2
Endpoint 1
H.245 Control Channel Messages
T1521310-96
Call Signalling Channel Messages
RAS Channel Messages
.
25
Roch H. Glitho
Telecommunication Services Engineering Lab
Megaco/H.248
Primary motives for decomposing gateways between
PSTN and next generation networks:
– Scalability
– Specialization
– Opening up of market to new players
Side-effect
– Possibility of using the part of the decomposed gateway for call
control
• Soft-switches
26
Roch H. Glitho
Telecommunication Services Engineering Lab
Megaco/H.248
Media Gateway controller
Media gateway control protocol
Media Gateway
Media Gateway
Media Gateway
.
27
Roch H. Glitho
Telecommunication Services Engineering Lab
Megaco/H.248: PSTN / NGN Interconnection
User in NGN
MGC
INVITE
MG
User in PSTN
ISUP “INVITE” to PSTN
ISUP “OK” to MGC
OK
ACK
Add RTP stream to context
Add PCM stream to context
PCM
RTP
.
28
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switches
1. Introduction
2. Overview
3. A simplified call case
29
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switch: Introduction
A “side effect” of media gateway decomposition
- Gateway controller (plus some additional features) acts as a
switch
- Switching in software instead of hardware
- Can act as local exchange (class 5) or toll centre (class 4)
- Lower entry costs for new incumbents
- New local telephony networks and “by pass” for long distance call
providers
- Soft-switches vs. classical switches debate
- Scalability
- Reliability
- QoS
30
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switches : Overview
ISUP
H.323 or SIP
Soft-switch
(Media Gateway Controller +
Some intelligence)
MGC protocols
Media Gateway
Media Gateway
Media Gateway
.
31
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switches : Overview
An example of soft-switch as class 5 replacement …
Signaling (e.g. ISUP, SIP)
Soft-switch
Soft-switch
MGC protocol
Media Gateway
(Residential gateway)
MGC protocol
Media (I.e RTP)
Media Gateway
(I.e. Residential gateway)
.
32
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switches : Overview
An example of soft-switch as class 4 replacement …
Soft-switch
Soft-switch
Signaling (e.g. ISUP, SIP)
MGC protocol
MGC protocol
RTP for media
Media Gateway
ISUP
signaling
Media Gateway
PCM for media
PCM for
media
Class 4 switch
ISUP
signaling
Class 4 switch
.
33
Roch H. Glitho
Telecommunication Services Engineering Lab
Soft-switch: A simplified call case (Calling card)
Caller
Local exchange
exchange
Call to access number
(I.e soft-switch)
Soft-switch
MG
MG
Soft-switch
Local
Info request (e.g. card number,
Callee number)
Verification
(e.g. account,
Digit analysis)
Call request (e.g. SIP, SIP-T)
Call request (ISUP)
PCM
PCM
RTP
.
34
Roch H. Glitho
Telecommunication Services Engineering Lab
3GPP Networks
-
Overview
-
IP Multimedia Subsystem (IMS)
.
