Questions tagged [transport-protocol]

For questions about or in relation to the transport protocol or OSI layer 4. For instance the best-known transport protocol of TCP/IP is the Transmission Control Protocol (TCP).

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I have issue with MSS and window size [duplicate]

I made a short example because I have tried understanding the difference between MSS and window size in tcp header when we consider a sender and a receiver. So let's say sender and receiver use the ...
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Nature of TCP Timeouts

Are timeouts in TCPs inherently part of sequence numbers, or is it an entirely different component of a TCP packet? I understand that timeouts provide some level of reliabilty to a data stream, in ...
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Is the TCP Reno Fast Recovery algorithm really linear?

I'm reading through Computer Networking, 8th Edition by Kurose & Ross, and I came upon this figure(Figure 3.52 pictured below), which graphs the operation of TCP Tahoe & TCP Reno. The graph ...
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Does the destination port change during TCP three-way handshake?

I'm learning networking programming in C and there is a question bothers me a lot, does the destination port change during TCP three-way handshake? Let's say I have a cilent application running on ...
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2answers
42 views

How are Ports Exposed to the Network?

When you register some server's port, whether it be an application, web, or something else - where exactly is this port registered? I understand how ports work in that they are essentially signposts ...
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2answers
689 views

Do these 2 packets belong to the same tcp socket?

Let's say we have two packets A and B. A: Has source-IP S1 , destination-IP D1 , source-port SP1 , destination-port DP1 B: Has source-IP S2 , destination-IP D1 , source-port SP2 , destination-port DP1 ...
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75 views

What is “TIME_WAIT” connection in a TCP connection and what is it's purpose?

I am requesting a webpage running on local server port 8080 and was expecting one connection to be established between the server (port 8080) and client (random port). But one additional port is also ...
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81 views

Why is a UDP port scan more complex than TCP port scan?

When I scour SO, I saw that it's a bit complex to port scan a UDP port than a TCP port, why?
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What is the relation between software and hardware ports?

A port number is a 16-bit unsigned integer, thus ranging from 0 to 65535 https://en.wikipedia.org/wiki/Port_(computer_networking) And I think computers have small number of hardware interfaces(ports) ...
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41 views

Does the first TCP FIN packet (active close) goes with just only FIN bit set?

Suppose we have established TCP connection. The active close process assumes the FIN packet been sent to trigger TCP connection closing. But I can't figure out, is this first (active close) FIN packet ...
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59 views

Is there any other network protocol than tcp/udp that works with ports?

Do you know at least one protocol (any OSI layer) that, like tcp and udp, works with ports ? Thank you
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Why is delayed segment prevention (TIME_WAIT) in TCP only done for one side?

One of the reasons for TIME_WAIT is to prevent old packets/duplicates, coming in late, to screw up subsequent connections on the same (src ip, src port, dst ip, dst port) quadruplet. That makes sense, ...
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Does UDP do anything at all?

It's my understanding that TCP has logic for ensuring reliable communication, but UDP just naively sends information along the channel set up for it using IP and things in lower layers. Does UDP ...
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Congestion control in transport and network layers in TCP/IP

Why do we need congestion control in BOTH the transport layer and network layer in TCP/IP model. Cant we be good enough with control in just one of the layers only? And how do they differ?
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What will happen if a server receives a duplicate SYN for an existing connection?

If a server receives a fresh SYN packet for a connection that is already established, what should it do? I have already seen What will happen at server side if it received 2 SYN packet from the same ...
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2answers
141 views

Is this UDP diagram wrong?

I was just wondering if anyone can tell me why all UDP diagrams I have seen list a request from the server to the client as the first point of communication? Take a look at the following diagram for ...
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How do I properly serialize a network packet [closed]

So I'm currently writing a program that is essentially just a server and a client. The idea is that I want them to be able to communicate with one and other by sending packets back and forth. And I'm ...
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2answers
121 views

What is the window size of TCP pipelined sending?

We know that instead of sending a packet and waiting a RTT then sending another (stop and wait), TCP uses pipelined sending as picture below shows: So, my question is, what's the maximum number of ...
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78 views

Sequence numbers and wrap around concept

I was reading an article about the topic and I came across this :"During connection establishment each party uses a Random number generator to create initial sequence number (ISN), which is ...
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2answers
79 views

how a transport-layer protocol can provide timing guarantees?

I'm reading a textbook which says: A transport-layer protocol can also provide timing guarantees. As with throughput guarantees, timing guarantees can come in many shapes and forms. An example ...
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1answer
112 views

Do both sides need to agree on MSS value?

By definition, The TCP Maximum Segment Size (MSS) is the maximum amount of data that a host is willing to accept in a single TCP/IPv4 datagram. And MSS is one of the parameters which is negotiated ...
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2answers
41 views

Two PC on the same LAN, communicating the same Server

Assume that we have 2 pc on the same LAN, local IP of pc1: 192.168.1.5 local IP of pc2: 192.168.1.6 Now suppose that both pc1 and pc2 wants to connect to a server on the internet, we all know that the ...
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245 views

TCP Handshaking Meaning of RST

I am trying to implement TCP handshaking but receive RST instead of ACK: No. Time Source Destination Protocol Length Info 62 24.622012890 192.168.0.147 ...
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2answers
361 views

Prevent TCP sequence prediction attack

Let's say an attacker gets the sequence number between me and my client. Now he continues the conversation with me and has changed the IP address. How do I prevent packages from being sent to ...
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25 views

Why we use IP address in sockets? [closed]

When a server want to create a socket, it will use a combination of its IP address and some well-known port, let us say 80. So, when a segment arrived, both the server IP and port 80 will be used to ...
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2answers
35 views

ICMP is a protocol working in the Network Layer. Why does it send few fields of the transport layer while reporting an error?

