Wireless and Mobile All-IP Networks

1
Wireless and Mobile All-IP Networks

• Yi-Bing Lin
• liny_at_csie.nctu.edu.tw

2
From Traditional Telecom to All-IP

• Circuit-Switched vs Packet-Switched
• Intellient Network (IN) vs. IP Multimedia
  Core Network Subsystem (IMS)
• Example Video Phone
• All-IP Telecom Services New Technologies vs.
  New Services
• VoIP Numbering, Number Portability
• Service Creation Dictatorship vs. Democracy
• Peer-to-Peer, Web 2.0

3
All-IP Architecture
4
Issues on Mobile All-IP Network

• Short Message Service (SMS) and IP Network
  Integration
• SMS is considered as the application level
  signaling mechanism.
• Mobility Management
• GSM Location Area (LA) tracking
• GPRS Routing Area (RA), cell tracking
• UMTS RA, UTRAN RA (URA), cell tracking
• Session Management
• PDP context is introduced.

5
Issues on Mobile All-IP Network

• Mobile Core Networks that Support All-IP
• UMTS GPRS
• cdma2000 PDSN (Packet Data Support Node)
• UMTS Charging Protocol
• On-line Charging System (OCS)
• Mobile All-IP Network Signaling
• Traditional SS7 is supported by MTP
• (Message Transfer Part)
• All-IP SS7 is supported by SCTP
• (Stream Control Transport
  Protocol)

6
Issues on Mobile All-IP Network

• UMTS Security and Availability Issues
• Virus, fraudulent Usage, Redundant
  Authentication
• Multicast for Mobile Multimedia Messaging Service
• UMTS All-IP Network
• SIP (Session Initiation Protocol)
• IPv6

7
Identities in UMTS

• Why is identity management important?
• Billing, Security, Service
• ANSI 41 MDN MIN
• GSM MAP MDN ? MIN
• How are identities assigned in UMTS PS service
  domain?
• Service APN
• MS IP address

8
Access Point Name (APN)

• An APN is used in UMTS/GPRS as a reference point
  to external PDN that supports the services to be
  accessed by an MS.
• The APN information is permanently distributed
  and maintained in the HLR, the GGSN and the
  Domain Name Server (DNS).

9
APN Allocation

• A set of APN labels is defined in the HLR.
• Each mobile user can subscribe to one or more
  APNs from this set.
• The labels of these subscribed APNs are then
  stored in the MS at the subscription time.
• Among the subscribed APNs, there is one default
  APN.
• If a user attempts to access a service without
  specifying the APN, then the default APN is used.
  
• Additionally, the HLR may also define a wild card
  APN ", which allows an MS to access any
  unsubscribed APNs.
• For each APN, the DNS keeps an IP address list of
  the GGSNs associated with this APN label.

10
APN Configurations
11
IP Address Allocation Access Modes

• Based on the APN setting specified in 3GPP TS
  29.060, the GGSN provides two access modes for IP
  address allocation to an MS
• Transparent
• Non-transparent

12
Transparent Access Mode

• In the transparent access mode, the mobile
  operator acts as an Internet service provider,
  and an MS is given an IP address from the
  operator's IP address space.
• The IP address can be allocated statically at the
  subscription time or dynamically at the
  activation of the PDP context.
• The transparent access mode is exercised if the
  requested APN INTERNET.

13
Non-transparent Access Mode

• In the non-transparent access mode, the mobile
  operator only provides a user the access channel
  to an Internet service provider (if the APN is
  ISP) or a company (if the APN is COMPANY).
• The IP address pool is owned by the Internet
  service provider or the corporate, and the IP
  address for an MS is dynamically allocated.

14
IP Address Allocation (I)

•  The IP addresses can be allocated by either the
  GGSN, a Dynamic Host Configuration Protocol
  (DHCP) server, or a Remote Authentication Dial-In
  User Service (RADIUS) server.
• In the transparent access mode, the GGSN may
  allocate the IP address for a user by using its
  own address pool.
• In the current implementation, IPv6 addresses can
  only be allocated by this alternative.

15
IP Address Allocation (II)

•  In either the transparent or the non-transparent
  access modes, the GGSN may negotiate with a DHCP
  server to allocate an IP address from the address
  pool maintained by this DHCP server.
• Alternatively, the IP address of an MS may be
  assigned by a RADIUS server, where the IP address
  pool is maintained by this RADIUS server.

