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Chapter 4

Internet Architecture

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OVERVIEW

• What is a Network?• IP Addresses• Networks• Information Transfer• Cable Types• Key Components of a Network• Factors in Designing a Network• Network Management System

Internet Architecture

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WHAT IS A NETWORK?

• A connection between at least two computers for the purpose of sharing resources

• Types:– Local Area Networks (LANs)– Wide Area Networks (WANs)– Metropolitan Area Networks (MANs)

Internet Architecture: What is a Network?

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PEER-TO-PEER NETWORK• Computers linked together as equals

• No centralized control

• Share resources on the same network in any way & at any time

• Promotes institutionalized chaos

• < 10 computers

Internet Architecture: What is a Network?

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PEER-TO-PEER NETWORK (CONT.)

• Benefits– Easy to install/configure

– Inexpensive

– Users able to control their own resources

– Independent from a dedicated server

– No need for a network administrator

• Drawbacks– Security problems

– Performance suffers when a computer is accessed

– Difficult to have backup

– Decentralized logon passwords

– No centralized data management

Internet Architecture: What is a Network?

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CLIENT/SERVER NETWORK• Server – designed to address a client’s request

• Client – any computer connected to the server within a network

• Allow authorized user to access any programs/application residing on the server

Internet Architecture: What is a Network?

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CLIENT/SERVER NETWORK (Cont’d)

• Benefits– Centralized security control– Simpler network

administration than peer-to-peer network

– Centralized password– More scalable– Ideal for computers that are

apart

• Drawbacks– Network failure = clients

are helpless

– Specialized staff are needed

– Higher costs

Internet Architecture: What is a Network?

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IP ADDRESSES• A host number to identify itself to other hosts• Consists of strings of 32 bits• E.g. 10111111010101010100000000001100

= 191.170.64.12 • Host Name

– Human-friendly Internet addresses– E.g. ema3z.mcintire.virginia.edu

Internet Architecture: IP Addresses

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NETWORKS

• Network vs. Local

• Networks are classified by three sizes:

Internet Architecture: Networks

Class Beginning Bit

Bits in remainder of network part

# of bits in local part

Max. # of networks

Max. # of hosts in network

A 0 7 24 136 16 million

B 10 14 16 16,000 65,000

C 110 21 8 2 million 254

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NETWORKS (Cont’d)

• Zones– Three-letter kind (com, gov, edu)– Two-letter kind (ca, uk, jp)– New general-purpose zones (firm, store)

Internet Architecture: Networks

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INFORMATION TRANSFER• Packet

– Grouping of data for transmission on a network– Large messages are split into a series of packets

for transmission

• Protocol– A rule governing how communication should

be conducted– Internet Protocol

• Set of rules used to pass packets

Internet Architecture: Information Transfer

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INFORMATION TRANSFER (Cont’d)

• Open Systems Interconnection (OSI)– A layered approach to networking– Each layer handles a different portion of the

communication process

Internet Architecture: Information Transfer

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OSI REFERENCE MODEL

Internet Architecture: Information Transfer

Layer Info Transacted TCP/IP Protocols

Application Application messages HTTP, FTP, SNMP

Presentation Compressed data

Session Session messages

Transport Multiple packets TCP

Network Packets IP

Data Link Frames Ethernet, PPP

Physical Bits Wiring, cables

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OSI REFERENCE MODEL (Cont’d)

• Application Layer– Defines requests & response formats– Standard: HTTP

• Governs requests & response between browser & web server application program

• Other standards: SMTP, POP• HTML-compatible

– File Transfer Protocol (FTP), Simple Network Management Protocol (SNMP), Domain Name Service (DNS)

Internet Architecture: Information Transfer

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OSI REFERENCE MODEL (Cont’d)

• Presentation Layer– Converts data into a format the receiving

application can understand

• Session Layer– Exchanges data for the duration of session– Keeps track of the status of exchange– Ensures only designated parties are allowed to

participate in the session– Enforces security protocols for controlling

access

Internet Architecture: Information Transfer

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OSI REFERENCE MODEL (Cont’d)

• Transport Layer– Manages the transmission of data across a

network– Transmission Control Protocol (TCP)

• Specifies how two host computers will work together

• Flow control

• Sequence assurance

• Reliability & integrity

Internet Architecture: Information Transfer

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OSI REFERENCE MODEL (Cont’d)

