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Retransmission Using Stored CRC Values

IP.com Disclosure Number: IPCOM000041376D
Original Publication Date: 1984-Jan-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Bederman, S: AUTHOR [+3]

Abstract

The article describes a technique which enables a transmitting station in a ring communication network to retransmit a packet which is presumed lost on the ring. The technique allows a token ring communication network to recover from errors due to lost packets. A sending station is allowed to retransmit the lost packets at a relatively high priority level (retransmission priority level). A recipient or target station keeps a record of the frame check sequence (cyclic redundancy check (CRC)) values of several most recently received packets. Preferably, the values are stored in a pushed-down stack. The CRC value which is associated with newly received packets are compared with the stored CRC values.

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Retransmission Using Stored CRC Values

The article describes a technique which enables a transmitting station in a ring communication network to retransmit a packet which is presumed lost on the ring. The technique allows a token ring communication network to recover from errors due to lost packets. A sending station is allowed to retransmit the lost packets at a relatively high priority level (retransmission priority level). A recipient or target station keeps a record of the frame check sequence (cyclic redundancy check (CRC)) values of several most recently received packets. Preferably, the values are stored in a pushed-down stack. The CRC value which is associated with newly received packets are compared with the stored CRC values. If the newly received packet has a different CRC value than any in the stack, the new packet is accepted by the recipient station and its CRC value is entered into the stack. If the newly received packet has the same CRC value as one of the values in the stack, this packet is rejected on the presumption that it is a duplicate of the previously received packet. When a packet is rejected (because of the presumption that it has already been received), the address recognized (AR) and frame copy bits are set to a "1". The technique further provides two conditions under which a sending station will revert into the retransmission mode. In the first condition the sending station sets a timing function at the time the message is sent. If th...