Download Wireless Data Communication

PhD Course: UMTS and IP based mobile networks
Werner Mohr, Ljupco Jorguseski, and Hans-Peter Schwefel
•
Day 1
Architecture and Core Network Aspects (HPS)
•
Day 2
Radio Resource Management and Radio Planning (LJ)
•
Day 3
Radio Propagation (WM)
•
Day 4
W-CDMA & TD-CDMA (WM)
•
Day 5
Cell Structure & Outlook Beyond 3G (WM)
Organized by Ramjee Prasad
PhD Course: UMTS
Lecture 2, Fall03
Page 1
Hans Peter Schwefel
Content
1. Performance & Network Planning
•
Performance Impacting Factors, circuit switched planning
approaches, packets switched planning
2. IP Quality of service and performance optimizations
•
•
Basic methods, implementation approaches
Protocol Enhancements (RoHC)
3. Session Initiation Protocol (SIP)
•
•
Architectures & Entities
Methods
4. IP based multimedia subsystems (IMS)
•
•
Architecture & components
Registration & Call Routing
5. Services
6. Outlook: Beyond 3G Networks
PhD Course: UMTS
Lecture 2, Fall03
Page 2
Hans Peter Schwefel
Core Network Planning
Determine topology, # and type of network elements and link capacities
• Plus planning of radio cells (topic in subsequent lecture)
Based on operator requirements on:
•
•
•
Security
Availability/Reliability
Performance (Transmission-, Processing-, Queueing delays)
Input data for planning:
•
Traffic and Mobility models
– # subscribers, # active users during busy hours, # active PDP contexts, traffic
characterisation
•
Functional Requirements
– E.g. number of supported APNs, supported security features, redundancy for high
availability
PhD Course: UMTS
Lecture 2, Fall03
Page 3
Hans Peter Schwefel
IP Protocol: Packet-Based Transport
• Advantages of Packet-Based Transport (as opposed to circuit switched)
– Flexibility
– Optimal Use of Link Capacities, Multiplex-Gain for bursty traffic
• Drawbacks
– Buffering/Queueing at routers can be necessary
– Delay / Jitter / Packet Loss can occur
– Overhead from Headers (20 Byte IPv4, 20 Byte TCP)
+

queueing
... and it makes performance modeling harder!!
Main motivation for Performance Modeling:
• Network Planning
• Evaluation/optimization of methods for congestion control & QoS provisioning
PhD Course: UMTS
Lecture 2, Fall03
Page 4
Hans Peter Schwefel
The circuit switched scenario
•
•
•
•
K channels
Users allocate one channel per call for certain call duration
If all channels are allocated additional starting calls are blocked
How many channels are necessary to achieve a call certain maximal
blocking probability?
Common Model Assumptions:
• Calls are arriving according to a Poission Process (justified for large user
population, limit theorems for stochastic processes) with rate 
• Call durations are exponentially distributed with mean T (okay for voice
calls)
PhD Course: UMTS
Lecture 2, Fall03
Page 5
Hans Peter Schwefel
Computation of Blocking Prob.: M/M/K/K model
• Poisson arrival of calls (first ’M’  Markovian) with rate 
– ti : arrival time of call i
– Xi:=ti+1-ti : interarrival time
– Poisson process of rate lambda:
• Xi independent and
• Pr(Xi<x)=1 - exp(- x)
• Exponentially distributed call holding times
of rate 1/T per call (second ’M’)
• K ’Servers’
• No additional waiting room for calls beyond K
Illustration of exponential distribution
(Prob. that call longer than x, leftmost
curve)
PhD Course: UMTS
Lecture 2, Fall03
Page 6
Hans Peter Schwefel
Computation of blocking probabilities:
M/M/K/K models 


K
1/T
2/T
3/T
K/T
• Finite Birth-Death Process (see e.g. [Cassandras & Lafortune]):
– Probability of i calls active [using Chapman-Kolmogorov Equations]
pi := Pr(n=i) = p0 (T)i /i! , i=1,…,K
where p0 = 1/[(T)i /i!] (sum taken over i=0 to K)
– Probability of blocked call:
p(B) = pK = p0 (T)K /K!
[also known as Erlang-B formula]
PhD Course: UMTS
Lecture 2, Fall03
Page 7
Hans Peter Schwefel
Challenges in Packet Switched Setting
Challenges in IP networks:
•
•
•
•
•
+
HTTP
L5-7
Multiplexing of packets at nodes (L3)
TCP
L4
Burstiness of IP traffic (L3-7)
L3
IP
Impact of Routing (L3)
L2
Link-Layer
Performance impact of transport layer, in particular TCP (L4)
Wide range of applications  different traffic & QoS requirements (L5-7)
Feedback: performance  traffic model, e.g. for TCP traffic, adaptive applications
(cross-layer optimization)
Traffic
Model
TCP / adaptive
applics.
