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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Can Safari(Mac OS Monterey) bypass a VPN and make connections? [closed]

Im monitoring traffic between a Mac OS device and router. For the purpose of garnering a smaller network capture, I've just restricted activity to web browsing(Capture using Wireshark on the Mac). The ...
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What are the downsides of setting a large tcp window size [duplicate]

I'm new to computer network and I encounter this formula: maximum network throughput <= TCP window size / latency If latency is more about the geographical factors or network hardware (e.g. 4g ...
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29 views

Latency between a churn and congestion event triggered in the TCP code

I am analyzing the time it takes between a churn occurring in the network (e.x. that causes packet drops or delays) and when the congestion event handling codes are triggered in the TCP kernel in the ...
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what is the meaning of TCP protocol is a connection oriented [duplicate]

I read some of Wikipedia pages about computer networks and learned how and why they evolved. about TCP and IP i learned that for reducing complexity of network, the intelligence in the network is ...
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26 views

Can UDP traffic be transmitted over TCP ports on OpenVpn to avoid the TCP meltdown

I understand the TCP meltdown problem is associated with overcompensation from errors and incorrect sequencing when arriving the the receiver end. OpenVpn connections are recommended to use the UDP ...
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2answers
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How can I use scapy to make a port appear open-device behind NAT?

This has been asked in stack overflow like 7 years back. I don't see the correct answer there. Is there any way to do this? While this packet keeps on being transmitting, doesn't the other end see the ...
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1answer
18 views

TCP payload error handling at the application layer [closed]

How are errors in the payload of TCP packets handled by the receiving application? The packet is received but for various reasons (including sending erroneous packets on purpose) the payload of the ...
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1answer
38 views

Hosting a website using dynamic public IP: What if the ISP did not assign any port forwarding? [closed]

Let's just say that I am a peasant that can only avail of a typical Dynamic Public IP address from my ISP. Just for the sake of example, let's say have the following: Domain Name: experiment626....
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38 views

Why loss of first Syn + Ack from the server will not establish a connection? [duplicate]

In TCP 3-way handshake, 3 segments will be sent (SYN, SYN ACK, ACK). What if loss of syn+ack from the server will not establish a connection? What if the third segment(ACK) is lost? Is the sender ...
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1answer
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Why sender window or congestion window size becomes 2^n mss after nRTT in slow start mechanism?

I seen everywhere in slow start mechanism if initial sender size denoted by cwnd= 1mss , then after 1 RTT cwnd becomes = 2 mss, and after 2 RTT cwnd becomes = 4 mss and so on. My question is why ...
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Is really TCP takes 3*RTT time to make a connection?

TCP takes 3 RTT time I have read from one stack overflow answer to make a connection with server. We know that TCP takes triple (Syn, Syn/Ack, Ack) to make a connection by 3-way handshake with server....
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In three-way hand shaking, if a port is established how would other packets be connected [duplicate]

If a tcp port is in state of establishment how is it possible for other clients to connect to server.
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Why client will send a RESET when it is closed state?

Suppose I have an TCP state transition diagram. And assume that the last ACK is lost. Then, B will think that A did not receive the FIN and will retransmit the FIN. From B point of view this is the ...
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29 views

How a single BGP-process establishes sessions with neighbours in different VRFs?

In VRF-lite solution scenario, when BGP session is established between CE connected to a VRF in PE. The BGP process or in other words TCP server, is listening on port 179(default) for incoming BGP ...
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47 views

Why in the TCP/IP model the link & physical are one?

I'm currently learning about the OSI model and the TCP/IP models, and I was wondering: Why in the TCP/IP model the physical layer and the data link layer are combined? I'll state how I understand the ...
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Why the pseudo-header is not transmitted with the UDP datagram?

I have read from E. Comer - Internetworking with TCP/IP 4th edition that "The purpose of using a pseudo-header is to verify that the UDP datagram has reached its correct destination. The key to ...
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68 views

UDP checksum calculation for checksum results in the value zero

I read UDP checksum from Wikipedia that "If the checksum calculation results in the value zero (all 16 bits 0) it should be sent as the one's complement (all 1s) as a zero-value checksum ...
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1answer
48 views

How UDP checksum get IP address to make pseudo header in transport layer?

