Transcript User access control and mobility management 2003-1

Implementation and Evaluation of
Mobility Management for Public Land Mobile
Networks deploying
the Session Initiation Protocol
Thesis for the degree Master of Science from the course
“Computer Science and Communicati0on Engineering”
By
Maximo Alves
[email protected]
February 2001
6. Requirements and Issues
for IP based Mobility Management
2003-1-VoIP 특론
Architecture for a wireless/wireline IP
infrastructure
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Architecture for a wireless/wireline IP
infrastructure
 Mobile access or Mobile Hosts(MH)
• uses devices such as PDA´s , Laptops and so on.
• have radio link connections with the Wireless Cells
 Fixed access or Fixed Hosts(FH)
• usually uses normal PCs or any device with one fixed
point of attachment to the network.
 Regional IP Networks
• connect together Fixed Hosts and Wireless Cells
 MAAAQ(mobility management, Authentication,
Authorization, Accounting and QoS management)
• User access control and mobility management
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Framework Requirements for
Mobility Management
 Mobility Management
• supports means of personal, service, and terminal
mobility
• supports global roaming
• allow users to roam across different technology platforms, and
across subnets within the same or different administrative
domain
• is wireless technology-independent
• supports both real-time and non-real-time multimedia
services
• such as mobile telephony, mobile web access, and mobile
data services
• should interact effectively with the QoS management and
authentication, authorization, and accounting (AAA) schemes
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Framework Requirements for
Mobility Management
• supports current TCP-based Internet application.
• interworks smoothly with PSTN and today's 1G/2G
wireless telephony
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Mobility Management Functions and
Requirements
 Hand-off
 Registration
 Configuration
 Dynamic address binding
 Location management
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Hand-off
 a process that allows a established
call/session to continue when a MS moves
from one cell to another (intercell) or
between radio channels in the same cell
(intracell) without interruptions in the
call/session
 Hard hand-off
 Soft hand-off
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Hard hand-off
 MH receives and accepts only one radio
signal from a radio channel or base station
within a single cell.
 As the mobile moves into a new cell, its
signal is abruptly handed over from its
current cell (or base station) to the new one
rapidly in a few seconds.
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Soft hand-off
 MH continues to receive and accept radio
signals from the base stations within its
previous as well as its new cell for a limited
period of time.
 Signal reception from the old base station
ceases when the signal strength
drops/reduces below a certain threshold.
 Soft hand-off smoothly transfers the MH's
session
 All third generation CDMA wireless
technologies use soft hand-off.
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Three levels of logical/virtual hand-off
 Cell hand-off (or micro-mobility)
• allows a MH to move from a cell to another in a
subnet within an administrative domain
 Subnet hand-off (or macro-mobility)
• allows a MH to move from a cell within a subnet
to an adjacent cell within another subnet that
belongs to the same administrative domain
 Domain hand-off (or global mobility)
• allows a MS to move from one subnet within an
administrative domain to another in a different
administrative domain
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Registration
 a process by which a network becomes
aware of the existence and the location of
an MH and its associated user.
• Beginning when an MH becomes active(i.e., is
turned on) in a network or roams into a new
subnet or domain
• Sending a registration request from the MS to
the network
• Performing an AAA (i.e., authentication,
authorization, and accounting) process
• Sending appropriate responses to the MH as
well as location management entities
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Registration
 There are two types of registration
 Complete Registration
• When a user turn on its MS or roams into a new
administrative domain (i.e., during domain hand-off)
• Performing AAA, and send appropriate responses to the
MS and location management entities.
 Expedited/Partial Registration
• When a user moves from one subnet to another within the
same administrative domain (i.e., subnet hand-off)
• Not including AAA process
• Only the location information up to date.
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Configuration
 a process by which a MH updates its IP
address as it roams between subnets
• getting a new IP address, possibly new default
gateway, subnet mask, etc.
 Requirements
• not taking more than a few hundred milliseconds
to complete
• updating the DNS to reflect the current address to
name and name to address mappings
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Dynamic address binding
 a process for allowing an MS to maintain a
constant identifier (e.g., a constant URL)
regardless of its point of attachment to the
network (e.g., its IP address).
• allowing a user to maintain a universal identifier
(e.g., a SIP URL)
• facilitating support of TCP-based applications by
informing each endpoint about the current address
of the other one.
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Location management
 a process by which the network updates the
location database and supports location/
redirect services to authorized users and
authorities.
• should be up to date and accurate, e.g., the
domain name service shall ensure correct name to
address and/or address to name mapping as soon
as possible
• should only be disclosed to authorized users
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7. Proposed Concept for a SIP Managed
IP Based Mobile System Architecture
2003-1-VoIP 특론
Introduction
 Presents one architecture for host mobility
managed by the SIP protocol
 Defining three entities
• The application programs that implement the
Session Initiation Protocol.
• The procedures used for Care-of-Address
discovery and configuration.
• The devices that support wireless connections
establishment to the fixed network.
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Defining the problem
 How to route packets to their destination based on IP
addresses ?
• IP changes whenever hand-off
• How get a new IP address, called Care-of-Address, for MH
• How to direct packets to the Care-of-Address
 Following questions must be answered
• Where does the MH registers itself on the network updating
always its most recent location?
• How does the MH gets a new Care-of-Address every time it
roams on a new network?
• How does the MH configures itself with a new Care-ofaddress?
• How does the MH updates the correspondent hosts in a
conference with its new point of attachment?
• How can be the MH found when other host tries calling it?
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Drafting the solution
 SIP protocol for MH Registration and Location
 Stateless Address Autoconfiguration and Router




