2. Most LAN Technologies use a shared medium
for all computers to transfer data.
The shared medium provides universal
communication between all computers in the
LAN.
◦ Q: How a single pair of computers communicate
across a LAN without other computers receive a
cope of the message?
◦ A: Using hardware addressing.
3. Most LAN technologies use an addressing
scheme to provide direct communication
between any two hosts.
Each computer is assigned a unique value
called a “Hardware address”, “Physical
address” or “MAC address”.
Any message sent across the LAN contains
two addresses, the address of the sending
computer (source) and the address of the
intended recipient (destination).
5. من الفيزيائي العنوان يتكون48وهناك غالبا بت3طرقلتحديده:
.1Static:وهوعنوانفيزيائيثابتمخزنداخلكارتالشبكةواليمكنتغييره
إالبتغييركارتالشبكةنفسة.
.2Configurable:فيهذاالنوعيستطيعمستخدمالحاسبتعيينالعنوان
الفيزيائيبنفسهبطريقةيدويةأوبطريقةالكترونيةعنطريقبرمجة
EPROM.
.3Dynamic:وهيطريقةتعطيكلحاسبعنوانفيزيائيعندبدايةإقالع
الحاسب.
ملحوظةهامة:شكلوطولالعنوانالفيزيائييختلفباختالفتكنولوجياالتصنيع
ونوعالشبكة.أيأنهاليمكنفهمهوقبولهفيكلالشبكات.
For Example: Ethernet uses one form of addressing
while FDDI uses another.
6. Static Addressing:
◦ Advantages:
1. Easy to use
2. NIC cards from different manufacturers can be
used in a single network without address
conflicts.
3. Permanent (does not change each time the
computer is rebooted)
7. Dynamic Addressing:
◦ Advantages:
1. No need for the hardware manufacturers to
coordinate addresses.
2. Addresses will be small, as each address has to be
unique in a single LAN.
◦ Disadvantages:
1. Address conflict may happen as two computers
may choose the same address.
2. Each time a computer boots, it obtains a new
address; other computers must learn the new
address before they can communicate.
8. Configurable Addressing:
Configurable addressing provide a compromise
between the static and dynamic schemes.
◦ Like static addresses, configurable addresses are
permanent.
◦ Like dynamic addresses, configurable addresses
do not need to be large because the address is
unique only on one network.
◦ When a NIC fails and must be replaced, a
configurable NIC can be replaced without
changing the physical address of the computer.
9. Computer networks do not transfer the message data
continuously, the network system divides data into small
blocks called PACKETS.
The term “FRAME” is used to denote the definition of a
packet used with a specific type of network.
Each LAN technology define a frame format.
Most technologies have frames that each consist of a header
followed by a data area.
Frame
Header
Frame Data Area
11. Ethernet and Wi-Fi are both “multi-access”
technologies
Broadcast medium, shared by many hosts
Simultaneous transmissions will result in collisions
Media Access Control (MAC) protocol required
Rules on how to share medium
LAN Technologies
12. CSMA/CD (carrier sense multiple access with collision
detection) media access protocol is used.
Data is transmitted in the form of packets.
Sense channel prior to actual packet transmission.
Transmit packet only if channel is sensed idle; else,
delay the transmission until channel becomes idle.
After packet transmission is started, the source
monitors its own transmission to see if the packet has
experienced a collision.
If the packet is observed to be undergoing a collision,
the transmission is aborted (stopped) and the packet
is retransmitted after a random interval of time.
LAN Technologies
13. End nodes are identified by their Ethernet
Addresses (MAC Address or Hardware Address)
which is a unique 6 Byte address.
