Sripatum University

SPU

Information Science Institute of Sripatum University

Sripatum University1

IS516

Computer Communication and Networks

การสื่��อสื่ารคอมพิ�วเตอร�และเคร�อข่�าย

Asst.Dr.Surasak Mungsing

[email protected] [email protected]

http://www.spu.ac.th/teacher/surasak.mu

2

Lecture 05: Guided Networks

3

LAN

SPU


4

Line Configuration

Computers are connected for data communication through transmission Medium, which may be either Guided Media or Unguided Media

Two types of connection configuration, point-to-point and multipoint

SPU


5

Point-to-Point Line Configuration A pair of computers or network devices have specific

connection points for connecting only those pairs of computers or devices

Communication capacity dedicated to the two connected computers or devices

Transmission media may be either guided or unguided medium

SPU


6

Multipoint Line Configuration

Use common medium for two or more computers and devices

SPU


7

Topology

Connection structure of computer network(computers or network devices)

Five types of topology: Mesh, Star, Tree, Bus and Ring

SPU


8

Mesh Topology All nodes are directly connected (linked) to

other nodes in the network Number of connection lines n(n-1) / 2

where n is number of computers in the network

Each node must have (n-1) I/O ports

SPU


9

Mesh Topology

Advantages: - better transmission rate and system

reliability - easy to detect errors - better security and privacy Disadvantages: - many connection point and I/O ports

required e.g. 100 nodes requires 4950

connection lines

SPU


10

Star Topology• Each node directly connects to the center device, called

“hup” , which a node must send data to other nodes through the hub

• Saves a lot of connection lines in comparison with mesh topology

• In star topology, as well as the mesh, if a line fails only the two connected nodes fails to communicate. But if the hub fails the whole network fails to work.

SPU


11

Tree Topology Based on star from star topology, in such a way that

each node connects to a hub, either active hub or passive hub

The center of the network structure is an active hub and repeaters are used to extend signal distance

Passive Hub is directly connected to nodes Longer distance network than star topology

SPU


12

Bus Topology Bus is Multipoint connection, but the previous

(Mesh, Star, and Tree) are point-to-point connection All node are connected to a cable, which acts as a

backbone for the network, so that all nodes can communicates to each other through this cable

SPU


13

Bus Topology Use less connection lines and connection ports

than Mesh, Star, and Tree Cable Terminators required at the two ends and all

nodes in the network tap to the cable Disadvantage: - if the cable fails, then the network fails

- Adding new node is more difficult than Mesh,Star,

and Tree topologies - low data transmission rate due to sharing

of a common cable

SPU


14

Ring Topology• Is a - - point to point connection between two nodes (a

node and its predecessor node) • Communication between nodes takes place from one

node to another in one direction until the intended received is reached while each node in the ring acts as a repeater to relay data to the next node

SPU


15

Ring Topology

Easy to install and change, e.g. adding a node only requires two connections

Requires longer time for sending data from a node to another due the moving is in one direction, in particular when there are many nodes in the ring

SPU


16

Hybrid Topology Connection in a network may be a

hybrid of more than one topology

SPU


17

802IEEE LAN The Institute of Electrical and Electronics

Engineers or IEEE (read eye-triple-ee) is an international non-profit, professional organization for the advancement of technology related to electricity. It has the most members of any technical professional organization in the world, with more than 395,000 members in around 150 countries

The services and protocols specified in IEEE 802 map to the lower two layers (Data Link and Physical) of the seven-layer OSI networking reference model

IEEE 802 describes CSMA/CD (Carrier Sense Multiple Access with Collision Detection), (Token Bus) and Token Ring LAN, which are different in Physical and MACsublayer

SPU


18

IEEE 802

SPU


19

Project 802

SPU


20

802 .3 Ethernet (1)

8023IEEE . began from 100-nodes set up at Xerox that can send data as far as 1 km. at the rate of 2.94 Mbps, called Ethernet

Follows by cooperation of Xerox, DEC and In tel in developing Ethernet standard that can

operate at the rate of 10Mbps, the IEEE 802.3

SPU


21

802 .3 Ethernet (2) The 8023. describes LANs that use the

principle of CSMA/CD (Carrier Sense Multiple Access with Collision Detection), which

operates at the data rate of 1 ถึ�ง 100 Mb ps and on variety of transmission media

8023IEEE . and Ethernet have some different information in the 8Header (IEEE

023. field length is used to identify type of Packet in the Ethernet standard )Therefore 8023IEEE . describes LANthat use CSMA/CD but Ethernet means a product of 8023IEEE . LAN

