1.1 Introduction Types of Mobility

Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Mobile Services (ST 2010)
Chapter 4: Mobile Internet
Axel Küpper
Service-centric Networking
Deutsche Telekom Laboratories, TU Berlin
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Mobile Services
Summer Term 2010
4 Mobile Internet
4.1 Problem Statement
4.2 Mobile IP
4.3 Network Layer Support in GPRS/UMTS
2
4.1 Problem Statement
Internet Protocol - Overview
Internet Protocol
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet





Primary protocol of the network layer
used for transmission in networks that
employ packet-switched data
communication
Packets can be sent without establishing
a connection before (unlike circuitswitched communication)
Packets can be lost
Packets may arrive at the receiver in
another order than initially sent
0
4
Version
8
IHL
12
16
Time to Live


20
Type of Service
Identification
Each data packet contains a header that
(besides other things) fixes the IP address of
the sender (source) and the address of the
receiver (destination)
Packet passes different routers along the
way from the source to the destination
Router receives a packet from a source or a
previous router, gets the destination
address from the IP header, and forwards
the packet to the next router
24
28
Total Length
Flags
Protocol (IP)
31
Fragment Offset
Header Checksum
Source Address
Destination Address
Options and Padding (optional)
TCP/UDP/… payload
3
4.1 Problem Statement
Internet Protocol - Addressing
Two-Level Classful Hierarchy

Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet

Internet is an interconnection of several
networks
IP addresses refer to the network a host
is connected to (network prefix) and to
the host within that network (host
number)
Network prefix
Host number
Three-Level Subnet Hierarchy
Network prefix
8, 16, or 24 bits for
class A, B, or C
network prefixes
Subnet number
24, 16, or 8 bits for
class A, B, or C
host number
Two-Level Classful Hierarchy
Three-Level Subnet Hierarchy



Initial addressing scheme for fixing the
length of network prefixes and number of
hosts within a network
Class A



Class B



8-bit network prefix for 126 networks
16,777,214 hosts per network
16-bit prefix for 16,384 networks
65,534 hosts per network
Class C


24-bit prefix for 2,097,152 networks
254 hosts per network
Host number
Division of Class A, B, and C networks into
smaller subnetworks that have a
common, designated IP addressing
routing index
 Subnet mask fixes the length of the prefix
(sum of length of network prefix and
subnet number)
 Breaks a network into smaller realms that
may use existing network address space
more efficiently
4
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
4.1 Problem Statement
Routing Example (I)
Host B
Destination
128.9.1.2
128.9.1.0
DEFAULT
Subnet mask
Route to
255.255.255.255 SELF
255.255.255.0 LAN 0
128.9.1.1
Host A
Destination
128.8.1.2
128.8.0.0
128.9.00
Subnet mask
255.255.255.255
255.255.0.0
255.255.0.0
Route to
SELF
LAN 0
128.8.1.1
Router
Destination
128.8.1.1
128.9.1.1
128.9.2.1
128.8.0.0
128.9.1.0
128.9.2.0
Subnet mask
255.255.255.255
255.255.255.255
255.255.255.255
255.255.0.0
255.255.255.0
255.255.255.0
Route to
SELF
SELF
SELF
LAN 0
LAN 1
LAN 2
128.8 network
LAN 0
Host C
Destination
128.9.2.2
128.9.2.0
DEFAULT
Subnet mask
Route to
255.255.255.255 SELF
255.255.255.0 LAN 0
128.9.2.1
Host A
LAN 0
LAN 0
Router
Host B
128.9.1 subnet


LAN 2
LAN 1
LAN 0
Host C
128.9.2 subnet
Problem: IP addresses contain routing information (network/subnet ID fixed by the subnet
mask)
What happens if Host C moves from the 128.8 network to the 128.9.1 subnet?
5
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
4.1 Problem Statement
Routing Example (II)
Host C
Destination
128.9.1.3
128.9.1.0
DEFAULT
Subnet mask
Route to
255.255.255.255 SELF
255.255.255.0 LAN 0
128.9.1.1
Host B
Destination
128.9.1.2
128.9.1.0
DEFAULT
Subnet mask
Route to
255.255.255.255 SELF
255.255.255.0 LAN 0
128.9.1.1
Host A
Destination
128.8.1.2
128.8.0.0
128.9.00
Subnet mask
255.255.255.255
255.255.0.0
255.255.0.0
Route to
SELF
LAN 0
128.8.1.1
Router
Destination
128.8.1.1
128.9.1.1
128.9.2.1
128.8.0.0
128.9.1.0
128.9.2.0
Subnet mask
255.255.255.255
255.255.255.255
255.255.255.255
255.255.0.0
255.255.255.0
255.255.255.0
Route to
SELF
SELF
SELF
LAN 0
LAN 1
LAN 2
128.8 network
LAN 0
Host A
Host C
LAN 0
LAN 0
LAN 0
Router
Host B
128.9.1 subnet