• Internet Layer– Routes messages across multiple nodes for

delivery– Handles network congestion to minimize

performance problems– Internet Protocol (IP)

• Standard for routing packets

Internet Architecture: Information Transfer

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OSI REFERENCE MODEL (Cont’d)

• Data Link Layer– Packages data into frames for delivery– Point-to-point (PPP)

• Framing – mark boundary between packets• Error detection

– Ethernet

• Physical Layer– Converts bits into signals for outgoing

messages & signals into bits for incoming messages

Internet Architecture: Information Transfer

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CABLE TYPES

• Twisted-Pair Cable

• Unshielded Twisted Pair (UTP)

• Shielded Twisted Pair (STP)

• Optical Fiber

• Coaxial Cable

• Wireless Technology

Internet Architecture: Cable Types

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TWISTED-PAIR CABLE• Consists of two pairs of insulated copper wires

twisted around each other• Advantages

– Protect against cross talk & interference– Easy to add computers to network– Well understood technology– Less expensive

• Disadvantages– Susceptibility to noise– Least secure– Distance limitations– Requires more expensive hubs

Internet Architecture: Cable Types

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UNSHIELDED TWISTED PAIR (UTP)

• Pair of wires do not have the shielding against electrical interference

• Advantages– Less expensive– Easy to install

• Disadvantages– Vulnerable to electromagnetic interference &

crosswalk– Subject to attenuation

Internet Architecture: Cable Types

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SHIELDED TWISTED PAIR (STP)

• An electrically grounded woven copper mesh wrapped around each twisted pair

• Advantage– Reduces electromagnetic interference (EMI)

• Disadvantage– Makes the wiring thick and is difficult to

maintain

Internet Architecture: Cable Types

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OPTICAL FIBER• Uses light rather than voltage to indicate ones and

zeros• Advantages

– High speed transmission– High security– Smallest in size– Supports voice & video data

• Disadvantages– Expensive– Difficult to install– Require two cables to transmit & receive data– Require special connections

Internet Architecture: Cable Types

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COAXIAL CABLE• Copper center shielded by a plastic insulating

material• Advantages

– Transmits up to 10Mbps over 500m– Easy to install– Low maintenance– Good resistance to noise over long distances

• Disadvantages– Inflexible– Low security– Limited distance

Internet Architecture: Cable Types

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WIRELESS TECHNOLOGY• Microwave

– Connect LANs in separate buildings

• Radio waves– No distance limitations– Susceptible to atmospheric and electronic

interference– Subject to government regulations

• Infrared transmissions– Interference from bright light

Internet Architecture: Cable Types

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KEY COMPONENTS OF A NETWORK

• Network Interface Card (NIC)

• Hubs & Switches

• Routers

• Gateways

Internet Architecture: Key Components of a Network

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NETWORK INTERFACE CARD

• Installed in a slot with a cable plugged into the back

• Plugged into a wall jack connection or into the hub/switch directly

• Modem – Converts digital signals into analog form for

transmission and incoming analog signals into digital signal across the telephone line

Internet Architecture: Key Components of a Network

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HUBS & SWITCHES

• Hub– Operates at Physical Layer– Acts as a connecting point– Passive, active, and intelligent hubs

• Switch– Offers direct connection to a particular PC– Available for almost every OSI level

Internet Architecture: Key Components of a Network

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ROUTERS

• Operate at Internet Layer

• Evaluate network traffic and stop local traffic from causing congestion

• Filter out packets that need not be received

• Expensive & difficult to operate

Internet Architecture: Key Components of a Network

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GATEWAYS

• Special-purpose computer allowing communications between dissimilar systems on the network

• Operate at Application Layer primarily

• Difficult to install & configure

• Expensive

Internet Architecture: Key Components of a Network

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FACTORS IN DESIGNING A NETWORK

• Location

• Capacity

• Distance limitations

• Cost

• Potential growth

• Security

Internet Architecture: Factors in Designing a Network

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FACTORS IN SELECTING NETWORK ARCHITECTURE

• Hardware requirements

• Software requirements

• Disaster recovery & fault-tolerance requirements

• Corporate culture and organizational factors

Internet Architecture: Factors in Designing a Network

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NETWORK MANAGEMENT SYSTEM

• Manager

• Managed Nodes

• Objects

• Management Information Base (MIB)

• Requests & responses

Internet Architecture: Network Management System

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Chapter 4

Internet Architecture