El Jueves, 27 de Enero de 2005 16:10, Harti Brandt escribió: > On Thu, 27 Jan 2005, Jose M Rodriguez wrote: > > JMR>Hi, > JMR> > JMR>get some free time to work in uadsl, but have a problem. Hope someone > that JMR>can read ITU I.363 can answer this. > JMR> > JMR>Every usb adsl modem implementation I see doesn't obey aal5 pdu > encoding JMR>standards, which requires that the PDU trailer come at the > begin of a fresh JMR>cell. > > That is not true. The trailer must be on the END of a cell. Before the > trailer there will be padding bytes so that this happens. If, for example, > you have a one byte PDU the AAL5 PDU will consist of 1 byte information, > 39 bytes padding and 8 bytes trailer. >
At last, rfc1483 and the received logic side seems to point that this is true. Most implementations sync the begin of a new PDU after detect the last cell by header test. Also, PDU lenght and crc is decode from a fixed ptr on the ENDPDU cell (lenght=cell[2]..cell[3], crc=cell[4]..cell[7]). > JMR> > JMR>So, I think that the modem must rework this and generate two cells on > the JMR>wire. Due how this modems works, I doubt that the modem > recalculate PDU CRC JMR>itself, So... > JMR> > JMR>Can someone confir if the CRC covers the PAD? I'm begin to think that > the CRC JMR>only covers the playload and the pdu-trailer. > > The CRC covers everything but the CRC. The PAD must be filled with zeros > though. > This is not so clean. This pad may be take as a cell pad or as a PDU pad. If this is take as a cell pad, it may not be part of the CRC (the ENDPDU cell is also paded from 8 to 48). My first guest is that the pad is part of the PDU, but I really doubt that the modem may be able to do a full CRC reclaculation. > harti -- josemi _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "[EMAIL PROTECTED]"
