Transcript TMA09 Skype Detection Paper Svoboda

Introduction to Mobile Cellular Networks
Part I: 3G Mobile Core Network in a Nutshell
VU 389.134
Video and Multimedia Transmissions over Cellular Networks
3.10.2011
What this lecture is about …
• Video and Multimedia Transmissions over Cellular
Networks
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Cellular networks (GSM, UMTS, LTE, LTE-A)
Packet switched data transmission
Video and other services
Cross layer approaches
• How to measure/analyze/optimize such services
• What you should already know
– Cellular network (basics)
– UDP, TCP, IP, …
– eMail / HTTP / streaming (basics)
HTTP
IP
TCP
UDP
HyperText Transport Protocol
Internet Protocol
Transport Control Protocol
User Datagram Protocol
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The Problem
• Today data services generate more traffic than voice
– Radio link is expensive and limit resource
• Data services
– consume more bandwidth at less revenue
– QoS definition is problematic
• Looking for ways to offer constant QoS at reduced datarate/bandwidth needs
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–
Measurement and analysis of existing traffic
Link layer modeling from IP point of view
Cross layer optimization (video streaming, …)
Traffic modeling with respect to cellular networks
QoS
Quality of Service
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Possible Solutions
• Communication system are split into independent atomic
layers
– Open Systems Interconnection (OSI) reference model
• Data transmission
– Two consecutive layers: payload
– Two corresponding layers: payload, signaling
• Processing information stays within the layer
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Some (more) Motivation
• Today every layer is optimized to a large extend
– e.g.: receivers fight for < 1dB improvement
• Idea: use processing information from multiple layers
– Soften the boundaries between two layers
– e.g.: variable priority for video streaming and web browsing
• Optimization problems get much harder
– Optimum often hard to prove
TCP Packet
X
X
X
TB
Transport Block
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Outline of this Lecture
• Cellular Mobile Networks: (5.10.2009 - 16.11.2009 / Svoboda)
– PS-Core Network
– Link Error Analysis
– Link Error Prediction
– Measurement and Analysis
• Video in Error Prone Environments (23.11.2009 - 14.12.2009 / Rupp)
– Principles of Video Encoding
– Error Detection and Concealment
– Cross Layer Error Resilience in Video Streaming
– End to End Video Quality Estimation
• Traffic in Mobile Networks (11.01.2010 - 25.01.2010 / Svoboda)
– Detection of Anomalies in a Network
– Traffic Flows
– Traffic Modeling in High-Delay Environments
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Outline of today's talk
• Evolution of mobile cellular networks
• 3G Network Hierarchy
• 3G core network Elements
• 3G protocol Hierarchy
• Simple procedures in mobile cellular networks
• Journey of a packet through the network
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Network Architecture
• Hierarchical ordering of functional groups
• Functional structures/groups
– Defined by “functions” / procedures
– Consist of one or several physical elements
• Interfaces (reference points)
– Points allowing for interconnection between functional structures
IP
MS
UE
Internet Protocol
Mobile Station
User Equipment
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Network Architecture: Example GSM/GPRS
• GSM (2G): digital circuit switched network for voice
– All services reserve the same fixed bandwidth
– Charging on time unit basis
– Data rate: 9.6 kbit/s
• GPRS (2.5G): extension for packet switched traffic
– Packet switched (PS) domain is introduced
– PS oriented shared data channels at the radio link
– Data rate: ~114 kbit/s
GSM
GPRS
SIM
BTS
BSC
PCU
MSC
SGSN
GGSN
Global System for Mobile
Communication
General Packet Radio Service
Subscriber Identity Module
Base Transceiver Station
Base Station Controller
Packet Control Unit
Mobile Switching Center
Serving GPRS Support Node
Gateway SGSN
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Network Architecture: Example UMTS/HSPA
• UMTS (3G):
– The UTRAN (UMTS RAN) is added to existing 2.5G networks
• WCDMA, soft handover, QoS, …
– Link speed is variable but fixed to certain values.