Advertisement Messages for Care-of-Address
discovery and dynamic configuration
Bluetooth to connect MH to the wireline network
Soft hand-off process for better quality on real
time multimedia transmissions.
No AAA service for domain hand-off support
Only for cell and subnet hand-off
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Drafting the solution
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Mobility Support using SIP
 SIP supports host mobility with three distinct tasks
 Call establishment
• the Caller invites the Callee sending a INVITE message to the
Callee´s home network
 Multimedia Conference Continuity
• MH hosts sends a re-INVITE message informing all the
conference participants about its new network location.
 MH position registration
• The REGISTER message is sent to the server by the MH
every time it acquires a new point-of-attachment.
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Mobility Management
 Figure 7.2 shows the necessary SIP messages
for host mobility support.
 Figure 7.2-a illustrates the call establishment
support function.
 Figure 7.2-b illustrates Multimedia Conference
Continuity support function when the MH moves
its base network.
 Figure 7.2-c illustrates how the MH registers its
new location.
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Call Establishment
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Call Establishment
 Tom using a INVITE message(Nr 1) calls Jerry
on Jerry’s home network;
 The SIP server on Jerry´s home network
answer with a 302 message(Nr 2). This
message contains in the contact field Jerry´s
current location which is on somewhere.com;
 Tom calls Jerry on somewhere.com sending a
INVITE message(Nr 4).
 As Jerry accepts the invitation the signaling
process proceeds with OK and ACK
messages(Nr 5 and Nr 6 respectively).
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Multimedia Conference Continuity
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Multimedia Conference Continuity
 During the session Jerry moves from
somewhere.com to anywhere.com.
 The Hand-off signal trigger one event which is
the re-INVITE message(Nr 1) delivery to Tom.
This message contains a contact field which
has the Jerry´s new point of attachment.
 Tom proceeds the multimedia applications to
redirect data streams to Jerry’s new network
position.
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MH position registration
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MH position registration
 Jerry sends a REGISTER message(Nr 1) to
the SIP server on its home network. The
Server records Jerry’s current point of
attachment.
 The Server redirects all new incoming calls
to Jerry’s new location.
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SIP Signaling on a mobile host Scenario
 Three different SIP signaling scenarios concerning
host mobility
 Scenario 1: MH <-> FH
•
Most common scenario composed from a Mobile Host and a
Fixed Host taking part on a already established multimedia
conference.
 Mobile Host
1. Receive Hand-off signal
2. Get new IP address
3. Send re-invite containing new point of attachment to Fixed
Host
4. Receive 200 Message
5. Send ACK Message
6. Send register Message to SIP Server
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Scenario 1, FH

Fixed Host
1.
2.
3.
4.
Receive re-invite
Send 200 Message
Receive ACK
Send command to multimedia applications
redirecting data stream.
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Scenario 2
 MH1 <-> MH2
• Both MHs receive the Hand-off signal at the
same time.
• Both of them will proceed according to this
signal sending a re-invite request.
 Case 2.1
• Suppose that MH2 is the first to receive a reinvite packet.
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Scenario 2, MH1
 Mobile host1
1. Receive Hand-off signal
2. Get new IP address
3. Send re-invite containing new point of attachment to MH2
4. Receive 200 Message in response to re-invite
5. Receive re-invite from MH2
6. Send 200 Message in response to re-invite
7. Send ACK Message in response to 200 message.
8. Send register Message to SIP Server
9. Receive ACK
10.Send command to multimedia applications redirecting
data stream.
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Scenario 2, MH2
 Mobile host2
1. Receive Hand-off signal
2. Get new IP address
3. Send re-invite containing new point of attachment to
MH2
4. Receive re-invite
5. Send 200 Message
6. Receive 200 Message
7. Send ACK Message
8. Send register Message to SIP Server
9. Receive ACK
10.Send command to multimedia applications redirecting
data stream.
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Scenario 3