Network
Model
Performance
Values
(Delay, Loss,
etc.)
Mobility
Model
PhD Course: UMTS
Lecture 2, Fall03
Page 8
Hans Peter Schwefel
Network model example: M/M/1/K queue
• Poisson arrival of packets (first ’M’  Markovian) with rate 
• Exponentially distributed service times
of rate  (second ’M’)
• Single Server (1)
• Finite waiting room (buffer) for K packets
• Often also specified: service discipline
– Default: First-In-First-Out
– Others: Processor Sharing, Last-In-First-Out,
Earliest Deadline First,...
PhD Course: UMTS
Lecture 2, Fall03
Page 9


Finite buffer
(size K)
Hans Peter Schwefel
M/M/1/K queue: Performance




K




• Finite Birth-Death Process (see e.g. [Cassandras & Lafortune]):
– Probability of i packets in queue [using Chapman-Kolmogorov Equations]
pi := Pr(n=i) = (1-)/(1- K+1) * i , where = /  1, i=0,…,K
– Probability of packet loss:
p(loss) = pK = (1-)/(1- K+1) * K
– Average Delay:
Ď = 1/[ (1-pK)] * /(1- K+1) * [(1- K)/ (1-) – K K ]
PhD Course: UMTS
Lecture 2, Fall03
Page 10
Hans Peter Schwefel
More realistic models: ON/OFF Models
Parameters:
• N sources, each average rate 
• During ON periods: peak-rate p
• Mean duration of ON and OFF times
ON & OFF Times exponential  MMPP representation with N+1 states
PhD Course: UMTS
Lecture 2, Fall03
Page 11
Hans Peter Schwefel
Traffic models: General hierarchical models
• Mathematical /stochastic description of traffic
• Frequently used: Several levels with increasing granularity
– E.g. 3 levels: sessions, connections, packets
– Or: 5-level model:
PhD Course: UMTS
Lecture 2, Fall03
Page 12
Hans Peter Schwefel
Example: HTTP traffic model
• ‘Main’ objects contain zero or more embedded objects that the browser retrieves
 Correlated requests for embedded objects within retrieval of main object
HTTP Session (User A)
Session Level
HTTP Session (User B)
HTTP Session (User C)
...
’start browser’
’click’
Download Phase 1
Idle time
Read time
Get Main Object
Download Phase 2
Get embedded Obj. 1
’click’
’exit
browser’
’click’
Dld. Phase 3
Get emb. Obj. 2
...
...
Dld. Phase K
Connection/
Flow Level
Get emb. Obj. N
Packet Level, TCP dynamics
•
(not shown here)
Statistics:
– # embedded objects: geometric
(measurements e.g. mean 5)
– Session arrivals: Renewal process (Poisson)
– Object size: heavy-tailed
– Idle time: heavy-tail
PhD Course: UMTS
Lecture 2, Fall03
Page 13
Hans Peter Schwefel
Content
1. Performance & Network Planning
•
Performance Impacting Factors, circuit switched planning
approaches, packets switched planning
2. IP Quality of service and performance optimizations
•
•
Basic methods, implementation approaches
Protocol Enhancements (RoHC)
3. Session Initiation Protocol (SIP)
•
•
Architectures & Entities
Methods
4. IP based multimedia subsystems (IMS)
•
•
Architecture & components
Registration & Call Routing
5. Services
6. Outlook: Beyond 3G Networks
PhD Course: UMTS
Lecture 2, Fall03
Page 14
Hans Peter Schwefel
IP QoS Solution I: Over-Provisioning
• Design network to be able to deal with worst-case traffic scenario
• Advantage:
– no impact on architecture, protocols and user equipment
– simplicity
• Problems:
– Traffic depends on number of active users, user mobility, type of
application, daily utilization profile  difficult forecasting
– Data traffic tends to be very bursty (even `self-similar´)
 waste of resources if planned for worst-case scenario
 can be very expensive
– Unforseeable events can occur (new applications; changes in user
behavior, e.g. always-on)
PhD Course: UMTS
Lecture 2, Fall03
Page 15
Hans Peter Schwefel
QoS Solutions II: DiffServ
•
•
•
•
•
Basic Idea: reduce queueing delay/loss for critical traffic by preferential
treatment at routers
 improve per-hop transmission behavior
Packets marked by DiffServ Code Points (DSCPs, 6bit)
Various scheduling disciplines at routers possible (e.g. static priority,
weighted fair queueing)
Advantage: Simple and scalable
Problem: No performance guarantees unless used in conjunction with
connection admission and traffic shaping/policing at ingress routers
Host
SLA
Customer
Network
SLA
Edge
Router
PhD Course: UMTS
DiffServ
Domain
Lecture 2, Fall03
SLA
Customer
Network
Boundary Router
SLA: Service Level Agreement
Page 16
Hans Peter Schwefel
QoS Solutions III: IntServ/RSVP
•
Fundamental Idea: Reserve necessary resources for each traffic flow along its
transmission path, which requires:
– Connection Admission Control (CAC): traffic specification + info about
available resources at router  admission decision (if no, then re-routing)
– Packet Classification: which flow does it belong to?
