Internet Mobility 4X4
발표자 : 금승원
5.12
Paper Outline
Need for Internet Mobility
Mobile IP
Project Goals
Protocol for outgoing packets
Protocol for incoming packets
4X4 Protocol
Implementation
Internet Mobility
Mobile IP
– Mobile hosts send and receive packets with their home
network IP address
IP correct layer to implement basic mobility support
Challenge in handling address changes
Three indicators of best method to send packet
– Characteristics that should be optimized
– Permissiveness of the network
– Correspondents awareness of mobility
Mobile IP
Basic Mobile IP
HA : Home Agent
MH : Mobile Host
CH : Correspondent Host
Mobile IP
Goal: send and receive packets using home IP
address
– Each mobile node given a home address that
remains constant despite location changes
– When mobile host at home, functions like non-
mobile Internet host
– When away, obtains temporary connection and
registers new location with home agent
Problems:
– packet dropping, foreign agent, security boundaries
Project Goals
Constraints
– No “special” support from routers
– Packets correctly deliverable to destination
Ensure Deliverability
Minimize Latency
Minimize Size
Project Goals
Ensure Deliverability
– Not deliver packets due to security or policy
The boundary router drop packets from outside the home
network
Forbidding transit traffic
Project Goals
Minimize Latency
– Packets deliver via the HA
Increasing the round-trip delay
Using care-of address(COA) :temporary address
Minimize Size
– The overhead due to encapsulation
Outgoing Packets
Unencapsulated
– Sending out normal IP packets as non mobile host does
– Source address: temporary care-of address, or mobile host
– Destination address : corresponding host
Encapsulated
– To achieve transparent mobility and delivery
– Allow us to use different address in the inner and outer
headers
– Source address: temporary care-of address
– Destination address: home agent, corresponding host
Outgoing Packets
Unencapsulated Encapsulated
Outgoing Packets
Out-IE : Indirect, Encpsulated
– (s,d,S,D)=(COA,HA,MH,CH)
– Ensure the reliable delivery and privacy
– Advantage
Avoiding the risk of discarding the packet
The CH is unaware that the packets originated on a
mobile host
– Disadvantage
Indirect delivery
Encapsulated overhead
Outgoing Packets
Out-DE : Direct, Encpsulated
– (s,d,S,D)=(COA,CA,MH,CH)
– The CH is able to process encapsulated packets
– Advantage
Direct delivery
Avoiding the risk of discarding the packet
– Disadvantage
The CH must have the capability of decapsulating
encapsulated IP packets
Encapsulated overhead
Outgoing Packets
Out-DH : Direct, HA
– (S,D)=(MA,CH)
– No source address filtering between MH and CH
– Advantage
Direct delivery
No encapsulation overhead
The CH is unaware that the packets originated on a
mobile host
– Disadvantage
An intervening router may discard the packet because of
invalid source address
Outgoing Packets
Out-DT : Direct, Temporary address
– (S,D)=(COA,CH)
– Transparent mobility is not required
– Advantage
Direct delivery
No encapsulation overhead
Avoiding the risk of discarding the packet
– Disadvantage
The Home address(MH) is not used at all
– MH loss the packet when MH move to a new location
Incoming Packets
Unencapsulated Encapsulated
Incoming Packets
IN-IE: Indirect, Encapsulated
– (s,d,S,D)=(HA,COA,CH,MH)
– Ensure the reliable delivery
– Advantage
The CH is unaware of the special status of the MH
– Disadvantage
Indirect delivery
Encapsulated overhead
Incoming Packets
IN-DE: Direct, Encapsulated
– (s,d,S,D)=(CH,COA,CH,MH)
– The CH is mobile-aware and knows the MH’s COA
– Advantage
Direct delivery
– Disadvantage
Encapsulated overhead
The CH needs the be aware of the special status of the MH
Incoming Packets
IN-DH: Direct, HA
– (S,D)=(CH,MH)
– Same physical network segment
– Advantage
Direct delivery
No encapsulation overhead
– Disadvantage
Only applicable when the CH and the MH are connected to
the same network segment
Incoming Packets
IN-DH: Direct, Temporary Address
– (S,D)=(CH,COA)
– Useful for short-live connections and short
connectionless datagram
– Advantage
Direct delivery
No encapsulation overhead
– Disadvantage
The Home address(MH) is not used at all
– MH loss the packet when MH move to a new location
Outgoing Indirect Direct Direct Home Direct
Encapsulated Encapsulated Address Temporary
Incoming Address
4X4 choices
Indirect Conservative: Decapsulation No security-
Encapsulated most reliable, capability of conscious
least efficient the CH routers
Direct - -
Fully mobile No security
Encapsulated aware CH conscious
routers
Direct Home Both hosts on
Address same network
segment
Direct Most efficient:
Temporary No mobile IP
Address
Implementation
Override IP route lookup with mobility policy
table.
Mobile Host Choices
– Temporary address or home address?
– Which home address method to use
Corresponding Host Choices
Conclusion
One size does not fit all
– Different situations call for different solutions
– The best choice depends on what characteristics
the protocol should optimize