Chapter 8: Internet Operation

1. Chapter 8: Internet Operation

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

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. Subnetworking Example

7. 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

8. 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 AS (Autonomous systems) • Exterior Router Protocol (ERP) passes information between routers in different AS

9. Border Gateway Protocol (BGP) • Preferred ERP for the Internet • BGP-4 is the current version • Three functional procedures • Neighbor acquisition • Neighbor reachability • Network reachability

10. 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

11. Autonomous System Example

12. Open Shortest Path First (OSPF) Protocol • Widely used interior protocol to TCP/IP networks • Computes a route through the network that incurs the least cost • User can configure the cost as a function of:-delay-data rate-cost

13. 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

14. 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

15. 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

16. 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

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

18. 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

19. Application Delay Sensitivity

20. 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.

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

22. Service Level Agreements (SLA) • Contract between the network providor and customer that defines sepecific aspects of the service provided. • Typically includes:-Service description-Expected performance level-Monitoring and reporting process

23. SLA ExampleMCI Internet Dedicated Service • 100% availability • Average round trip transmissions of ≤ 45 ms with the U.S. • Successful packet delivery rate ≥ 99.5% • Denial of Service response within 15 minutes • Jitter performance will not exceed 1 ms between access routers

24. IP Performance Metrics • Three Stages of Metric Definitions-Singleton-Sample-Statistical • Active techniques require injecting packets into the network • Passive techniques observe and extract metrics