Transcript 4 Communication networks

Communication
Networks
Fourth Meeting
Types of Networks

What is a circuit network?


Two people are connected and
allocated
them
their
own
physical path for the duration of
the their connection.
What is packet networks?



Message is broken into many
small pieces
Packets are sent separately.
Each packet has a header,



Contains address
Message data is carried in the
body of the packet.
A message is successfully sent
when all the packets have
arrived at the destination.
12 3
3
1
2
23 1
What is Communication?

Telecommunication
 Communication at a distance,



Normally communication over the telephone network.
Data communication
 Either local or regional
 Joins together data-using equipments
Communication network
 Shared communication network
 Support a wide range of services,

Send e-mails

Transfer and access data files

Static telephony
Mobile telephony
Watch video sequences


Looking Inside a Network

What is a clouds?



The cloud contains detail
that is unnecessary for the
user’s understanding.
The users on both sides of
the cloud communicate with
each other.
How can we communicate
through the cloude

channel is established
across the cloud.
x
International and National Networks

Types of connection



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Why cables?
Why satellite?
International access links,


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Equipment problems or
Environmental interference.
Protection


Located at populated areas
Small number of locations,
Failure


Satellites and
Cables
Moving traffic from a failed path
protection path

the new path is
Capacity of the Network Links

Asymmetric Digital Subscriber Line (ADSL).

Base on Synchronous Digital Hierarchy (SDH),


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SDH

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Is a hierarchy of bit-rates
uses TDM (Time Division Multiplexing) techniques.
Standardized bandwidth (bit-rate) include



155 Mbit/s
2.5 Gbit/s
Connect signals coming in on one link to signals going out on other
links.
TAT-1



155
Mbps
Cross-connect is an SDH switch


Takes blocks of digital data
Organizes them into a signal with a higher bit-rate
so they can be sent together on a line transmission system.
The first trans-Atlantic telephone cable installed in 1956
Carry 36 simultaneous telephone calls.
TAT-12 and TAT-13,


1996,
Carry 60,000 phone calls.
2.5Gbps
Connecting Networks

Local area networks (LANs).

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Network in buildings.
Has a limited range,
Connect other devices

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
Wide area network (WAN)


A network that can connect widely
dispersed computers or LANs
together I
Internet


Printers and
Servers.
A combined network of WANs and
LANs is called an Internet.
Router



A devices connect a LAN to a WAN,
Route packets across wide area
network.
Convert data between LAN and WAN
protocols.
IP network architecture

IP networks


POP (Point of Presence)
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Universal Internet addressing scheme
Access point to a LAN that access to the internet
Internet service provider (ISP)


AS
sub-networks that use the Internet which uses the
Internet protocol (IP) .
The gateway to the Internet from home
Autonomous System (AS)

Contains of many nodes,

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AS
interior gateway protocol (IGP).
Exterior gateway protocol (EGP)



Routers
Links
Routes between autonomous systems
Example: Border gateway protocol (BGP)
Backbones

join together the nodes of autonomous systems.
Router
IP network architecture
Shamel
AS2
Routing Table
W
to
from
A
B
D
A
B
C
E
F
D
W
-
A
B
B
A
A
A
B
-
B
B
A
A
A
A
F
B
5
AS1
9
C
B
E (?)
-
C
E
E
E
E
B
E
E
-
B
B
B
C
1
E
wafi
Router
Ethernet architecture

Initially

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
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Today,

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10 Mbps
Thick co-axial cable
Connected to a bus configuration.
1 Gbps
Connected to a star configuration.
Use twisted pair cable
Topologies

Star topology



Use a hub (repeater)
Bus
Hub



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Regenerate (bit-by-bit) each packet received
Send data to every other computer.
Most hubs can accept a maximum of 24 connections
Can be extended by connecting two or more hubs together.
Collision Domain


Broadcast.
 Easy protocol to implement to send to
every PC
 Generates a lot of traffic
 Collision domain.
Bridge
 Avoid spread data across a network
 Directs traffic intelligently using destination
address in the packet’s header
 Has forwarding table



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Analyze source address in each packet it
receives,
Record which port the packet arrived on.
Create a list of addresses of all the
computers on the lan, and
For each address, indicate which port will
reach that computer.
Bridge
Network Interface Card


States
 Transmitting,
 Receiving, or
 Cycling its state between transmission
and reception.
Collision
 NIC detects signals simultaneously at
its receives and transmit interfaces
 The station closest detects the collision
 transmits a 32-bit jam message onto
the channel.
 NIC Waits a period of silence (9.6 μs
according to IEEE 802.3 standard)
 Start transmitting
Transmitting
Wait
Yes
No
Collision
Transmit
jam message