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Chapter 5 : The Internet:
Addressing & ServicesBusiness Data Communications, 4e
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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
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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
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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
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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
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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
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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)
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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
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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
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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
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DNS Database
Hierarchical database containing name, IP address, and related information for hosts
Provides name-to-address directory services
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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
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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
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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
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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)
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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
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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
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RSVP Data Flows
Session Data flow identified by its destination
Flow Descriptor (reservation request) Flowspec Filter Spec
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RSVP Message Types
Resv Originate at multicast group receivers Create “soft states” within routers to define
resources Propagate upstream
Path Provides upstream routing information
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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
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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
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Token Bucket Scheme