Ethernet II Frame:
7 bytes |
1 byte |
6 bytes |
6 bytes |
2 bytes |
64-1500 bytes |
4 bytes |
Preamble |
Start of Frame Delimiter
|
Destination Address
|
Source Address
|
Type |
Data |
FCS
Frame Check Sequence
|
802.3 Frame:
7 bytes |
1 byte |
6 bytes |
6 bytes |
2 bytes |
46-1500 bytes |
4 bytes |
Preamble |
Start of Frame Delimiter
|
Destination Address
|
Source Address
|
Length |
802.3 Header and Data |
FCS
Frame Check Sequence
|
Preamble – Synchronization. They give components in the network
time to detect the presence of a signal and read the signal before the
frame data arrives.
Start of Frame (SOF) – Start of Frame sequence
Destination and Source Addresses – Physical or MAC addresses. The
source address is always a unicast address, the destination address can
be unicast, multicast, broadcast.
Length – Indicates the number of bytes of data that follow this
field.
Type – Specifies the upper layer protocol to receive the data.
Data – User or application data. Ethernet II expects a minimum of
46 bytes of data.
If the 802.3 frame does not have a minimum of 64 bytes, padded bytes
are added to make 64.
Frame Sequence Check (FCS) – CRC value is used to check for
damaged frames. This value is recalculated at the destination network
adapter. If the value is different from what is transmitted, the
receiving network adapter assumes that an error has occurred during
transmission and discards the frame.
Ethernet Cabling:
Type |
10Base5 |
10BaseT |
100BaseFl |
100BaseTX |
100BaseFX |
1000BaseT |
Media |
Thick Coax RG-8,
RG-11 |
UTP Cat 3, 4, 5+ 4 Pair cable,
Uses 2 pair |
62.2/125 micron multi-mode fiber |
UTP Cat 5+ 4 Pair cable,
Uses 2 pair |
62.2/125 micron multi-mode or single
mode fiber |
UTP Cat 5+ 4 Pair cable,
Uses 4 pair
|
Max
Segment
Length |
500
Meters |
100
Meters |
2000
Meters |
100
Meters |
400/2000
Meters (full/half duplex) 10,000 Meters (single mode) |
100
Meters |
Physical
Topology |
Bus |
Star,
Extended Star |
Star |
Star |
Star |
Star |
Logical
Topology |
Bus |
Bus |
Bus |
Bus |
Bus |
Bus |
Transfer
Rate |
10Mbps |
10Mbps |
100Mbps |
100Mbps |
100Mbps |
1000Mbps |
|
|
|
|
|
|
|
EIA/TIA Horizontal Cabling:
(Using CAT5 cabling in an Ethernet
network)
3 Meters – 90 Meters – 6 Meters
3 Meters:
Work area patch cable. From computer to wall
|
90
Meters: What is considered the Horizontal Cabling. From wall
outlet to the patch panel in the MDF or IDF (Server Room). |
6 Meters:
The patch cable that cross connects a patch panel |
Collision Domains - A collision domain is defined as a network
segment that shares bandwidth with all other devices on the same
network segment. When two hosts on the same network segment transmit
at the same time, the resulting digital signals will fragment or
collide, hence the term collision domain. It's important to know
that a collision domain is found only in an Ethernet half-duplex
network
Broadcast Domain - A broadcast domain is defined as all
devices on a network segment that hear broadcasts sent on that segment.
All devices plugged into a hub are in the same collision
domain and the same broadcast domain.
All devices plugged into a switch are in separate collision
domains but the same broadcast domain. Although, you can buy special
hardware to break up broadcast domains in a switch, or use a switch
capable of creating VLANs. VLANs breakup broadcast domains.
Hubs and Repeaters extend collision and broadcast
domains.
Switches, Bridges and Routers break up collision
domains.
Routers (and Switches using VLANs) break up broadcast domains.
Device |
OSI Layer |
Filtering |
Breaks
up Collision Domains |
Extends
Collision Domains |
Breakups
Broadcast Domains |
Extends
Broadcast Domains |
Hubs |
1 |
No |
|
X |
|
X |
Repeaters |
1 |
No |
|
X |
|
X |
Bridges |
2 |
Yes |
X |
|
|
X |
Switches |
2 |
Yes |
X |
|
|
X |
Switches
using VLANs |
2 |
Yes |
X |
|
X |
|
Routers |
3 |
Yes |
X |
|
X |
|
Repeater Rules in 10baseT Networks (802.3 / UTP Cabling) |
(5, 4, 3 Rule)
|
- Between any two points on the network, the maximum number of
Ethernet cable segments, each with a 100-meter diameter, is 5 (five).
- Between any two points on the network, the maximum number of
repeaters is 4 (four).
- Between any two points on the network, only 3 (three) of the
five cable segments can have network devices on them (other than
repeaters), with the other segments serving only as inter-repeater
links.
When counting the number of repeaters, count only the repeaters
between any two points along the path on the network. |
|