Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: CR: Structured Data Transfer in AAL Type 1 !
Hi, Pointer field is 7 bits, so max offset which it can idicate is 127 Octets which < 3 ATM cells p and > 2 ATM cells, so standard maker decided to use 96 as max number wich align with 2 ATM cells. You put a pointer in no.0 cell, it can cover all possible offset in no.0 and no.1, so second pointer only need to appear in no.2, the same thing happen to no.4 and no.6 cell. Yes, a octet means 8 bits, means one sample of a voice channel. How many octets in your structure means how many voice channels in your structure. wish it help XuHonggang SwitchingSystemDepartment CET Techologies of Singapore Technologies 24 AngMoKio Str. 65 Singapore 569061 -----Original Message----- From: Nuzhath Shereen <shereen@chequemail.com> To: sasos@nortelnetworks.com <sasos@nortelnetworks.com> Cc: rajagopalan.sampath@wipro.com <rajagopalan.sampath@wipro.com>; cell-relay@cell.onecall.net <cell-relay@cell.onecall.net> Date: Thursday, July 27, 2000 5:26 PM Subject: Re: CR: Structured Data Transfer in AAL Type 1 ! > > >Hello Saso, > >Can you explain more about this SDT format. The ITU-T I.363.1 says that the pointer format may be used only if the sequence count value is 0,2,4 or 6. This is because the 1,3,5 and 7 values are reserved for SRTS. > > I didn't understand the rest of the explanation in the standard. What is this 93-octet payload it refers to. By octet, Is it referring to one 64kps channel (I had read that somewhere) or is the digital 8 bits. > >Please give links or references , if you have any > >Regards, >Shereen@chequemail.com > >On Wed, 26 July 2000, "Saso Stojanovski" wrote: > >> >> >> hi rajagopalan, >> >> when using AAL-1 for circuit emulation, you either care to specify to the >> receiver where the TDM frame boundary is or you don't. >> >> in the former case you would use SDT, and in the latter case you would >> rely on the sync mechanism which is built in the TDM frame itself. >> >> for instance, if you emulate a whole E-1 circuit, then you could use UDT, >> since the first timeslot (out of 32) in the E-1 frame contains a sync >> pattern. >> >> on the other hand, if you are to emulate a fractional E-1 circuit (say >> only k 64 kbit/s channels), then you must use SDT in order to tell the >> receiver where exactly in the ATM payload the TDM frame (whose length is >> only k octets) starts. that is exactly what the pointer points at. >> >> cheers, >> v >> --saso >> >> >> >> >> rajagopalan.sampath@wipro.com wrote: >> >> > Hi, >> > >> > Can somebody help me in implementing AAL type 1 ( ITU-T I.363.1 )? >> > >> > What's SDT ( Structured Data Transfer ) and why it's used? >> > How SDT is performed at transmitting and receiving end? It's basically >> > about when to select P-format and when to select Non-P format PDUs? >> > What does the pointer value represent in the P-format PDUs? >> > >> > Thanks. >> > >> > Regds, >> > Rajagopalan Sampath. > > >Chequemail.com - a free web based e-mail service that also pays!!! >http://www.chequemail.com > >
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