1. 1 Ram Dantu University of North Texas, rdantu@unt.edu Practical Networking

2. 2 Agenda r Nuts and Bolts of Internet r Access, Edge, and Core Networks r LAN Design r End-user Protocols, Services and QoS r Edge and Core Networks r Performance m Bandwidth and Delay r Security

3. 3 Performance

4. 4 Different Types of Links Sometimes you install your own!

5. 5 Bigger Pipes! Sometimes leased from the phone company STS: Synchronous Transport Signal

6. 6 Delay in packet-switched networks packets experience delay on end-to-end path r four sources of delay at each hop r nodal processing: m check bit errors m determine output link r queueing m time waiting at output link for transmission m depends on congestion level of router A B propagation transmission nodal processing queueing

7. 7 Delay in packet-switched networks Transmission delay: r R=link bandwidth (bps) r L=packet length (bits) r time to send bits into link = L/R Propagation delay: r d = length of physical link r s = propagation speed in medium (~2x10 8 m/sec) r propagation delay = d/s A B propagation transmission nodal processing queueing Note: s and R are very different quantitites!

8. 8 Bandwidth (throughput) r Amount of data that can be transmitted per time unit r Example: 10Mbps r link versus end-to-end r Notation m KB = 2 10 bytes m Mbps = 10 6 bits per second Performance

9. 9 Latency (delay) r Time it takes to send message from point A to point B r Example: 24 milliseconds (ms) r Sometimes interested in in round-trip time (RTT) r Components of latency Latency = Propagation + Transmit + Queue + Proc. Propagation = Distance / SpeedOfLight Transmit = Size / Bandwidth

10. 10 r Relative importance of bandwidth and latency m small message (e.g., 1 byte): 1ms vs. 100ms dominates 1Mbps vs. 100Mbps m large message (e.g., 25 MB): 1Mbps vs. 100Mbps dominates 1ms vs. 100ms r Consider two channels of 1Mbps and 100 Mbps respectively. For a 1 byte message, the available bandwidth is relatively insignificant given a RTT of 1 ms. The transmit delay for each channel is 8  s and 0.08  s, respectively.

11. 11  Delay x Bandwidth Product e.g., 100ms RTT and 45Mbps Bandwidth = 560KB of data r We have to view the network as a buffer. This may have interesting consequences: m How much data did the sender transmit before a response can be received? Bandwidth Delay

12. 12 Example: Hospital Network

13. 13 W V U P Intensive Care Unit Operating Room T U R S Q ON M F G Out-patient RIS Floors HIS PACS Network INTERNET A Hospital Distribution PACS B C D E H IJK L X r PACS Network and Remote Connectivity