Chapter 11

Network Fundamentals

Agenda

• Definition

• Classification

• Information Routing

• Connection

• Telecommunication software

• Architecture

Definition

• Network

• Backbone network

Classification

• Topology

• Ownership

• Geography

• Transmission

Network Topology

• Star

• Hierarchical

• Mesh

• Bus

• Ring

• Hybrid

Star Network

• Circuits– Point-to-point, multipoint, or combination

• Pros– Expand – Implement– No limit to no. and length of arms

• Cons– Single point of failure– Overload of mater during peak traffic

Hierarchical Network

• Tree structure with a root

• pro– No single point of failure– Divisional communications and processing

Mesh Network

• Web structure• Usage

– Public telephone system

• Pro– Alternative communication route– Virtually fail-safe

• Con– Line cost

Bus Network

• Usage– High speed, short distance between nodes– Local area network

• Pros– Independent between nodes– High reliability

• Cons– Limited number of attached device– Hard to locate the problems

Ring Network

• Usage– Nodes are relatively close together

• Pros– Less attenuation– Error control– Network management

• Cons– Failing of a node

• Two opposite direction channels

Hybrid Networks

• Usage– Connecting different networks

• Pro– Communication between different networks

• Con– Conversion device and costs

Network Ownership

• Private networks

• Public networks

• Valued added networks

Private networks

• Full control

• Special needs

• Expense

Public networks

• Controlled by carriers

• Regulated by government

• Inexpensive

Valued Added Networks

• Public network

• Functions– Code translation– Speed conversion– Store message and delivery

• Examples– Telex– SWIFT– SITA (airline)– IVAN (insurance)

Networks by Geography

• Wide area network (WAN)

• Metropolitan area network (MAN)

• Local area network (LAN)

Wide Area Networks

• Public Switched Telephone Network (PSTN)

• Provided by carriers

• Inexpensive

• High quality service for infrequent users

Metropolitan Area Networks

• IEEE 802.6

• Distance up to 30 miles

• High bandwidth for data, voice, and video

• T1, T3, or fiber optic cable

• Private own or dark fiber supplied by MAN provider

Network Transmission Types

• Circuit Switching

• Packet data networks (PDNs)

• Frame relay

• Asynchronous transfer mode: ATM (Cell relay)

Circuit Switching

• Temporarily Dedicated communications line between two stations for transmission

• Efficient for constant voice and video transmission

• Inefficient for non-constant data transmission

Packet Data networks (PDNs) - I

• Packet– Less than 1,000 bytes– PAD (packet assembly/disassembly)– Address and control fields for error checking

• Connection types– Switched virtual circuit: dial-in (switched)– Permanent virtual (leased) circuit: heavy &

frequent traffic– Datagram: short message, no error checking

Packet Data networks (PDNs) - II

• Standard– ITU-T’s X.25

• Between terminal and PDN on public network

– ITU-T’s X.75• Interface between two PDNs

• Examples– USA: APARANET, Telenet, Tymnet, General

Electric Information Services (GEIS)

Packet Data networks (PDNs) - III

• Characteristics– Reliable service– Nationwide service– Lower error rates– Variety of transmission speeds– Cost-effectiveness

Frame Relay

• Acknowledge only by final node• Benefits

– Variable-length frames (1- 64,000 bytes)– Reduce overhead– More efficient transmission

• Problems– Circuit congestion– Committed information rate (CIR) & port speed

for service guarantee & discarding frames

ATM (Cell-Relay)

• Asynchronous transfer mode (ATM)• Cells : fixed length packets of 53 bytes• 45Mbps (T3) or higher speeds• Pros

– High throughput, low delay, transparency, flexibility, and high capacity

• Con– Expensive

ATM Services

• Realtime service– Constant bit rate (CBR) for telephone and

videoconference– Realtime variable bit rate (rt-VBR) for compressed

video

• Non-realtime service– Non-realtime variable bit rate (nrt-VBR) for airline

reservation or financial transaction– Available bit rate (ABR) for LAN-to-LAN– Unspecified bit rate (UBR) for TCP-based traffic

Routing Message

• Connection-oriented routing & connection less routing

• Broadcast routing

• Centralized routing

• Distributed routing

• Static and dynamic routing

Broadcasting Routing

• CSMA/CD

• Pros and cons– Simplest– For small network– Not for moderate to heavy traffic

Centralized Routing

• Star or hierarchical networks– IBM’s SNA networks

• Using static routing table in one central computer

• Pros and cons– Simple– Potential performance bottleneck– Single point of failure