Description
• Here the SIP call establishment hand-shake process is not
yet complete
• One of the peers roam to other network. At that stage there
is no active multimedia communication.
• Hand-off does not affect the correspondent host(CH) but
only the mobile host(MH).
• There are 4 possible sub cases in such a scenario.
 Case 3.1
• A MH has just sent an Invite request when the Hand-off
signal comes.
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Scenario 3, Case 3.1

Caller(MH)
1. Receives Hand-off signal
2. Get new IP address
3. Send another invite request containing the new point of
attachment
4. The signaling proceeds normally.
 Callee(CH)
1. Receives a first invite request
2. Sends 200 response but does not get a ACK for that
3. Receives a new and address-updated Invite message
4. The signaling proceeds normally.
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Scenario 3, Case 3.2
 Case 3.2
• A MH host moves just after it has received a Invite request.
 Callee(MH)
1. Receive Invite
2. Receives Hand-off signal
3. Get new IP address
4. Sends 200 response containing the new point of attachment
5. The signaling proceeds normally.
 Caller(CH)
1. Send Invite
2. Receive 200 with a new point of attachment
3. Send ACK to the point of attachment
4. The signaling proceeds normally.
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Scenario 3, Case 3.3
 Case 3.3
• A MH has just received a 200 response when the Hand-off
signal comes.
 Caller(MH)
1. Send invite
2. Receive 200
3. Receive Hand-off signal comes.
4. Get new IP address
5. Send ACK containing the new point-of-attachment
6. Start multimedia applications
 Callee(CH)
1. Receive invite
2. Send 200
3. Receive ACK
4. Start multimedia applications sending data to the new point of
attachment received in the ACK message.
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Scenario 3, Case 3.4
 Case 3.4
• A MH has just sent a 200 response when the Hand-off signal comes.
 Callee(MH)
•
•
•
•
•
•
•
receive invite
send 200
Receive Hand-off signal.
Get new IP address
Receive ACK
Send re-invite with new point of attachment
Start multimedia applications
 Caller(FH)
•
•
•
•
send invite
receive 200
Send ACK
Start multimedia applications sending data to the new point of
attachment received in the re-invite message
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Care-of-Address Discovery and
Configuration
 Stateless Address Autoconfiguration procedure
• RFC 2462 specifies the steps a host takes on deciding
how to autoconfigure its network interfaces on Ipv6.
 Router Advertisement Messages
• RFC 1256 provides hosts with necessary information for
Care-of-Address generation.
 Together they provide ways for mobility support
enabling mobile hosts to acquire and configure
new IP address every time they reach a new
network.
• how to solve the Care-of-Address discovery and
Configuration issue on the architecture.
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Stateless Address Autoconfiguration
1. On system startup nodes generate link-local address
for the interface appending the interface’s identifier to
the well-know link-local prefix(FE80::0)
2. Before a host starts effectively using a link-local
address it verifies when this address is unique on link
level.
3. If the link-local address is unique it assigns the
address to its interface and acquire IP-level
connectivity.
4. The next step consists on wait for router
advertisements messages or send a router solicitation
message.
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Stateless Address Autoconfiguration
4. Each router advertisement message contains prefix
information(network prefix, subnet) which is used by
hosts to generate site-local addresses
5. While in the same subnet all router advertisements
have the same prefix and there by they will be
discarded by host without any effect.
6. Once a mobile host gets a physical link on a new
network it starts receiving router advertisement
messages for this network.
•
As this router advertisement messages contain new prefixes
they trigger the autoconfiguration process starting again from
step 4.
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SITE-LOCAL ADDRESS GENERATION
 It is formed by appending an interface identifier(host)
to a prefix(network) of appropriate length.
• The sum of the interface identifier with the prefix can not
exceed 128 bits.
• On Ethernet based networks the interface identifier is created
based on the 48 bit MAC address.
• This is to insert two octets with hexadecimal values of 0xFF
and 0xFE in the middle of the 48 bit MAC address.
• The Figure 7.3 bellow shows how an Ipv6 address based on
MAC address is generated.
• Example link local address
fec0:0:c0:c866 280:48ff:feea:e932
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SITE-LOCAL ADDRESS GENERATION
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Wireless Link
 For wireless link, Bluetooth is used.
• Bluetooth Access Point(AP) module fixed to the LAN
• Bluetooth module installed on the mobile host
• During the connection the Bluetooth module present on MH
acts like a client while the AP acts like a server
• The server waits for client initiative to connect and disconnect.
 The mobile host must be able to:
• have control over the Hand-off process.
• connect two or more Access Points at the same time.
• connect and disconnect the link when necessary.
• scan the surroundings searching for other Access Points.
• measure Access Points quality of signal
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Wireless link control algorithm
 Algorithm in order to keep communicability
while moving
• The module which implements this control
algorithm is called Wireless Link Manager(WLM).
• Figure 7.5 illustrates the control algorithm with a
diagram.
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Wireless link control algorithm
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