Browse Prior Art Database

End of Packet Optimization when Cell Routing with Early Drop

IP.com Disclosure Number: IPCOM000118692D
Original Publication Date: 1997-May-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Slane, AA: AUTHOR

Abstract

Disclosed is a method for increasing the probability of not losing an End of Packet (EOP) cell in an ATM Adaptation Layer (AAL) five cell stream when an early drop protocol is being used. Multiple buffer pools are automatically used for EOP cells to improve the odds that a buffer is available when an EOP cell is routed, thus preserving the EOP cell.

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End of Packet Optimization when Cell Routing with Early Drop

      Disclosed is a method for increasing the probability of not
losing an End of Packet (EOP) cell in an ATM Adaptation Layer (AAL)
five cell stream when an early drop protocol is being used.  Multiple
buffer pools are automatically used for EOP cells to improve the odds
that a buffer is available when an EOP cell is routed, thus
preserving the EOP cell.

      The Figure shows an AAL five packet divided into cells.  The
last cell contains the EOP information (uind bit=1), which specifies
that this is the last cell in an AAL five packet stream.

      An early drop protocol can be used in a switch to limit the
propagation of bad AAL five packets.  When used, the remainder of an
AAL five packet is dropped except for the EOP cell.  The EOP cell is
still sent on to the destination to clear the error condition at the
target system.  If this EOP cell is dropped, the next frame will be
received bad also because the target merges the two packets together.

      To increase the odds of not dropping EOP cells, an EOP buffer
pool can be added.  This pool is in addition to the normal buffer
pool that is used and is only used in the extreme condition that a
normal buffer is not available for the EOP cell.  The normal pool is
always tried first, and if no normal buffers are available, then the
EOP pool is used.

This mechanism can be broadened to other AALs.