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 February 2001

6. Requirements and Issues for IP based Mobility Management

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 3 Architecture for a wireless/wireline IP infrastructure

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 4 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 5 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 6 Framework Requirements for Mobility Management supports current TCP-based Internet application. interworks smoothly with PSTN and today's 1G/2G wireless telephony

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 7 Mobility Management Functions and Requirements  Hand-off  Registration  Configuration  Dynamic address binding  Location management

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 8 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 9 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 10 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 11 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 12 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 13 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 14 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 15 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 16 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

7. Proposed Concept for a SIP Managed IP Based Mobile System Architecture

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 18 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 19 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-of-address? 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?

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 20 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 21 Drafting the solution

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 22 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 23 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 24 Call Establishment

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 25 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).

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 26 Multimedia Conference Continuity

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 27 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 28 MH position registration

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 29 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 30 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 31 Scenario 1, FH  Fixed Host 1.Receive re-invite 2.Send 200 Message 3.Receive ACK 4.Send command to multimedia applications redirecting data stream.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 32 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 re-invite packet.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 33 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 34 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 35 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 36 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 37 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 38 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 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 Receive ACK 4.Start multimedia applications sending data to the new point of attachment received in the ACK message.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 39 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 40 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 41 Stateless Address Autoconfiguration  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)  Before a host starts effectively using a link-local address it verifies when this address is unique on link level.  If the link-local address is unique it assigns the address to its interface and acquire IP-level connectivity.  The next step consists on wait for router advertisements messages or send a router solicitation message.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 42 Stateless Address Autoconfiguration  Each router advertisement message contains prefix information(network prefix, subnet) which is used by hosts to generate site-local addresses  While in the same subnet all router advertisements have the same prefix and there by they will be discarded by host without any effect.  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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 43 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:c :48ff:feea:e932

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 44 SITE-LOCAL ADDRESS GENERATION

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 45 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

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 46 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.

VoIP 특론 순천향대학교 정보기술공학부 이 상 정 47 Wireless link control algorithm