– Packet Scheduling: make sure, flow obtains resources as specified
PhD Course: UMTS
Lecture 2, Fall03
Page 17
Hans Peter Schwefel
QoS Solutions III: IntServ/RSVP
•
•
•
(cont`d)
Signalling by Resource Reservation Protocol (RSVP)
– Path Message: sender initiated, description of traffic parameters
and path
– Resv Message: receiver initiated, causes connection
admission/reservation along path; specifies QoS parameters
– Other messages for reservation teardown and error treatment
– Soft-State concept: periodic refresh of reservation required
Advantages:
– Fine Granularity: per flow treatment, flexible set of QoS parameters
– Able to provide QoS guarantees (if admission, classification,
scheduling is performed correctly)
Disadvantages
– Scalability problem: management of state for each single flow
– Complexity (already connection admission can be complex, e.g.
effective bandwidths, etc.)
PhD Course: UMTS
Lecture 2, Fall03
Page 18
Hans Peter Schwefel
Protocol Enhancements: Motivation
• Wireless links tend to show poor performance
– Large delays
– Low throughput
– Bit errors / packet losses due to radio transmission
• Protocols in IP family not originally designed for such links
– Increased volume due to headers
– Deficiencies of TCP flow control
– ... many more (e.g. applications HTTPWAP)
• Protocol Enhancements are required,
two examples discussed here
– Robust Header Compression (RoHC)
– Enhancements for Wireless TCP
PhD Course: UMTS
Lecture 2, Fall03
Page 19
Hans Peter Schwefel
Robust Header Compression (RoHC)
•
•
•
•
Motivation
– IP voice packets: header 40/60Bytes, average payload 25Bytes
– TCP ACK packets: header 40/60 Bytes, payload often 0Bytes
Data in many header fields …
– … hardly ever changes e.g. source/destination address within
same IP flow
– … or changes in a regular pattern
Idea: reduce header length by
compression, e.g.
– differential encoding of fields
– and/or variations of Huffman
compression
Compression can be applied to
several protocol headers, e.g. RTP/UDP/IP
PhD Course: UMTS
Lecture 2, Fall03
Page 20
Hans Peter Schwefel
Robust Header Compression (RoHC)
•
•
•
Synchronized compression context required in compressor and
decompressor
Lost packets Synchronization disturbed
Additional mechanisms for context synchronisation required: Robustness
– Error detection by Cyclic Redundancy Codes (CRC)
– Loss detection through sequence numbers
Reduced compression efficiency price for error robustness
Current RoHC methods: 40 Bytes RTP/UDP/IP header on average 1 or 2
bytes
PhD Course: UMTS
Lecture 2, Fall03
Page 21
Hans Peter Schwefel
RoHC in UMTS
Application
IP
v4 or v6
IP
v4 or v6
Relay
IP
v4 or v6
Relay
PDCP
PDCP
GTP-U
GTP-U
GTP-U
GTP-U
RLC
RLC
MAC
MAC
UDP/IP
v4 or v6
AAL5
UDP/IP
v4 or v6
AAL5
UDP/IP
v4 or v6
L2
UDP/IP
v4 or v6
L2
L2
L1
ATM
ATM
L1
L1
L1
L1
Uu
MS
Iu-PS
UTRAN
Gn
3G-SGSN
Gi
3G-GGSN
•
RoHC optional part of Packet Data Convergence Protocol (PDCP)
 headers compressed only over radio link (RNC-UE)
• In principle compression already in GGSN possible, but
– Flow identification/separation necessary
– Large number of flows (up to 104 active flows)
PhD Course: UMTS
Lecture 2, Fall03
Page 22
Hans Peter Schwefel
Content
1. Performance & Network Planning
•
Performance Impacting Factors, circuit switched planning
approaches, packets switched planning
2. IP Quality of service and performance optimizations
•
•
Basic methods, implementation approaches
Protocol Enhancements (RoHC)
3. Session Initiation Protocol (SIP)
•
•
Architectures & Entities
Methods
4. IP based multimedia subsystems (IMS)
•
•
Architecture & components
Registration & Call Routing
5. Services
6. Outlook: Beyond 3G Networks
PhD Course: UMTS
Lecture 2, Fall03
Page 23
Hans Peter Schwefel
Session Initiation Protocol -- SIP
SIP: Application layer signalling protocol (RFC 3261)





Provides call control for multi-media services
 initiation, modification, and termination of sessions
 terminal-type negotiation and selections
 call holding, forwarding, forking, transfer
 media type negotiation (also mid-call changes)
using Session Description Protocol (SDP)
Provides personal mobility support
Independent of transport protocols (TCP, UDP, SCTP,…)
ASCII format SIP headers
Separation of call signalling and data stream
Application types/examples:
 Interactive Voice over IP (VoIP)
 Multimedia conferences (multi-party, e.g. voice & video)
 Instant messaging
 Presence service
 Support of location-based services
PhD Course: UMTS
Lecture 2, Fall03
Page 24
Hans Peter Schwefel
SIP – Basic messages
• Selected Requests (Methods)
• Responses
–
–
–
–
–
– 1xx Intermediate results
