![]() This is called packetization, where the TCP header contains the sequence number of the current index in the stream. Only when the data is deemed intact, TCP can hand the data over to the application’s socket.Īs TCP operates on data as a stream, the “chunks” from the stream have to be converted into packets that IP can carry. Rather, the TCP implementation has to buffer the data and when packets get lost, reordered or corrupted, TCP has to wait and organize the the data in the buffer. Unlike UDP, TCP does not guarantee applications steady “chunks” of data as they are sent and received. The other important property of TCP is that it is a streaming protocol. This connection is being actively taken care of by both sides: Establishing the connection (Handshaking), informing the other party of the data’s state and possible problems. Namely, TCP is a connection-oriented protocol, which means that an unicast communication channel is established between exactly two sides as a first step. The underlying mechanisms in TCP are much more involved than in other protocols like UDP and IP. Overall, congestion control is a complex, recurrent networking problem with accompanying research still being done to this day. In the implicit version, the sender tries to guess when the network is congested and should throttle its output. There are two general methods for this: in the explicit version, the protocol has a field for specifically informing the sender about the congestion status. In this scenario, the size of the sliding window would be negotiated to be lower, resulting in throttled output from the sender.Ĭongestion control, on the other hand, helps the networking stacks in between the sender and receiver to not get congested. Flow control is required, when the receiver cannot process data as fast it is sent. The convenient property of using this kind of a sliding window is that it also alleviates the problem of flow control. The window data is considered to be sequential (like a slice of an array) and that window “slides” forward as data is processed (and acknowledged) by both sides: Left window edge Right window edge Perhaps the most common is the sliding window technique, where both parties keep an account of the transmitted data. ![]() To combat these problems, several mechanisms can be used. ![]() In all of the scenarios, the underlying dangers of packet-switched networks apply - an acknowledgement from the receiver can be corrupted or even lost in transmit, which leaves the sender in a tricky situation.
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