Lecture 1 Networking Concepts

7/28/2019 Lecture 1 Networking Concepts

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Networking Concepts

Lecture 1

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LAN

Concepts

Attenuation, Noise

Hardware

Repeater, Amplifier Bridge, Router, Gateway, Switch, Hub

Twisted pair, Coaxial cable, Fiber optics

Server, Workstation

Wireless access point

Topology Bus, Tree, Star, Ring

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LAN

Standard

OSI (Open Systems Interconnection)

IEEE (Institute of Electrical and Electronic Engineers)

ITU-T (Intl Telephone Union Telecom. Sector)

ISO (International Standards Organization)

EIA (Electronic Industries Association)

ETS (European Telecom. Standard)

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Communications Hardware

Repeater

Extends distance limitation on networks (both voice and data)

Filters noise

Regenerates signals

For twisted pair wire, repeaters are placed every 100 meters Amplifier

Extends distance limitation on networks (both voice and data)

Amplifies both signal and noise

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Bridge

Connects two LANs using same protocol

Single path between LANs

Minimal sophistication Router

Connects multiple LANs using same protocol

Choice of paths between LANs

Mainstay of internetworking

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Gateway

Connects multiple LANs using any protocol

Very sophisticated

Supports todays internet by providing access points to severalnetworks

Hub

Connects nodes to a network

Sometimes acts as repeater

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Switch

Connects multiple LAN segments using the same protocol

Connections may use twisted pair, coaxial cable, or fiber optics

wiring Faster than bridges

Enables simultaneous communication between multiple network

segments

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Ethernet

Ethernet was developed jointly by Xerox, Intel, and DEC in 1980

DEC (Digital Equipment Corporation) a computer company thatspecialized in mini-computers in the 1970s. It was acquired byCompaq and Compaq merged with HP.

This was the first commercial LAN system

Ethernet is a simple protocol to implement

Ethernet addresses the layers 1 and 2 functionality for the OSI model Ethernet standard is very close to IEEE 802.3 standard, but has some

minor differences

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Ethernet

Ethernet uses bus topology (which we will discuss next)

Ethernet transmits a baseband signal at 10 Mbps Baseband signals are digital and bidirectional

Ethernet allows the user data to have a variable length up to 1500 bytes

Unlike HDLC(High Level Data Link Control) and SDLC(Synchronous Data Link Control) protocols, Ethernet uses a length

field in the header to identify the length of the user data in bytes.Because of this, no special bit pattern is needed to recognize the startand end of the user data.

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Ethernet frame format

6-bytes 6-bytes 2-bytes Variable length 4-bytes

Destination

address

Source

address

length User data CRC-32

CyclicRedundancy

Check

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Ethernet diagram

PC1

PC2

PC3

Segment 1

Repeater

PC-B

PC-A

PC-C

Segment 2

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Bus topology

It is a contention-based topology, which means that each node on thenetwork must contend for access

Each node listens to traffic on the network

When a node has packets to transfer and the bus is not busy, then the

packets are put on the bus in both directions, with the destination

address marked on the packets All nodes listen to traffic on the network and the node that has packets

addressed to it, receives the packets

No routing or switching is involved in data transfer

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Bus topology diagram

PC1 PC3PC2 PC4

Tap for a new node

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Tree topology

Tree topology is a variation on bus topology

A special node is designated as root

The primary reason for this topology is to segment nodes so that not allnodes need to listen to packets broadcast on a segment

This adds a layer of security in the form of unwanted nodes notlistening to the network traffic

Speeds up data transfer since there will be fewer nodes on eachsegment

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Tree topology diagram

Root

PC 1 PC 2

PC 3

PC 4PC 5

PC 6

PC 7

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Star topology

This is another variation on bus topology

This has a central hub, a passive device

Star is a logical bus and a physical ring

Hub has ports in multiples of 8. Multiple hubs can be connected in adaisy chain format

Easy to add nodes to the network and remove nodes from the network

Central node does switching between nodes

Multiple nodes can communicate simultaneously without collision

Potential problem is the single point of failure for the network whenthe central node fails

