1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer...
-
Upload
conner-packman -
Category
Documents
-
view
212 -
download
0
Transcript of 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer...
![Page 1: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/1.jpg)
1
Wireless and Mobile Networks Part 2November 25, 2008
Department of Electrical and Computer Engineering
University of Western Ontario
ECE 436aNetworking: Principles,
Protocols, and Architectures
![Page 2: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/2.jpg)
2
What is mobility?
spectrum of mobility, from the network perspective:
no mobility high mobility
mobile wireless user, using same access point
mobile user, passing through multiple access point while maintaining ongoing connections (like cell phone)
mobile user, connecting/ disconnecting from network using DHCP.
![Page 3: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/3.jpg)
3
Mobility: Vocabularyhome network: permanent “home” of mobile(e.g., 128.119.40/24)
Permanent address: address in home network, can always be used to reach mobilee.g., 128.119.40.186
home agent: entity that will perform mobility functions on behalf of mobile, when mobile is remote
wide area network
correspondent
![Page 4: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/4.jpg)
4
Mobility: more vocabulary
Care-of-address: address in visited network.(e.g., 79,129.13.2)
wide area network
visited network: network in which mobile currently resides (e.g., 79.129.13/24)
Permanent address: remains constant (e.g., 128.119.40.186)
home agent: entity in visited network that performs mobility functions on behalf of mobile.
correspondent: wants to communicate with mobile
![Page 5: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/5.jpg)
5
How do you contact a mobile friend:
search all phone books?
call her parents? expect her to let you
know where he/she is?
I wonder where Alice moved to?
Consider friend frequently changing addresses, how do you find her?
![Page 6: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/6.jpg)
6
Mobility: approaches
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
![Page 7: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/7.jpg)
7
Mobility: approaches
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
![Page 8: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/8.jpg)
8
Mobility: registration
End result: Foreign agent knows about mobile Home agent knows location of mobile
wide area network
home network
visited network
1
mobile contacts foreign agent on entering visited network
2
foreign agent contacts home agent home: “this mobile is resident in my network”
![Page 9: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/9.jpg)
9
Mobility via Indirect Routing
wide area network
homenetwork
visitednetwork
3
2
41
correspondent addresses packets using home address of mobile
home agent intercepts packets, forwards to foreign agent
foreign agent receives packets, forwards to mobile
mobile replies directly to correspondent
![Page 10: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/10.jpg)
10
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
![Page 11: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/11.jpg)
11
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!
![Page 12: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/12.jpg)
12
Mobility via Direct Routing
wide area network
homenetwork
visitednetwork
4
2
41correspondent requests, receives foreign address of mobile
correspondent forwards to foreign agent
foreign agent receives packets, forwards to mobile
mobile replies directly to correspondent
3
![Page 13: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/13.jpg)
13
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?
![Page 14: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/14.jpg)
14
wide area network
1
foreign net visited at session start
anchorforeignagent
2
4
new foreignagent
35
correspondentagent
correspondent
new foreignnetwork
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)
![Page 15: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/15.jpg)
15
Mobile IP
RFC 3220 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
![Page 16: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/16.jpg)
16
Mobile IP
Mobile IP is best understood as the cooperation of three separable mechanisms:
Discovering the care-of address Registering the care-of address Tunneling to the care-of address
![Page 17: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/17.jpg)
17
Capabilities of Mobile IP
Discovery – mobile node uses discovery procedure to identify prospective home and foreign agents
Registration – mobile node uses an authentication registration procedure to inform home agent of its care-of address
Tunneling – used to forward IP datagrams from a home address to a care-of address
![Page 18: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/18.jpg)
18
Operation of Mobile IP
Mobile node is assigned to a particular network – home network
IP address on home network is static – home address
Mobile node can move to another network – foreign network
Mobile node registers with network node on foreign network – foreign agent
Mobile node gives care-of address to agent on home network – home agent
![Page 19: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/19.jpg)
19
Mobile IP: indirect routing
Permanent address: 128.119.40.186
Care-of address: 79.129.13.2
dest: 128.119.40.186
packet sent by correspondent
dest: 79.129.13.2 dest: 128.119.40.186
packet sent by home agent to foreign agent: a packet within a packet
dest: 128.119.40.186
foreign-agent-to-mobile packet
![Page 20: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/20.jpg)
20
Wireless, mobility: impact on higher layer protocols
logically, impact should be minimal … best effort service model remains unchanged TCP and UDP can (and do) run over wireless,
mobile … but performance-wise:
packet loss/delay due to bit-errors (discarded packets, delays for link-layer retransmissions), and handoff
TCP interprets loss as congestion, will decrease congestion window un-necessarily
delay impairments for real-time traffic limited bandwidth of wireless links
![Page 21: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/21.jpg)
21
IP addresses: how to get one?
DHCP: Dynamic Host Configuration Protocol
![Page 22: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/22.jpg)
22
IP addresses: how to get one?
Q: How does host get IP address?
hard-coded by system admin in a file Wintel: control-panel->network->configuration->tcp/ip-
>properties UNIX: /etc/rc.config
DHCP: Dynamic Host Configuration Protocol: dynamically get address from as server “plug-and-play”
![Page 23: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/23.jpg)
23
DHCP: Dynamic Host Configuration Protocol
Goal: allow host to dynamically obtain its IP address from network server when it joins networkCan renew its lease on address in use
Allows reuse of addresses (only hold address while connected an “on”
Support for mobile users who want to join network (more shortly)
DHCP overview: host broadcasts “DHCP discover” msg DHCP server responds with “DHCP offer” msg host requests IP address: “DHCP request” msg DHCP server sends address: “DHCP ack” msg
![Page 24: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/24.jpg)
24
DHCP client-server scenario
223.1.1.1
223.1.1.2
223.1.1.3
223.1.1.4 223.1.2.9
223.1.2.2
223.1.2.1
223.1.3.2223.1.3.1
223.1.3.27
A
BE
DHCP server
arriving DHCP client needsaddress in thisnetwork
![Page 25: 1 Wireless and Mobile Networks Part 2 November 25, 2008 Department of Electrical and Computer Engineering University of Western Ontario ECE 436a Networking:](https://reader035.fdocuments.in/reader035/viewer/2022070307/551aca3d550346b2288b5895/html5/thumbnails/25.jpg)
25
DHCP client-server scenarioDHCP server: 223.1.2.5 arriving
client
time
DHCP discover
src : 0.0.0.0, 68 dest.: 255.255.255.255,67yiaddr: 0.0.0.0transaction ID: 654
DHCP offer
src: 223.1.2.5, 67 dest: 255.255.255.255, 68yiaddrr: 223.1.2.4transaction ID: 654Lifetime: 3600 secs
DHCP request
src: 0.0.0.0, 68 dest:: 255.255.255.255, 67yiaddrr: 223.1.2.4transaction ID: 655Lifetime: 3600 secs
DHCP ACK
src: 223.1.2.5, 67 dest: 255.255.255.255, 68yiaddrr: 223.1.2.4transaction ID: 655Lifetime: 3600 secs