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Chapter 5 : The Internet: Addressing & Services. Business Data Communications, 4e. Internet History. Evolved from ARPANet (Defense Department’s Advanced Research Projects Agency Network) ARPANet was developed in 1969, and was the first packet-switching network
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Chapter 5 : The Internet: Addressing & Services Business Data Communications, 4e
Internet History • Evolved from ARPANet (Defense Department’s Advanced Research Projects Agency Network) • ARPANet was developed in 1969, and was the first packet-switching network • Initially, included only four nodes: UCLA, UCSB, Utah, and SRI
Switching Methods • Circuit Switching: Requires a dedicated communication path for duration of transmission; wastes bandwidth, but minimizes delays • Message Switching: Entire path is not dedicated, but long delays result from intermediate storage and repetition of message • Packet Switching: Specialized message switching, with very little delay
NSF and the Internet • In the 1980s, NSFNet extended packet-switched networking to non-ARPA organization; eventually replaced ARPANet • Instituted Acceptable Use Policies to control use • CIX (Commercial Internet eXchange) was developed to provide commercial internetworking
The World Wide Web • Concept proposed by Tim Berners-Lee in 1989, prototype WWW developed at CERN in 1991 • First graphical browser (Mosaic) developed by Mark Andreessen at NCSA • Client-server system with browsers as clients, and a variety of media types stored on servers • Uses HTTP (hyper text transfer protocol) for retrieving files
Connecting to the Internet • End users get connectivity from an ISP (internet service provider) • Home users use dial-up, ADSL, cable modems, satellite • Businesses use dedicated circuits connected to LANs • ISPs use “wholesalers” called network service providers and high speed (T-3 or higher) connections
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)
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
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 • See Table 5.2 for method of calculating subnet masks
Domain Name System • 32-bit IP addresses have two drawbacks • Routers can’t keep track of every network path • Users can’t remember dotted decimals easily • Domain names address these problems by providing a name for each network domain (hosts under the control of a given entity) • See Figure 5.6 for example of a domain name tree
DNS Database • Hierarchical database containing name, IP address, and related information for hosts • Provides name-to-address directory services
Quality of Service (QoS) • Real-time voice and video don’t work well under the Internet’s “best effort” delivery service • QoS provides for varying application needs in Internet transmission
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
IPv4 Type of Service Field • Allows user to provide guidance on individual datagrams • 3-bit precedence subfield • Indicates degree of urgency or priority • Queue Service & Congestion Control • 4-bit TOS subfield • Provides guidance on selecting next hop • Route selection, Network Service, & Queuing Discipline
Integrated Services • Routers require additional functionality to handle QoS-based service • IETF is developing suite of standards to support this • Two standards have received widespread support • Integrated Services Architecture (ISA) • Resource ReSerVation Protocol (RSVP)
Enables provision of QoS over IP-networks Features include Admission Control Routing Algorithm Queuing Discipline Discard Policy ISA Background Functions Reservation Protocol Admission Control Management Agent Routing Protocol Forwarding Functions Classifier and Route Selection Packet Scheduler Integrated Services Architecture
Resource Reservation Protocol • A tool for prevention of congestion through reservation of network resources • Can be used in unicast or multicast transmissions • Receivers (not senders) initiate resource reservations
RSVP Data Flows • Session • Data flow identified by its destination • Flow Descriptor (reservation request) • Flowspec • Filter Spec
RSVP Message Types • Resv • Originate at multicast group receivers • Create “soft states” within routers to define resources • Propagate upstream • Path • Provides upstream routing information
Differentiated Services (DS) • Provides QoS based on user group needs rather than traffic flows • Can use current IPv4 octets • Service-Level Agreements (SLA) govern DS, eliminating need for application-based assignment
DS Operation • Routers are either boundary nodes or interior nodes • Interior nodes use per-hop behavior (PHB) rules • Boundary nodes have PHB & traffic conditioning • Classifier • Meter • Marker • Shaper • Dropper
