Chapter 5 : The Internet: Addressing & Services Business Data Communications, 4e

Internet History 8Evolved from ARPANet (Defense Department’s Advanced Research Projects Agency Network) 8ARPANet was developed in 1969, and was the first packet-switching network 8Initially, included only four nodes: UCLA, UCSB, Utah, and SRI

Switching Methods 8Circuit Switching: Requires a dedicated communication path for duration of transmission; wastes bandwidth, but minimizes delays 8Message Switching: Entire path is not dedicated, but long delays result from intermediate storage and repetition of message 8Packet Switching: Specialized message switching, with very little delay

NSF and the Internet 8In the 1980s, NSFNet extended packet- switched networking to non-ARPA organization; eventually replaced ARPANet 8Instituted Acceptable Use Policies to control use 8CIX (Commercial Internet eXchange) was developed to provide commercial internetworking

The World Wide Web 8Concept proposed by Tim Berners-Lee in 1989, prototype WWW developed at CERN in First graphical browser (Mosaic) developed by Mark Andreessen at NCSA 8Client-server system with browsers as clients, and a variety of media types stored on servers 8Uses HTTP (hyper text transfer protocol) for retrieving files

Connecting to the Internet 8End users get connectivity from an ISP (internet service provider) 8Home users use dial-up, ADSL, cable modems, satellite 8Businesses use dedicated circuits connected to LANs 8ISPs use “wholesalers” called network service providers and high speed (T-3 or higher) connections

Internet Addressing 832-bit global internet address 8Includes network and host identifiers 8Dotted decimal notation (binary) (decimal)

Network Classes 8Class A: Few networks, each with many hosts All addresses begin with binary 0 8Class B: Medium networks, medium hosts All addresses begin with binary 10 8Class C: Many networks, each with few hosts All addresses begin with binary 11

Subnets & Subnet Masks 8Allows for subdivision of internets within an organization 8Each LAN can have a subnet number, allowing routing among networks 8Host portion is partitioned into subnet and host numbers 8See Table 5.2 for method of calculating subnet masks

Domain Name System 832-bit IP addresses have two drawbacks 8Routers can’t keep track of every network path 8Users can’t remember dotted decimals easily 8Domain names address these problems by providing a name for each network domain (hosts under the control of a given entity) 8See Figure 5.6 for example of a domain name tree

DNS Database 8Hierarchical database containing name, IP address, and related information for hosts 8Provides name-to-address directory services

Quality of Service (QoS) 8Real-time voice and video don’t work well under the Internet’s “best effort” delivery service 8QoS provides for varying application needs in Internet transmission

Categories of Traffic 8Elastic 8Can adjust to changes in delay and throughput access 8Examples: File transfer, , web access 8Inelastic 8Does not adapt well, if at all, to changes 8Examples: Real-time voice, audio and video

IPv4 Type of Service Field 8Allows user to provide guidance on individual datagrams 83-bit precedence subfield 8Indicates degree of urgency or priority 8Queue Service & Congestion Control 84-bit TOS subfield 8Provides guidance on selecting next hop 8Route selection, Network Service, & Queuing Discipline

Integrated Services 8Routers require additional functionality to handle QoS-based service 8IETF is developing suite of standards to support this 8Two standards have received widespread support 8Integrated Services Architecture (ISA) 8Resource ReSerVation Protocol (RSVP)

Integrated Services Architecture 8Enables provision of QoS over IP-networks 8Features include 8Admission Control 8Routing Algorithm 8Queuing Discipline 8Discard Policy 8ISA Background Functions 8Reservation Protocol 8Admission Control 8Management Agent 8Routing Protocol 8Forwarding Functions 8Classifier and Route Selection 8Packet Scheduler

Resource Reservation Protocol 8A tool for prevention of congestion through reservation of network resources 8Can be used in unicast or multicast transmissions 8Receivers (not senders) initiate resource reservations

RSVP Data Flows 8Session 8Data flow identified by its destination 8Flow Descriptor (reservation request) 8Flowspec 8Filter Spec

RSVP Message Types 8Resv 8Originate at multicast group receivers 8Create “soft states” within routers to define resources 8Propagate upstream 8Path 8Provides upstream routing information

Differentiated Services (DS) 8Provides QoS based on user group needs rather than traffic flows 8Can use current IPv4 octets 8Service-Level Agreements (SLA) govern DS, eliminating need for application-based assignment

DS Operation 8Routers are either boundary nodes or interior nodes 8Interior nodes use per-hop behavior (PHB) rules 8Boundary nodes have PHB & traffic conditioning 8Classifier 8Meter 8Marker 8Shaper 8Dropper

Token Bucket Scheme