– Data rate: 384 kbit/s
• HSPA (3.5G):
– Real packet switched radio bearers (similar to GPRS)
– No more soft handover
– Data rate: 7.2 Mbit/s
PS
UMTS
HSPA
USIM
NodeB
RNC
Packet Switched
Universal Mobile
Telecommunications System
High Speed Packet Access
Universal SIM
NodeB
Radio Network Controller
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Evolution of (digital) Cellular Networks
• GSM (2G)  GPRS (2.5G)
– No changes on the radio interface
– Large changes in RAN
– Birth of the PS-Core (!)
• GPRS (2.5G)  UMTS (3G)
– Large changes in the RAN
• The first network designed for PS traffic
– Small changes in the Core
• UMTS R99 (3G)  HSPA (3.5G)
– Changes in the radio interface
– No changes in the Core
RAN
PS
GSM
GPRS
UMTS
HSPA
Radio Access Network
Packet Switched
Global System for Mobile
Communication
General Packet Radio Service
Universal Mobile
Telecommunications System
High Speed Packet Access
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The Complete Picture of a 3G Core Network
2G
3G
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Summary of (digital) Cellular Networks
• Main Components of a Cellular Network
– User equipment
– Radio access network
– Core network
RAN
PS
GSM
• GSM: digital and circuit switched
GPRS
UMTS
HSPA
Radio Access Network
Packet Switched
Global System for Mobile
Communication
General Packet Radio Service
Universal Mobile
Telecommunications System
High Speed Packet Access
• GPRS: adds the CN PS-domain to GSM
• UMTS: pseudo PS radio links, RAN  UTRAN
• HSPA: PS radio links for UMTS, no soft handover
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The Core Network Elements
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The Mobile Switching Center (MSC)
• Routing grid for Circuit Switched (CS) services
• Main functions:
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Interconnect of CS services
Mobility Management
Localization
Signaling
• Protocols:
– PCM30 / PCM30 (not AMR!)
• Interfaces:
– IuCS / SS7(E)
MSC
E
G-MSC
PSTN
Iu-cs
RNC
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The Serving GPRS Support Node
• Counter part to the MSC in the Packet Switched (PS)
domain
• Main functions:
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Security / authentication
Mobility Management (MM): cell update, etc.
Handling of data sessions (routing)
Caching user subscriber data
• Protocols:
– GTP / GTP (not terminated in SGSN!)
• Interfaces:
– IuPS / Gn
RNC
Iu-ps
SGSN
Gn
SGSN
Gn
GGSN
Gr
HLR
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The Gateway GPRS Supporting Node (GGSN)
• „The Gatekeeper to the outer Territories“
• GGSN ‘hides’ the GPRS infrastructure
• Main functions:
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Handling of the PDP Context
Building a bridge to the external networks – eg. Internet
Converting the IP packets to GTP protocol
Billing, QoS, …
• Protocols:
– GTP / IP
• Interfaces:
– Gn (GTP) / Gi (IP)
SGSN
Gn
GGSN
Gi
INTERNET
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The Home Location Register (HLR)
• Database holding static user information
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MSISDN = MS - ISDN
CC Country Code
NDC National Dest. Code
SN Subscriber Number
Telephone number (MSISDN = CC + NDC + SN)
Subscriber number (IMSI = MCC + MNC + MSIN)
Security issues – AUC (key)
IMSI Int. Mobile Subscriber Id
MCC Mobile Country Code
QoS parameters
MNC Mobile Network Code
MSIN Mobile Station Id Number
Available services (voice, packet....)
Position information: Visitor Location Register (VLR)
• Protocols:
– IP
G-MSC
• Interfaces:
C
– Gr, C
Gr
HLR
SGSN
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Summary of Core Network Elements
• Core Network Elements
– CS: MSC, G-MSC
– PS: SGSN, GGSN
– OM: HLR, VLR, EIR, …
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•
•
•
•
MSC / SGSN interconnect RAN to the CN
G-MSC / GGSN interconnect CN with other networks
HLR holds all “static” user information
VLR local copy of HLR in SGSN
CS
Circuit Switched
PS
Packet Switched
Further Management units:
OM
Operation and Maintenance
– EIR, OMC, …
MSC
G-MSC
SGSN
GGSN
HLR
VLR
Mobile Switching Center
Gateway MSC
Serving GPRS Supporting Node
Gateway GPRS Supporting Node
Home Location Register
Visiting Location Register
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The Protocols
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The Protocol Hierarchy
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The Control Plane
PDP context Management
SM/ GMM
RANAP
RANAP
RRC
SCCP
SCCP
RLC
SCTP/IP
MAC
ATM
SCTP/IP GTP-C
ATM
UDP/
ATM
GTP-C
UDP/
ATM
SDH
L1
RNC
SM
SGSN
GGSN
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The User Plane
PDP context
IP
PDCP
Iu - UP
Iu - UP
RLC
GTP-U
GTP-U
GTP-U
GTP-U
MAC
ATM/
UDP
ATM
UDP/
ATM
UDP/ATM
L1
UE
RNC
SDH
SGSN
GGSN
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The GPRS Mobility Management (GMM)
• GPRS version of the MM protocol (MM still needed)
• Managing the mobility of the terminals
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Present location
Connections management services
User identity confidentiality
User states:
– Idle: the subscriber is not attached
– Standby: the subscriber is attached
– Ready: the subscriber is active
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The RAN Application Part (RANAP)
• Handles the signaling between UTRAN and PS-CN (Iu)
– Booking ATM lines, Changing Setup, ….
