-1- Georgia State UniversitySensorweb Research Laboratory CSC4220/6220 Computer Networks Dr. WenZhan Song Professor, Computer Science

-2- Georgia State UniversitySensorweb Research Laboratory Course roadmap Introduction Application Layer: WWW, FTP, , DNS, multimedia Transport Layer: reliable end-end data transfer principles, UDP, TCP Network Layer: IP addressing, routing and other issues Data Link Layer: framing, error control, flow control Medium Access Control (MAC) Layer: multiple-access, channel allocation Physical Layer: wired, wireless, satellite Other Topics: network security, social issues, hot topics, research directions

-3- Georgia State UniversitySensorweb Research Laboratory Roadmap Network Layer Network layer design issues overview of service models Virtual circuits and datagram networks IP: Internet Protocol datagram format, IPv4 addressing NAT, IPv6 ICMP, ARP, DHCP Routing algorithms distance vector link state Routing Protocol in Internet RIP OSPF BGP Other issues in network layer

-4- Georgia State UniversitySensorweb Research Laboratory Other issues in network layer Congestion control (in network) QoS Internetworking

-5- Georgia State UniversitySensorweb Research Laboratory Congestion When too much traffic is offered, congestion sets in and performance degrades sharply.

-6- Georgia State UniversitySensorweb Research Laboratory General Principles of Congestion Control Monitor the system. detect when and where congestion occurs. Pass information to where action can be taken. Adjust system operation to correct the problem.

-7- Georgia State UniversitySensorweb Research Laboratory Congestion Prevention Policies Policies that affect congestion.

-8- Georgia State UniversitySensorweb Research Laboratory Congestion Control in Virtual-Circuit Subnets (a) A congested subnet. (b) A redrawn subnet, eliminates congestion and a virtual circuit from A to B.

-9- Georgia State UniversitySensorweb Research Laboratory Hop-by-Hop Choke Packets (a) A choke packet that affects only the source. (b) A choke packet that affects each hop it passes through.

-10- Georgia State UniversitySensorweb Research Laboratory Quality of Service Requirements Techniques for Achieving Good Quality of Service Integrated Services Differentiated Services Label Switching and MPLS

-11- Georgia State UniversitySensorweb Research Laboratory Requirements How stringent the quality-of-service requirements are.

-12- Georgia State UniversitySensorweb Research Laboratory Techniques to achieve good QoS Overprovisioning used in telephone network, providing enough router capacity, buffer space and bandwidth Traffic shaping Smooth out the traffic on the server side, rather than on client side Proportional routing Split traffic over multiple paths Buffering Leaky bucket algorithm The token bucket algorithm Resource reservation Admission control Packet scheduling

-13- Georgia State UniversitySensorweb Research Laboratory Buffering Smoothing the output stream by buffering packets.

-14- Georgia State UniversitySensorweb Research Laboratory The Leaky Bucket Algorithm (a) A leaky bucket with water. (b) a leaky bucket with packets.

-15- Georgia State UniversitySensorweb Research Laboratory The Token Bucket Algorithm (a) Before. (b) After Token Bucket provide different traffic shaping than leaky bucket: (1)Allow burst traffic (2)May throw tokens, but not packets

-16- Georgia State UniversitySensorweb Research Laboratory Traffic shape (a) Input to a leaky bucket. (b) Output from a leaky bucket. Output from a token bucket with capacities of (c) 250 KB, (d) 500 KB, (e) 750 KB (f) Output from a 500KB token bucket feeding a 10-MB/sec leaky bucket.

-17- Georgia State UniversitySensorweb Research Laboratory Admission Control An example of flow specification. 5-34

-18- Georgia State UniversitySensorweb Research Laboratory Packet Scheduling (a) A router with five packets queued for line O. (b) Finishing times for the five packets. Byte-by-byte round robin

-19- Georgia State UniversitySensorweb Research Laboratory Label Switching and MPLS Transmitting a TCP segment using IP, MPLS, and PPP. MPLS: MultiProtocol Label Switching MPLS vs. VC network:  Similarity: based on label switching, differ than routing  Difference: no pre-connection setup, it is on-demand “VC” creation

-20- Georgia State UniversitySensorweb Research Laboratory Switch and Router (a) Two Ethernets connected by a switch. (b) Two Ethernets connected by routers.

-21- Georgia State UniversitySensorweb Research Laboratory Tunneling Tunneling a packet from Paris to London.

-22- Georgia State UniversitySensorweb Research Laboratory Tunneling (2) Tunneling a car from France to England.

-23- Georgia State UniversitySensorweb Research Laboratory Reading Assignment Chapter 5