We know that UDP checksum's pseudo header contains the most important parts of the IP header, that is, source and destination address, protocol number and data length. I hope that the concept of IP ...
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2answers
99 views

Why router can't be used for converting different model of network but gateway can do this?

We know that Router can't be used for converting different model (e.g OSI model to TCP/IP or TCP/IP model to OSI) of network. It isn't a multiprotocol converter. But gateway is a highly sophisticated ...
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1answer
19 views

Maximum value of file that can be sent [closed]

this is the following question I have encountered in school. There is a file of X bytes that needs to be transferred from Host A to Host B. The MSS is 10 bytes. What is the maximum value of X such ...
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How is UDP used in multimedia system inspite of being connectionless

We know that UDP does not care about segment (packet) in-order and their arrival on the destination.Then how on YouTube or VoIP (skype) are we able to stream videos? If a packets is lost (doesn't ...
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Is it possible for TCP can accept out of order segments?

TCP is connection-oriented protocol whereas IP isn't connection-oriented protocol. Any packets before sending into transport layer sorted operation must have been done in network layer. That's why we ...
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Why is bandwith-delay product the maximum in-flight datas in TCP? [duplicate]

I have often read, for example https://en.wikipedia.org/wiki/Bandwidth-delay_product that: The result, an amount of data measured in bits (or bytes), is equivalent to the maximum amount of data on ...
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72 views

Are duplicate sequence numbers from different TCP-connections possible?

While learning about Sequence and Acknowledgment numbers one thing bugged me. I wasn't able to rule out for myself if the following scenario in which Host A sends data to Host B by using some ...
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Definition of a socket [duplicate]

I wanted to confirm whether the definition of a socket I've understood in a computer network context is true. A socket is file who is unique and named by local IP,Local port, Foreign IP and foreign ...
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1answer
52 views

What would happen if SYN and ACK are in the initial request?

I understand that a three-way handshake is used to form a TCP connection and that the basic outline of a handshake is: A sends a packet to B with a SYN bit B sends a packet to A with a SYN bit and an ...
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Congestion control behaviour of TCP Reno

Which behaviour of TCP Reno after 3 DUP ACK is correct: The one described in the Italian Wikipedia (https://it.wikipedia.org/wiki/Controllo_della_congestione_in_TCP#TCP_Reno). It says the new cwnd is:...
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Are NAT external:internal mapping types the same for UDP and TCP

Suppose I use a STUN server (UDP) to determine that a client's NAT randomly assigns external port values. Does this imply that the client's NAT will also assign random external port values when using ...
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63 views

Is it possible to move a persistent TCP connection?

Context: Say I have a global cloud service. In each datacenter, I have numerous persistent TCP connections to various client devices. The TCP connections are distributed across various nodes in the ...
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1answer
54 views

Is the distinction between ports under and above port 1024 exists only in TCP and UDP protocols?

Is the distinction between ports under and above port 1024 exists only in TCP and UDP protocols? I want to know if in other protocols (i.e. not TCP and UDP) such a distinction between "root" ...
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42 views

Does UDP can be exposed to stateful analysis?

From protocol theory we know that TCP is stateful protocol. Different stateful packet filters do filtration based on connection state. I.e. it can distinguish responses and replies. It's obviously for ...
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What does it mean for a website to return syn:false ack:true to my connect attempt? [closed]

I'm using a userspace TCP stack and I send a syn:true, ack:false to a website: [2021-06-20T19:30:24Z DEBUG async_smoltcp::packet_log] PHY >>>> [2021-06-20T19:30:24Z DEBUG async_smoltcp::...
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How to create a mapping between TCP segments or IP packets or fragments and TCP Windows? [closed]

I am searching for a method how I practically can determine the segments within a TCP window both when sending and receiving them? I want to modify IP packets per TCP window. I already looked into the ...
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Why large queueing delays are experienced as a packet arrival rate nears the link's capacity? [duplicate]

From the book "Computer Networks A top Down Approach": It says if hosts A and B both are sending at rate R/2 and router's outgoing link has a capacity of R. There will be delays experienced ...
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Why does the Transport layer break data into packets? How does that make things reliable? Isn't the Network layer doing the same thing?