• Includes all control information for UTRAN
• 3 Classes of elementary procedures:
– General control services
– Notification services
– Dedicated control services
• Some functions:
– Iu Release (1)
– Overload Control (2)
– RAB Assignment (3)
RAB
Radio Access Bearer
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The Signaling Connection Control Part (SCCP)
• Task:
– Abstraction between UMTS and transport system (ATM, IP)
–  Transport System is hidden.
• Supports
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connection -less and –oriented extension to MTP
Address translation
Full OSI layer 3 compatibility
Below SS7 protocol
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The GPRS Tunneling Protocol (GTP v0)
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•
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For the connection between RNC, SGSN, GGSN
Payload is attached to GTP headers (8Bytes)
Used for signaling and data
Fields:
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Version: GTP v0 or v1
Protocol Type: GTP, GTP’ (GTP’ protocol is used to transfer charging data to the
Charging Gateway Function)
Flags: Extension, Sequence, N-PDU
Message Type: What is this GTP message about
Length: length of payload
Tunnel Endpoint Identifier: Start/End point of the GTP tunnel (user, APN)
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The GTP -U / -C
• GTP-C(ontrol)
– GPRS mobility management between GSNs
– Logically attached to the GTP-U tunnel – physically separated
– Functions:
• Create/Update/Change PDP Context
• Echo Request/Response
• RAN Information
• GTP-U(ser)
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Hides mobility from IP layer
Supports reordering of T-PDUs
TEID is always unique
Functions:
• Data Transmission
• Tunnel Setup/Release/Error
• Echo Request/Response
TEID
Tunnel Endpoint IDentifier
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Summary of Core Network Protocols
• Protocol hierarchy
– Non-access / Access Stratum
– Radio / Transport Network Layer
• Core network protocols:
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GMM:
RANAP:
SCCP:
GTP-U:
GTP-C:
location, user mobility, …
signaling between UTRAN and CN
abstraction between UMTS layers and transport layer
transport of user data payload
managing of corresponding GTP-U (always in pairs)
• Every user has a least one GTP tunnel (pair) active
• SGSN records the states of these protocols for every user
CS
PS
Circuit Switched
Packet Switched
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Let's start the Journey . . .
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Processed Steps
•
•
•
•
Now we will use the basics.
GPRS attach
PDP context activation
Mobile Station starts to send data (IP Packets)
PDP
PAYLOAD
UTRAN
PDP
GTP
GTP
GTP
GTP
UDP
UDP
UDP
UDP
IP
IP
IP
IP
AAL-5
AAL-5
AAL-5
AAL-5
ATM
ATM
ATM
ATM
PDH
PDH
PDH
PDH
PAYLOAD
SGSN
GGSN
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Activating a PDP Context
Svoboda
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Protocol Mapping
Original
Image Size = 2000 Bytes
1472
20
Data1 (1472)
TCP
0
20
528
IP
1500
20
20
Data2
TCP
0
IP
IP – Layer
USER
1500
UTRAN
48 5
20
8
8
GTP
UDP
IP
48 5
48 5
48 5
48 5
8
8
GTP
UDP
20
IP
GTP Layer +
UDP, IP Core
48 5
ATM Layer
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Sending the Packet: UTRAN-SGSN
RNC
Iu-ps
SGSN
Gn
PAYLOAD
(1500)
UTRAN
SGSN
TCP Header (20)
IP Header (20)
PAYLOAD
(1500)
GTP Header (8)
TCP Header (20)
UDP (8)
IP Header (20)
IP (20)
ATM (5)
PDH (var)
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Sending the Packet: SGSN-GGSN
SGSN
GGSN
Gn
PAYLOAD
(1500)
PAYLOAD
(1500)
PAYLOAD
(1500)
TCP Header (20)
TCP Header (20)
TCP Header (20)
IP Header (20)
IP Header (20)
IP Header (20)
GTP Header (8)
GTP Header (8)
UDP (8)
IP (20)
ATM (5)
PDH (var)
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Sending the Packet: Outer Regions
Where
is the
bird?
