Transcript 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
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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
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.
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.
3.
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4.
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5.
2.
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.
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
establishment through the use of a MigratePermitted 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
Initial sequence number of host i
which initiated the connection
with an active open.
This token, T, is computed using
the Secure Hash Algorithm
(SHA-1)
Initial sequence number of host j
which is performing a passive
open.
After the initiating host’s reception of
the SYN/ACK with the MigratePermitted , both hosts can then
compute a shared secret key. This
secret key is then used to compute a
connection validation token.
Sequence number of host i
Sequence number of host j
Connection key
Sequence number of Migrate SYN segment
Request sequence number
Token and Comparison
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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,
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• 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)
Session Initiation
Protocol (SIP)
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
spans considerable space, often between several administrative
domain.
• Micromobility
– Micromobility protocols operate in a restricted administrative
domain 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 endto-end connection, whereas the lower
layer is completely ignorant of this end-toend semantic.
• Transport-Layer Mobility Protocol
– TCP-Migrate
SIP Mobility
• Precall mobility
– Terminal mobility requires SIP to establish connection at the start
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
middle of a session.
– The terminal need to intimate the CH by sending an INVITE
message 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.