I'm new to CNs and there is something that I can't yet grasp. Why doesn't the Transport layer let the Network layer do all the splitting up? How does segmentation make things reliable? Also, I ...
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In TCP, when a receiver starts sending duplicate ACKs to the sender, does it also send ACKs for packets it has received past the hole?

I know that if a receiver sees holes in the packets it receives, it starts sending duplicate ACKs containing seq numbers of missing packets. At this time, the receiver is also receiving packets that ...
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1answer
26 views

nmap correct TCP traceroute [closed]

Why is only hop 1 & 6 displayed? Note: I can't use ICMP, due to firewall. The target is an educational website in the AWS cloud.
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What is the difference in reliability of sending a pure ACK packet (without any data), as opposed to a data packet in TCP?

I was going through the book TCP/IP Illustrated and in the zero windows section, I noticed the use of a TCP persist timer - which is used to avoid losing a window update message from a receiver after ...
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Difficulty in understanding the concept of "artificial inflate" and "deflate" in the fast recovery phase of TCP

I was going through the text Computer Networking- A Top-Down Approach by Kurose and Ross, there I found subtleties with the TCP congestion control FSM which is shown below: Mainly I am having ...
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Difficulty in understanding the action "transmit new segment(s), as allowed" in TCP congestion control

I was going through the text Computer Networking- A Top-Down Approach by Kurose and Ross, there I found subtleties with the TCP congestion control FSM which is shown below: Mainly I am having ...
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Tearing down the FSM description of congestion control

I was going through the text Computer Networking- A Top-Down Approach by Kurose and Ross, there I found subtleties with the TCP congestion control FSM which is shown below: Mainly I am having ...
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1answer
29 views

Who should reset TCP connection after VIP has moved onto another host? [closed]

Imagine such a situation - TCP connection(NFS4 or database) between client(Linux) and virtual IP hosted on a server(Linux). Server fails and VIP is taken over by another server(using ARP). The client ...
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1answer
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Port 8080 closed over VPN (Linux, OpenVPN, webpack, Node.js application). How to troubleshoot? [closed]

I am running a node application that uses webpack. The application starts and automatically selects the port 8080 on localhost: The website works correctly on the browser on my machine. I want now to ...
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Some random client requests fails with unexpected TCP [RST] packets [duplicate]

I have a service doing listen that serves clients over a TCP sockets connection with a raw binary protocol. The principle is basic: the connection is established, the client sends a request with data, ...
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Is OSI model merely used for troubleshooting purpose? [duplicate]

I'm a student and recently started understanding OSI model, from what I understand is that OSI model is just theoretical and not really used in real world. It's mainly for troubleshooting purpose. I'...
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1answer
43 views

TCP ACK confusion

When a packet is being sent after the SYN ACK connection has been established between a host and a server, packets can now be sent between the hosts and a server. Sometimes, there’s a window size ...
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139 views

Slow SMB transfer rates with client direct to Cisco switch, normal when connected to a downstream Netgear switch

I have encountered a rather unusual problem that I'm having difficulty getting to the bottom of... Here is the configuration: SMB server ->(2x10Gb SFP+ LAG) Cisco SG500X-24 switch ->(1x10Gb SFP+)...
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How TCP sequence numbers work in bidirectional communication/sliding window?

I was trying to understand how TCP works (not in detail of course). I was surfing the web for easy-to-understand flow diagrams and a question arose and couldn't find a straight answer. Let's suppose ...
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Why does one say IP fragmentation is bad and to be avoided when in reality data always needs to be fragmented for MTU compatibility?

Why does one say fragmentation is bad and must be avoided due to performance issues when in reality fragmentation intrinsically occurs within the communication ? Example: User1 wants to send 100 000 ...
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Is packet transfer still possible, if the routers don't have the updated link cost information in the Bellman-Ford Algorithm?

In the Bellman-Ford Algorithm, the principle of "Good news travels fast but bad news travels slow" is implemented. So if the cost of the link between two routers is increased, then the ...

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