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IST 228\Ch1\Internetworking
Collision/Broadcast Domain
• The term collision domain defines the set of
devices for which their frames could collide
• A broadcast domain is a set of NICs for which a
broadcast frame sent by one NIC will be received
by all other NICs in the broadcast domain.
• Hub?
• Bridge?
• Switches?
• Routers?
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IST 228\Ch1\Internetworking
Identify collision and broadcast domains for each case
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IST 228\Ch1\Internetworking
10-Mbps Ethernet
• No hub, switch, or wiring panel. The series of cables
creates an electrical bus
• the carrier sense multiple access collision detect
(CSMA/CD)
• 10Base2: 10Mbps, baseband technology, almost 200
meters
• 10Base5: 10Mbps, baseband technology, almost 5 00
meters
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IST 228\Ch1\Internetworking
Ethernet Networking with a Hub
Half-Duplex 10BaseT
1. The network interface card
(NIC) sends a frame.
2. The NIC loops the sent frame
onto its receive pair.
3. The hub receives the frame.
4. The hub sends the frame
across an internal bus so that
all other NICs can receive the
electrical signal.
5. The hub repeats the signal to
each receive pair to all other
devices.
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IST 228\Ch1\Internetworking
Ethernet Networking with a Switch
Full Duplex Ethernet
• Full-duplex means that an
Ethernet card can send
and receive concurrently.
• Use a switch or direct
connection from host to
using a crossover cable.
• The switch interprets the
electrical signal as an
Ethernet frame and
processes the frame to
make a decision.
• Hub – Layer 1
• Switch – Layer 2
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IST 228\Ch1\Internetworking
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Basic Ethernet Features
10Base2, 10Base5
Single bus cabled serially between devices using coaxial
cable.
10BaseT with a Hub
One electrical bus shared among all devices creating a single
collision domain, cabled in a star topology using twisted-pair
cabling
10BaseT with a Switch
One electrical bus per switch port creating multiple collision
domains, cabled in a star topology using twisted-pair cabling
Half Duplex
Logic that requires a card to only send or receive at a single
point in time. Used to avoid collisions
Full Duplex
Logic that enables concurrent sending and receiving, allowed
when one device is attached to a switch port, ensuring that
no collisions can occur.
IST 228\Ch1\Internetworking
Ethernet Addressing
• Ethernet uses MAC address burned into
each NIC.
• 48 bits (6 bytes)
• First 3 bytes assigned by IEEE
• Unicast MAC Address
• Broadcast MAC Address (FFFF.FFFF.FFFF)
• Multicast Address
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IST 228\Ch1\Internetworking
Ethernet Frames
• Framing defines how
a string of binary
numbers is
interpreted
•
•
•
•
•
•
•
•
Preamble
SD: Start frame eliminator
Destination MAC address
– Unicast
– Broadcast
– Multicast
Source address
Length of file
DSAP SSAP, SNAP (Subnet Network Access Protocol)
Control/Data
Frame Check Sequence (FCS)
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IST 228\Ch1\Internetworking
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Ethernet Cabling
Straight-Through Cable
• Host to Switch or hub
• Router to Switch or hub
Rolled Cable
• Serial Port
Crossover Cable
• Switch to Switch
• Hub to Hub
• Host to Host
IST 228\Ch1\Internetworking
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Data Encapsulation
&@$
Hello!
• Step 1: Data Conversion
Application
hello
Presentation
PDU1 101010011100100100100
PDU2 PDU1 101010011100100100100
Session
PDU3 PDU2 PDU1 101010011100100100100
Name: Data Stream
• Step 2: Data segmentation
Transport
TCP PDU3 PDU2 PDU1
0101010
TCP PDU3 PDU2 PDU1
0100100
:
:
Name: Segment
IST 228\Ch1\Internetworking
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• Step 3: Packet creation for routing
Network
IP
TCP PDU3 PDU2 PDU1
0101010
IP
TCP PDU3 PDU2 PDU1
0100100
:
:
Name: Packet or Datagram
• Step 4: Frame Header
Data Link
LLC 802.2
MAC 802.3
MAC
LLC
IP
TCP PDU3 PDU2 PDU1
0101010
Name: Frame
• Step 5: Transmission
Physical
10010100001
Layer
FCS
IST 228\Ch1\Internetworking
LAN Design Models
• Mesh design
• Hierarchical design
– Three-layer network
model
– Two-layer network
model
– One-layer network
model
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IST 228\Ch1\Internetworking
Three Layer Model
• Core-layer
• Distribution Layer
– a backbone network
connecting all LANs
– no end user at this
level
– implementation of
security and network
policies
• Access Layer
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IST 228\Ch1\Internetworking
Two and One-Layer Model
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