GGSN
INTERNET
PAYLOAD
(1500)
PAYLOAD
(1500)
TCP Header (20)
IP Header (20)
TCP Header (20)
IP Header (20)
Ethernet
Ethernet
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Summary of this lecture
•
•
•
•
Network hierarchy
Core network elements
Protocol hierarchy
How a data (IP) transmission over mobile cellular networks
works
• Important things/abbreviations
–
–
–
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Subscriber:
Elements:
Interfaces:
Procedures:
IMSI, TIMSI, GTP
RNC, SGSN, GGSN, NodeB
Gi, Gn, IuCS, IuPS
PDP, GMM
• Next stop: UTRAN
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Thank you for your attention
Questions?
[email protected]
Where to look?
[1]
RANAP on Iu: 3gpp 25.413; 23.108 (E Interface)
[2]
Iu User Plane: 3gpp 25.415
[3]
GTP: 3gpp 29.060
[4]
Core Network Basics: 3gpp 23.002
[5]
www.umtslink.at
[6]
http://www.techfest.com/networking/
[7]
http://www.manualy.sk/protocols2/pbook/gprs.htm#GTP
[8]
http://www.manualy.sk/protocols2/pbook/umts.htm
[9]
http://www.tkn.tu-berlin.de/curricula/ws0405/vl-umts/
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AAL2
ALCAP
APN
AS
ASN.1
ATM
BSC
BTS
CC
CN
CRNC
CS
DCH
DL
DRNC
DRNS
DSCH
EP
GERAN
GGSN
G-MSC
GMM/SM
Management
GPRS
GSM
GTP
GWCN
HLR
IE
IMEI
IMSI
ATM Adaptation Layer type 2
Access Link Control Application Part
Access Point Name
Access Stratum
Abstract Syntax Notation One
Asynchronous Transfer Mode
Base Station Controller
Base Transceiver Station
Call Control
Core Network
Controlling RNC
Circuit Switched
Dedicated Channel
Downlink
Drift RNC
Drift RNS
Downlink Shared Channel
Elementary Procedure
GSM/EDGE Radio Access Network
Gateway GPRS Supporting Node
Gateway Mobile Switching Center
GPRS Mobility Management / Session
Abbreviations (1)
General Packet Radio System
Global System for Mobile communications
GPRS Tunneling Protocol
GateWay Core Network
Home Location Register
Information Element
International Mobile Equipment Identity
International Mobile Subscriber Identity
IPv4
IPv6
MAC
MBMS
MM
MOCN
MSC
MTP
NACC
NAS
NRT
N-PDU
P-TMSI
PCM
PCU
PDCP
PDP
PDU
PLMN
PS
PSTN
QoS
RAB
RANAP
RLC
RNC
RNS
RRC
RT
Internet Protocol (version 4)
Internet Protocol (version 6)
Media Access Control
Multimedia Broadcast Multicast Service
Mobility Management
Multi Operator Core Network
Mobile services Switching Centre
Message Transfer Part
Network Assisted Cell Change
Non Access Stratum
Non-Real Time
Network – Protocol Data Unit
Packet TMSI
Puls Code Modulation
Packet Control Unit
Packet Data Convergence Protocol
Packet Data Protocol
Protocol Data Unit
Public Land Mobile Network
Packet Switched
Public Switched Telephone Network
Quality of Service
Radio Access Bearer
Radio Access Network Application Part
Radio Link Control
Radio Network Controller
Radio Network Subsystem
Radio Resource Control
Real Time
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