16
IP Address Allocation (III)
APN label INTERNET WAP ISP COMPANY
GGSN access mode Transparent Transparent Non- transparent Non- transparent
IP address allocator GGSN/ DHCP server GGSN/ DHCP server DHCP server RADIUS RADIUS
IP address type IPv6/IPv4 IPv4 IPv4 IPv4
17
PDP Context

• Before an MS can access any mobile data service,
  the Packet Data Protocol (PDP) context for the
  service must be activated.
• The PDP context specifies the application-layer
  packet data protocol and the routing information
  used for the communication session.
• The PDP context is maintained in the MS, the
  SGSN, and the GGSN.

18
PDP Context Activation

• During the PDP context activation procedure , the
  MS specifies a requested APN.
• Then the SGSN uses this requested APN to select a
  GGSN.
• If the user does not specify any requested APN in
  the activation procedure, the default APN is
  chosen by the SGSN.

19
PDP Context Activation Step 1
MS
UTRAN
SGSN
GGSN
DNS
1. Activate PDP Context Request

• The MS specifies the APN in the Activate PDP
  Context Request message and sends it to the SGSN.

20
PDP Context Activation Step 2
MS
UTRAN
SGSN
GGSN
DNS
1. Activate PDP Context Request
2. Radio Access Bearer Assignment Procedure
The SGSN negotiates with the UTRAN to allocate
the radio bearer bandwidth for the data session.
21
PDP Context Activation Step 3
MS
UTRAN
SGSN
GGSN
DNS
1. Activate PDP Context Request
2. Radio Access Bearer Assignment Procedure
3. APN Query and response
The SGSN checks if the requested APN (obtained
from the Activate PDP Context Request message
sent by the MS) is specified in the APN list of
the subscription data for the MS. If not, the
default APN is used. Then the SGSN creates
the PDP context for the user, and sends the
requested APN to the DNS server. The DNS server
uses this APN to derive the GGSN's IP address.
22
PDP Context Activation Step 4
MS
UTRAN
SGSN
GGSN
DNS
1. Activate PDP Context Request
2. Radio Access Bearer Assignment Procedure
3. APN Query and response
4. Create PDP Context Request
Based on the GGSN's IP address obtained from the
DNS, the SGSN sends the Create PDP Context
Request message to the GGSN to establish a GTP
tunnel between the SGSN and the GGSN, which will
be used as the packet routing path between the
GGSN and the MS.
23
Step 5. The GGSN creates a PDP context for the
MS. This PDP context records the requested APN,
PDP type, MSISDN, and IP address. The GGSN
allocates an IP address for the MS by using
either transparent or non-transparent access
mode, and determines the tunneling mechanism to
the destination external PDN.
MS
UTRAN
SGSN
GGSN
DNS
1. Activate PDP Context Request
2. Radio Access Bearer Assignment Procedure
3. APN Query and response
4. Create PDP Context Request
5. Create PDP Context Response
24
Step 6. Finally, the SGSN informs the MS that the
session setup is completed
25
All-IP Telecom. Trial in Taiwan

• Under the M-Taiwan Program, FarEasTone is
  developing IMS Service Platform.
• APTG is conducting VoIP Service Trial.

26
Call Setup in APTG Trial
27
Performance Measurement

• Mean Opinion Score (MOS)

28
Conclusions

• The SIP protocol does not provide all features
  needed to implement existing telecommunications
  services. For example, the flash-hook signal for
  the call waiting service is implemented
  proprietarily in the APTG trial.
• There are too many kinds of IP CPEs. Some of them
  may not be compatible with the networks, and may
  show very poor performance. Furthermore, some
  CPEs may be complicate to operate, and cannot be
  simply plug-and-play.
• Although the cost for deploying All-IP VoIP
  network is lower than traditional PSTN network,
  it is not clear if the same advantages are
  guaranteed for maintenance and operations of the
  VoIP network.

29
Appendix A IPv4 vs IPv6

• The above procedure assumes IPv4 IP address
  allocation. For IPv6, the IP address allocation
  is different.
• Support of public IP address is a major
  difference for UMTS address allocation between
  IPv4 and IPv6.
• For IPv4, the MS is typically allocated a private
  address because of limited IPv4 address space.
• For IPv6, the MS is always allocated a public
  address.

