Make your own free website on Tripod.com
BACK

OSI Layer 2 Protocols 



Ethernet

Ethernet frame (read right to left)

FSC Data Type Source  Destination  SOF Preamble
Frame Check Sequence Data to be handed to the upper layer protocol Defines which upper layer protocol will receive the packet  MAC Address MAC Address Start of Frame Beginning of the frame
4 bytes 46-1500 bytes 2 bytes 6 bytes 6 bytes 1 byte 7 bytes

IEEE 802.3

802.3 frame (read right to left)

FSC Data Length Source  Destination  SOF Preamble
Frame Check Sequence Contains 802.2 header and the encapsulated data to be passed to an upper layer protocol that is defined in data field Defines how many bytes the 802.2 header and data field is  MAC Address MAC Address Used to synchronize the frame reception portions of all the machines on the segment  Beginning of the frame
4 bytes 46-1500 bytes 2 bytes 6 bytes 6 bytes 1 byte 7 bytes

 

Token Ring / IEEE 802.5

Tokens

Token Frame (read right to left)

End Delimiter Access control Start Delimiter
Indicates end of frame Defines frame type Indicate start of frame
1 byte 1 byte 1 byte

 

Data / Control Frame (read right to left)

Frame Status End Delimiter FCS Data Source Destination Frame Control Access Control Start Delimiter
Can relay 2 statuses Frame copied or address recognized Indicates end of frame Error checking, used in CRC calculations All data that is to be encapsulated. length is determined by how long the station can hold a token Packet's address Packet's address Info Regarding Frame Control  Assigns Priority to the frame, distinguishes frame type Alerts each station that the frame is Data/Control Frame 
1 byte 1 byte 1 byte varies 6 bytes 6 bytes 1 byte 1 byte 1 byte

FDDI

Specifications

  1. Physical Layer Medium Independent (PMD) - defines physical transmission characteristics - light levels, allowable bit errors, decibel loss, actual physical equipment
  2. Physical Layer Protocol (PHY) - encodes and decodes data, before and after transmission over the physical medium
  3. MAC - bridges FDDI with layer 2 of OSI model, responsible for how FDDI runs as layer 2 technology, the physical device, and the way data is presented to the physical layer
  4. Station Management (SM) - responsible for station and ring configuration, fault recovery and other management duties

PPP

PPP frame (read right to left)

FCS Data Protocol Control Address Flag
Used for CRC calculations Information handled by the upper layer protocols Indicates the encapsulated data's protocol Request a transmission of user data Holds a broadcast address Specifies beginning of frame
1 byte varies 2 bytes 1 byte 1 byte 1 byte

 

 

 

 

BACK