February 2009
Intermediate to advanced
280 pages
9h 6m
English
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6
Reliability, Flow and Congestion Control
In OSI, reliability and flow control are tasks for both the data link and transport layers. Error correction and/or detection schemes, explained in Chapter 4, are used to ensure reliability during transmission on a link basis by the data link layer. The transport layer provides reliability as well as flow and congestion control on an end-to-end basis. We elaborate on the challenges and solutions related to transport layer issues for wireless ad hoc networks in this chapter.
6.1 Reliability
The reliability schemes in the transport layer are generally based on retransmission. A data segment is resent by the source node, or sometimes by an intermediate node that has the segment, when it was not delivered successfully on the previous attempt. There are two challenges to achieving this:
- detecting that a data segment has not been delivered successfully, i.e. has been lost or garbled during transmission;
- initiating the retransmission of the segment.
Detection of an unsuccessful delivery can be made either by the source or the destination. If a node that receives the data always acknowledges a successful delivery, this is called positive acknowledgement. When the positive acknowledgement scheme is used, if the source node does not receive an acknowledgement for a transmitted segment, it indicates that either the segment has not been delivered successfully or the acknowledgement has been lost. In this scheme the responsibility for detection is ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.