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Re: Cell sequence

  • From: Baris Aksoy <baris.aksoy@gte.net>
  • Date: Tue, 25 Jul 2000 23:44:13 GMT
  • Distribution: world
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> > As far as I know, it is used in AAL for detecting:
> > 1. Lost cell

> > 2. Mis-inserted cells.

I'd agree with Thomas. Suppose one of the switch in the network is
malfunctioning in a way that, it screws up during switching process. I mean,
when queueing and sequencing, it may mix up the the cells that belong to same
connection so that cell#1 is scheduled much later than cell#2. The switches
on the way to destination doesn't process AAL layer, so it doesn't know
sequence numbers. You have a disorder at the receiving end.

Based on today's switch architectures, this shouldn't happen. Have you ever
experienced something like that on the field?

> Sequence numbering of cells is only used in AAL type 1 (3 bit) and type 2
> (1 bit).

Just one addition here. AAL1 also uses CSI(Convergence Sublayer Indication)
bit, which can carry RTS values. That's helps to define the offset for
receive and transmit clocks. Hence, AAL1 is commonly used for circuit
emulation.