S7C2 – Legacy Ethernet

From the Old to the New

Legacy Ethernet Characteristics

• CSMA/CD

• Shared Bandwidth

• 10 Mbps

• Common Broadcast

• Physical Star Topology; logical bus

Broadcasts

• Ethernet characteristic

• Routers use to announce routing tables

• ARP request

To Increase Bandwidth

• Upgrade the user to 10BASE-T full duplex and immediately double the bandwidth.

• Upgrade the user to 100BASE-X half duplex.

• Upgrade the user to 100BASE-X full duplex

Frame Transmission

• Unicast– One source to one destination

• Multicast– Single data stream from one source to multiple

clients• Saves bandwidth and controls network traffic

• Broadcast– Single data stream to all hosts on the subnet

Multicast

• Cisco has a special multicast address reserved, 01-00-0C-CC-CC-CC, which enables Cisco devices to transmit to all other Cisco devices on the segment.

• The reserved multicast OSPF IP addresses 224.0.0.5 and 224.0.0.6 translates to MAC multicast addresses of 01-00-5E-00-00-05 and 01-00-5E-00-00-06.

LAN FRAMES

• Layer 2 Header – 14 octets– MAC DA 6 octets– MAC SA 6 octets– Type (Ev2) or length (802.3/802.2) 2 octets

• Layer 2 Data field – 1500 octets– V2 and 802.3 data– 802.2 DSAP, SSAP, Control, Data

Duplex• Half-Duplex

– Transmit and Receive wires– Relies on Collision Detection

• Full-Duplex– No loopback– No collision detection– Full duplex ethernet controller

• Transmit circuit connects directly to receive circuit• No collisions• Significant performance improvement (almost 100%)• Eliminates contention for line• Uses single port for each full-duplex connection

Media Comparisons

Standard CabType Mode Pairs Dis-Met

10B-T 3,4,5 Half 2 100

100B-TX 5 H &F 2 100

100B-T4 3 H 4 100

100B-T2 3,4,5 H and F 2 100

100B-FX Multi

Single

H and F 1 412(H) 2000(F)

10 KM