LAN 2
LAN 1
128.9.2 subnet
Because an IP address is not only a reference to a particular host, but also addresses the
network and subnet the host is connected to, a host gets a new IP address when getting
connected to another network
Original Internet Protocol does not support mobility!
6
4.1 Problem Statement
Solutions for Mobility Support in the Internet
Problem: TCP connection cannot survive IP address change
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet


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TCP connections are identified by the tuple (source address, source port, destination
address, destination port)
TCP connection cannot survive any address change
Solution: inform all communication partners of the mobile node about the new address
Drawback: requires modification of existing, proven protocol software
Problem: Mobile hosts acting as servers are not reachable after an address change


Solution #1: simply assign a new, topologically correct address after the movement
Drawback: nobody knows about this new address – it is almost impossible to find a host on
the Internet that has just changed its address

Solution #2: Use of Dynamic DNS (DynDNS) for updating the mapping between a logical
domain name and an IP address
Drawback: because of caching methods, DynDNS is not able to cope with frequent updates



Solution #3: create dedicated routes for a mobile node
Drawback: routing tables are based on network prefixes – storing entries of millions of
mobile nodes would not scale
7
4.2 Mobile IP
Components and Addresses (I)
MN
CoA
Home
Network
Router HA
Router FA
Foreign
Network
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Internet
CN
Router
Mobile Node (MN)
Home Network




Mobile device that moves to other
networks and for which mobility support
is to be provided
Keeps its IP address and can continuously
communicate with any other system in
the Internet as long as link-layer
connectivity is given
Correspondent Node (CN)


Communication partner of the MN
May invoke services offered by the MN

Subnet the MN belongs to
Responsible for assigning an IP address to
the MN
No mobility support required inside the
home network
Foreign Network

Current subnet the MN visits and which is
not the home network
8
4.2 Mobile IP
Components and Addresses (II)
MN
CoA
Home
Network
Router HA
Router FA
Foreign
Network
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Internet
CN
Router
Foreign Agent
Foreign Agent CoA




Implemented in the router of the foreign
network
Acts a tunnel endpoint that decapsulates
packets and forwards them to the MN
CoA is an IP address referring to the FA
FA is tunnel endpoint and forwards
packets to the MN
Care-of Address (CoA)



IP address associated with the MN in the
foreign network
IP packets sent to the MN are delivered to
the CoA, not directly to the MN‘s IP address
CoA marks the tunnel endpoint
9
4.2 Mobile IP
Basic Procedure
MN
CoA
Home
Network
2
Router HA
Router FA
3
Foreign
Network
4
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Internet
CN
1
Router
CN → HA


2
1
CN transmits an IP datagram destined to
the MN, with MN’s home address in the
IP header
IP datagram is routed to the home
network of the MN

3
FA → MN

HA → FA


At the home network, IP datagram is
intercepted by the HA
HA encapsulates the datagram inside a
new IP datagram with the MN’s CoA in its
header
4
Encapsulated IP datagram is
retransmitted and routed to the FA
FA decapsulates the original IP datagram
and delivers it to the MN across the
foreign network
MN → CN

When the MN sends a reply to CN, the
associated datagram travels directly
across the Internet to the CN
10
4.2 Mobile IP
Alternative: “FA Inside”
Co-located CoA
Home
Network
2
Router HA
3
Router
MN
Foreign
Network
4
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Internet
CN





1
Router
Initial version of Mobile IP worked only
with a FA in the foreign network
Alternative proposal: MN may act as its
own FA
Tunnel is established between HA and
MN, and MN is addressed by a Co-located
CoA
Advantage: no enhancements need to
made in the foreign network
Disadvantage: scarcity of IP addresses (if
MN received a permanent address)
Co-located CoA



CoA is assigned to the MN, and hence is
topologically correct
May be acquired using DHCP
May be assigned as a long-term address
for use when the MN visits the foreign
network
11
4.2 Mobile IP
How to Detect the Entering of a New Network? (I)
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet

