Mobileip
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How Mobile IP Works?
Presenter: Ajoy Singh
Agenda
Required background What problems does Mobile IP solve? Mobile IP: protocol overview
5/2/2002
Scope Requirements Design goals Functional entities How Mobile IP Works?
2
Agenda (continued)
The gory details
Agent discovery Registration Packet delivery
Case study: campus mobility Q&A
5/2/2002
How Mobile IP Works?
3
Required Background I am assuming you already know:
the different layers of the OSI model, what IP and ICMP are, what ARP, proxy ARP and gratuitous ARP are, IP: how IP routing works. IP:Internet InternetProtocol Protocol ICMP: ICMP:Internet InternetControl Control Message MessageProtocol Protocol ARP: ARP:Address Address Resolution ResolutionProtocol Protocol
5/2/2002
How Mobile IP Works?
4
What Problems Does Mobile IP Solve?
An IP address not only identifies a host but also a point-of-attachment. Host-specific routes approach suffers from serious scalability, robustness and security concerns if applied to the global Internet. Mobility Mobilityisisthe theability abilityofofaanode nodetoto change changeits itspoint-of-attachment point-of-attachmentwhile while maintaining all existing communications maintaining all existing communications and andusing usingthe thesame sameIP IPaddress. address.
5/2/2002
How Mobile IP Works?
5
What Problems Does Mobile IP Solve? (continued)
A host cannot change its IP address without terminating on-going sessions and restarting them after it acquires a new address. Other link layer mobility solutions exist but are not sufficient enough for the Nomadicity Nomadicityallows allowsaanode nodetotomove move global Internet. but butititmust mustterminate terminateall allexisting existing
communications communicationsand andthen thencan caninitiate initiate new connections with a new address. new connections with a new address.
5/2/2002
How Mobile IP Works?
6
Mobile IP: Protocol Overview
5/2/2002
How Mobile IP Works?
7
Scope
Mobile IP is a network layer solution for homogenous and heterogeneous mobility on the global Internet which is scalable, robust, secure and which allows nodes to maintain all ongoing communications while moving.
5/2/2002
How Mobile IP Works?
8
Requirements
MN must be able to communicate with other nodes after changing its LL POA. MN must be able to communicate using only its home (permanent) IP address regardless of its current LL POA. MN: MN:mobile mobilenode node LL: LL:link linklayer layer POA: POA:point-of-attachment point-of-attachment
5/2/2002
How Mobile IP Works?
9
Requirements (continued)
MN must be able to communicate with other nodes that do not implement Mobile IP mobility functions. MN must not be exposed to any new security threats over and above those which any fixed node on the Internet is exposed to.
5/2/2002
How Mobile IP Works?
10
Design Goals
Mobile IP was designed to make the size and the frequency of required routing updates as small as possible. It was designed to make it simple to implement mobile node software. It was designed to avoid solutions that require mobile nodes to use multiple addresses.
5/2/2002
How Mobile IP Works?
11
Functional Entities
Mobile Node (MN): a node which can change its POA while maintaining any ongoing communications and using only its home (permanent) IP address. Home Agent (HA): a router with at least one interface on the MN’s home link which:
5/2/2002
MN keeps informed of its current location, i.e., its care-of-address (COA), intercepts packets destined to the MN’s home address and tunnels them to the MN’s current location (or COA). How Mobile IP Works?
12
Functional Entities (continued)
Foreign Agent (FA): a router on a foreign link which:
5/2/2002
assists the MN in informing its HA of its current COA, sometimes, provides a COA and de-tunnels packets for the MN, acts as the default router for packets generated by the MN while connected to this foreign link.
How Mobile IP Works?
13
Correspondent Node
Home Agent Router 3
Internet
Router 1
Foreign Agent
Router 2 Mobile Node
5/2/2002
How Mobile IP Works?
14
Common Scenario (1) HA
CN 4
Router 3
Router 1
3
FA
MN
Home Link
Internet
2 5 1
Router 2 Foreign Link 5/2/2002
How Mobile IP Works?
15
Common Scenario (2) CN
HA
1 3
Router 3
2
Router 1
6
FA
MN
Home Link
Internet
4 5
Router 2 Foreign Link 5/2/2002
How Mobile IP Works?
16
Agenda Progress
Required background What problems does Mobile IP solve? Mobile IP: protocol overview The gory details
Agent discovery Registration Packet delivery
Case study: campus mobility Q&A
5/2/2002
How Mobile IP Works?
17
The Gory Details
5/2/2002
How Mobile IP Works?
