LANs are Subnet Standards
• Only Physical and Data Link Layer standards
• Implemented by the NICs:
Application
Application
Transport
Transport
Internet
Internet
LAN Subnet
(NIC)
LAN Subnet
(NIC)
1
Subnets
8 pin RJ-45 jack
f or 10Base-T
Jumpers to
enable/disable
media
interfaces
BNC connector
for 10Base-2
(thin coax
ethernet)
DB-15
AUI
AUI or transceiver
cable
DB-15 AUI
connector for
10Base-5 (thick
coax ethernet)
DB-15
AUI
Transceiver
thick coax ethernet
GOLDMAN: DATACOMM
FIG. 06-07
2
Ethernet (802.3)
Transmits signal
Detects signal
Carrier Sense Multiple Access
Characteristics
Collision detected
Collision Detection
Description
Access Method
CSMA/CD
Transfer Speed
Standard Ethernet – 10 Mbps
Fast Ethernet – 100 Mbps
Gigabit Ethernet – 1 Gbps (1000 Mbps)
3
Ethernet: CSMA/CD
CSMA/CD process
4
Sample Ethernet Frame
5
Ethernet
Ethernet frame
6
Logical Topology
• Bus logical topology: signals travel from one network device
to all other devices on network
– Broadcast
– Required by bus, star, star-wired physical topologies
7
Bus
• Single cable connects all network nodes without
intervening connectivity devices
• Devices share responsibility for getting data from one
point to another
• Terminators stop signals after reaching end of wire
– Prevent signal bounce
• Inexpensive, not very scalable
• Difficult to troubleshoot, not fault-tolerant
8
Bus
9
Star
A typical star topology network
10
Star
• Any single cable connects only two devices
– Cabling problems affect two nodes at most
• Requires more cabling than ring or bus networks
– More fault-tolerant
• Easily moved, isolated, or interconnected with other
networks
– Scalable
• Supports max of 1024 addressable nodes on logical
network
11
Hybrid: Star-Wired Ring
A star-wired ring topology network
12
Star-Wired Bus
A star-wired bus topology network
13
Network Cables
Twisted-Pair
10BaseT
Unshielded (UTP)
Shielded (STP)
Coaxial
10Base2, 10Base5
ThinNet
ThickNet
Fiber-Optic
14
10Base2 /Thinnet
15
The 5-4-3 Rule
• A thinnet network can combine as many as five cable
segments connected by four repeaters; but only three
segments can have stations attache
– " This is known as the 5-4-3 rule.
• repeaters can be used to join Ethernet segments and
extend the network
16
ThinNet 5-4-3 Rule
17
10Base2 Standard
• Coaxial cable, or thinnet,
which has a maximum
segment length of 185
meters.
• Thinnet cabling components
include:
• BNC barrel connectors.
• BNC T connectors.
• BNC terminators
18
10Base-5 / Thicknet
19
Thicknet 5-4-3 rule
20
10BaseT Standard
• In 1990, the IEEE committee published the 802.3
specification for running Ethernet over twisted-pair
wiring.
– UTP
• Most networks of this type are configured in a star
pattern, but internally they use a bus signalling
system like other Ethernet configurations
21
10BaseT Specifications Summary
22
10BaseFL Standard
• is an Ethernet network that typically uses fiber-optic
cable to connect computers and repeaters.
• The maximum distance 2000 meters (about 6500
feet).
23