Business data communications 4e chapter 5

Chapter : 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 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 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) Integrated Services Architecture  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 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 Token Bucket Scheme ... 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... multicast transmissions  Receivers (not senders) initiate resource reservations RSVP Data Flows  Session  Data flow identified by its destination  Flow Descriptor (reservation request)  Flowspec... identifiers  Dotted decimal notation  11000000 11100100 00010001 00111001 (binary)  192.228.17 .57 (decimal) Network Classes  Class A: Few networks, each with many hosts All addresses begin with