iselin@IAM.UNIBE.CH (Nicolas Iselin) (03/19/91)
To all hardware specialists ! We have here quite a tricky problem which seems to be hardware dependent. Can anyone tell me what a transputer does, when a link receives an acknowledge packet without having sent a data byte ? Our guess is that it brings the whole Transputer to halt without setting the errorflag. Who knows more ? Nicolas Iselin, Bern
davidb@brac.inmos.co.uk (David Boreham) (03/27/91)
In article <57*.S=iselin.OU=iam.O=unibe.PRMD=SWITCH.ADMD=ARCOM.C=CH.@MHS> iselin@IAM.UNIBE.CH (Nicolas Iselin) writes: >To all hardware specialists ! > >We have here quite a tricky problem which seems to be hardware >dependent. Can anyone tell me what a transputer does, when a >link receives an acknowledge packet without having sent a >data byte ? > >Our guess is that it brings the whole Transputer to halt without >setting the errorflag. > >Who knows more ? > The link interface is either ``expecting'' an ACK or it isn't. If it is and it receives and ACK, it takes it as a indication that transmission can proceed. If it isn't expecting an ACK, it ignores it. ACK's are only ``expected'' when a byte has been transmitted and before the corresponding ACK has been received. So, for example merely injecting ACK packets onto a quiet link should not cause a problem. Injecting ACKs onto an active link could cause data overrun at the receiver, depending upon where the ACK falls in time. That could certainly lock up a network. Note that the error flag has nothing whatsoever do to with links. David Boreham, INMOS Limited | mail(uk): davidb@inmos.co.uk or ukc!inmos!davidb Bristol, England | (us): uunet!inmos.com!davidb +44 454 616616 ex 547 | Internet: davidb@inmos.com