15-441: Computer Networking Lecture 21: Wireless Networking
15-441: Computer Networking Lecture 21: Wireless Networking
Wireless Challenges Force us to rethink many assumptions Need to share airwaves rather than wire Don't know what hosts are involved Host may not be using same link technology Mobility Other characteristics of wireless Noisy→ lots of losses Interaction of multiple transmitters at receiver Collisions, capture, interference Multipath interference 1-08-07 ecture 21: Wireless Networking 2
11-08-07 Lecture 21: Wireless Networking 2 Wireless Challenges • Force us to rethink many assumptions • Need to share airwaves rather than wire • Don’t know what hosts are involved • Host may not be using same link technology • Mobility • Other characteristics of wireless • Noisy → lots of losses • Slow • Interaction of multiple transmitters at receiver • Collisions, capture, interference • Multipath interference
Overview Internet mobility TCP over noisy links Link layer challenges 1-08-07 ecture 21: Wireless Networking 3
11-08-07 Lecture 21: Wireless Networking 3 Overview • Internet mobility • TCP over noisy links • Link layer challenges
Routing to Mobile Nodes Obvious solution have mobile nodes advertise route to mobile address /32 Should work ! Why is this bad? Consider forwarding tables on backbone routers Would have an entry for each mobile host ° Not very scalable What are some possible solutions? 1-08-07 ecture 21: Wireless Networking
11-08-07 Lecture 21: Wireless Networking 4 Routing to Mobile Nodes • Obvious solution: have mobile nodes advertise route to mobile address/32 • Should work!!! • Why is this bad? • Consider forwarding tables on backbone routers • Would have an entry for each mobile host • Not very scalable • What are some possible solutions?
How to handle mobile nodes? (Addressing) Dynamic Host Configuration (DHCP) Host gets new IP address in new locations Problems Host does not have constant name/address how do others contact host What happens to active transport connections? 1-08-07 ecture 21: Wireless Networking
11-08-07 Lecture 21: Wireless Networking 5 How to Handle Mobile Nodes? (Addressing) • Dynamic Host Configuration (DHCP) • Host gets new IP address in new locations • Problems • Host does not have constant name/address → how do others contact host • What happens to active transport connections?