The Network Layer Chapter

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Congestion Control Algorithms (1) a)Approaches to congestion control b)Traffic-aware routing c)Admission control d)Traffic throttling e)Load shedding

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Congestion Control Algorithms (2) a)When too much traffic is offered, congestion sets in and performance degrades sharply.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Approaches to Congestion Control a)Timescales of approaches to congestion control

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic-Aware Routing a)A network in which the East and West parts are connected by two links.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Throttling (1) a)(a) A congested network. (b) The portion of the network that is not congested. A virtual circuit from A to B is also shown.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Throttling (2) a)Explicit congestion notification

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Load Shedding (1) a)A choke packet that affects only the source..

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Load Shedding (2) a)A choke packet that affects each hop it passes through.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Quality of Service a)Application requirements b)Traffic shaping c)Packet scheduling d)Admission control e)Integrated services f)Differentiated services

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Application Requirements (1) a)How stringent the quality-of-service requirements are.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Categories of QoS and Examples a)Constant bit rate –Telephony b)Real-time variable bit rate –Compressed videoconferencing c)Non-real-time variable bit rate –Watching a movie on demand d)Available bit rate –File transfer

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Shaping (1) a)(a) Shaping packets. (b) A leaky bucket. (c) A token bucket

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Shaping (2) a)(a) Traffic from a host. Output shaped by a token bucket of rate 200 Mbps and capacity (b) 9600 KB, (c) 0 KB.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Traffic Shaping (3) a)Token bucket level for shaping with rate 200 Mbps and capacity (d) KB, (e) 9600 KB, and (f) 0KB..

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Scheduling (1) a)Kinds of resources can potentially be reserved for different flows: b) Bandwidth. c) Buffer space. d) CPU cycles.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Scheduling (2) a)Round-robin Fair Queuing

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Scheduling (3) (a)Weighted Fair Queueing. (b)Finishing times for the packets.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Admission Control (1) a)An example flow specification

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Admission Control (2) a)Bandwidth and delay guarantees with token buckets and WFQ.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Integrated Services (1) a)(a) A network. (b) The multicast spanning tree for host 1. (c) The multicast spanning tree for host 2.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Integrated Services (2) a)(a) Host 3 requests a channel to host 1. (b) Host 3 then requests a second channel, to host 2. (c) Host 5 requests a channel to host 1.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Differentiated Services (1) a)Expedited packets experience a traffic-free network

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Differentiated Services (2) a)A possible implementation of assured forwarding

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Internetworking a)How networks differ b)How networks can be connected c)Tunneling d)Internetwork routing e)Packet fragmentation

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 How Networks Differ a)Some of the many ways networks can differ

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 How Networks Can Be Connected (a)A packet crossing different networks. (b)Network and link layer protocol processing.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Tunneling (1) a)Tunneling a packet from Paris to London.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Tunneling (2) a)Tunneling a car from France to England

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (1) a)Packet size issues: b)Hardware c)Operating system d)Protocols e)Compliance with (inter)national standard. f)Reduce error-induced retransmissions g)Prevent packet occupying channel too long.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (2) (a)Transparent fragmentation. (b)Nontransparent fragmentation

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (3) a)Fragmentation when the elementary data size is 1 byte. (a) Original packet, containing 10 data bytes.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (4) a)Fragmentation when the elementary data size is 1 byte b)(b) Fragments after passing through a network c)with maximum packet size of 8 payload bytes plus header.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (5) a)Fragmentation when the elementary data size is 1 byte b)(c) Fragments after passing through a size 5 gateway.

Computer Networks, Fifth Edition by Andrew Tanenbaum and David Wetherall, © Pearson Education-Prentice Hall, 2011 Packet Fragmentation (6) a)Path MTU Discovery