e.g. 180 Ringing
– 2xx Successful Responses
e.g. 200 OK
– 3xx Redirections
e.g. 302 Moved Temporarily
– 4xx Request Failures
– 5xx Server Failures
– 6xx Global Errors
INVITE: initiate call
ACK: confirm final response (after ‘invite’)
BYE: terminate call
CANCEL: cancel pending requests
OPTIONS: queries features supported by
other side
– REGISTER: register with location service
PhD Course: UMTS
Lecture 2, Fall03
Page 25
Hans Peter Schwefel
SIP Addressing and header format
Addressing:
• Addresses specified SIP URL, in the format: user@host.
• Examples of SIP URLs:
• sip:[email protected]
• sip:[email protected]
• sip:[email protected]
• Example: SIP Header
PhD Course: UMTS
Lecture 2, Fall03
INVITE sip:[email protected] SIP/2.0
Via: SIP/2.0/UDP 192.168.6.21:5060
From: sip:[email protected]
To: <sip:[email protected]>
Call-ID: [email protected]
CSeq: 100 INVITE
Expires: 180
User-Agent: Cisco IP Phone/ Rev. 1/ SIP enabled
Accept: application/sdp
Contact: sip:[email protected]:5060
Content-Type: application/sdp
Page 26
Hans Peter Schwefel
SIP: Architecture & Entities
Location
Server
User Agent





Redirect
Server
Proxy Server
Registrar
Server
Proxy Server
User Agent
User agent: An application program which initiates SIP requests (User agent client) and also acts
upon (accepts, rejects or re-directs) incoming SIP requests (User agent server)
Location server provides SIP redirect or proxy servers information about a callee's possible
location(s).
Proxy server takes requests on behalf other user agents or servers and forwards them to the next
hop.
Redirect server accepts a SIP request, maps the address into zero or more new addresses and
returns these addresses to the client. Unlike a proxy server, it does not initiate its own SIP request.
Registrar is a server that accepts REGISTER requests. A registrar is typically co-located with a
proxy or redirect server and may offer location services.
PhD Course: UMTS
Lecture 2, Fall03
Page 27
Hans Peter Schwefel
SIP Call Signalling: Example
Proxy Server
User Agent
INVITE
Location/Redirect Server
INVITE
302
(Moved Temporarily)
User Agent
Proxy Server
ACK
INVITE
Call
Setup
180 (Ringing)
180 (Ringing)
INVITE
180 (Ringing)
200 (OK)
ACK
200 (OK)
ACK
200 (OK)
ACK
Media
Path
Call
Teardown
PhD Course: UMTS
RTP MEDIA PATH
BYE
BYE
BYE
200 (OK)
200 (OK)
200 (OK)
Lecture 2, Fall03
Page 28
Hans Peter Schwefel
SIP: Separation of signalling and data
• Route of SIP messages (proxy chain) different than media stream route:
 Potential Problems with Firewalls & NATs
PhD Course: UMTS
Lecture 2, Fall03
Page 29
Hans Peter Schwefel
SIP: Mobility support
User Mobility (change of terminal)
•
•
Registration via SIP ‘REGISTER’
mid-session mobility (application mobility):
call transfer, SIP method ‘REFER’ (RFC3515)
Host Mobility (change of IP address)
•
•
Pre-call: re-register, routing of ‘INVITE’ based
on SIP-URL
mid-call: re-invite
PhD Course: UMTS
Lecture 2, Fall03
Page 30
Hans Peter Schwefel
SIP: additional topics
Not touched in this lecture, see IETF SIP WG:
• Multitude of SIP extensions: new methods (e.g. instant messages)
• SIP over NAT/FW
• Authentication and security aspects
• Support of location based services
• Discovery of SIP entities (e.g. DNS SRV records)
• Service Discovery (e.g. SLP)
• Reliability aspects of SIP-based call control
PhD Course: UMTS
Lecture 2, Fall03
Page 31
Hans Peter Schwefel
Content
1. Performance & Network Planning
•
Performance Impacting Factors, circuit switched planning
approaches, packets switched planning
2. IP Quality of service and performance optimizations
•
•
Basic methods, implementation approaches
Protocol Enhancements (RoHC)
3. Session Initiation Protocol (SIP)
•
•
Architectures & Entities
Methods
4. IP based multimedia subsystems (IMS)
•
•
Architecture & components
Registration & Call Routing
5. Services
6. Outlook: Beyond 3G Networks
PhD Course: UMTS
Lecture 2, Fall03
Page 32
Hans Peter Schwefel
IP based Multimedia Subsystem (IMS)
Additional domain in UMTS Rel. 5, based on Packet-switched domain
Establishment and Control of IP based multimedia calls based on SIP
Standardized interfaces to applications
Authentication and authorisation of service access
Service based charging
QoS control
Global roaming and access to home services
Originally planned to be based on IPv6
‘Network centric’ approach (as opposed to IETF SIP)
In principle access independent (e.g. also WLAN access)
No Network layer mobility support in IMS (mobility via SIP or in access
networks)
PhD Course: UMTS
Lecture 2, Fall03
Page 33
Hans Peter Schwefel
Network Entities and Protocols
R-SGW
?
