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

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Whether every TCP packet have a Ack Reply?

The TCP Acknowledgements you see in the diagram's green arrows, have ACK numbers separated by 3000(two 1500 bytes). I have a question, why the Ack number is separated by two packets? Or is it just ...
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1answer
49 views

What is the relationship between throughput and latency

Looking at the structure of a TCP packet, such as discussed here: What is the internal structure of a mobile phone call packet/datagram?, this indicates that a TCP packet size is 192 bytes excluding ...
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1answer
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Client drops packet from server when SNAT is not enabled at Load Balancer

I understand that one reason we use SNAT on a load balancer for incoming requests is so that the response packet from server will go through the load balancer, where the source IP of returning packet ...
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10 views

Cradlepoint IBR1100 Router Randomly Looses GPS Position [closed]

I have an IBR1100 CradlePoint router on a Truck in Ontario, Canada. The router reports back the GPS of the vehicle to a TCP server. GPS fails occasionally with no clear pattern. The router is still ...
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1answer
34 views

How TCP and firewall handle security?

I'm a newbie in networking, still don't quite understand about security. Let's say a person A uses TCP to establish a TCP connection with a server. And there is a hacker B who is sniffing, so B ...
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1answer
23 views

Can I force a higher TCP segment size with netcat?

I'm using netcat to send random data from A to B, both Linux machines on Ethernet networks, with a router in the middle. For pedagogic purposes I'd like to force IP fragmentation on the router (Cisco ...
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24 views

Changing the TCP initial congestion window value in Windows 10 [closed]

I would like to do some testing with the TCP Initial congestion window on Windows 10 Pro, but it seems the settings are disabled in the Pro version: Set-NetTCPSetting -SettingName InternetCustom -...
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8 views

Does TCP server has to run on public IP address only [closed]

I have interfaced a GSM (Uni4 SIM800) module to a Raspberry-pi-3B module using AT commands to run a simple TCP server, and another pair of GSM and Rospberry-pi to run a TCP client. Now the Telecom ...
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1answer
88 views

Linux TCP stack repeatedly sends “TCP window update” without acknowledging any data

My company is developing its own TCP stack for low-latency purposes and one of the tests involves running 128 instances of ncat on Linux 4.11 to listen to ports 55000 through 55127 and sending data in ...
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1answer
51 views

How IP datagram know its upper layer protocol?

Hi I'm a newbie in networking, I just want to know how IP datagram know its upper layer protocol is TCP or UDP? I know there is protocol field inside the IP datagram header that can tell the layer ...
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2answers
48 views

What are the differences between TCP iRTT and ICMP Ping?

I’m attempting to estimate latency between my PC and any servers/clients it interacts with. I don’t want to use Ping for various reasons (requires both ends to allow it, would require additional ...
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1answer
33 views

difference between ip checksum and tcp checksum

If an error on a packet occurs on a router, who does detect the error, IP checksum or TCP checksum? I have understood that the ipv4 checksum detects errors only inside the ip header and the tcp ...
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66 views

How to determine whether files are downloaded serially or in parallel using Wireshark?

In the http-ethereal-trace provided in the link below there are three HTTP GET request.The 2nd and 3rd request downloads a GIF and JPG format image recpectively.How can we determine wether the two ...
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22 views

Setting up a GPS TCP server [closed]

I am working on a project where we are using a GSM modem with built in GPS system. The modem has setting to send GPS signal NMEA format to a remote TCP server. Can someone consult on where should i ...
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1answer
114 views

Is a FIN only packet legal?

It would be convenient to mark TCP packets with just the FIN flag set, as an intrusion (without tracking the reply). I have always assumed that a FIN without an ACK, while rude and rare, is legal, ...
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Wireshark editcap create a tcp.payload file

I want a file of just the payloads from a 5min. tcp exchange between two hosts. I believe I can use Wireshark to just capture those packets which contain a tcp.payload. But after that, I believe I ...
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2answers
50 views

What are the resources that the server allocates to a client when it receives a TCP SYN request before receiving the ACK? [closed]

So lets say someone sends a lot of SYN requests to a server by spoofing IP, before receiving the ack from the client, does the server reserves the connection's Window size in its memory? if not, then ...
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1answer
57 views

Can TCP session be closed by the server depending on the packet content?

