Business data communications 5e by stallings chapter 08

Chapter 8: Internet Operation Business Data Communications, 5e Network Classes • Class A: Few networks, each with many hosts All addresses begin with binary • Class B: Medium networks, medium hosts All addresses begin with binary 10 • Class C: Many networks, each with few hosts All addresses begin with binary 11 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) 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 Subnet Mask Calculations 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 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 Border Grouping Protocol (BGP) • Preferred ERP for the Internet • Three functional procedures – Neighbor acquisition – Neighbor reachability – Network reachability 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 Autonomous System Example The “Need for Speed” and Quality 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 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 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 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 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 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 Application Delay Sensitivity 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 not have to save state information on packet flows DS Service: Performance Parameters • • • • Service performance parameters Constraints on ingress/egress points Traffic profiles Disposition of excess traffic 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 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 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 DS Configuration Diagram 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 Traffic Conditioning Diagram Token Bucket Scheme ... Routing algorithm Autonomous Systems • Key characteristics – Set of routers and networks managed by single organization – group of routers exchanging information via a common routing protocol –... 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... 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 Digital Electronics • Major contributors