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