Last Updated:
Friday, 27 February 2009 By: Steve Warner

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TOKEN RING



RIF (Routing Information Field)

RIF packets are split into two fields called RC (Route Control) and RD (Route Descriptor), the RC contains information about the Token Ring RIF frame and the RD field contains information on the route taken.

Bits 0..3 Type field

000    Direct Frame
10X   All rings, all routes
11X   Spanning Route

Bits 4..8    RIF Length field

4    always zero because of restrictions of length Bridge-Ring pairs

Bit 9    Direction

0    RIF is read from Left to Right
1    RIF is read from Right to Left

Bits 10..12    MTU

000    516 Bytes
001    1500 Bytes
010    2052 Bytes
011    4472 Bytes
100    8144 Bytes
101    11407 Bytes
110    17800 Bytes
111    64000 Bytes

Bits 13..16    Reserved and set to zero

 


Example

Lets analyse 0830, converted to binary is

0000 1000 0011 0000

Bits 1..3        Direct Frame
Bits 4..8        Length
Bit  9            Read from Left to Right
Bit 10..12     MTU 4472 Bytes
Bits 13..16    Zero

The second Hexadecimal character could be either 8, A, C or E.

 

Typical RIF values seen are as follows: -

0830, C

 


Converting an Ethernet MAC address to Token Ring

Ethernet MAC Address 00:60:97:FA:D5:AE

Hex 00 60 97 FA D5 AE
Binary 00000000 01100000 10010111 11111010 11010101 10101110
Mirror Binary 00000000 00000110 11101001 01011111 10101011 01110101
Hex 00 06 E9 5F AB 75

 

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