Sh
HSS
SIP
Cx
Sc
Dx
Mi
Mw
Sr
?
Gm
Gr
COPS
MAP
Gc
Mr
SIP
MRF-C
Go
SIP
MT
TE
R
PhD Course: UMTS
Lecture 2, Fall03
Uu
GERAN
UTRAN
BGCF
SIP
Mg
MGCF
Mp
H248
?
T-SGW
H248
Mc
R-SGW
MRF-P
MGW
„Gi-Cloud“
GGSN
UE
Mm
SIP Mj
CSCF
PCF
AS
CAP
SLF
?
SIP
SCP
SIP Mk
SIP
OSA-SCS
SIP
CAP
IM-SSF
OSA
ISC
Others
Multimedia
IP
Networks
BGCF
CSCF
Diameter
?
HTTP
IM Subsystem
?
SIP
Applications
and
Services
TCP
UDP
CS Domain
-orPSTN
-orLegacy
-orExternal
TCP/IP/UDP/RTP/…
Gn
SGSN
PS Domain
Iu
Page 34
Alternative
Access Networks
Hans Peter Schwefel
Network Entities
•
•
•
•
•
•
•
•
•
•
•
•
•
•
CSCF (Call State/Service Control Function)
PCF (Policy Control Function)
HSS (Home Subscriber Service)
SLF (Subscription Locator Function)
MRF (Multimedia Resource Function)
BGCF (Breakout Gateway Control Function)
MGCF (Median Gateway Control Function)
MGW (Media Gateway)
T-SGW (Transport Signaling Gateway)
R-SGW (Roaming Signaling Gateway)
AS (Application Server)
SCP (Service Content Provider)
IM-SSF (Service Switching Function)
OSA-SCS (Service Capability Server)
PhD Course: UMTS
Lecture 2, Fall03
Page 35
Additionally:
- Charging Entities
- Security Entities
- Lawful Interception
- Firewalls
- DNS, DHCP, TRIP, …
- QoS Entities
- OAM and NM
-…
Hans Peter Schwefel
IMS: Important Network Elements
HSS : Home Subscriber Service
Database for subscriber related information
•
•
•
•
Identification (SIP, Mail, E.164, Label, IMSI, ...)
Location management (P-CSCF, S-CSCF, IP address)
List of authorized services, List of subscribed services
Quintuplets for Security
Proxy Call State Control Function (P-CSCF)
First contact point of an operator‘s network (for the mobile terminal)
•
•
•
•
•
•
•
•
Forwarding of SIP messages between terminal and core network
Generation of charging records
Translation of IDs other than SIP URIs into SIP URIs
(e.g. E.164 numbers)
Termination of confidentiality and integrity, Lawful interception
Authorisation of bearer resources and QoS management
Detection of emergency calls and selection of a emergency S-CSCF
Translation of SIP URIs for local services
SIP header compression
PhD Course: UMTS
Lecture 2, Fall03
Page 36
Hans Peter Schwefel
IMS: Important Network Elements (cntd.)
Interrogating Call State Control Function (I-CSCF)
First contact point of an operator‘s network (for other operators)
•
•
•
•
Forwarding of SIP messages (proxy functionality)
Assignment of a S-CSCF
– during registration and during invite (for services for not registered subscribers)
Generation of charging records
Hiding of internal network configuration/capacity/topology
Serving Call State Control Function (S-CSCF)
Performs session control and service triggering
•
•
•
•
Acts as a registrar according to RFC2543
May behave as a Proxy Server as defined in RFC2543, i.e. it accepts requests and services
them internally or forwards them on, possibly after translation.