35
Roch H. Glitho
Telecommunication Services Engineering Lab
Overview
Essentials
- Made of:
- Legacy
- Circuit switched part (GSM)
- Packet switched (GPRS)
- Next generation part (IP multimedia Subsystem (IMS))
- Inter-working
- Some of the functional entities are common to both legacy and NGN
(e.g. Home Subscriber Server)
- Adoption/extension of existing NGN technologies:
- SIP instead of H.323
- H.248/Megaco
36
Roch H. Glitho
Telecommunication Services Engineering Lab
IP multimedia portion
IP M u ltim e d ia e tw o r k s
L e g a c y m o b ile
s ig n a llin g e tw o r k s
PST
Mb
Mb
PSTN
BGCF
CSCF
Mm
PSTN
Mk
Mk
Mw
Mj
C, D,
G c, G r
BGCF
Mi
Cx
IM S MGW
M GCF
Mg
Mn
Dx
Mr
Mb
M RFP
M RFC
PD F
Mb
Mb
SLF
Mw
P -C S C F
Dh
UE
Gm
M p
Mb
HSS
CSCF
S h ,S i
IS C
IM S u b s y s te m
Go
AS
37
Roch H. Glitho
Telecommunication Services Engineering Lab
IP multimedia portion
AS
AS
S C IM
S SIPIPAAp ppli
plic ca at io
t ion n
S Se ervrve er r
Sh
IS C
HHSSSS
Cx
Si
MAP
SS-C
-CSSCCFF
IS C
OOSA
SA s serv
er vice
ice
ca
p
a
b
ilit
y
ca p ab ilit y s serv
er verer
(SC
(S CS)
S)
OOSA
SA
aapppplicat
licatioionn
s serv
erverer
O SA AP I
IS C
IM
IM-S-SSSFF
C AP
CCam
amelel Serv
Ser vi ice
ce
EEnnvviro
n
ir o nmmen
ent t
38
Roch H. Glitho
Telecommunication Services Engineering Lab
IP Multimedia portion
Some of the functional entities
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
.
39
Roch H. Glitho
Telecommunication Services Engineering Lab
IP Multimedia portion
Media Gateway Function (MGF):
Signaling conversion between PSTN/2G and IMS
Media Gateway (MG)
Media conversion between PSTN/2G and IMS
Megaco / H.248: Protocol used between the two
.
40
Roch H. Glitho
Telecommunication Services Engineering Lab
IP Multimedia portion
Some of the functional entities
Call Session Control Function (CSCF) “The switch”
Proxy-CSCF:
- First contact point in the IM network
- Outbound / In-bound SIP proxy (All requests from/to IMS
terminals go through it)
Serving CSCF
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
purpose
- Translation services (Telephone number / Sip URIs)
- Routing
41
Roch H. Glitho
Telecommunication Services Engineering Lab
IP Multimedia portion
Some of the functional entities
Call Session Control Function (CSCF)
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
purpose
- Translation services (Telephone number / Sip URIs)
- Routing
42
Roch H. Glitho
Telecommunication Services Engineering Lab
IP Multimedia portion
Some of the functional entities
Application server (AS)
Host services and execute services
Communicate using SIP
Two types
SIP AS: Signaling specific architecture (Services can work only
in SIP environment
Open Service Architecture – Service Capability Server
(OSA/SCS)
- Signaling neutral architecture
- Happens to work in a SIP environment, but can work in other
environments
43
Roch H. Glitho
Telecommunication Services Engineering Lab
Conclusions
-
ITU-T NGN remains a vision that may
never be fully realized !!!
44
Roch H. Glitho
Telecommunication Services Engineering Lab
ITU-T NGN remains a vision that may never be
fully realized
• The easy part of the vision
– Broadband and multiple last mile technologies (e.g. ASDL, Wimax,
LTE)
– IP Telephony
– Inter-working with legacy
• True open interface (e.g. Megaco / H.248)
• The more challenging part
– Business model related
• Division of networks in separate strata (e.g. transport, service
control. Value, added services) with open and standardized
interfaces that may be operated by different operators
– End-user service related
• Wide range of services and service provision by assembling
building blocks
45
Roch H. Glitho
Telecommunication Services Engineering Lab
ITU-T NGN remains a vision that may never be
fully realized
• Where are we today?
– 2G and 2.5G
• GSM has the largest market footprint
• Replacement of many CDMAOne infrastructure by GSM
– Few real deployment of 3G, mostly at the transport / access stratum
• True open interface (e.g. Megaco / H.248)
• Cautious prognosis for the future
– 3GPP UMTS will take off as the telcos standard for 3G, with
fixed/mobile convergence
– UMTS may not have the same level of success as GSM
• There are many and there will be more and more alternatives to
provide the same services to end-user with a better price – quality
ratio
46
Roch H. Glitho