Questions tagged [tcp]

For questions about Transmission Control Protocol (TCP), a transport protocol used to encapsulate data across a network for reliable communication.

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Linux Kill TCP Connection (FIN_WAIT1) [closed]

I want to kill the TCP connection(FIN_WAIT1) when I forced the client to disconnect from my broker. I try to ss -K dst IPADDRESS dport = PORT and restart mosquito service, but the TCP connections ...
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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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DNS spoofing over https [closed]

If a device sends a request to https://example.com and someone spoofs the DNS response to redirect the request to some malicious server. Would the attacker be able to modify the packets during the TLS ...
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Chunked transfer encoding does not work through TCP tunnel [closed]

Consider the following setup +-------+ +--------+ +----------+ | | | | | | | +----------->+ +---------->+ ...
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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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high occurrence of TCP resets happening [closed]

I have started having issues that I had started noticing while using discord. Discord would start restarting and reconnecting me to the server I was on but this started to happen pretty frequently and ...
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Learning wireshark RST frames [duplicate]

I recently got into Wireshark and I'm just trying to grasp the basics. I've watched a few videos and they say to look out for reset frames on your WiFi, so I saw a few. They are an exchange between my ...
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Data sent with the “three way handshake” ack , but it is not TCP fast open

Hello guys this is my first question here. For my customer i was analyzing this ( anonymized ) capture because a SSL Handshake issue but i noted at first that TCP three way handshake is not as ...
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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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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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tcp how the receiver behaves if it received an incomplete window

Suppose, for example, that the window has a size of 5 MSS, the sender sends 5 segments to the network, the fifth is lost. Actually the question: how does the recipient behave? It just doesn't ...
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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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Would a bidirectional exchange of data between two hosts, one using TCP Reno and the other using TCP Tahoe, be possible?

I know Reno and Tahoe are TCP congestion control algorithms and one recovers much faster than the other when a packet is lost, but would they affect how data are exchanged between the hosts? ...
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TCP Congestion Window

Looking at example of congestion window graph pasted below and wanted to confirm my understanding. Looking at the red bar would that be the timeout happening here due to ACK being lost? and the b1 ...
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How to connect to a machine which is sitting behind NAT router?

I have a server that needs to push a message to a client from which it received a request a few days ago. Now request which was received has the IP address of the NAT router behind which the client ...
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Can Cumulative ACK number be higher than Selective ACK left edge number

I had recently been reading about selective ACK in TCP and had a question: Can Cumulative ACK's number be higher than Selective ACK's left edge number ? A hypothetical example: Receiver advertised ACK ...
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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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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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what is happening when a host receives a datagram with its MAC address as a destination but different destination IP

In a specific network say the host receives this datagram what is happening ?
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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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How does a device get a response from a HTTP request without an open port on the router?

I don't know much about how TCP/IP works, so please bear with me here. I was wondering how, when your computer makes an HTTP request from a random port(on that device) to port 80 on a server, it gets ...
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How to use the TCP traceroute in Juniper?

How to use the TCP traceroute in Juniper? In Juniper OS I only know traceroute ip_address I don't know how to traceroute a destination with TCP protocol. is it possible to implement it?
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How to find the client's application port during communication [closed]

After reading firewall rules about inbound and outbount I have some questions and the most sources focus on the server's ports. What happens to the client side when is trying to make a connection to ...
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IPv4 and UDP/TCP packets inside of ICMP packet?

A week ago, after opening wireshark, i was surprised by seing a storm of ICMP packets from different IP addresses. While deep analysing of thoses packets, i noticed that those ICMP packets contains ...
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RFC 6298 application

I got this? How many Fragments that are going to be sent are: 10800 / 1200 = 9 segments to Host B. And the full time is: (9*1200) / 1600000 = 6.75 ms According to RFC 6298 [1]: (2.2) When the first ...
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how data are fragmented based on MTU and MSS?

just to be clear.. if a sender wants to send a data of 1800bytes ( assuming MTU be 1500bytes so MSS = 1500-40 (taking min ip and tcp header) = 1460bytes) Then there will be three segments 750 + 750 + ...
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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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What flow control mechanism does ethernet uses?

Datalink layer is basically responsible for 3 major functions - Error detection/correction - CRC is used by ethernet Collision detection - CSMA/CD is used by ethernet But I couldn't find what flow ...
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What if receiver changes its IP address during the transmission process?

Suppose I am sending data to a laptop with IP address say x but before data could reach its destination the laptop is moved to another network and now its IP address becomes Y. Will the receiver still ...
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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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Suspect MTR showing incorrect packet loss through router; other tools are not showing loss

Using MTR (sending TCP with or without SYN), I'm consistently seeing packet loss on one intermediate router in the path. UDP does the same. I'm use TCP to avoid the ICMP packet flood limits set. I ...
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Propogation delay vs time required to send out a complete frame on channel

I was reading Data Communications and Networking by Behrouz A. Forouzan in which for simple Aloha protocol the vulnerable time given was T(fr) (time required to send out a complete frame on the ...
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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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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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what does PSH flag in TCP header do when the receiver is not reading data?

we know that when TCP data is received with PSH set, it will immediately transfer the received data to the application.and let's when pushed data arrives the receiver side and the receiver application ...
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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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TCP Congestion Control, Sender window = minimum ( Congestion window, Receiver window)

When can the congestion window size be greater than the receiver window size? An example of a scenario will be helpful. I know that the congestion window is used by the sender to gauge the network ...
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what's the acknowledgement number after retransmitting the missing segment [duplicate]

I was reading a textbook which describes TCP fast tetransmit, below is a picture If the TCP sender receives three duplicate ACKs for the same data, it takes this as an indication that the segment ...
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why double TimeoutInterval to avoid a premature timeout occurring for a subsequent segment that will soon be acknowledged?

I was reading a textbook which describes how TCP managing the retransmission timeout interval as: TimeoutInterval = EstimatedRTT + 4 *DevRTT An initial TimeoutInterval value of 1 second is recommended....
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Estimating the Round-Trip Time in TCP

I was reading a textbook which says: Let’s begin our study of TCP timer management by considering how TCP estimates the round-trip time between sender and receiver. This is accomplished as follows. ...
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Sequence number in acknowledgement

Let's say there are two host A and B, and host A sends data to host B and host B only sends ack segement(I know TCP is full-duplex but in this scenario, only A sends data to B, B only sends ack to A). ...
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Confused with packet reordering

I was reading a textbook which says about TCP protocol "Selective Repeat": We have assumed that packets cannot be reordered within the channel between the sender and receiver. This is ...
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no way of knowing whether or not the receiver has correctly received the last piece of transmitted data when checksum is corrupted? [closed]

I was reading a text book which shows a simple reliable data transfer service that is similiar to TCP: And the author said: Protocol rdt2.0 may look as if it works but, unfortunately, it has a fatal ...
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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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Connecting to device which requires specific IP [closed]

[Disclaimer: I'm a complete networking novice, and this question might not even be well suited for this site. I welcome pointers to other stack exchanges if appropriate.] I'm trying to connect a ...
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How does UDP control the flow of data in file transferring?

I know that transferring files over UDP is possible even though TCP is preferred. My question is how does the server know how much the client can handle or vice versa, or any router in between. TCP ...
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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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TCP/IP conditions to end an etabilished connection

What happens if the Client crashes and never closes the connection? Or the server crashes before being able to send a ACK FIN packet. Are those cases implemented in software?
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Can the network devices run out of ephemeral ports due to high use of websockets?

This might be a really stupid question, but something I really want to understand. My understanding is a tcp connections staying open indicates that each of the network devices between the client and ...

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