1. DMET 602: Networks and Media Lab
Amr El Mougy
Yasmeen Essam
Hana Medhat
Mariam Samy

2. Mobile IP

3. IP Addressing: introduction
IP address: 32-bit identifier for host, router interface
interface: connection between host/router and physical link
router’s typically have multiple interfaces
host typically has one interface
IP addresses associated with each interface =
223 1 1 1
Network Layer

4. Subnets IP address: What’s a subnet ? subnet
subnet part (high order bits)
host part (low order bits)
What’s a subnet ?
device interfaces with same subnet part of IP address
can physically reach each other without intervening router
subnet
network consisting of 3 subnets
Network Layer

5. Subnetting A class B address is divided into two parts:
network part and
local part
Local part is further divided locally into:
subnet and
host parts
Splitting is done internally, yet looks like a single network to the outside world Network

6. What is mobility? spectrum of mobility, from the network perspective:
no mobility
high mobility
mobile wireless user,
using same access
point
mobile user, connecting/ disconnecting from network using DHCP
mobile user, passing through multiple access point while maintaining ongoing connections (like cell phone)
Wireless, Mobile Networks

7. How do you contact a mobile friend:
Consider friend frequently changing addresses, how do you find her?
I wonder where Alice moved to?
search all phone books?
call her parents?
expect her to let you know where he/she is?
Wireless, Mobile Networks

8. Mobility: vocabulary home network: permanent “home” of mobile
(e.g., /24)
home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote
wide area network
permanent address: address in home network, can always be used to reach mobile
e.g.,
Wireless, Mobile Networks

9. Mobility: more vocabulary
visited network: network in which mobile currently resides (e.g., /24)
permanent address: remains constant (e.g., )
care-of-address: address in visited network.
(e.g., )
wide area network
foreign agent: entity in visited network that performs mobility functions on behalf of mobile.
correspondent: wants to communicate with mobile
Wireless, Mobile Networks

10. Mobility: approaches routing tables indicate where each mobile located
let routing handle it: routers advertise permanent address of mobile-nodes-in- residence via usual routing table exchange.
routing tables indicate where each mobile located
no changes to end-systems
let end-systems handle it:
indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remote
direct routing: correspondent gets foreign address of mobile, sends directly to mobile
Wireless, Mobile Networks

11. Mobility: approaches routing tables indicate where each mobile located
let routing handle it: routers advertise permanent address of mobile-nodes-in- residence via usual routing table exchange.
routing tables indicate where each mobile located
no changes to end-systems
let end-systems handle it:
indirect routing: communication from correspondent to mobile goes through home agent, then forwarded to remote
direct routing: correspondent gets foreign address of mobile, sends directly to mobile
not
scalable
to millions of
mobiles
Wireless, Mobile Networks

12. Mobility: registration
visited network
home network 1
mobile contacts foreign agent on entering visited network 2
foreign agent contacts home agent home: “this mobile is resident in my network”
wide area network
end result:
foreign agent knows about mobile
home agent knows location of mobile
Wireless, Mobile Networks

13. Mobility via indirect routing
foreign agent receives packets, forwards to mobile
home agent intercepts packets, forwards to foreign agent
visited
network
home
network 3 4 1 2
wide area network
correspondent addresses packets using home address of mobile
mobile replies directly to correspondent
Wireless, Mobile Networks

14. Indirect Routing: comments
mobile uses two addresses:
permanent address: used by correspondent (hence mobile location is transparent to correspondent)
care-of-address: used by home agent to forward datagrams to mobile
foreign agent functions may be done by mobile itself
triangle routing: correspondent-home-network-mobile
inefficient when correspondent, mobile
are in same network
Wireless, Mobile Networks

15. Indirect routing: moving between networks
suppose mobile user moves to another network
registers with new foreign agent
new foreign agent registers with home agent
home agent update care-of-address for mobile
packets continue to be forwarded to mobile (but with new care- of-address)
mobility, changing foreign networks transparent: on going connections can be maintained!
Wireless, Mobile Networks

16. Mobility via direct routing
foreign agent receives packets, forwards to mobile
correspondent forwards to foreign agent
visited
network 1 2 3 4
home
network
mobile replies directly to correspondent
correspondent requests, receives foreign address of mobile
Wireless, Mobile Networks

17. Mobility via direct routing: comments
overcome triangle routing problem
non-transparent to correspondent: correspondent must get care-of-address from home agent
what if mobile changes visited network? 1 2 3 4
Wireless, Mobile Networks

18. Accommodating mobility with direct routing
anchor foreign agent: FA in first visited network
data always routed first to anchor FA
when mobile moves: new FA arranges to have data forwarded from old FA (chaining)
foreign net visited
at session start
anchor
foreign
agent
wide area network 2 1 4 3 5
new
foreign
network
correspondent
agent
new foreign
agent
correspondent
Wireless, Mobile Networks

19. Changing of Foreign Agent
Wireless, Mobile Networks

20. Changing of Foreign Agent
Wireless, Mobile Networks

21. Mobile IP RFC 3344 has many features we’ve seen:
home agents, foreign agents, foreign-agent registration, care-of-addresses, encapsulation (packet-within-a-packet)
three components to standard:
indirect routing of datagrams
agent discovery
registration with home agent
Wireless, Mobile Networks

22. Mobile IP: indirect routing
dest:
foreign-agent-to-mobile packet
dest:
dest:
packet sent by home agent to foreign agent: a packet within a packet
Permanent address:
Care-of address:
dest:
packet sent by correspondent
Wireless, Mobile Networks

23. IP-in-IP Tunneling • Mandatory in RFC 2003 • tunnel between HA and COA
• Minimal encapsulation (optional)
• avoids repetition of identical fields such as TTL, IHL, version, TOS
• only applicable for unfragmented packets, no space left for fragment identification
Modified IP header
Minimal forwardingheader
Payload
Wireless, Mobile Networks

24. Mobile IP: agent discovery
agent advertisement: foreign/home agents advertise service by broadcasting ICMP messages (typefield = 9)
H,F bits: home and/or foreign agent
R bit: registration required
Wireless, Mobile Networks

25. Mobile IP: registration example
visited network: /24
home agent
HA:
foreign agent
COA:
mobile agent
MA:
ICMP agent adv.
COA: ….
registration req.
COA:
HA:
MA:
Lifetime: 9999
identification:714 ….
registration req.
COA:
HA:
MA:
Lifetime: 9999
identification: 714
encapsulation format ….
registration reply
HA:
MA:
Lifetime: 4999
Identification: 714
encapsulation format ….
registration reply
HA:
MA:
Lifetime: 4999
Identification: 714 ….
time

26. Reverse Tunneling
Wireless, Mobile Networks

27. Reverse Tunneling
• Router accept often only “topologically correct“ addresses (firewall!)
– a packet from the MN encapsulated by the FA is now topologically correct
• Reverse tunneling does not solve
– problems with firewalls, the reverse tunnel can be abused to circumvent security mechanisms (tunnel hijacking)
– optimization of data paths, i.e. packets will be forwarded through the tunnel via the HA to a sender (double triangular routing)
• Reverse tunneling is backwards compatible
– the extensions can be implemented easily and cooperate with current implementations without these extensions
Wireless, Mobile Networks