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行動多媒體通訊標準參考模式 (Reference Models). 報告者：陳俊義. Outline. Introduction Subnetwork-Layer Mobility Network-Layer Mobility Transport-Layer Mobility Application-Layer Mobility Conclusion. Introduction.
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行動多媒體通訊標準參考模式(Reference Models) 報告者：陳俊義
Outline • Introduction • Subnetwork-Layer Mobility • Network-Layer Mobility • Transport-Layer Mobility • Application-Layer Mobility • Conclusion
Introduction • Mobility means the ability of a mobile host (MH) to overcome the location-dependent nature of IP address by a suitable translation mechanism, and to send and receive datagrams efficiently from any location.
Subnetwork-Layer Mobility • GPRS (General Packet Radio Service) • UMTS (Universal Mobile Telecommunication System)
UMTS • Universal Mobile Telecommunication System (UMTS) is currently being developed with Europe as a third generation system for mobile telecommunication. • UMTS Features: • Support broadband flexible bandwidth allocation • Support multimedia and internet services up to 2 Mbs • Integrate the provision of cordless, paging, and broadband mobile services into one system. • Support hign mass market service provision efficiently and at a low cost. • Be a global system allowing global roaming and global service provision.
UMTS Functional Architecture • Building upon the concepts of GSM by extending the separation between the switching layer and the service and mobility layer across the whole system. • Recognise that the access network structure and capabilities will vary depending upon the environment that it is being served (e.g. domestic, business, satellite environments). • Support the different access networks by providing a common interface structure.
Mobility Procedures-Handover • When an access network part identifies that a handover between cells dose not solely take place within its control domain (e.g. access network 1), it passed control to the Service Control Point (SCP) to continue handover processing. 1.
Mobility Procedures-Handover • The SCP then attempts to identify which access network the target cell is in based upon information provided by the mobile terminal and then ascertains whether the target cell is within its control domain. If the access network is within its control domain, it attempts to set up fixed links to the access network and requests the access network and requests the access network to allocation radio resources. 2.
Mobility Procedures--Handover • The SCP then tells the mobile through the old access network (e.g. access network 1) the radio information that it will need to reattach on the new access network. 3. 3.
Mobility Procedures--Handover • The SCP then instructs the switch to change traffic and signalling paths without affecting the call. At the same time the mobile terminal reattaches to the target cell on the new access network (e.g. access network 2). 4.
3. 1. 2. 4. 5. 4. Mobility Procedures--Handover • If at the second step, the SCP identifies that the target access network is attached to another switch, the SCP negotiates with other SCPs.
Network-Layer Mobility Protocol • Macromobility Protocols • Mobile IP • Micromobility Protocols • HAWAII • Cellular IP (CIP) • Terminal Independent Mobile IP (TIMIP) • Intra Domain Mobility Management Protocol (IDMP)
Mobile IP • Mobile Node • A host or router that changes its point of attachment from one network or subnetwork to another. • A mobile node may change its location without change its IP address. • it may continue to communicate with other Internet nodes at any location using its (constant) IP address, assuming link-layer connectivity to a point of attachment is available.
Mobile IP • Home Agent • A router on a mobile node’s home network which tunnels datagrams for delivery to the mobile node when it is away from home, and maintains current location information for the mobile node.
Mobile IP • Foreign Agent • A router on mobile node’s visited network which provides routing services to the mobile node while registered. • The foreign agent detunnels and delivers datagrams to the mobile node that were tunneled by the mobile node’s home agent. • For datagrams sent by a mobile node, the foreign agent may serve as a default router for registered mobile node.
Mobile IP • Care-of address • The termination point of a tunnel toward a mobile node, for datagrams forwarded to the mobile node while it is away from home. • The protocol can use two different types of care-of address: • foreign agent care-of address • an address of a foreign agent with which the mobile node is registered, • co-located care-of address • an externally obtained local address which the mobile node has associated with one of its own network interfaces.