I was confused if ICMP is a network layer protocol why does it send transport layer fields in its error reporting messages.
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TCP Checksum Calculation

I recently started with networking and tcp/ip. The RFC 793 document tells the checksum is made of: pseudo header+tcp header+tcp payload+zeroes(if not divisible by 16). So I have to take 16bit ...
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90 views

Which exact bytes are transmitted while TCP zero window probing?

I read the post about TCP zero window probe and it seems that such a probing segments transmit some payload. But I can't figure out which exactly bytes are sent in probing segments? Is it one (or more)...
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139 views

Can TCP stand for “Transport Control Protocol”

I know it might sound like a silly question, but afaik TCP stands for transmission control protocol. However I found a couple of websites using the term Transport Control Protocol. So I was wondering ...
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73 views

How does triple handshake avoid establishing connection for duplicate packets(coming later down the line)

The idea behind triple handshake seems to be for duplicates to not cause issues. The way I understand it host sends a sequence x to server. Server acknowledges it and sends it's own sequence y. Host ...
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1answer
153 views

Do sequence and acknowledgment numbers treat 3-Way Handshake differently?

1- Just as the message ID that is assigned to each message in PAR, the "sequence number" is a means of providing reliability in a transfer of a byte stream. So sequence numbers are assigned to every ...
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1answer
72 views

Does UDP perform packet re-ordering at the destination?

User Datagram Protocol is a simpler message-based connectionless protocol. Connectionless protocols do not set up a dedicated end-to-end connection. Communication is achieved by transmitting ...
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1answer
111 views

Transport layer segmentation and Ip layer fragmentation [duplicate]

From the OSI Model's point of view: If we already have Ip fragmentation which happen due to the network limitation, why the transport layer provides the segmentation mechanism via TCP protocol? why ...
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78 views

TCP flow control active waiting

To perform flow control between a sender and a receiver during a TCP connection, the receiver includes in each packet to the sender, the size of available space ‘rwnd’ in its receiving buffer. This is ...
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4answers
175 views

How do networks protocols communicate with each other?

We know that before sending information, TCP has to establish a connection with another host. So, does the request from TCP get encapsulated by lower levels of stack protocols or is it just sent ...
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2answers
136 views

Which port determines the protocol?

If we have a common protocol port on both ends.. say source point is 443 and destination port is 80 (hypothetical situation, I know this combination of ports probably makes no sense).. how do we ...
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2answers
576 views

Sequence numbers of segments in three way handshakes of TCP connection establishment or termination

I was trying to understand TCP connection establishment and termination steps from Forouzan's book. In third step of three way handshake of connection establishment, it says following The client ...
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1answer
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Question on windowing and determing connection speed

Hi i'm just learning computer networks and i have learned about windowing in tcp And my question is does we determine connection speed using windowing? I mean computer know the number of packets and ...
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1answer
721 views

When TCP sender window shrinks?

I was learning TCP from Forouzan's book. It explains sender side window as follows: In that it defines size of receiver window as follows: rwnd = receiver buffer size - number of bytes waiting to ...
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102 views

ports and security

I'm thinking about how the "port" operates for the network connections and tried reading the CCNA cert. guide to understand the details, however, I need to clarify doubts: does occupying all the TCP/...
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1answer
67 views

Finding MSS for a remote connection that uses tunnelling

I'm working on a codebase where we're trying to test network health by verifying if we can ping the remote site having payload = MSS without any packet fragmentation (using -df flag). Typically, for ...
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why we need to make the size of our burst 2 times the product of bandwidth and delay? [duplicate]

A textbook which says: The bandwidth-delay product defines the number of bits that can fill the link. This measurement is important if we need to send data in bursts and wait for the acknowledgment ...
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50 views

How is port 80 associated with application port?

I'm new to networking, just a question on port numbers. We know that port 80 is for HTTP. But if I want to access a web application whose web server handles http requests, normally I type below url ...
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1answer
39 views

Pros and cons of the idea of parallell data transmission

I am learning the basics of internet protocols and related principles. I recently performed experiments comparing UDP and TCP. But when I did that (using the ttcp program) it was only one process and ...
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1answer
52 views

What's the word of a Transmission Control Protocol port in the Wireshark captured package?

What's the meaning of the dict there? why the port have the paraphrase? you see the Destination port 39578 (39578) do not have.
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265 views

How does browser decide which destination port to use?

Suppose I have a Vanilla machine and this is the first time I am connecting it to Internet. There is no Cache at any level. I access a website through browser by typing example.com (no http//: or ...
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60 views

How TCP find the correct application?

I am learning how TCP and application communicate with each other. I am not sure if my understanding is correct, I will use below example to illustrate my understanding and want to ask some questions. ...
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65 views

Overload PAT Question

Learning details of NAT PAT. I understand basics wherein the PAT router incorporates a source port to ID the private address computer communicating out on the public address, enabling the public ...
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1answer
427 views

Why server cannot send data in TCP three-way handshaking?

In the three-way handshaking, only from the ACK packet we can send data. Why cannot the server send data with SYN-ACK packet? I understated why a client cannot send data to a server (preventing, for ...
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3answers
623 views

What's the use of an acknowledgement number without the ACK flag set?

Isn't it redundant if the ACK flag in the header isn't also on? Do you ever mix an acknowledgement with a normal message - send data and acknowledge a message in the same TCP segment? I feel like ...