piacenti@granite.ma30.bull.com (Paul Piacentini) (05/30/91)
Most of our ethernet equipment, analyzers, etc report counters on bytes,
packets, CRC errors, collisions, runts, giants, and frame alignment errors.
I'm a little fuzzy on exactly what consistutes a frame alignment error.
Is it a packet that was transmitted within the minimum IEEE inter-packet delay
spec window (9.6 usec?) ?
If that's the case, is it tallied up as an aligment error by every device that
saw it, ALONG with being tallied as a transmitted packet? Or does it count as
an error and get discarded as a non-valid packet? Does the destination ignore
it and wait for a retransmit?
Are they caused by a bad transceiver? controller timing problems? bad carrier
detection? software greedy for the bandwidth?
Can anyone enlighten me on this .. an inquiring mind wants to know
thanks, Paul
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_\ /_ Paul E. Piacentini | Bull Worldwide Info Systems
/ \ piacenti@granite.ma30.bull.com | 300 Concord Rd. MA30-857 _\ /_
(508) 294-3450 | Billerica, Mass 01821 / \chw@hpctdlbcol.hp.com (Charlie Whiteside) (05/31/91)
/ hpctdlb:comp.protocols.tcp-ip / piacenti@granite.ma30.bull.com (Paul Piacentini) / 8:27 pm May 29, 1991 / > Most of our ethernet equipment, analyzers, etc report counters on bytes, >packets, CRC errors, collisions, runts, giants, and frame alignment errors. >I'm a little fuzzy on exactly what consistutes a frame alignment error. >Is it a packet that was transmitted within the minimum IEEE inter-packet delay >spec window (9.6 usec?) ? No. 802.3/Ethernet frames are required to send their data in 8 bit units called octets or bytes. If the frame ends (CSN goes false) and the number of bits is not divisible by eight then the frame had an alignment error. An alignment error can be divided into two categories. (These are terms we use here, the industry may use variations on these) a. Dribble frame - This occurs when a frame is not octet aligned but the FCS was good. Usually means the CSN line went false a few bits after the frame ended, FCS good shows that data integ- rity for the frame exists. b. Misaligned frame - Non-octet aligned frame with bad FCS. Could be an extra bit(s) was added in the data field, caused shift of data, FCS caught the extra bits. Inter Frame Spacings of less than 9.6 uS is a totally different measurement. Hope this helps. Charlie chw@hpctdlb.hp.com 719-531-4388