Mobile IP • A mobile node is given a long-term IP address on a home network. • This home address is administered in the same way as a “permanent” IP address is provided to a stationary host. • When away from its home network, a “care-of address” is associated with the mobile node and node uses its home address as the source address of all IP datagrams that it sends.
Transport-Layer Mobility • TCP-Migrate
Sliding windows are used to transmit data stream efficiently and for flow control
TCP-Migrate • Migrate TCBs from established connections • Special SYN packets include a Migrate option • Migrate SYNs do not establish new connections, but migrate previously-established ones • Established connections are referenced by a token • Maintain all old state (sequence space, options, etc.) • Tokens negotiated during initial connection establishment through the use of a Migrate-Permitted option.
TCP-Migrate • After a successful token negotiation, TCP connections may be uniquely identified • < source address, source port, dest address, dest port > • < source address, source port, token > • A mobile host may restart a previously-established TCP connection from a new address by sending a special Migrate SYN packet that contains the token identifying the previous connection.
TCP Migrate Permitted option , TCP Migrate option TCP Migrate Permitted option TCP Migrate option
TCP Migrate Permitted option • Hosts wishing to initiate a migrateable TCP connection send a Migrate-Permitted option in the initial SYN segment. • the Migrate-Permitted option comes in two variants—the insecure version, of length 3, and the secure version, with length 20. • Computing value of token in the Migrate-Permitted option exchange. • Hosts wishing to cryptographically secure the connection token may conduct an Elliptic Curve Diffie-Hellman (ECDH) key exchange through the option negotiation.
TCP Migrate option • The Migrate option is used to request the migration of a currently open TCP connection to a new address.It is sent in a SYN segment to a host with which a previously-established connection already exists. • A token • is computed in the Migrate-Permitted option exchange. • is negotiated between both ends during the initial connection establishment. • identifies a previously established connection on the same destination < address, port > pair. • The previously broken TCP connection can be resumed
Initialsequence number of host i which initiated the connection with an active open. Initialsequence number of host j which is performing a passive open. After the initiating host’s reception of the SYN/ACK with the Migrate-Permitted , both hosts can then compute a shared secret key. This secret key is then used to compute a connection validation token. This token, T, is computed using the Secure Hash Algorithm (SHA-1)
Sequence number of host i Sequence number of host j Connection key Sequence number of Migrate SYN segment Request sequence number
Token and Comparison • Upon receipt of a SYN packet with the Migrate option, a TCP stack that supports migration attempts to locate the connection on the receiving port with the corresponding token. • If the token is valid, meaning an established connection on this < address, port > pair has the same token. The fixed host then computes R = SHA1(Ni,Nj,K, S, I), and compares it with the value of the request in the Migrate SYN. • If the comparison fails, or the token was invalid, a RST is sent to the address and port issuing the Migrate SYN. • If the token and request are valid, • the reqNo is smaller than a previously received request, the SYN is assumed to be out-of-order and silently discarded. • If the reqNo is identical to the most recently received migrate request, and processed accordingly. • The destination address and port associated with the matching connection should be updated to reflect the source of the Migrate SYN, and a SYN/ACK packet generated. Upon receipt of an ACK, the connection continues as before.
Application-Layer Mobility • Session Initiation Protocol (SIP)
Session Initiation Protocol (SIP) • The Session Initiation Protocol (SIP) is gaining aceptance as an application-layer signaling protocol for Internet multimedia and telephony services, as well as for wireless Internet application. • These session include Internet multimedia conference, distance learning , Internet telephone calls , multimedia distribution and similar applications.
Session Initiation Protocol (SIP) • Session can be advertised using multicast protocols such as SAP, electronic mail, news groups, web pages or directories ( LDAP), among others. • SIP transparently supports name mapping and redirection services, allowing the implementation of ISDN and Intelligent Network telephony subscriber services.
Incorporating protocols Resource Reservation Protocol (RSVP) Real-time protocol (RTP) Session Initiation Protocol (SIP) Real-time Streaming protocol (RSTP) Session Announcement protocol (SAP) Session Description protocol (SDP)
SIP Addressing User @ host The user part is a user name or a telephone number The host part is either a domain name or a numeric network address