• May behave as a User Agent as defined in RFC2543, i.e. it may terminate and
independently generate SIP transactions.
Interaction with service platform(s), provides endpoints with service event related information
Authentication (based on quintuplets from HSS), Generation of charging records
PhD Course: UMTS
Lecture 2, Fall03
Page 37
Hans Peter Schwefel
Levels of Registration
Visited Network
UE
xGSN
DHCP
Home Network
CSCF
HSS
HLR
CSCF
AS
UMS
Bearer Level
DHCP
IM Subsystem
Application?
PhD Course: UMTS
Lecture 2, Fall03
Page 38
Hans Peter Schwefel
Registration in a Roaming Scenario
Home Network of MS A
HSS-A
Home Network of MS B
User Profile
User Profile
5
5
I-CSCF-A
S-CSCF-A
4
S-CSCF-B
I-CSCF-A
4
REGISTER
2
1
1
P-CSCF-A
Network visited by MS A
PhD Course: UMTS
MS B
REGISTER
2
MS A
HSS-A
Lecture 2, Fall03
P-CSCF-B
Network visited by MS B
Page 39
Hans Peter Schwefel
Routing of Mobile-To-Mobile Calls
Home Network of MS A
HSS-A
Home Network of MS B
I-CSCF-B
User Profile
4
5
3
I-CSCF-A
HSS-B
S-CSCF-A
S-CSCF-B
1
6
2
7
P-CSCF-A
Network visited by MS A
PhD Course: UMTS
Lecture 2, Fall03
MS B
REGISTER
INVITE
REGISTER
MS A
Call Control
User Profile
P-CSCF-B
Network visited by MS B
Page 40
Hans Peter Schwefel
Routing of Mobile Calls to CS or PSTN
(3GPP)
Home Network of MS A
HSS-A
BGCF-A
User Profile
A
3
INVITE
1
I-CSCF-B
5
2
Gateway
Control
P-CSCF-A
Network visited by MS A
Lecture 2, Fall03
B
MGCF-B
Call Control
S-CSCF A
REGISTER
I-CSCF-A
PhD Course: UMTS
BGCF-B
4
User Profile
MS A
PSTN
6
T-SGW-B
7
MGW-B
Foreign Network
Page 41
Hans Peter Schwefel
SIP in IMS
•
•
Mandatory existence of P-CSCF as first point of contact
Network initiated call release (e.g. due to missing coverage or administrative reasons)
–
•
Network Control of Media Types
–
–
•
•
For example Cell-ID, Mobile Network/Country Code, Charging-IDs
Information transported P-header based solution
Compression
–
–
•
P/S-CSCF checks the SDP in the SIP body
If SDP contains invalid parameters (e.g. not supported codecs), P/S-CSCF rejects the SIP
request by sending a 488 (“not acceptable here”) response that contains a SDP body
indicating parameters that would be acceptable by the network
Network Hiding (Encryption of Route and Via Headers)
Additional Signaling Information
–
–
•
Proxies are able to send BYE
SIP Compression is mandatory as radio interface is a scarce resource
Compression / decompression of SIP will be performed by the UE and the P-CSCF
Authentication & Integrity protection
–
–
S-CSCF performs the Authentication using AKA
P-CSCF checks the integrity of messages received via the air interface via IPsec ESP
PhD Course: UMTS
Lecture 2, Fall03
Page 42
Hans Peter Schwefel
IMS: Services are Home Controlled
 The Serving CSCF (S-CSCF) is located in the Home Network
 The Visited Network only provides a proxy (P-CSCF): all calls are always first
routed to the Home Network.
3rd Party
Service
Provider
Application
Server
Application
Server
UE
SIP
Proxy
CSCF
Application
Server
?
SIP
Lecture 2, Fall03
ISC
Serving
CSCF
SIP
Home Network
Visited Network
PhD Course: UMTS
?
Page 43
Hans Peter Schwefel
IMS Security Architecture
IM Core Network Subsystem
ISIM
Home / Serving Network
Mutual
authentication
HSS
IMS AKA
IPSec: Confidentiality and
Integrity Protection
S-CSCF
I-CSCF
UE
UA
IPSec:
Integrity
Protection
IPSec: Confidentiality and
Integrity Protection
P-CSCF
Visited / Home Network
PhD Course: UMTS
Lecture 2, Fall03
Page 44
Hans Peter Schwefel
End User Services: Categorization
Entertainment
•Voice over IP
•Buddy list
•Unified Messaging
•m-Gaming
•MMS
•Gambling
•Chat
•Audio
•Video
•Conferencing
•Presence configuration
•Availability configuration
Commerce
•m-Banking
Information
•Dynamic Info Svcs.
•m-Shopping
•Static Info Svcs.
