IST 201

1
IST 201

• Chapter 8

2
Environments

• Shared- media
• lots of hosts accessing same medium
• common collision domain
• 10Base2
• 10Base5
• 10BaseT using hubs
• Extended Shared-media
• longer cable runs using hubs/repeaters
• extended collision domain
• Point to Point
• Dial up connection
• User to ISP
• No collisions

3
Indirectly Connected Networks

• Circuit-switched
• electrical circuits maintained for length of
  communication
• bandwidth is dedicated point to point connection
• no collisions
• Packet switched
• shared media but logical point to point
  connection

4
Collision Domain Devices

• Layer 2 and Layer 3 devices break up collision
  domains
• Segmentation process of breaking up collision
  domains

5
5-4-3-2-1 Rule

• 5 sections of media
• 4 repeaters/hubs
• 3 sections w/connected hosts
• 2 sections extension purposes only
• 1 collision domain
• Repeater latency
• Propagation delay
• NIC latency

reasons for the 4 repeater rule
6
Late collisions

• Violating 5-4-3 rule
• Collision after 64 bytes of the frame are
  transmitted
• NICs arent programmed to resend after late
  collisions
• Add delay called consumption delay
• Decreases network performance

7
Segmentation

• Breaking up the collision domain into smaller
  segments
• Created by layer 2 devices (layer 3 also)
• Leads to more efficient network
• More bandwidth is available to each host

8
Problem

• If theres too much traffic between segments, the
  switch or bridge can become a bottleneck.

9
Broadcast Radiation

• Bridges switches forward broadcasts and
  multicasts
• Broadcast radiation amount of traffic caused by
  all the bridges/switches on a network forwarding
  broadcasts/multicasts
• Degrades network performance

10
Sources of Broadcasts/Multicasts

• Workstations
• Routers
• Multicast applications

11
ARP-Address Resolution Protocol

• Has IP address of destination host
• Needs MAC address of destination host
• Sends a broadcast to all hosts to get MAC address.

12
Broadcast Domains

• A network segment consisting of a number of
  collision domains
• Routers (Layer 3) divide broadcast domains.
• Routers do not forward broadcasts from one
  network to another.

13
Data Flow Responsibility

• Layer 1 transmission across the medium
• Layer 2 collision domain management
• Layer 3 broadcast domain management

14
Segment

• Section of network bounded by bridges/switches/rou
  ters
• In a bus network the continuous circuit
  connected with repeaters
• PDU _at_ the transport layer