Cell Relay Archive

["Dominic Richens" <dominicr@no-spam.nortelnetworks.com>]

<jessmcclelland@my-deja.com> wrote in message
8d2nd9$dvq$1@nnrp1.deja.com">news:8d2nd9$dvq$1@nnrp1.deja.com...
> I am a little bit in the lurch about how an ATM switch recives FR
> packets and converts/tranlates/encapsulates? into an ATM packet.  If FR
> packets are variable in length and how do they fit into a 53 octet
> packet???

You use AAL5 (Atm Adaption Layer 5), which segments the frame into cells,
marking the last cell with a special PTI code, adding padding if necessary, and
writing a length and CRC32 to the end of the last cell.  Then the other end
collects the cells, until it gets the one with the special PTI code,
re-assembles them into a frame, does CRC and length check - and voila!  Also
knows as SAR (Segmentation And Reassembly).

The ITU-T standard for AAL5 is I.363.5

--
       Dominic Richens | dominicr@nortelnetworks.com | (613) 765-5840
 Passport NW | Nortel Networks, Dept. CS53, 3500 Carling, Ottawa, ON, K2H 8E9
    "I have seen the future, and it is just like the present, only longer"
                                        - Kehlog Albran, "The Profit"     McQ!