SPU


22

802 .3 Ethernet (3) วิ�ธีการร บส่�งข้�อมู�ลข้องแลน IEEE 802.3 ซึ่��งเป็�นแบบ

CSMA/CD ก�ทำ างานในล กษณะเดียวิก น คื(อโหนดีใดีทำ�ต้�องการส่�งข้�อมู�ลลงในส่(�อกลางการส่�งข้�อมู�ล จะต้รวิจส่อบดี�ส่ ญญาณในส่(�อกลาง ถึ�าหากส่(�อกลางในการส่�งข้�อมู�ลวิ�างก�จะทำ าการส่�งข้�อมู�ลไดี�ทำ นทำ แต้�หากโนดีต้ /งแต้� 2 โนดีข้�/นไป็ส่�งข้�อมู�ลลงไป็ในส่(�อกลางพร�อมูๆก น ส่ ญญาณข้�อมู�ลจะเก�ดีการชนก นข้�/น ทำ3กๆส่ถึานจะต้�องหย3ดีการส่�งข้�อมู�ลแล�วิรอเวิลา ซึ่��งช�วิงเวิลาข้องการรอแต้�ละคืร /งจะทำ าการส่3�มูข้�/นมูา (Random Time) หล งจากหมูดีเวิลารอแล�วิก�จะทำ าการต้รวิจส่อบส่ ญญาณในส่(�อกลางเพ(�อส่�งข้�อมู�ลลงไป็ใหมู�อก

SPU


23

Collision Detection (1)

เมู(�อเก�ดีการชนก นข้องส่ ญญาณข้�อมู�ลแล�วิ เวิลาจะถึ�กแบ�งออกเป็�นช�องๆ (slots) แต้�ละช�องมูช�วิงเวิลา 512.ไมโครว�นาที� (น �นคื(อเวิลาส่ถึานทำ�ส่�งข้�อมู�ลร� �วิ�าเก�ดีการชนก นข้องข้�อมู�ลหร(อไมู� ส่ าหร บคืวิามูยาวิข้องแลน

2500 เมูต้ร อ ต้ราการส่�งข้�อมู�ล 10Mbps)หล งจากการชนก นคืร /งแรก แต้�ละส่ถึานจะส่ร�างต้ วิเลข้ส่3�มู

(Random) ทำ�มูคื�า 0 หร(อ 1 (เลข้ส่3�มู 2 ^1 คื�า ) ส่ถึานทำ�ไดี�คื�า 0 จะส่�งข้�อมู�ลออกไป็ในช�องเวิลา 0 และ

ส่ถึานทำ�ไดี�คื�า 1 จะส่�งข้�อมู�ลในช�องเวิลาทำ� 1 หากส่องส่ถึานไดี�คื�าเลข้ส่3�มูเดียวิก นและส่�งข้�อมู�ลภายในช�องเวิลาเดียวิก น จะเก�ดีการชนก นอกคืร /ง

SPU


24

Collision Detection (2)

หล งจากการชนก�นคร��งที�� 2 แต้�ละส่ถึานจะสื่ร!างต�วเลข่สื่"�มที��ม�ค�า 012 หร�อ (3 น��นค�อเลข่สื่"�ม 2 ^ 2ค�า) แล�วิส่�งข้�อมู�ลภายในช�องเวิลาข้องต้นเอง หากชนก นอกก�จะส่ร�างเลข้ส่3�มูจ านวิน 2 ^ 3 คื�า กล�าวิคื(อหล งจากการชนก น i คืร /ง แต้�ละส่ถึานก�จะมูการส่ร�างเลข้ส่3�มูต้ /งแต้�คื�า 0 ถึ�ง 2 ^ - i 1 คื�า และส่ถึานก�จะส่�งข้�อมู�ลภายในช�องเวิลาข้องต้นเอง กระบวินการในการแก�ไข้การชนก นข้องข้�อมู�ลแบบน/เรยกวิ�า Bi nary Exponenti al

Back off ซึ่��งจะเห�นไดี�วิ�ากระบวินการน/ทำ าให�โอกาส่ในการทำ�จะเก�ดีการชนก นข้องข้�อมู�ลมูน�อยลง เมู(�อจ านวินคืร /งข้องการชนก นข้องข้�อมู�ลมูากข้�/น

SPU


25

SPU


26

SPU


27

Type Cable Length of

Segment

Number of

nodes per

Segment

Advantage

10Base5

Thick Coaxial

500 meter

s

100 Use as Backbone

10Base2

Thick Coaxial

200 meter

s

30 Least expensive

10BaseT

Twisted Pair

100 meter

s

1,024 Easy to maintain

10BaseF

Fiber Optic

2,000 meter

s

1,024 Connection between buildings

Cable for IEEE802.3 LAN

SPU


28

Figure 12-9-continued

10BASE5

SPU


29

Ethernet Segments

SPU


30

10BASE2

SPU


31

10BASET

SPU


32

Fast Ethernet High speed demand due to multimedia

applications IIII decided to improve 802.3 standard to

803.2u, called Fast Ethernet Fast Ethernet operates at the speed of

100Mbps, with no change in frame structure and collision detection and control but reduce time of transmission of each bit from 100 nanoseconds to 10 nanoseconds to obtain 10 time faster

