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SCTP send single file using multiple stream and TCP send single file using single stream. now question is "

how SCTP is better then TCP ?

" (in traffic scenario)

Pradip G. Vanparia
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    This question has nothing to do with programming. – edmz Oct 07 '15 at 11:54
  • Worth noting though, while SCTP may have nice features, but in terms of throughput it would not be faster than TCP. [According to a network subsystem Linux developer](https://lore.kernel.org/netdev/f45c281f37724eec868ae72180ab3cdd@AcuMS.aculab.com/), it wouldn't because it is more complicated, it has slower checksum algos, it's much harder to fill ethernet frames with it, and for other unmentioned reasons. – Hi-Angel Apr 10 '20 at 12:03
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    @edmz protocols and algorithms sound as much related to programming to me as programming-language-specific nuances. The question may arguably be "too broad" but certainly not "offtopic". – Hi-Angel Apr 10 '20 at 12:07

2 Answers2

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SCTP is not "better" than TCP in any way, but it does something different.

TCP emulates a reliable, ordered stream of octets over an unreliable unordered packet transport, which is conceptually very similar to reading from a file (without the ability to seek).

SCTP emulates a reliable in order distinct message delivery system (where "message" means as much as a defined chunk of data of some known length). Like UDP, it delivers one complete message at a time. Like TCP, it guarantees that messages arrive, and in the relative order in which they were sent.

SCTP has the ability to send different messages in separate streams, which allows to reduce latency, prevents head-of-line blocks, and makes better use of the available bandwidth in some scenarios. A web page with style information and images is the classic examples.
It does not send a single file via multiple streams (which would not make any sense).

(There are a few other features that I'm not naming because they have little relevance to the question)

Damon
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SCTP can be considered as mix of UDP and TCP because it is message based like UDP and connection oriented like TCP to ensure in sequence delivery of messages along with congestion control mechanism. That is, SCTP is connection oriented but operates at message level.

It involves bundling of several connections into a single SCTP association operating on messages or chunks rather than bytes. This capability of SCTP to transmit several independent streams of chunks in parallel is referred to as Multistreaming which avoids head of line blocking. That is, in case of TCP, even though 3rd & 4th packet are fine, but if 2nd packet was lost, TCP shall do retransmission due to which 3rd and 4th packet has to wait until the 2nd packet is successfully/correctly received. However, incase of SCTP, this head of line blocking is reduced as single association is split into multiple independent streams of chunks(messages).

Also, note that SCTP facilitates to send messages in unordered mode too, which can completely avoid the head of line blocking wherein the upper layers should have mechanism for reordering of messages if required.

Karthik Balaguru
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