•m-ticketing & reservations
•m-advertisement
PhD Course: UMTS
Lecture 2, Fall03
Page 45
Hans Peter Schwefel
Service Market Analysis
Willing to Use (W2U)
/
Willing to Pay (W2P)
Service Revenue Potential (W2P)
Service Desirability (W2U)
Information
29 %
Communication
30 %
Information
3%
Commerce
27 %
Entertainment
14 %
Communication
57 %
Commerce
12 %
Entertainment
28 %
Commerce
Entertainment
Commerce
Entertainment
Communication
Information
Communication
Information
Source: Adopted from Siemens End-User Survey 2000
PhD Course: UMTS
Lecture 2, Fall03
Source: Durlacher UMTS Report
Page 46
Hans Peter Schwefel
Prediction: services in mobile NWs
350
300
Browsing & Download
250
Mbit/
User/
Month
Messaging
200
150
Real-Time Multimedia
100
Voice
50
(Minutes of Use x 9,6 kb/s)
0
2003
2004
2005
2006
2007
2008
 Within the next six years data and multimedia traffic will overrule voice
 In 2008 Multimedia Communication will account for ¼ of mobile traffic
PhD Course: UMTS
Lecture 2, Fall03
Page 47
Hans Peter Schwefel
Summary
1. Performance & Network Planning
•
Performance Impacting Factors, circuit switched planning
approaches, packets switched planning
2. IP Quality of service and performance optimizations
•
•
Basic methods, implementation approaches
Protocol Enhancements (RoHC)
3. Session Initiation Protocol (SIP)
•
•
Architectures & Entities
Methods
4. IP based multimedia subsystems (IMS)
•
•
Architecture & components
Registration & Call Routing
5. Services
6. Outlook: Beyond 3G Networks
PhD Course: UMTS
Lecture 2, Fall03
Page 48
Hans Peter Schwefel
Outlook: Beyond 3G networks
•
•
•
•
•
•
Services and
Unifies different
applications
access technologies
New radio
IP as convergence
interface
layer
download channel
Wireline
DAB
Mobility support on
xDSL
DVB
IP
based
core
network
the network layer
Ad-hoc networks can
WLAN
cellular
return
channel:
extend geographic
type
GSM
IMT-2000
e.g.
GSM
reach of cellular
UMTS
wireless technologies
Personal Area
Networks (PAN)
Ubiquitous Computing
short
other
entities
range
connectivi
ty
PhD Course: UMTS
Lecture 2, Fall03
Page 49
Hans Peter Schwefel
Mobile IP Motivation: Host mobility & Routing
Problem: IP address identifies host as well as topological location
Reason: IP Routing:
– Routes selected based on IP destination address
– network prefix (e.g. 129.13.42) determines physical subnet
– change of physical subnet  change of IP address to have a topological correct address
Subnet A
Mobile Node
Subnet B
IP network
•
Solution? Host-based routing: Specific routes to each host
– Handover  change of all routing table entries in each (!) router
– Scalability & performance problem
•
Solution? Obtain new IP-address at hand-over
– Problem: how to identify host after handover? DNS update  performance/scalability problem
– Higher protocol layers (TCP/UDP/application) need to ‘handle’ changing IP address
 Development of mobile IP
PhD Course: UMTS
Lecture 2, Fall03
Page 50
Hans Peter Schwefel
Mobile IP: Principles & Terminology
Home network
HA
IP network
FA
Correspondent Node
Mobile Node
Home Address IP1
Home Address IP1
Care of Address: CoA1
Visited network
Underlying Approach:
separate host identifier and location identifier
 maintain multiple IP addresses for mobile host
Terminology:
•
•
•
•
•
•
Mobile Node (MN) with fixed IP address IP1 (home address)
Home Network: subnet that contains IP1
Home Agent (HA): node in home network, responsible for packet forwarding to MN
Visited Network: new subnet after roaming / handover
Care-of Address (CoA): temporary IP address within visited network
Foreign Agent (FA): node in visited network, responsible for packet forwarding to CoA
PhD Course: UMTS
Lecture 2, Fall03
Page 51
Hans Peter Schwefel
Mobile IP: Tunneling &Triangle Routing
FA
Visited Network
Home Network

CoA1
Mobile Node
IP1, CoA1
IP2 
Home Agent

Subnet
IP1 
Source: Mobile IPv4 illustrated
 CN sends packets to the MN using its Home Address IP1
Correspondent Node (CN)
IP2
 HA tunnels them to FA, using CoA1; FA forwards them to MN
 MN sends packets back to the CN using IP2 (without any tunneling)
 Home Agent needs to contain mapping of care-of address to home address
(location register)
PhD Course: UMTS
Lecture 2, Fall03
Page 52
Hans Peter Schwefel
Mobile IP: Agent Discovery & Registration
[Agent Solicitation] (opt.)
