1. Session 2

2. Delay, Loss, and Throughput in Packet-Switched Networks

3. Delay, Loss, and Throughput in Packet-Switched Networks
Processing Delay: The time required to examine the packet’s header and determine where to direct the
packet is part of the processing delay.
Queuing Delay: At the queue, the packet experiences a queuing delay as it waits to be transmitted onto the link
Transmission Delay: Assuming that packets are transmitted in a first-come-first-served manner, as is common in packet-switched networks, our packet can be transmitted only after all the packets that have arrived before it have been transmitted.
The transmission delay is L/R
R: transmission rate (bits/sec)
L: length of the packet by L bits
Propagation Delay: The time required to propagate from the beginning of the link to router B is the propagation delay.

4. Delay, Loss, and Throughput in Packet-Switched Networks
Comparing Transmission and Propagation Delay
The transmission delay is the amount of time required for the router to push out the packet; it is a function
of the packet’s length and the transmission rate of the link, but has nothing to do with the distance between
the two routers.
The propagation delay, on the other hand, is the time it takes a bit to propagate from one router to the next;
it is a function of the distance between the two routers, but has nothing to do with the packet’s length or the
transmission rate of the link.
Nodal delay
Queuing Delay and Packet Loss

5. Delay, Loss, and Throughput in Packet-Switched Networks
Traffic intensity
La/R
L: packet length
a: average rate at which packets arrive at the queue( packet/sec)
R: Transmission rate (bits/sec)
Design your system so that the traffic intensity is no greater than 1.

6. Delay, Loss, and Throughput in Packet-Switched Networks
End-to-End Delay
N - 1 routers And Uncongested ( no queueing )
Traceroute (RFC 1393)

7. Delay, Loss, and Throughput in Packet-Switched Networks
Throughput in Computer Networks
throughput =min{Rs, Rc}.

8. Protocol Layers and Their Service Models

9. Networks Under Attack Malware Viruses Worm
Attack servers and network infrastructure
Denial-of-service (DoS) attacks
Vulnerability attack
Bandwidth flooding: The attacker sends a deluge of packets to the targeted host.
Connection flooding. The attacker establishes a large number of half-open or fully open TCP connections at the target host.

10. Networks Under Attack
Sniff packets
Masquerade as someone you trust
IP spoofing (The ability to inject packets into the Internet with a false source address)