行動多媒體通訊標準參考模式 (reference models)

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.

Introduction

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 mobil

e services into one system.– Support hign mass market service provision efficiently and at a l

ow cost.– Be a global system allowing global roaming and global service pr

ovision.

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.

UMTS Functional Architecture

Mobility Procedures-Handover

1. 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

2. 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

3. 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

4. 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.

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.

1.

2.

3.

4.

4.

5.

Network-Layer Mobility Protocol

• Macromobility Protocols– Mobile IP

• Micromobility Protocols– HAWAII– Cellular IP (CIP)– Terminal Independent Mobile IP (TIMIP)– Intra Domain Mobility Management Protocol (I

DMP)

Mobile IP

• Mobile Node– A host or router that changes its point of attachment fr

om one network or subnetwork to another. – A mobile node may change its location without chang

e its IP address.– it may continue to communicate with other Internet no

des 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 wh

ich 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 whi

ch 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 nod

e, 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 regi

stered,

• 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.

Mobile IP

Mobile IP

HAWAII

Cellular IP

Transport-Layer Mobility

• TCP-Migrate

TCP Segment Encapsulation

TCP Segment Format

TCP breaks data stream into segments

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 establish

ment 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

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.

Initial sequence number of host i which initiated the connection with an active open.

Initial sequence number of host j which is performing a passive open.

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 m

igration 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

Session Initiation Protocol (SIP)

Resource Reservation Protocol (RSVP)

Real-time protocol (RTP)

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

SIP Request

Figure 1 : Example of SIP proxy server

Figure 2 : Example of SIP redirect server

SIP mobility: setting up a call

SIP mobility : mobility host moves

SIP INVATE request

Mobile host registration

Conclusion

References

Network-Layer Mobility

• Network-Layer Mobility protocols can be classified into two class, micromobility and macromobility, base on their scope of operation with respect to the adminstrative domains in the Internet.

• Micromobility protocols work within a domain, while macromobility protocols operate across domain.

Macro and Micromobility

• Macromobility– Macromobility refers to user mobility that is infrequent and also s

pans considerable space, often between several administrative domain.

• Micromobility– Micromobility protocols operate in a restricted administrative do

main and provide the MHs within that domain with connections to the core network, while keeping signaling cost, packet loss, and handover latency as low as possible.

Subnetwork-Layer Mobility

• Subnetwork layer mobility is transparent to network and upper layers because an MH changes its point of attachment using solely layer 2(link layer) mechanisms.

• Ex.– GPRS (General Packet Radio Service)– UMTS (Universal Mobile Telecommunication

System)

Transport-Layer Mobility

• The transport layer maintains the true end-to-end connection, whereas the lower layer is completely ignorant of this end-to-end semantic.

• Transport-Layer Mobility Protocol– TCP-Migrate

SIP Mobility

• Precall mobility– Terminal mobility requires SIP to establish connection at the star

t of a new session, when the terminal or the MH has already moved to a different location.

– The MH reregisters its new IP address with its home (e.g. the redirect or SIP server) by sending a REGISTER message.

• Mid-call mobility– Terminal mobility requires SIP to establish connection in the mid

dle of a session.– The terminal need to intimate the CH by sending an INVITE mes

sage about the terminal’s new IP address and updated session description.

SIP mobility management

SIP mobility management

SIP Mobility

• SIP is capable of handling terminal, session, personal, and services mobility.

• Terminal mobility support that allow a device to move between subnets while being reachable to other hosts and maintaining any ongoing session.

UMTS Functional Architecture

• The general structure of both interfaces separated functional interfaces will separate transport related signalling from mobility and service signalling.

• The separated functional interface between the core and access networks will help minimise the functional and processing impact on the switches of mobility procedures.

• The separated functional will be mirrored within the access network and across the air interface in order to help reduce the complexity of access network design .

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, independent of access network type, both across the air interface and between the access network and the core network.