it’s probably at llc layer ! LLC is managed by the SGSN.
but (as far as i recall) LLC is not supposed to retransmit data (except some signalling, i believe). The retransmission is done at higher layers (applications, such as TCP).
LLC retransmission occurs at the LLC layer and not at the RLC layer.
Have you ever wondered why there is an requirement of another logical link, i.e. LLC, above RLC, between the MS and SGSN?
——–
There could scenario where LLC retransmissions will be required, for example, for an application that works in an unacknowledged mode and which do not have an error checking and correction mechanism on it own.
———
Due to LLC retransmission, timer running at TCP layer may expire. This will make the TCP to re-send the Network PDU (NPDU), for whom an ack was awaiting, to the LLC layer , which could further add to a delay in the TBF establishment or even a dip in throughput.
are you saying that the application layer might force the LLC to work in an ack mode, thus enabling LLC retransmissions?
Maybe I am wrong, but as far as i remember, LLC ack mode is enabled only for specific messages (flow control or signalling msg, or something like this).
For user place, LLC is always unack.
==> no llc retransmission
==> no delay due to LLC retransmission
Actually I want to know when UL/DL LLC frame changes during the UL/DL GPRS TBF transmission at that time resource re-allocation request is made at RLC layer for UL/DL TBF.
And also let me know how the LLC frame changes.
Author
Posts
Viewing 10 posts - 1 through 10 (of 10 total)
The forum ‘Telecom Design’ is closed to new topics and replies.