HAs and FAs periodically broadcast their
presence using an Agent Advertisement
Message (extension of ICMP messages)
MNs listen to the broadcast …
 … to detect whether they entered a
new subnet
 … to detect whether the new subnet
is their home or foreign network
 … to receive special features of the
new subnet
 … to receive a CoA if they entered a
new foreign network
Agent Solicitations


Agent Advertisements are only broadcast
periodically
MN may explicitly solicit for an Agent
Advertisement Message if it needs it
immediately
0
Standard ICMP message

Agent Advertisement Message
Extensions for Mobile IP
Agent Advertisement
4
8
12
Type
Code
#Addresses
Addr. Size
16
20
24
28
Checksum
31
Lifetime
Router address 1
Preference level 1
Router address 2
Preference level 2
Type=16
Sequence number
Lentgh
Registration lifetime
RBHFMGrT
reserved
CoA 1
CoA 2
12
4.2 Mobile IP
How to Detect the Entering of a New Network? (II)
Use of lifetime field
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
MN receiving an Agent Advertisement
Message from an agent records the
lifetime field as a timer
If the timer expires before the MN has
received the next message, it assumes
that it has lost contact to that agent
If, in the meantime, it has received an AA
message from another agent (and that
advertisement has not yet expired), the
MN registers with this new agent
If it has not received an AA message, MN
uses Agent Solicitation
Use of network prefix


MN checks whether any newly received
AA is on the same network as the MN’s
current CoA
If not, MN assumes that it has moved and
may register with the agent whose
advertisement it has just received.
Old
Router FA
New
Router FA
MN
Agent Advertisement
AA Broadcast
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet

MN may move from one subnet to
another without the IP layer being aware
of it
Agent discovery process enables the MN
to detect such a move
AA
Solicitation

Agent Advertisement
Agent Advertisement
Agent Advertisement
Agent Advertisement
Agent Solicitation
Agent Advertisement
13
4.2 Mobile IP
Registration with a Foreign Network
Registration via the FA:
Registration directly with the HA:
Foreign
Network
Home
Network
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
MN
Router FA
Router HA
MN
Registration
Request
1 Registration
Registration
2 Request
Registration
3
Registration
Reply
Reply 4
Request

1
2
3
4
Once an MN has detected that it entered
a (new) foreign network, it has to register
with the FA and alert the HA.
MN sends a registration request to the FA
FA relays request to the HA
HA accepts or denies request and sends a
registration reply to the FA
FA forwards reply to the MN
Router HA
Registration
Reply

If the MN uses a co-located CoA, then it
registers directly with its HA
14
4.2 Mobile IP
Tunneling and Encapsulation (I)
Tunnel
Encapsulation/Decapsulation


Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet




Establishes a virtual pipe for data packets
between a tunnel entry and a tunnel
endpoint
Packets entering a tunnel are forwarded
inside the tunnel and leave the tunnel
unchanged
Tunneling, i.e., sending a packet through
a tunnel is achieved by using
encapsulation
Whole tunnel is considered as single hop
from the packet’s point of view
Tunneling allows the MN to behave as if it
were attached directly to the home
network
Original IP
header
New IP
header
OR
Outer
header



Encapsulation: mechanism of taking a
packet consisting of packet header and
data and putting it into the data part of
the new packet
Decapsulation: taking a packet out of the
data part of another packet
Encapsulation/decapsulation are
operations typically performed when a
packet is transferred from a higher
protocol layer to a lower one (or from a
lower layer to a higher layer respectively)
Mobile IP uses
encapsulation/decapsulation within the
same layer
Original data
New data
Inner
header
Original data
15
4.2 Mobile IP
Tunneling and Encapsulation (II)
IP-in-IP Encapsulation
0
4
Version
8
IHL
12
16
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Version
20
Type of Service
Identification
Time to Live
Minimal Encapsulation
24
28
Total Length
Flags
IP-in-IP
31
0
4
8
IHL
Version
Fragment Offset
12
16
Time to Live
Min. Encaps.
24
Flags
Header Checksum
Source Address (HA Address)
Destination Address (Care-of Address)
Destination Address (Care-of Address)
Identification
Time to Live
Total Length
Type of Service
IPv4
Flags
IPv4
Fragment Offset
S
reserved
31
Fragment Offset
Source Address (HA Address)
IHL
28
Total Length
Type of Service
Identification
Header Checksum
20
Header Checksum
Destination Address (Home Address of MN)
Header Checksum
Source Address (CN Address, is not present if S=0)
Source Address (CN Address)
TCP/UDP/… payload
Destination Address (Home address of MN)
TCP/UDP/… payload



