manello@BI1.SIMPACT.COM ("MIKE ANELLO") (10/25/89)
I have a question about running IP over 802.5. RFC 1042 says that the largest frame field of the routing control bytes for source routing are as follows: Postel & Reynolds [Page 8] RFC 1042 IP and ARP on IEEE 802 Networks February 1988 The RIF consists of a two-octet Routing Control (RC) field followed by 0 to 8 two-octet Route-Designator (RD) fields. The RC for all-routes broadcast frames is formatted as follows: 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | B | LTH |D| LF | r | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Note that each tick mark represents one bit position. LF - Largest Frame: 3 bits The LF bits specify the maximum MTU supported by all bridges along a specific route. All multi-ring broadcast frames should be transmitted with a value at least as large as the supported MTU. The values used are: LF (binary) MAC MTU IP MTU 000 552 508 001 1064 1020 010 2088 2044 011 4136 4092 100 8232 8188 All other values are reserved for future use. The TMS380 Adapter CHipset User's Guide Supplement uses the following: page 7-4 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | B | LTH |D| LF | r | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ LF (4 bits) 0000 reserved 0001 upto 516 octets in the information field 0010 reserved 0011 upto 1500 octets in the info field 0100 reserved 0101 upto 2052 octets in the info field 0110 reserved 0111 upto 4472 octets in the info field 1000 reserved 1001 upto 8191 octets in the info field 1010 - 1110 reserved 1111 initial value of broadcast frames Does anyone know which values should be used for the LF bits and what IP MTU should be used? Is there a standard for 4-Mb Token Ring and 16-Mb Token RIng? Mike Anello Simpact Associates manello@simpact.com