improving tcp performance over manet using ABRA approach
Improving TCP Performance over Mobile Ad
Hoc Networks Using an Adaptive Backoff
Response Approach
Tamer F. Ghanem, Wail S. Elkilani, Mohiy M. Hadhoud
Department of Information Technology, Faculty of Computers and Information, Minufya University tamerfg@hotmail.com, welkilani @gawab.com, mmhadhoud@yahoo.com
Abstract- Mobile Ad Hoc Network (MANET) suffers
decreasing both the congestion window (CWND) and slow start threshold (SSThr). Then it retransmits the first unacknowledged packet and executes back-off by doubling the value of retransmission timer. With multiple successive back-offs, the value of the retransmission timer will be too long. However during the long retransmission period, the route may come back but TCP will not try to retransmit the first unacknowledged packet until the retransmission timer expires. So there is a wasted time that TCP will not use although the route may come back some period ago. The ideal solution for the route failure problem is to freeze its state as soon as the route breaks and resume as soon as a new route is found [1,02,3].
However, this requires instant notification or feedback from the intermediate nodes to all TCP senders and from the network layer to the transport layer. Such a feedback system is difficult to implement and expensive to operate.
In this paper, we explore a new adoption technique of TCP to frequent route failures without relying on feedback from the network. It is based on adapting the TCP back-off after the expiration of the retransmission timer. When the sender receives an acknowledgement (Ack) for a retransmitted packet,
TCP returns to its state before the expiration of its retransmission timer. Moreover, CWND and SSThr will be divided by 2 and 4 respectively. We call it the adaptive back-off response approach (ABRA). Our study has shown that this approach can improve TCP performance over mobile ad-hoc networks.
The rest of this paper is organized as follows: In
Hoc Networks Using an Adaptive Backoff
Response Approach
Tamer F. Ghanem, Wail S. Elkilani, Mohiy M. Hadhoud
Department of Information Technology, Faculty of Computers and Information, Minufya University tamerfg@hotmail.com, welkilani @gawab.com, mmhadhoud@yahoo.com
Abstract- Mobile Ad Hoc Network (MANET) suffers
decreasing both the congestion window (CWND) and slow start threshold (SSThr). Then it retransmits the first unacknowledged packet and executes back-off by doubling the value of retransmission timer. With multiple successive back-offs, the value of the retransmission timer will be too long. However during the long retransmission period, the route may come back but TCP will not try to retransmit the first unacknowledged packet until the retransmission timer expires. So there is a wasted time that TCP will not use although the route may come back some period ago. The ideal solution for the route failure problem is to freeze its state as soon as the route breaks and resume as soon as a new route is found [1,02,3].
However, this requires instant notification or feedback from the intermediate nodes to all TCP senders and from the network layer to the transport layer. Such a feedback system is difficult to implement and expensive to operate.
In this paper, we explore a new adoption technique of TCP to frequent route failures without relying on feedback from the network. It is based on adapting the TCP back-off after the expiration of the retransmission timer. When the sender receives an acknowledgement (Ack) for a retransmitted packet,
TCP returns to its state before the expiration of its retransmission timer. Moreover, CWND and SSThr will be divided by 2 and 4 respectively. We call it the adaptive back-off response approach (ABRA). Our study has shown that this approach can improve TCP performance over mobile ad-hoc networks.
The rest of this paper is organized as follows: In