Simple encapsulation of one IP packet
into another one
Mandatory of Mobile IP
Drawback: several redundant fields


Removes redundant fields
Source address in the inner header is
omitted if original sender is identical to
the HA
16
4.2 Mobile IP
HA Realizations
MN
CoA
Home
Network
Router HA
Router FA
Foreign
Network
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Internet
CN
Router
Home Agent (HA)
HA Realization #2



Tunnel for packets toward the MN starts
at the HA
HA maintains a location registry, which
stores the CoA of all MNs that have their
origins in the home network

HA could be implemented on an arbitrary
node in the subnet
Disadvantage: double crossing of the router
by all packets if the MN is in a foreign
network
HA Realization #1
HA Realization #3



HA is implemented on a router that is
responsible for the home network
Good solution as all packets have to pass
the router anyway

No home network, but only a virtual home
network represented by a router and all MNs
are always connected to foreign networks
HA is again implemented on the router
17
4.2 Mobile IP
Optimization (I)
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Router HA
Router FA
CN
MN
Problem: Triangular Routing



With basic Mobile IP, all packets to the MN have to go through the HA
May cause unnecessary overhead for the network between CN and HA, but also between
HA and CoA, depending on the current location of the MN
Figure: although the communicating computers might only be a few meters away, the
packets have to travel around the world
18
4.2 Mobile IP
Optimization (II)



Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
1
Binding request


2
Used by the HA to inform the CN about the current location of the MN
Contains the MN’s fixed address and CoA
Binding acknowledgement

4
Any CN that wants to know the current location of an MN sends a binding request to the
HA
If HA is allowed to disclose the MN’s location, it returns a binding update
Binding update


3
Idea: Optimize routing by informing the CN of the current location of the MN
Binding cache: part of the local routing table of the CN
Introduction of four additional messages
CN returns an acknowledgement after receiving an update
Binding warning



If an FA decapsulates a packet for an MN, but is not the MN’s current FA, it sends a
warning to the CN
Warning contains the MN’s fixed home address
After receiving a warning, the CN knows that the MN has probably moved, and initiates a
19
binding request
4.2 Mobile IP
Optimization (III)
CN
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Data
3 ACK
Router HA
Data
Update 2
Data
Old
Router FA
New
Router FA
MN
Data
Data
Registration
Update
MN changes
location
ACK
Data
Data
1
Warning 4
Request
Data
Update 2
3
ACK
Data
Data
20
4.3 Network Layer Support in GPRS/UMTS
GPRS/UMTS Basic Procedures
GERAN
Packet-switched domain
UE
BTS
BSC
SGSN
GGSN
Internet
GPRS Attach
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Connection Setup (Activation of a PDP Context)
Transmission of the User Data

Before data can be transmitted between the UE and an external host, some preparations
are necessary
 UE must be introduced to the network
 Appropriate SGSN must be found (according to the user’s location)
 Features and capabilities of the data service must be negotiated
 An GGSN must be selected and a setup between UE and GGSN has to be established
 Path for routing data packets has to prepared for tunneling

Three procedures
 GPRS Attach
 Activation of PDP Context
 Data Transfer
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
4.3 Network Layer Support in GPRS/UMTS
PDP Context
PDP Context
Access Point Name (APN)







PDP: Packet Data Protocol
Describes characteristics of the session
Contains routing information for packet
transfer between a UE and a GGSN to
have access to an external packetswitching network
Stored in the mobile station, the SGSN,
and the GGSN
Once a mobile station has an active PDP
context, it is visible for the external
network and can send and receive
packets
Each UE may be assigned several PDP
contexts for …
 … getting access to different
networks
 … different services
 … different charging methods

Logical name for the desired data
network
Refers to the GGSN enabling access to
that network
PDP type

Type of the packet network used (e.g.,
IPv4 or IPv6)
PDP address



Address assigned to the mobile station
(e.g. an IP address)
Static address: permanent IP address of
UE
Dynamic address: dynamically assigned,
usually for the duration of a session
QoS class

Four QoS parameters: service
precedence, reliability, delay, and
throughput
4.3 Network Layer Support in GPRS/UMTS
GPRS/UMTS Packet Addresses
Packet Data Protocol (PDP) Address
Packet TMSI (P-TMSI)


Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet



Address of a UE in the format of the used
PDP (e.g., IP address)
Static
 UE permanently owns a PDP address
assigned by the operator of the
user’s home GSM network
Dynamic
 UE is assigned a new PDP address
whenever it attaches to the network
 Dynamic Home-PLMN Address:
Dynamic address assigned by the
user’s home PLMN
 Dynamic Visited-PLMN Address:
dynamic address assigned by the
operator of the visited PLMN
GGSN is responsible for the allocation
and deactivation of PDP addresses


Assigned during an GPRS attach
procedure and after a location update
Used to page the UE when packets have
to be delivered
Mapping between PDP address and PTMSI by the SGSN makes the
transmission of packets between GGSN
and UE possible
Routing Area Identifier (RAI)


In order to optimize location
management, GSM location areas are
subdivided into several routing areas
RAI is transmitted from the MS to the
network instead of the LAI
4.3 Network Layer Support in GPRS/UMTS
Quality of Service
Quality of Service Classes
Reliability


Required to support diverse applications
(ranging from real-time video
conferencing to E-Mail)
Enable operators to offer different
billing options
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet

Service precedence

Reliability of a service with regard to
probability of packet loss, packet
duplication, wrong sequencing, packet
corruption
Delay

Priority of a service in relation to other
services (high, normal, low)
Maximum values for mean and 95% delay
with regard to end-to-end delay between
UEs or between a UE and the serving
GGSN
Throughput

Rel.
class
Lost packet
1
2
3
10-9
10-4
10-2
Probability
Duplicated
Out of sequ.
packet
packet
10-9
10-5
10-5
10-9
10-6
10-5
Peak bit rate and mean bit rate
Seconds
Corrupted
packet
Mean delay
95% delay
Delay
class
10-9
10-9
10-2
< 0.5
<5
< 50
Best effort
< 1.5
< 25
< 250
Best effort
1
2
3
4
4.3 Network Layer Support in GPRS/UMTS
Multiple PDP Contexts
Multiple PDP contexts
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet


UE with different PDP contexts
Operators may use different PDP contexts with different APNs for charging different
services in the Internet differently, for example
 Mobile Web
 Email
 Tethering
wap.carrier.de
GGSN
internet.carrier.de
WAP
GW
Internet
GGSN
UE
BTS
BSC
SGSN
ims.carrier.de
GGSN
IMS
mms.carrier.de
GGSN
MMS
Server
Adopted from http://www.support.apple.com/
Current PDP context(s)
Adopted from http://www.support.apple.com/
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
4.3 Network Layer Support in GPRS/UMTS
PDP Context Example and Configuration
Configuration of PDP context
26
4.3 Network Layer Support in GPRS/UMTS
GPRS Attach (I)
New
SGSN
UE
Old
SGSN
HLR
AttachRequest(P-TMSI/IMSI, old RAI, attach type, old P-TMSI signature,…)
IdentificationRequest(old RAI, attach type, old P-TMSI signature,…)
IdentificationResponse(Cause, IMSI, authentication triplet,…)
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
Authentication
GPRSUpdateLocation(SGSN number, SGSN address, IMSI,…)
CancelLocation(IMSI, cancellation type,…)
CancelLocationAck(IMSI,…)
InsertSubscriberData(IMSI, GPRS subscription data,…)
InsertSubscriberDataAck(IMSI, SGSN area restricted,…)
GPRSUpdateLocationAck(…)
AttachAccept(P-TMSI, P-TMSI signature,…)
AttachComplete(…)



GPRS Attach is executed when subscriber
switches on his device or he explicitly
activates GPRS while in GSM mode
Result of GPRS Attach: current SGSN
knows that the UE has activated GPRS
If UE was already registered with another
SGSN, the HLR is notified about the new
SGSN



HLR provides data for assembling a PDP
context
Several PDP contexts can be set up for a
UE such that the UE can get connected to
several IP networks with different QoS
Alternative: different contexts for
accessing the same network with
different services and different QoS
Adopted from: Martin Sauter – Grundkurs Mobilkommunikation. Vieweg Verlag
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
4.3 Network Layer Support in GPRS/UMTS
GPRS Attach (II)
28
4.3 Network Layer Support in GPRS/UMTS
Activation of PDP Context
UE
SGSN
DNS
GGSN
Radius DHCP
HLR
IP PDU arrives
Network-initiated PDP Context Activation
UE-init. PDP Context Activation
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
SendRoutingInfoForGPRS(IMSI,…)
SendRoutingInfoForGPRSAck(IMSI, SGSN address,…)
PDUNotificationRequest(PDP address,…)
PDUNotificationResponse(cause,…)
RequestPDPContextActivation(PDP address, APN,…)
ActivatePDPContextRequest(requested NSAPI, requested QoS, …)
Security Functions
DNSQuery(APN,…)
DNSResponse(GGSN IP address,…)
CreatePDPContextRequest(APN,PDPaddress,negotiatedQoS…)
RadiusAuthenticationRequest
RadiusAuthenticationResponse
DHCP address request
DHCP address response
Not used if IP
addresses
are static
CreatePDPContextResponse(Cause,PDPaddress,negotiatedQoS…)
ActivatePDPContextAccept(SAPI, negotiatedQoS, …)
4.3 Network Layer Support in GPRS/UMTS
Data Transfer
GTP Packet
Header
IP Packet
Header
Payload
IP source
IP destination
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
SGSN Address
Tunnel Identifier
SGSN


