What is TCP’s sliding window?
In a naïve implementation of TCP, every packet is immediately acknowledged with an ACK packet. Until the ACK arrives from the receiver (in this naïve implementation, at any rate), the sender does not send another packet. If the ACK does not arrive within some particular time frame, the sending stack retransmits the packet. The problem with this is that all that waiting limits network throughput drastically. The minimum time between packets with such a scheme must be at least twice the minimum round trip time for that network, for the time to send the packet and for the time for the receiver to send back an ACK. Add in processing time on each end, temporary hardware faults (e.g. Ethernet collisions), retransmissions, routing delays, and who knows what else: the stacks end up spending more time waiting for ACKs than sending data. This is a problem because it means you can’t effectively fill a network pipe with a single socket. The limit of data throughput over a network link is the maxim
In a naïve implementation of TCP, every packet is immediately acknowledged with an ACK packet. Until the ACK arrives from the receiver (in this naïve implementation, at any rate), the sender does not send another packet. If the ACK does not arrive within some particular time frame, the sending stack retransmits the packet. The problem with this is that all that waiting limits network throughput drastically. The minimum time between packets with such a scheme must be at least twice the minimum round trip time for that network, for the time to send the packet and for the time for the receiver to send back an ACK. Add in processing time on each end, temporary hardware faults (e.g. Ethernet collisions), retransmissions, routing delays, and who knows what else: the stacks end up spending more time waiting for ACKs than sending data. This is a problem because it means you can’t effectively fill a network pipe with a single socket. The limit of data throughput over a network link is the maxim