MAC Address is represented in Hexa Decimal
format e.g (00:05:5D:FE:10:0A)
The first 3 bytes identify a vendor (also called
prefix) and the last 3 bytes are unique for every
host or device
LAN Technologies
14. Preamble:
7 bytes with pattern 10101010 followed by one byte
with pattern 10101011
Used to synchronize receiver, sender clock rates
Addresses: 6 bytes, frame is received by all adapters on a
LAN and dropped if address does not match
Length: 2 bytes, length of Data field
CRC: 4 bytes, checked at receiver, if error is detected,
the frame is simply dropped
Data Payload: Maximum 1500 bytes, minimum 46 bytes
If data is less than 46 bytes, pad with zeros to 46 bytes
LAN Technologies
Length
15. 10 Base 5 (Thicknet) (Bus Topology)
10 Base 2 (Thinnet) (Bus Topology)
10 Base T (UTP) (Star/Tree Topology)
10 Base FL (Fiber) (Star/Tree Topology)
LAN Technologies
18. Physical Media :-
10 Base5 - Thick Co-axial Cable with Bus Topology
10 Base2 - Thin Co-axial Cable with Bus Topology
10 BaseT - UTP Cat 3/5 with Tree Topology
10 BaseFL - Multimode/Singlemode Fiber with Tree
Topology
Maximum Segment Length
10 Base5 - 500 m with at most 4 repeaters (Use Bridge to extend
the network)
10 Base2 - 185 m with at most 4 repeaters (Use Bridge to extend
the network)
10 BaseT - 100 m with at most 4 hubs (Use Switch to extend the
network)
LAN Technologies
19. 100 Mbps bandwidth
Uses same CSMA/CD media access protocol and packet
format as in Ethernet.
100BaseTX (UTP) and 100BaseFX (Fiber) standards
Physical media :-
100 BaseTX - UTP Cat 5e
100 BaseFX - Multimode / Singlemode Fiber
Full Duplex/Half Duplex operations.
LAN Technologies
20. Auto-Negotiation of media speed is provided:
10 Mbps or 100Mbps .
Maximum Segment Length
100 Base TX - 100 m
100 Base FX - 2 Km (Multimode Fiber)
100 Base FX - 20 km (Singlemode Fiber)
LAN Technologies
21. 1 Gbps bandwidth.
Uses same CSMA/CD media access protocol as in Ethernet
and is backward compatible (10/100 modules are
available).
1000BaseT (UTP), 1000BaseSX (Multimode Fiber) and
1000BaseLX (Multimode/Singlemode Fiber) standards,
1000BaseLH (Singlemode Fiber).
Maximum Segment Length
1000 Base T - 100m (Cat 5e/6)
1000 Base SX - 275 m (Multimode Fiber)
1000 Base LX - 512 m (Multimode Fiber)
1000 Base LX - 20 Km (Singlemode Fiber)
1000 Base LH - 80 Km (Singlemode Fiber)
LAN Technologies
22. 10 Gbps bandwidth.
Uses same CSMA/CD media access protocol as in
Ethernet.
Maximum Segment Length
1000 Base-T - Not available
10GBase-LR - 10 Km (Singlemode Fiber)
10GBase-ER - 40 Km (Singlemode Fiber)
LAN Technologies
23. Provides network connectivity over wireless media
An Access Point (AP) is installed to act as Bridge between
Wireless and Wired Network
The AP is connected to wired network and has an
antennae to provide wireless connectivity
LAN Technologies
Network
connectivity to
the legacy
wired LAN
Desktop
with PCI 802.11 LAN card
Laptop
with PCMCIA 802.11 LAN card
Access Point
24. Range ( Distance between Access Point and WLAN client)
depends on structural hindrances and power of the
antenna at the Access Point
To service larger areas, multiple APs may be installed with
a 20-30% overlap
A client is always associated with one AP and when the
client moves closer to another AP, it associates with the
new AP.
LAN Technologies
25. Before every data transmission
Sender sends a Request to Send (RTS) frame containing
the length of the transmission
Receiver respond with a Clear to Send (CTS) frame
Sender sends data
Receiver sends an ACK; now another sender can send data
When sender doesn’t get a CTS back, it assumes collision
LAN Technologies
sender receiver
other node in
sender’s range
RTS
CTS
ACK
data
other node in
receiver’s range