After activation of the PDP context, the
logical path between UE and external
network is defined and can be used for
the exchange of user data
GPRS/UMTS applies same principles for
mobility support during the data transfer
as Mobile IP: tunneling/encapsulation
User data
GGSN




Internet
Gateway Tunneling Protocol (GTP)
between GGSN (Home Agent) and SGSN
(Foreign Agent)
GPRS: tunnel between GGSN and SGSN
UMTS: tunnel between GGSN and RNC
LTE: tunnel between gateway and eNB
4.3 Network Layer Support in GPRS/UMTS
GPRS/UMTS Roaming Example
3
Access networks
Access network
Operator A
UE
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
BTS
Core network
(Intra-operator
backbone)
Operator A
1
BSC
3
4
UE
SGSN
SGSN
Inter-operator
Backbone
Network
BG
BG
GGSN
4
2
2
GERAN
BSC
GGSN
1
Access network
Operator B
Mobile-originated traffic
Mobile-terminated traffic (home
network)
User roams to foreign network
Mobile-terminated traffic (foreign
network)
Internet
Local Area
Network
Host
BTS
Core network
(Intra-operator
backbone)
Operator B
4.3 Network Layer Support in GPRS/UMTS
GPRS versus UMTS versus LTE
GPRS (2.5G)
GTP
BTS
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
UE
SGSN
BSC
Internet
GGSN
IMS
UMTS (3G)
UE
Node B
GTP
GTP
RNC
SGSN
Internet
GGSN
IMS
LTE (4G)
UE
eNB
Base Transceiver Station
Base Station Controler
General Packet Radio Services
Gateway Tunneling Protocol
Gateway GPRS Support Node
GTP
SAEGW
IP Multimedia Subsystem
Radio Network Controler
Serving GPRS Support Node
System Architecture Evolution Gateway
Internet
32
4.3 Network Layer Support in GPRS/UMTS
Protocol Layer in GPRS and UMTS
GPRS Transmission Plane (User Plane)
Application
PDP context
Axel Küpper | Technische Universität Berlin | Service-centric Networking
Mobile Services – ST 2010 | 4 Mobile Internet
IP
IP
IP
SNDCP
SNDCP
GTP-U
GTP-U
LLC
LLC
UDP/TCP
UDP/TCP
RLC
RLC
BSSGP
BSSGP
IP
IP
MAC
MAC
Layer 2
Layer 2
Layer 2
Layer 2
Layer 1
Layer 1
Layer 1
SGSN
Layer 1
Layer 1
Layer 1
BSC
GERAN
Layer 2
Layer 1
GGSN
UMTS Transmission Plane (User Plane)
Application
PDP context
IP
PDCP
PDCP
RLC
RLC
MAC
Layer 1
UDP/TCP
GTP-U
GTP-U
UDP/TCP UDP/TCP
IP
GTP-U
UDP/TCP
IP
IP
IP
IP
MAC
Layer 2
Layer 2
Layer 2
Layer 2
Layer 1
Layer 1
Layer 1
Layer 1
SGSN
Layer 1
UTRAN
Base Station Controler
Base Station System GPRS Protocol
Internet Protocol
Gateway GPRS Support Node
GTP-U
IP
RNC
Gateway Tunneling Protocol – User Plane
GSM/EDGE Radio Access Network
Logical Link Control
Medium Access Control
Packet Data Convergence Protocol
Radio Link Control
Radio Network Controler
Serving GPRS Support Node
Layer 2
Layer 1
GGSN
Subnetwork Dependent Convergence Protocol
Transmission Control Protocol
UMTS Terrestrial Radio Access Network
33
User Datagram Protocol