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Star topology diagram

HubPC 1 PC 5

PC 3

PC 7

PC 4PC 2

PC 8PC 6

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Ring topology

The nodes are connected in a ring pattern

Unlike bus topology, each node on the ring acts as a repeater on thenetwork

Nodes access the network using a token, which eliminates the need forcontention as in bus topology

Token is a series of bits that identifies the node that has the right to

transmit at any given time

Example of a token: Assume that there are 6 nodes on the network.The nodes are labeled 1 through 6 and the token would consist of 3

bits. The token 100 will indicate that node 4 has the token.

Tokens circulate in a single direction from a node to its neighbor

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Ring topology diagram

PC 1

PC 2

PC 3

PC 4

PC 5

PC 6

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OSI 7-layer model

Source Destination

Application

Presentation

Session

Transport

Network

Data link

Physical

Application

Presentation

Session

Transport

Network

Data link

Physical

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IEEE 802

802.1 General LAN management of OSI

layers 3 through 7

802.2 LLC sublayer(Logical Link Control)

802.3 Ethernet

802.4 Token bus

802.5 Token ring

802.6 MAN

802.7 Broadband, in general

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IEEE 802

802.10 Network Security

802.11 Wireless LAN

802.12 100VG-AnyLAN (Voice Grade)

802.13 unused

802.14 Cable Modem

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WAN

Concepts

Gateway, Frame Relay, ATM, DSL, T1, T3, STS (Synchronous

Transport Signal)

Standard TCP/IP (Transmission Control Protocol /Internet Protocol)

IETF (Internet Engineering Task Force)

ATM Forum (Asynchronous Transfer Mode)

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STS, STM, OC equivalencies

STS level STM level OC level Data Rate

STS-1 -- OC-1 52 Mbps

STS-3 STM-1 OC-3 155 Mbps




STS-24 STM-8 OC-24 1.2 Gbps



Synchronized Transfer Signal

Synchronized Transfer Mode Level-1Optical Carrier

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ATM VPI and VCI

VPI 1 VPI 5

VPI 3

VC I 1

VC I 2

VC I 1

VC I 2

VPI 3

VPI 2VC I 2

VC I 6

VCI 2

VCI 6

VCI 4

VCI 7

VCI 7

VCI 4

VP Switch

VPI 6

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TCP/IP functions

Establish a connection between nodes Manage data flow on the network

Handle transmission errors

Terminate connection at the end

TCP is a connection-oriented protocol, meaning that a packet sent to

the next node is monitored for proper receipt

IP is a connection-less protocol, meaning that a packet sent to the nextnode is not monitored for proper delivery

Since TCP and IP work together, the packet delivery is reliable

Connection-less mode is known as User Datagram Protocol (UDP)

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TCP/IP 5-layer model

TCP/IP protocol is divided into 5 layers

Application layer

Transport layer

Network layer

Data link layer Physical layer

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IP Addressing

IP address consists of 4 octets: n.n.n.n where n is in the range 0 to 255

This form of IP address is known as IPv4, denoting IP address Version

4

A new form of IP address known as IPv6, denoting IP address Version

6, has been proposed. It uses 128-bit addressing instead of 32-bit

addressing.

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IP Address Hierarchy

There are 3 main classes of IP addresses in use and two additionalclasses of IP addresses available for multicast and testing

Class A First octet range: 1126

IBM, AT&T, HP, Merck, Stanford University

Class B First octet range: 128191

U of L and most other universities Class C First octet range: 192223

IGLOU, Louisvilles first ISP

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UDP

User Datagram Protocol is a best effort protocol best effort means no guarantee of delivery

This is a connection-less protocol

UDP does not provide reliability

UDP sends out packets without first establishing a connection

RFC 768 describes UDP UDP header consists of source port, destination port, length, checksum

Example of UDP: TFTP (Trivial File Transfer Protocol). TFTP is usedwhen bootsrapping diskless system

TFTP is on UDP port 69

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Documents

Lecture 1 Networking Concepts