Computer Network 01/24

Network of networks

Connecting each access ISP to each other can’t scale. (O(N^2))
Solution: Global transit ISP, connected to access net.

* IXP : Internet exchange point. Interconnect each ISP.
* Peering link : Direct link between ISPs.
* Regional net

Content Provider Network: private network that connects its data centers to Internet. (Google)

Delay, Loss, Throughput

Packets queue : packet arrival rate exceeds output link capacity
Free buffers: arriving packets dropped (loss) if no free buffers
Delay: d(total) = d(proc) + d(queue) + d(trans) + d(propagation)

Queueing delay

    * R: link bandwidth
    * L; packet length
    * A: average packet arrival rate
    * Traffic intensity: La/R
    * Higher intensity, longer average queueing delay
* traceroute program : delay measurement

Throughput

Throughput: rate at which bits transferred between sender/receiver
Bottleneck link : link on end-end path that constrains end-end throughput

Why layering

Deal with complex systems.

Internet protocol stack

• application
  • supporting network applications
  • FTP, SMTP, HTTP
• transport
  • Process-Process data transfer
  • TCP, UDP
• network
  • routing of datagrams from src to dest
  • IP, routing protocol
• link
• physical