30
IPv6 Address Allocation

• At Step 5 of the PDP context activation
  procedure, the GGSN allocates a complete IP
  address for IPv4.
• For IPv6, there are two alternatives for dynamic
  address allocation stateless address allocation
  and stateful address allocation.
• Like IPv4, the stateful IPv6 address is allocated
  by DHCP server at Step 5.
• On the other hand, in stateless address
  auto-configuration, the GGSN allocates a part of
  the IPv6 address called link-local address for
  the MS by using its own IPv6 address pool at Step
  5.
• Then the MS generates the public IP address by
  combining the link-local address and a
  network-prefix address.

31
IPv6 Stateless Auto-configuration Procedure
32
Stateless Address Auto-configuration (I)

• Step 1 the MS first obtains the link-local
  address in the PDP context activation procedure.
• Step 2 the MS activates the IPv6 address
  auto-configuration by sending the Router
  Solicitation message to the GGSN.
• Step 3 The GGSN replies with the Router
  Advertisement message, which includes the
  network-prefix address.
• After the MS has received the Router
  Advertisement message, it obtains the IPv6
  address by concatenating the link-local address
  and the network-prefix address.
• Step 4 Then the GGSN updates the IPv6 address of
  the PDP contexts in the SGSN and the MS.

33
Stateless Address Auto-configuration (II)

• To avoid conflict of link-local address
  assignment, the GGSN shall exercise neighbor
  discovery with other GGSNs.
• Note that in traditional IPv6 stateless address
  allocation, neighbor discovering is conducted by
  the mobile host. In UMTS, neighbor discovery is
  exercised by the GGSNs.
• Also note that existing UMTS core network is
  developed based on the IPv4 transport network.
• Therefore, IPv6 packets are carried on top of the
  IPv4-based GTP tunnel, which are invisible to the
  UMTS core network.

34
UMTS and External PDN Interworking

• The GGSN interworks the external data network
  through the Gi interface. The interworking
  mechanisms may be different for various APN
  configurations.
• For the INTERNET and WAP APNs, the GGSN connects
  to the external PDN directly through Ethernet or
  leased lines.
• For the ISP APN, the external PDN can be
  connected to the GGSN either through the leased
  lines or the VPN. If the Internet service
  provider connects to the GGSN through VPN, then
  tunneling is required.
• For the COMPANY APN, tunneling is always required
  for interworking between the GGSN and the
  corporate intranet.

35
Tunneling Methods

• Three tunneling methods have been proposed for
  UMTS.
• IP-in-IP tunneling.
• Generic Routing Encapsulation (GRE) tunneling
• Layer 2 Tunneling Protocol (L2TP) tunneling

36
IP-in-IP Tunneling
37
(No Transcript)
38
(No Transcript)
39
Tunneling method Overhead Multiprotocol support Transport support MS support
IP-in-IP low no IP IP
GRE(PPTP) medium yes IP PPP
L2TP high yes IP/UDP, FR, ATM IP
40

• Each of the above three methods can be used
  together with IPsec to provide protection for
  packet delivery.
• If an MS supports both PPP and IP, then all these
  three tunneling methods can be used to provide
  data sessions to this MS.

41
Quality of Service

• UMTS defines four QoS classes for user data
  traffic conversational, streaming, interactive,
  background
• The conversational and the streaming classes
  support real-time traffic for services such as
  voice and streaming video.
• The interactive and the background classes
  support non real-time traffic for services such
  as web browsing and email.
• Each class defines parameters including maximum
  bit rate, guaranteed bit rate, bit error ratio,
  transfer delay, etc.