18
Agent Discovery
Agent discovery allows the MN to:
Agent discovery consists of 2 messages:
determine whether it is @ home or not, detect whether it has moved, obtain a COA when away from home. Agent Advertisement Agent Solicitation
MN determines it has moved in 2 ways:
5/2/2002
move detection using advertisement lifetimes move detection using network prefixes How Mobile IP Works?
19
Registration
Mobile IP registration allows the MN to:
5/2/2002
request routing services from a FA, inform its HA of its current COA, renew a registration which is about to expire, deregister when it returns home, have multiple simultaneous COA’s registered with its HA, deregister a particular COA while retaining others, dynamically discover the address of a potential HA. How Mobile IP Works?
20
Registration (continued)
Registration consists of 2 messages:
5/2/2002
registration request registration reply
How Mobile IP Works?
21
Q&A
Any Questions?
5/2/2002
How Mobile IP Works?
22
Agent Solicitation Message IP Header Fields
Type = 10
Code = 0
Checksum
reserved 5/2/2002
How Mobile IP Works?
IP header
ICMP Router Solicitation
23
Agent Advertisement Message IP Header Fields
IP Header
Type = 9
Code
Checksum
Num Addrs
Addr Entry Size
Advertisement Lifetime
Router Address [1] Preference Level [1]
ICMP Router Advertisement
… Type = 16
Length
Max Registration Lifetime
Sequence Number R
B
H
F
M G
V
reserved
Care-of-address [1]
Mobility Agent Advertisement Extension
… Type = 19
Length
…
…
5/2/2002
Prefix-Length[1] Prefix-Length[2]
How Mobile IP Works?
Prefix-Length Extension (Optional)
24
Registration Request Message Type = 1
S
B
D
IP Header Fields
IP Header
UDP Header Fields
UDP Header
M G
V
rsv
Lifetime (requested)
MN’s Home Address HA Address COA Address
Fixed-Length Portion of Registration Request
Identification (64 bits) Optional Extensions Type = 32
Length
Security Parameter …
… Index (SPI) Authenticator (Default equals Keyed MD5)
Mobile-Home Authentication Extension
More Optional Extensions … 5/2/2002
How Mobile IP Works?
25
Registration Reply Message (Fixed Portion Only) Type = 3
Code
Lifetime (granted)
MN’s Home Address HA Address
FixedLength Portion of Registrati on Reply
Identification
5/2/2002
How Mobile IP Works?
26
Presenter: Ajoy Singh
Agenda
Required background What problems does Mobile IP solve? Mobile IP: protocol overview
5/2/2002
Scope Requirements Design goals Functional entities How Mobile IP Works?
2
Agenda (continued)
The gory details
Agent discovery Registration Packet delivery
Case study: campus mobility Q&A
5/2/2002
How Mobile IP Works?
3
Required Background I am assuming you already know:
the different layers of the OSI model, what IP and ICMP are, what ARP, proxy ARP and gratuitous ARP are, IP: how IP routing works. IP:Internet InternetProtocol Protocol ICMP: ICMP:Internet InternetControl Control Message MessageProtocol Protocol ARP: ARP:Address Address Resolution ResolutionProtocol Protocol
5/2/2002
How Mobile IP Works?
4
What Problems Does Mobile IP Solve?
An IP address not only identifies a host but also a point-of-attachment. Host-specific routes approach suffers from serious scalability, robustness and security concerns if applied to the global Internet. Mobility Mobilityisisthe theability abilityofofaanode nodetoto change changeits itspoint-of-attachment point-of-attachmentwhile while maintaining all existing communications maintaining all existing communications and andusing usingthe thesame sameIP IPaddress. address.
5/2/2002
How Mobile IP Works?
5
What Problems Does Mobile IP Solve? (continued)
A host cannot change its IP address without terminating on-going sessions and restarting them after it acquires a new address. Other link layer mobility solutions exist but are not sufficient enough for the Nomadicity Nomadicityallows allowsaanode nodetotomove move global Internet. but butititmust mustterminate terminateall allexisting existing
communications communicationsand andthen thencan caninitiate initiate new connections with a new address. new connections with a new address.
5/2/2002
How Mobile IP Works?
6
Mobile IP: Protocol Overview
5/2/2002
How Mobile IP Works?
7
Scope
Mobile IP is a network layer solution for homogenous and heterogeneous mobility on the global Internet which is scalable, robust, secure and which allows nodes to maintain all ongoing communications while moving.
5/2/2002
How Mobile IP Works?
8
Requirements
MN must be able to communicate with other nodes after changing its LL POA. MN must be able to communicate using only its home (permanent) IP address regardless of its current LL POA. MN: MN:mobile mobilenode node LL: LL:link linklayer layer POA: POA:point-of-attachment point-of-attachment
5/2/2002
How Mobile IP Works?