Distributed Routing

• Routing tables on several nodes

• Pros and cons– No single point of failure– Routing table update problem– Complicated to implement

Static and Dynamic Routing

• Static routing– Predetermined route– Simple but inflexible

• Dynamic routing– Use routing algorithms to evaluate traffic

volumes, error rates, and other conditions for the best path

– Flexible but high overhead and complicated to implement

Interconnecting Networks

• Transmission control protocol/ internet protocol (TCP/IP)

• Internet

• Intranet & extranet

Transmission Control Protocol

• OSI transport layer

• Connection oriented

• Functions– Assemble and reassemble message packets– Reliable & error free message delivery– Urgency or priority– Security (encryption)

Internet Protocol

• OSI network layer

• Routing & addressing messages to other networks

• Connectionless operation

• IPv6– 128 bits for addressing– Quick and efficient

TCP/IP Application protocols

• File Transfer Protocol (FTP)• Tenet• Simple Mail Transfer Protocol (SMTP)• Multipurpose Internet Mail Extensions

(MIME)• Remote Procedure Call (RPC)• Simple Network Management Protocol

(SNMP)

Internet

• Usages– Electronic mail, remote log in to various computers,

discussion groups, information search and retrieval

• Electronic mail (e-mail)– Edu, com, org, gov, mil, net

• Web servers & web browsers• Hypertext Markup Language (HTML)• Uniform Resource Locator (URL)• Home page• Internet service provider (ISP)

Intranets & Extranets

• Intranets

• Extranets

• Benefits: fast information transmission

• Problems: security & privacy

Connect Network to Computer

• Methods– Direct connection between circuit and computer

• Small network

• Low cost

• Cycle stealing

– Network interface card– Use a front-end processor: telecommunication

control unit or transmission control unit• Large host computer

• Better utilize computer resources

Front-end Processors (FEPs)

• Types– Hardware (interface or port): speed– Software ( network control program NCP):

flexible

FEPs - Functions

• Circuit control

• Assembly messages

• Message queuing or storing

• Error control

• Administration functions

Functions of Telecommunication Softwarein Host Computer

• Security• Buffer management• Routing a message to a program• Queuing messages• Scheduling application program• Providing continuity between part of a transaction• Message formatting• Checkpoint/restart• Preventing messages from lost or duplicated

Software for Network Management

• Control and monitor the network status– Start/stop network, terminal, and line– Performance

• Log network operation

• Display network data

Manufacturers’ Architectures

• IBM’s System Network Architecture (SNA)

• Digital Equipment Corporation’s Digital Network Architecture (DNA)

IBM’s SNA Concepts

• Physical units• Logical units• Sessions• Network addressing units (NAUs)• Data link protocols• SNA software

– Network Control program (NCP)

– Virtual Telecommunications Access Method

SNA Physical Units

• Terminals (1)

• Cluster controllers (2)

• Front-end processors (4)

• Host computers (5)

SNA Logical Units

• People

• Application programs

SNA Sessions

• Types– Terminal-to-terminal– Terminal-to-program– Program-to-program

• Modes– Interactive– Batch– Multiple simultaneous

SNA Network Addressable Units

• Physical units

• Logical units

• Address: 24 bits

SNA Data Link Protocols

• Synchronous Data Link control (SDLC)

• Binary Synchronous Communications (BISYNC or BSC)

• X.25

System Network Architecture• Physical control

– Physical and electrical connections

– Transmission codes

– Voltages

• Data link control– Format

– Reliability

• Path control– Routing information

• Transmission control– Security & compression

• Data flow control– Flow control

• Presentation services– Format

• Transaction services– Coordinating application software

Digital’s DNA -I

• Protocols– Digital Data Communication Message Protocol

(DDCMP)

– X.25

– Ethernet

• DECNET Layers– Application

– Network service

– Transport

– Data link control

– Physical link control

Points to Remember

• Definition

• Classification

• Information Routing

• Connection

• Telecommunication software

• Architecture

Discussion

• Does CSUS need a backbone network?• What type of backbone do you think that CSUS

needs (give your justifications)?• What type of network does CSUS needs in terms

of topology, ownership, geography and transmission technology?

• What type of network does a grocery chain store needs in terms of topology, ownership, geography and transmission technology?