Transcript Document

行動多媒體通訊標準參考模式
(Reference Models)
報告者：童曉儒
Outline
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Introduction
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
Network-Layer Mobility Protocol
• 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.
Network-Layer Mobility Protocol
• Macromobility Protocols
– Mobile IP
• Micromobility Protocols
– Cellular IP (CIP)
– Intra Domain Mobility Management Protocol
(IDMP)
Mobile IP
• Mobile Node (MN)
– the node under consideration
• Home Agent (HA)
– a stationary network node (e.g., a router) at the home network
• Foreign Agent (FA)
– A network node (e.g. a router) in the foreign network
• Care-of Address (COA)
– The address in the foreign network
• Correspondent Node (CN)
– communication partner
Illustration
HA
MN
router
home network
mobile node
Internet
(physical home network
for the MN)
FA
foreign
network
router
(current physical network
for the MN)
CN
end-system
router
Mobile IP Operations
• Basic idea of Mobile IP: a MN acquires a COA in a foreign
network from a foreign agent and registers to the home
agent; all messages sent to its home address is
forwarded by its home agent to its COA
• Three steps
– discovering home/foreign agents and the care-of
address (COA)
– registering the care-of address
– data transfer using the care-of address
Discovering the Agents and
Care-of Address
• Mobile IP discovery process
– (home or foreign) agent broadcasts advertisements at
regular intervals
• announce the network
• list one or more available care-of addresses
– mobile node takes a care-of address
– mobile node can also send solicitation to start the
process
Registering the Care-of Address
• Once a mobile node has a care-of address, its home
agent must find out about it
• Registration process
– mobile node sends a registration request to its home agent with
the care-of address information
– home agent approves/disapproves the request
– home agent adds the necessary information to its routing table
– home agent sends a registration reply back to the mobile node
Registration Operations in Mobile IP
• MH = Mobile Host
• FA = Foreign Agent
HA = Home Agent
Discussion: what is the major challenge of the registration process?
Data Transfer from the Mobile Node
HA
1
home network
sender
Internet
FA
foreign
network
1. Sender sends to the IP address
of the receiver as usual,
FA works as default router
CN
receiver
MN
Data Transfer from the Mobile Node
HA
2
MN
home network
Internet
receiver
3
FA
1
CN
sender
foreign
network
1. Sender sends to the IP address of MN,
HA intercepts packet
2. HA tunnels packet to COA, here FA,
by encapsulation
3. FA forwards the packet to the MN
Tunneling Operations in Mobile IP
Correspondent
Node X
Micromobility Solutions
• To reduce signaling load and delay to the home network during
movements within one domain
 Tunnel-based micro-mobility schemes
 Mobile IP regional registration (MIP-RR)
 Hierarchical Mobile IP (HMIP)
 Intradomain mobility management protocol (IDMP)
 Routing-based micro-mobility schemes
 Cellular IP (CIP)
 Handoff Aware Wireless Access Internet Infrastructure (HAWAII)
Simple Comparison
CIP/HAWAII
IDMP
Handoff/
Path setup
Routing
Table update
Tunnel
Update
Paging
Paging cache
/Multicast
Multicast
All nodes
Some nodes
Function
Deployment
Cellular IP
• Cellular IP represents a new mobile host
protocol
• simple, and flexible protocol for highly mobile
hosts
• CIP supports local mobility & efficiently
internet works with Mobile IP
Cellular IP architecture
Packets will be first routed to the host's home
agent and then tunneled to
the gateway
Packets transmitted by mobile hosts
are first routed to the gateway and
from there on to the Internet
MOBILE IP
The gateway "detunnels'' packets and
forwards them toward base stations
CELLULAR IP
Cellular IP Handoff
X : from D
X : from C
X : from D, E
X : from E
X : from F
E
Internet with
Mobile IP
G
C
GW
R
D
A
F
B
X
Handoff
• Cellular IP handoff
– Hard handoff
– Semi handoff
• Hard handoff
– During the Handoff Latency the downlink packets
are lost.
• Semi handoff
– Improvement over Hard Handoff
Hard-Handoff
1.MN From Old BS to
New BS
2.MN send Route
Update Packet to GW
3.BSs are refresh RS
4.GW send data packets
to MN
Semi soft-Handoff
• Improvement over Hard Handoff ; NO packet
loss & smooth handoff.
