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Chapter 5 : The Internet:
Addressing & ServicesBusiness 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)
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