chapter 1: ethernet networking

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?


Identify collision and broadcast domains for each case


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


Ethernet Networking with a HubHalf-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.


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


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.


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


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)


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


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


• 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


LAN Design Models

• Mesh design• Hierarchical design

– Three-layer network model

– Two-layer network model

– One-layer network model


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


Two and One-Layer Model

chapter 1: ethernet networking

Documents

switch hub

hub layer

switch layer

hub host

duplex ethernet

hub crossover cable

layer network model

switch port