• Need for buffering at the cross over point :For
smooth handoff
IDMP
• IDMP is a two-level generalization of the Mobile IP architecture,
with a special node called the mobility agent (MA) providing an
MN a domain-wide stable point of packet redirection
• It will be independent of any specific solution for global
(interdomain) mobility management
• IDMP offers intradomain mobility by using multi-CoA
• The mobility agent (MA) is similar to a MIP-RR GFA and acts
as a domain-wide point for packet redirection
• A subnet agent (SA) provides subnet-specific mobility services
IDMP (cont’d)
• Local care-of address (LCoA)
– This identifies the MN’s attachment to the subnet
– Unlike MIP’s CoA, the LCoA in IDMP only has local scope
– By updating its MA of any changes in the LCoA, the MN ensures that
packets are correctly forwarded within the domain
• Global care-of address (GCoA)
– This address resolves the MN’s current location only up to a domainlevel granularity and hence remains unchanged as long as the MN stays
within a single domain
– By issuing global binding updates that contain this GCoA, the MN
ensures that packet are routed correctly to its present domain
The architecture of IDMP
Path setup
•
At power-up, MN obtains a LCoA
from SA
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In IDMP’s SA mode, MN must
obtain LCoA from Agent
Advertisement of its SA
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In collocated mode, MN obtains its
LCoA from DHCP server
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MN receives MA’s CoA, GCoA,
from SA or DHCP server
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MN informs the MA of its new LCoA
using intradomain location update
msg and updates its HA with GCOA
Now, packers from remote CN are
forwarded to MN’s GCoA and
intercepted by MA, tunnels them to
MN’s current LCoA
•
IDMP message flow during the initial intradomain
location update
IDMP call flow during subsequent intradomain
movement
Handoff
•
MN moves from SA2 to SA3 subnet,
MN or SA2 generated
movementImminent msg to MA
•
On reception of this msg, MA
multicasts all inbound packets to the
entire set of neighboring SA(SA1,SA3)
which buffer them in per-MN buffers
•
When MN performs a subnet-level
registration with SA3, SA3 can
immediately forward all buffered
packets to the MN
– Buffered packets at other SAs are
discarded after specified time
•
MN updates the MA with its intradomain location
Paging
•
Paging Area
– A set of subnets
– An idle MN updates its location
only if it detects moved out of its
current PA
•
When MA receives packets for a MN
which is currently registered but in
idle mode, it multicasts Page
Solicitation packet to all subnets in
current PA
•
When the dormant MN is paged, it
obtains LCoA from the SA to which it
is currently attached and sends a
location update to the MA
•
When the MN reregisters with the MA,
the buffered packets in the MA are
Transport-Layer Mobility
• The transport layer maintains the true endto-end connection, whereas the lower layer
is completely ignorant of this end-to-end
semantic.
• Transport-Layer Mobility Protocol
– 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 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 >
-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 MigratePermitted option exchange.
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.
– The previously broken TCP connection can be
resumed
Sequence number of host i
Sequence number of host j
After the initiating host’s reception of the SYN/ACK with the
Migrate-Permitted , both hosts can then compute a shared
secret key.
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
Message Name
Function
INVITE
Invite user(s) to a session.
ACK
BYE
Acknowledgment of an INVITE
request
Sent when a call is to be released
OPTIONS
Query server about capability
CANCEL
Cancel a pending request
REGISTER
Register with a SIP server
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
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[1] C. Perkins, “IP Mobility Support for IPv4,” IETF RFC 3344, Aug 2002.
[2] T. La. Porta et al., “IP-Based Access Network Infrastructure for NextGeneration Wireless Data Networks,” IEEE Pers. Commun., vol. 7, no. 4,
Aug 2000.
[3] C-Y. Wan, A. T. Campbell, and A. G. Valko, “Design, Implementation,
and Evaluation of Cellular IP,” IEEE Pers. Commun., vol. 7, no. 4, Aug.
2000, pp. 42–49.
[4] A. Grilo, P. Estrela, and M. Nunes, “Terminal Independent Mobility for
IP (TIMIP),” IEEE Commun. Mag., Dec. 2001, pp. 34–41.
[5] S. Das et al., “IDMP: An Intra-Domain Mobility Management Protocol
for Next-Generation Wireless Networks,” IEEE Wireless Commun., vol. 9,
no. 3, June 2002, pp. 38–45.
[6] A. C. Snoeren and H. Balakrishnan, “An End-to-End Approach to
Host Mobility,” Proc. 6th Int’l. Conf.Mobile Comp. and Net., Boston, MA,
Aug. 2000.
[7] M. Handley et al., “SIP: Session Initiation Protocol,” IETF RFC 2543,
Mar. 1999.
References
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[8] J. Manner et al., “Evaluation of Mobility and Quality of Service
Interaction,” Comp. Networks, vol. 38, 2002, pp. 137–63.
[9] C. Perkins and D. Johnson, “Route Optimization in Mobile IP,” draftietf-mobileip-optim-11.txt, Sept. 2001, work in progress.
[10] 3GPP TS 23.060, “General Packet Radio Service (GPRS), Service
Description, Stage 2,” Dec 2001.
[11] E. Gustafsson, A. Jonsson, and C. Perkins, “Mobile IPv4 Regional
Registration,” draft-ietf-mobileip-reg-tunnel- 06.txt, Mar. 2002, work in
progress.
[12] D. A. Maltz and P. Bhagwat, “MSOCKS: An Architecture for
Transport Layer Mobility,” INFOCOM, vol. 3, pp. 1037–45, 1998.
[13] D. E. Eastlake, “ Secure Domain Name System Dynamic Update,”
IETF RFC 2137, Apr. 1997.
[14] E. Wedlund and H. Schulzrinne, “Mobility Support Using SIP,” 2nd
ACM/IEEE Int’l. Wksp. Wireless and Mobile Multimedia, Aug. 1999, pp.
76–82.
[15] F. Vakil et al., “Supporting Mobility for TCP with SIP,” draft-itsumosipping-mobility-tcp-00.txt, Dec. 2001, work in progress.