I am new to networking. I have some confusions regarding CBR and FTP? Are they any protocols like TCP or UDP or something else? When do we use them?

  • CBR=constant bit rate? – Ron Trunk Dec 1 '15 at 15:52
  • yes. constant bit rate @Ron Trunk – user5520111 Dec 1 '15 at 15:53
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can provide your own answer and accept it. – Ron Maupin Aug 7 '17 at 15:31

They are unrelated to each other.

FTP is an application (and protocol) used for file transfer. It uses TCP for transport, but FTP is considered an application protocol.

CBR is a quality of service term usually used in the context of codecs, describing how they convert analog signals to digital (and vice versa). It's not a term commonly used in the TCP/IP suite.

  • Is CBR a traffic agent? @Ron Trunk – user5520111 Dec 1 '15 at 16:03
  • I'm not sure what you mean by traffic agent, but it is not a protocol, nor a function. – Ron Trunk Dec 1 '15 at 16:09

Constant Bit rate is not a protocol, but a description for an ideal situation.

FTP is a protocol, but it is above OSI layer-4 (transport layer), and it uses the transport layer to do its work. Questions about protocols above layer-4 are specifically off-topic.

TCP and UDP are layer-4 protocols. UDP is a best-effort, fire-and-forget transport protocol. TCP guarantees delivery.

  • what is meant by best effort protocol? @Ron Maupin – user5520111 Dec 1 '15 at 16:06
  • Best effort is a Quality of Service term. you can read up on it here: en.wikipedia.org/wiki/Quality_of_service – Ron Trunk Dec 1 '15 at 16:08
  • When an application uses UDP, it sends out segment, but the segment is not guaranteed to arrive at the other end, nor are segments guaranteed to arrive in the order in which they are sent. TCP makes these guarantees because it negotiates with the other end. – Ron Maupin Dec 1 '15 at 16:09

Both CBR and FTP are traffic generators not traffic agents. Traffic agents are like UDP and TCP. Their main difference is as they said: FTP uses TCP for transferring packet and CBR uses UDP for transferring packet. And Note that: As its known the request through TCP has an Ack while the one through UDP has no ACK and in Network simulation the same scenario works if you are familiar with it.

  • Can you quote a source on that, specifically for CBR? – Marc 'netztier' Luethi Jan 21 '19 at 16:48
  • go through NS2 tutorial. For sample nile.wpi.edu/NS/simple_ns.html – bekan kitaw Jan 28 '19 at 8:49
  • Well, even that document does not say what a CBR actually looks like on the host. One can infer that it is just simply an application generating a UDP stream at a given packet rate with a given packet size, subject to the serialization delay as given by the lower layer. As other commenters pointed out, CBR ("constant bit rate") is a term describing the behavior of a (UDP) traffic generator, not more. What also seems to be missing in this whole discussion (and the paper/script) is TCP's own flow control and congestion avoidance mechanisms. – Marc 'netztier' Luethi Jan 28 '19 at 8:59
  • So when comparing CBR to anythiung else, that should be against the different flow control/congestion avoidance mechanisms (Reno, Vegas, CTCP...) that the various TCP implementations have to offer. Picking "FTP" is a case of mis-labelled apple vs. not-quite-oranges. Other than that, at the traffic generator, one should pick identitcal starting conditions, for example Lets send this amount "A" of data as a 1Mpbs stream, as a sequence of chunks of 1kbyte". Let's compare the results of TCP Reno, Vegas, CTCP (etc.) and UDP-with-CBR. "FTP" is just the odd one out in this context. – Marc 'netztier' Luethi Jan 28 '19 at 9:09
  • My friend, @Marc'netztier'Luethi ,I thought you miss the way I wanna to describe here. You see when you design or modify certain protocol in networking, there are a number of ways by which you can simulate the working of ur network/protocol using different event simulators: Packet tracer, Contiki Cooja, OMNET++,NS2 etc.. and those parameters: UDP,TCP,CBR and FTP are common there and that is why I took for you as an instance. Spare a minute and understood the diagram shown on the previous site! Then after, I hope you'll get my idea. – bekan kitaw Jan 28 '19 at 15:11

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