IST 228\Ch1\Internetworking 1
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?
IST 228\Ch1\Internetworking 3
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
IST 228\Ch1\Internetworking 4
Ethernet Networking with a HubHalf-Duplex 10BaseT
3. The network interface card (NIC) sends a frame.
4. The NIC loops the sent frame onto its receive pair.
5. The hub receives the frame.6. The hub sends the frame
across an internal bus so that all other NICs can receive the electrical signal.
7. The hub repeats the signal to each receive pair to all other devices.
IST 228\Ch1\Internetworking 5
Ethernet Networking with a SwitchFull 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
IST 228\Ch1\Internetworking 6
Basic Ethernet Features
Logic that enables concurrent sending and receiving, allowed when one device is attached to a switch port, ensuring that no collisions can occur.
Full Duplex
Logic that requires a card to only send or receive at a single point in time. Used to avoid collisions
Half Duplex
One electrical bus per switch port creating multiple collision domains, cabled in a star topology using twisted-pair cabling
10BaseT with a Switch
One electrical bus shared among all devices creating a single collision domain, cabled in a star topology using twisted-pair cabling
10BaseT with a Hub
Single bus cabled serially between devices using coaxial cable.
10Base2, 10Base5
IST 228\Ch1\Internetworking 7
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
IST 228\Ch1\Internetworking 8
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)
IST 228\Ch1\Internetworking 9
Ethernet CablingStraight-Through Cable• Host to Switch or hub• Router to Switch or hub
Crossover Cable• Switch to Switch • Hub to Hub • Host to Host
Rolled Cable• Serial Port
IST 228\Ch1\Internetworking 10
Data Encapsulation
• Step 1: Data Conversion
• Step 2: Data segmentation
Hello! &@$
Application
Presentation
Session
hello 101010011100100100100PDU1
101010011100100100100PDU1PDU2
101010011100100100100PDU1PDU2PDU3
Transport
Name: Data Stream
0101010
0100100PDU1PDU2PDU3
PDU1PDU2PDU3TCP
TCP
: : Name: Segment
IST 228\Ch1\Internetworking 11
• Step 3: Packet creation for routing
• Step 4: Frame Header
• Step 5: Transmission10010100001
Network
Name: Packet or Datagram
0101010
0100100PDU1PDU2PDU3
PDU1PDU2PDU3TCP
TCP
: :
Name: Frame
IP
IP
Data Link
0101010PDU1PDU2PDU3TCPIPLLCMAC
LLC 802.2
MAC 802.3 FCS
Physical Layer
IST 228\Ch1\Internetworking 12
LAN Design Models
• Mesh design• Hierarchical design
– Three-layer network model
– Two-layer network model
– One-layer network model
IST 228\Ch1\Internetworking 13
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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