HA
FA
Agent Advertisement
MN
Obtain c/o address
Registration Request
Registration Reply
•
Time
Mobile Node finds out about FA through Agent Advertisements
– FAs broadcast Advertisements in periodic intervals
– Advertisements can be triggered by an Agent Solicitation from the MN
•
Care of Address of the MN is determined, either
– Dynamically, e.g. using Dynamic Host Configuration Protocol (DHCP)
– Or: use IP address of FA as CoA
•
MN registers at FA and HA: Registration Request & Reply
– MN signals COA to the HA via the FA
– HA acknowledges via FA to MN
•
Registration with old FA simply expires (limited life-time, soft-state)
PhD Course: UMTS
Lecture 2, Fall03
Page 53
Hans Peter Schwefel
MIP messages:Agent advertisement
Procedure:
0
• HA and FA periodically broadcast
advertisement messages into their subnets
type
#addresses
7 8
• MN listens to these messages and
detects, if it is in the home or a (new?)
foreign network
15 16
code
addr. size
router address 1
preference level 1
router address 2
preference level 2
23 24
checksum
lifetime
31
...
• when new foreign network: MN reads a
COA from the advertisement (opt.)
type = 16
length
sequence number
ICMP Router Discovery extension:
R B H F M G r T reserved
registration lifetime
type = 16
COA 1
R: registration required
COA 2
B: busy, no more registrations
H: home agent
...
F: foreign agent
M: minimal encapsulation
G: GRE encapsulation
r: =0, ignored (former Van Jacobson compression)
T: FA supports reverse tunneling
reserved: =0, ignored
PhD Course: UMTS
Lecture 2, Fall03
Page 54
Hans Peter Schwefel
MIP messages: registration request & reply
Registration
Request
(via UDP)
S: simultaneous bindings
B: broadcast datagrams
D: decapsulation by MN
M mininal encapsulation
G: GRE encapsulation
r: =0, ignored
T: reverse tunneling requested
x: =0, ignored
0
7 8
type = 1
15 16
S B DMG r T x
home address
home agent
COA
23 24
lifetime
31
identification
extensions . . .
Registration
Reply (UDP)
Example codes:
registration successful
• 0 registration accepted
•68 home agent failed
authentication
•69 requested Lifetime too long
0
7 8
type = 3
• 1 registration accepted, but registration denied by HA
simultaneous mobility bindings •129 administratively prohibited
•131 mobile node failed
unsupported
registration denied by FA authentication
•65 administratively prohibited •133 registration Identification
mismatch
•66 insufficient resources
•135 too many simultaneous
•67 mobile node failed
mobility bindings
authentication
PhD Course: UMTS
Lecture 2, Fall03
15 16
code
home address
home agent
31
lifetime
identification
extensions . . .
Page 55
Hans Peter Schwefel
MIP: Care-of addresses
MN obtains local care-of address either
• from FA Advertisement (see before)
•
Or via Dynamic Host Configuration Protocol (DHCP)
– supplies systems with all necessary information, such as IP address, DNS server
address, domain name, subnet mask, default router etc.
– Client/Server-Model: client sends request via L2 broadcast
server
(not selected)
server
(selected)
client
initialization
DHCPDISCOVER
DHCPDISCOVER
determine the configuration
determine the configuration
DHCPOFFER collection of repliesDHCPOFFER
selection of configuration
DHCPREQUEST
DHCPREQUEST
(reject)
(options)
DHCPACK
confirmation of
configuration
initialization completed
PhD Course: UMTS
Lecture 2, Fall03
Page 56
Hans Peter Schwefel
The future of mobile networks
“Much of the initial enthusiasm for the concept appears to have evaporated
and the original launch target of autumn this year has been slipping. When
the government asked companies to apply for licences, international
consortia rushed to compete.
(…) Since then, the economy has sunk into recession, forecasts of the
number of subscribers have been scaled down and the need for heavy
investment has scared many of the original shareholders.”
Financial Times: September 1992
“The Future of GSM Mobile Communications”
PhD Course: UMTS
Lecture 2, Fall03
Page 57
Hans Peter Schwefel
Acknowledgements (Lectures 1 & 2)
• Tutorial: IP Technology in 3rd Generation mobile networks,
Siemens AG (J. Kross, L. Smith, H. Schwefel)
• Lecture notes: Wireless Data Communication, MM5,
www.kom.auc.dk/~hps/teaching
• Tutorial: Voice over IP Protocols – An Overview, www.vovida.org
• Various 3GPP slide-sets
• Siemens ICM N PG U SE and Siemens CT IC 3
Other References
•
•
IETF (www.ietf.org)
– WGs: MMUSIC (old), SIP
3GPP: www.3gpp.org
PhD Course: UMTS
Lecture 2, Fall03
Page 58
Hans Peter Schwefel