IEEE 802.4 Token Bus

• IEEE 802.4
• GM.
• A Logical Ring
• A Physical Coaxial Cable
• Elaborate Protocols are required for entering or leaving the ring.

Field                       Size                
Preamble                1 or more                
Start Delimiter              1                
Destination Address        2 to 6                
Source Address             2 to 6                 
Data                       0 - 8182                 
Checksum                     4                
End Delimiter                1 

Maintaining the logical ring

Control Field            Name                 Meaning                	
00000000          Claim_token            Claim Token During 
                                           Initialization                
00000001           Solicit_sucessor_1    Allow Stations to 
                                         enter the ring                
00000010           Solicit_sucessor_2     Allow Stations to 
                                          enter the ring                
00000011            Who_follows           Recover from lost token                
00000100            Resolve_contention    Used when multiple 
                                          stations want in                
00001000            Token                 Pass the token                
00001100            Set_Sucessor          Allow station to 
                                          leave the ring

Return to Networks home page

Last Changed: 15 September 1995