42
QoS VoIP and Internet Access
QoS parameter VoIP (conversational) Internet access (Interactive )
Maximum bit rate 16 Kbps 128 Kbps
Guaranteed bit rate 12.2 Kbps 100 Kbps
Bit error ratio 104 10-6
Transfer delay 100 ms unguaranteed
43
End-to-end IP QoS Models (I)
Scenario 1 2 3 4 5
MS -- DS DS RSVP RSVP SBLP
GGSN DS DS DS DS RSVP DS SBLP
External PDN DS DS DS DS RSVP DS
Remote host DS DS DS RSVP DS RSVP DS SBLP
RSVP Resource Reservation Protocol SBLP
Service-Based Local Policy
44
End-to-end IP QoS Models (II)

• The end-to-end QoS for packet switched service is
  negotiated among the MS, the GGSN and the remote
  host located in the external PDN.
• 3GPP TS 23.207 assumes that the external PDN
  supports Diffserv QoS mechanism, and the GGSN is
  required to perform the Diffserv edge function in
  all scenarios.
• Within the UMTS network (MS-UTRAN-SGSN-GGSN), the
  IP QoS is translated and maintained by the UMTS
  QoS mechanism where the QoS parameters are set in
  the PDP contexts.

45
GGSN QoS Architecture
46
UMTS QoS vs DSCP
UMTS QoS class DSCP codepoint Delivery Priority
Conversational Expedited Forward 1 (high)
Streaming Assured Forward class 1 2
Interactive Assured Forward class 2 3
Background Best Forward 4 (low)
47
Remarks on GGSN QoS

• The Resource Manager and the Admission Controller
  are involved in PDP context activation.
• The Packet Classifier, Traffic Conditioner,
  Packet Mapper and Packet Scheduler are involved
  in packet delivery.

48
Appendix B Multicast for Mobile Multimedia
Messaging Service

• Short Message Service (SMS) allows mobile
  subscribers to send and receive simple text
  message in 2G systems (e.g. GSM).
• Multimedia Message Service (MMS) is introduced to
  deliver messages of sizes ranging from 30K bytes
  to 100K bytes in 2.5G systems (e.g. GPRS) and 3G
  systems (e.g. UMTS)
• The content of an MMS can be text (just like
  SMS), graphics (e.g., graphs, tables, charts,
  diagrams, maps, sketches, plans and layouts),
  audio samples (e.g., MP3 files), images (e.g.,
  photos), video (e.g., 30-second video clips), and
  so on.

49
MMS Architecture 1/2
50
MMS Architecture 2/2

• The MMS user agent (a) resides in a Mobile
  Station (MS) or an external device connected to
  the MS, which has an application layer function
  to receive the MMS.
• The MMS can be provided by the MMS value added
  service applications (b) connected to the mobile
  networks or by the external servers (d) (e.g.,
  email server, fax server) in the IP network.
• The MMS server (c) stores and processes incoming
  and outgoing multimedia messages.
• The MMS relay (e) transfers messages between
  different messaging systems, and adapts messages
  to the capabilities of the receiving devices. It
  also generates charging data for the billing
  purpose. The MMS server and the relay can be
  separated or combined.
• The MMS user database (f) contains user
  subscriber data and configuration information.
• The mobile network (g) can be a WAP (Wireless
  Application Protocol) based 2G, 2.5G or 3G
  system. Connectivity between different mobile
  networks is provided by the Internet protocol.

51
Short Message Multicast Architecture
MCH (HLR)
VLR1 1
VLR2 2
VLR3 0
MCV (VLR3)
LA5 0
LA6 0
MCV (VLR1)
MCV (VLR2)
LA3 0
LA4 2
LA1 0
LA2 1
52
Appendix C Short Message Service and IP Network
Integration
GSM SMS Network Architecture
53
SMS-IP Integration SM-SC-based
In most commercial implementations, SMS and IP
networks are integrated through SM-SC.
Mobile Network
IP Network
SM-SC
Gateway
54
NCTU-SMS
55
iSMS
56
Simple Tone Language (STL)

• The regular expressions are used for the STL
  grammar. In STL, a music tone is defined as
• tone style tempo volume repeat
  (note-expression)
• where style is of the format
• style S 0 (0 1 2)
• S00 Natural Style (rest between notes)
• S01 Continuous Style (no rest between notes)
• S02 Staccato Style (shorter notes and longer
  rest period)

57
STL Representation for a Taiwanese Song
58
Appendix C GGSN Functionalities

• The GGSN plays the role as a gateway, which
  controls user data sessions and transfers the
  data packets between the UMTS network and the
  external PDN.
• The meta functions implemented in the GGSN are
  described as follows
• Network access control
• Packet routing and transfer
• Mobility management

59
Functions of UMTS Network Elements