SPU


33

Gigabit Ethernet

Gigabit Ethernet operates at the speed of 1000 Mbps or 1 Gbps by improving data encoding and data transmission technique and using Fiber Optic media instead of Twisted Pairs

SPU


34

8024 LAN Token Bus is 8024 standard, which

cannot guarantee whether a node can send data at the time it wants

Physical topology is Bus but operation is logical ring

Each node knows the addresses of node on its left and node on its right

SPU


35

8024IEEE . LAN When ring is established, a token will be

send from one node to another in the same direction

The node that wants to send data will have to wait for the token with available flag to have the right to send data therefore there will be only one sender at a time

SPU


36

802IEEE .5 LAN Each node in 8025IEEE . LAN or Token

Ring LAN connects to the ring (which is different from Ethernet and Token Bus)

Signals move in one direction from sender passing other nodes to the receiver

SPU


37

A สื่�งข่!อม%ล ถึ'ง C

Token Ring

SPU


38

39

WAN

SPU


40

Wide Area Networks Relation between hosts on LANs and the subnet.

SPU


41

Switching Techniques Circuit switching Packet switching

SPU


42

Circuit Switching Characteristics Channel capacity dedicates to the sender and

receiver, even through there is no data sending

Once communication line connected, users feel like they have direct connection with no more delays

Was developed for voice communication, but now also used for data communication

SPU


43

Circuit Switching Applications Public Telephone Network (PSTN)

Private Branch Exchanges (PBX)

Private Wide Area Networks (often used to interconnect PBXs in a single organization)

Data Switch

SPU


44

Traditional Circuit Switching Illustration

SPU


45

Packet-Switching Networks Developed in 1970s for long distance data

communication due to the limitations of circuit switching

During communication with circuit-switching, data traffic on the transmission line is rather light, so inefficiently use of data transmission line

sender and receiver must communicate at the same data rate

SPU


46

Packet Switching Operation Data are arranged into small pieces called

packets, which can be sent to the destination in different routes

Advantage: more efficiently use of transmission line, signals can be transmitted on different line, and priority can be arranged

Disadvantage: delays of data at nodes, each data packets arrive at different time (jitter), and all packets have extra information, e.g. addresses

SPU


47

Packet Switching Illustration

SPU


48

Integrated network access using dedicated channels

SPU


49

Integrated network access using public switched WAN

SPU


50

X.25 The first public data network developed in

1970s

Is connection-oriented network

Support switched virtual circuit and permanent virtual circuitมู similar to Leased Line

Replaced by newer network, the Frame Relay, in 1980s

How to use X.25 networkFirst establish connection between sender and receiver by dial telephone number: connection number for data communicationEach data packet consists of 3-byte header and not more than 128 bytes of dataHeader consists of 12-bit connection number, packet sequence number, acknowledgement number and 2-3 bits for other

SPU


51

Frame Relay

Designed to reduce overhead of X.25

Use simple protocol with no flow control and error control between point-to-point communication

Use “permanent virtual circuit” (like virtual leased line) between points of communication

Packet size of 1,600 bytes

Data rate of 1.5 Mbps, which is 23 times faster than that of X.25

SPU


52

Frame Relay protocol vs. X.25 protocol

Reliability Frame relay looses capability in flow control and error

control and error control for point-to-point communication

X.25 has connection protocol for reliability point-to-point communication

No advantage on this point due to more reliability of transmission and switching devices

Streamlining Frame relay reduce user interface connection protocols

requirements and processing requirements within network

Better throughput than that of X.25, at least an order of magnitude

SPU


53

Asynchronous Transfer Mode (ATM)

Technology used in B-ISDN network , called cell relay

faster than X.25

Sending data continuously faster than frame relay in many order of magnitude

Packets are small, called “cell”

Cell size is 53 bytes (5 byte for header and 48 bytes for data)

No link-by-link error control or flow control

SPU


54

ATM Cell

Format

SPU


55

ATM Virtual Circuits

SPU


56

Cell-switching vs Circuit switching Cell-switching is more flexible and effective

for services with both data of almost constant size, e.g. multimedia data, and variable data such as data from database

Data transmission at rate of Gbps, using Cell-switching technique, which more efficient than using multiplexor ร( Circuit- switching, especially on fiber cable

Cell-switching supports information broadcasting, such as television broadcasting, while circuit- switching does not directly support

SPU


57

Next Lecture:Next Lecture:

Switching and routing

Documents

Sripatum University