Chapter 8: Internet Operation

1. Chapter 8: Internet Operation Business Data Communications, 5e

2. Network Classes • Class A: Few networks, each with many hostsAll addresses begin with binary 0 • Class B: Medium networks, medium hostsAll addresses begin with binary 10 • Class C: Many networks, each with few hosts All addresses begin with binary 11

3. Internet Addressing • 32-bit global internet address • Includes network and host identifiers • Dotted decimal notation • 11000000 11100100 00010001 00111001 (binary) • 192.228.17.57 (decimal)

4. Subnets & Subnet Masks • Allows for subdivision of internets within an organization • Each LAN can have a subnet number, allowing routing among networks • Host portion is partitioned into subnet and host numbers

5. Subnet Mask Calculations

6. Internet Routing Protocols • Responsible for receiving and forwarding packets between interconnected networks • Must dynamically adapt to changing network conditions • Two key concepts • Routing information • Routing algorithm

7. Autonomous Systems • Key characteristics • Set of routers and networks managed by single organization • group of routers exchanging information via a common routing protocol • connected (in a graph-theoretic sense); that is, there is a path between any pair of nodes • Interior Router Protocol (IRP) passes information between routers in an AP • Exterior Router Protocol (ERP) passes information between routers in different Aps

8. Border Grouping Protocol (BGP) • Preferred ERP for the Internet • Three functional procedures • Neighbor acquisition • Neighbor reachability • Network reachability

9. Open Shortest Path First (OSPF) • Widely used as IRP in TCP/IP networks • Uses link state routing algorithm • Routers maintain topology database of AS • Vertices • Router • Network • Transit • Stub • Edges • Connecting router vertices • Connecting router vertex to network vertex

10. Autonomous System Example

11. Directed Graph of Example

12. The “Need for Speed” andQuality of Service (QoS) • Image-based services on the Internet (i.e., the Web) have led to increases in users and traffic volume • Resulting need for increased speed • Lack of increased speed reduced demand • QoS provides for varying application needs in Internet transmission

13. Emergence of High-Speed LANs • Until recently, internal LANs were used primarily for basic office services • Two trends in the 1990s changed this • Increased power of personal computers • MIS recognition of LAN value for client/server and intranet computing • Effect has been to increase volume of traffic over LANs • Result exceeds capacity of standard 10mbps and 16mbps networks

14. Corporate WAN Neds • Greater dispersal of employee base • Changing application structures • Increased client/server and intranet • Wide deployment of GUIs • Dependence on Internet access • More data must be transported off premises and into the wide area

15. Digital Electronics • Major contributors to increased image and video traffic • DVD (Digital Versatile Disk) • Increased storage means more information to transmit • Digital cameras • Camcorders • Still Image Cameras

16. Categories of Traffic • Elastic • Can adjust to changes in delay and throughput access • Examples: File transfer, e-mail, web access • Inelastic • Does not adapt well, if at all, to changes • Examples: Real-time voice, audio and video

17. Requirements of Inelastic Traffic • Throughput • Minimum value may be required • Delay • Services like market quotes are delay-sensitive • Delay variation • Real-time applications, like teleconferencing, have upper bounds on delay variation • Packet loss • Applictions vary in the amount of packet loss allowable

18. Application Delay Sensitivity

19. Differentiated Services • Provide QoS on the basis of user needs rather than data flows • IP packets labeled for differing QoS treatment • Service level agreement (SLA) established between the provider (internet domain) and the customer prior to the use of DS. • Provides a built-in aggregation mechanism. • Implemented in routers by queuing and forwarding packets based on the DS octet. • Routers do not have to save state information on packet flows.

20. DS Service:Performance Parameters • Service performance parameters • Constraints on ingress/egress points • Traffic profiles • Disposition of excess traffic

21. DS Services Provided • Traffic offered at service level A will be delivered with low latency. • Traffic offered at service level B will be delivered with low loss. • 90% of in-profile traffic delivered at service level C will experience no more than 50 ms latency. • 95% of in-profile traffic delivered at service level D will be delivered. • Traffic offered at service level E will be allotted twice the bandwidth of traffic delivered at service level F • Traffic with drop precedence X has a higher probability of delivery than traffic with drop precedence Y.

22. DS Field • Packets labeled for handling in 6-bit DS field in the IPv4 header, or the IPv6 header • Value of field is “codepoint” • 6-bits allows 64 codepoints in 3 pools • Form xxxxx0 - reserved for assignment as standards. • Form xxxx11 - reserved for experimental or local use. • Form xxxx01 - also reserved for experimental or local use, but may be allocated for future standards action as needed. • Precedence subfield indicates urgency • Route selection, Network service, Queuing discipline • RFC 1812 provides two categories of recommendations for queuing discipline • Queue Service • Congestion Control

23. DS Configuration Diagram

24. DS Configuration & Operation • Routers are boundary or interior nodes • Forwarding treatment is per-hop behavior (PHB) • Boundary nodes handle traffic conditioning • Classifier • Meter • Marker • Shaper • Dropper

25. Traffic Conditioning Diagram

26. Token Bucket Scheme