9
Requirements (continued)
MN must be able to communicate with other nodes that do not implement Mobile IP mobility functions. MN must not be exposed to any new security threats over and above those which any fixed node on the Internet is exposed to.
5/2/2002
How Mobile IP Works?
10
Design Goals
Mobile IP was designed to make the size and the frequency of required routing updates as small as possible. It was designed to make it simple to implement mobile node software. It was designed to avoid solutions that require mobile nodes to use multiple addresses.
5/2/2002
How Mobile IP Works?
11
Functional Entities
Mobile Node (MN): a node which can change its POA while maintaining any ongoing communications and using only its home (permanent) IP address. Home Agent (HA): a router with at least one interface on the MN’s home link which:
5/2/2002
MN keeps informed of its current location, i.e., its care-of-address (COA), intercepts packets destined to the MN’s home address and tunnels them to the MN’s current location (or COA). How Mobile IP Works?
12
Functional Entities (continued)
Foreign Agent (FA): a router on a foreign link which:
5/2/2002
assists the MN in informing its HA of its current COA, sometimes, provides a COA and de-tunnels packets for the MN, acts as the default router for packets generated by the MN while connected to this foreign link.
How Mobile IP Works?
13
Correspondent Node
Home Agent Router 3
Internet
Router 1
Foreign Agent
Router 2 Mobile Node
5/2/2002
How Mobile IP Works?
14
Common Scenario (1) HA
CN 4
Router 3
Router 1
3
FA
MN
Home Link
Internet
2 5 1
Router 2 Foreign Link 5/2/2002
How Mobile IP Works?
15
Common Scenario (2) CN
HA
1 3
Router 3
2
Router 1
6
FA
MN
Home Link
Internet
4 5
Router 2 Foreign Link 5/2/2002
How Mobile IP Works?
16
Agenda Progress
Required background What problems does Mobile IP solve? Mobile IP: protocol overview The gory details
Agent discovery Registration Packet delivery
Case study: campus mobility Q&A
5/2/2002
How Mobile IP Works?
17
The Gory Details
5/2/2002
How Mobile IP Works?
18
Agent Discovery
Agent discovery allows the MN to:
Agent discovery consists of 2 messages:
determine whether it is @ home or not, detect whether it has moved, obtain a COA when away from home. Agent Advertisement Agent Solicitation
MN determines it has moved in 2 ways:
5/2/2002
move detection using advertisement lifetimes move detection using network prefixes How Mobile IP Works?
19
Registration
Mobile IP registration allows the MN to:
5/2/2002
request routing services from a FA, inform its HA of its current COA, renew a registration which is about to expire, deregister when it returns home, have multiple simultaneous COA’s registered with its HA, deregister a particular COA while retaining others, dynamically discover the address of a potential HA. How Mobile IP Works?
20
Registration (continued)
Registration consists of 2 messages:
5/2/2002
registration request registration reply
How Mobile IP Works?
21
Q&A
Any Questions?
5/2/2002
How Mobile IP Works?
22
Agent Solicitation Message IP Header Fields
Type = 10
Code = 0
Checksum
reserved 5/2/2002
How Mobile IP Works?
IP header
ICMP Router Solicitation
23
Agent Advertisement Message IP Header Fields
IP Header
Type = 9
Code
Checksum
Num Addrs
Addr Entry Size
Advertisement Lifetime
Router Address [1] Preference Level [1]
ICMP Router Advertisement
… Type = 16
Length
Max Registration Lifetime
Sequence Number R
B
H
F
M G
V
reserved
Care-of-address [1]
Mobility Agent Advertisement Extension
… Type = 19
Length
…
…
5/2/2002
Prefix-Length[1] Prefix-Length[2]
How Mobile IP Works?
Prefix-Length Extension (Optional)
24
Registration Request Message Type = 1
S
B
D
IP Header Fields
IP Header
UDP Header Fields
UDP Header
M G
V
rsv
Lifetime (requested)
MN’s Home Address HA Address COA Address
Fixed-Length Portion of Registration Request
Identification (64 bits) Optional Extensions Type = 32
Length
Security Parameter …
… Index (SPI) Authenticator (Default equals Keyed MD5)
Mobile-Home Authentication Extension
More Optional Extensions … 5/2/2002
How Mobile IP Works?
25
Registration Reply Message (Fixed Portion Only) Type = 3
Code
Lifetime (granted)
MN’s Home Address HA Address
FixedLength Portion of Registrati on Reply
Identification
5/2/2002
How Mobile IP Works?
26
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