I am analyzing a pcap of command-and-control traffic caught during execution of a malicious file. First, a DNS request for a malicious domain was sent and after response is received and TCP connection ...
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3answers
58 views

Do OSI and TCP/IP models use the same protocols?

OSI is known for using hundreds of protocols to do its job. Both OSI and TCP/IP have Transport and Network(Internet) layers where TCP and IP protocols work respectively. It is clear that TCP/IP model ...
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2answers
159 views

If TCP is a reliable data transfer method, then how come its checksum is not 100% reliable?

So in the networking book by Kurose, we define UDP as a unreliable method because it might not detect errors and therefore transfer a corrupted packet or transfer the data without the order so its ...
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1answer
14 views

IP packets get queued in intermediate routers and can delay their delivery to the destination?

TCP segment go inside IP packets,there are many problems IP packets get queued in intermediate routers and can delay their delivery to the destination?
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1answer
24 views

IP packets can get dropped with TCP payloads?

TCP segment encapsulate it IP payload,if some way ip packet is lost in transmission. some time IP packet will be fragmented, i ask if this one fragment part will be lost in transmission.how can fix ...
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3answers
54 views

How does any program identify the protocol header next from TCP?

I need to know how does wireshark or any other program knows the protocol next from TCP. I mean, for instance: The Ethernet layer has a field named Type which carry the IPv04 The Internet protocol ...
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1answer
24 views

tcpreplay packet flooding?

I have limited networking knowledge so bear with me here on this explanation... In my companies datacenter we have some devices that run tcpreplay traffic and usually, there are no issues as the ...
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1answer
40 views

Is there anything inside the application layer in the three way handshake phase?

So is the application layer of TCP handshake packets empty no matter what the protocol is? and when the first packet of TCP handshake(phase 1) arrives at the server, which process does the server ...
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1answer
59 views

Is the first segment which is sent by the client in the 3 way handshake counted in the tcp congestion control?

So lets say we want to make a TCP connection with a server since in TCP we double the sending segments(the number of segments we send or window) after receiving the acks because of tcp congestion ...
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1answer
62 views

End-to-End delay

I’m working through questions from computer networking top down approach and was hoping to get some clarity on the end-to-end delay calculation. At this stage we are not considering processing, ...
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3answers
68 views

Do TCP implementations retransmit bytes or segments?

The sequence number and acknowledgement number in the TCP header is specified to contain byte counts. However, a lot of resources, including RFCs, say that "lost segments are retransmitted" instead ...
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1answer
52 views

Wireshark capture only TCP packets with the RST flag set

I'm quite new to networking and I got stuck while reading "Practical Packet Analysis: Using Wireshark to Solve...". On page 61 it is written: A common scenario is to capture only TCP packets ...
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15 views

Is there a retransmission timer for each segment of TCP? if not, why? [duplicate]

So if there is only timer for all of the segments of our connection, in this case lets assume timeout timer is 1.01 sec, and we send 10 packets at the same time then if we have only 1 timer and that ...
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1answer
148 views

Is there any TCP segment that both of its SYN bit and ACK bit are 0?

So i read this somewhere that there is no such TCP segment and 0 for both of SYN and ACK is not possible, and i wanted to check whether its true or not if the segment is not the first segment of the ...
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1answer
47 views

Is this a normal TCP retransmission pattern?

Our organisation's desktop computers have been performing not satisfactorily during their accessing of network resources. Out of suspicion, I perform a TCP retransmission statistics. Below picture is ...
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116 views

Sender and Receiver timers in GBN, SR and TCP?

So basically for each of the GBN, SR and TCP's retransmission method, i have 2 question: 1.Is there a Timeout timer for EACH packet or one timeout timer for all of the packets? 2.Is there a ...
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1answer
28 views

Does anyone know why certain TCP inner workings are called FLAGS? [closed]

What's the reason for calling certain TCP inner workings flags?
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1answer
31 views

How to add new tasks to layers of OSI or TCP/IP?

Which software and hardware parts of a computer are responsible for adding or removing values to the initial payload of a data packet in every layer of OSI or TCP/IP model? In other words, which parts ...
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1answer
61 views

Why does software mention TCP or TCP/IP when it means just IP?

When I configure a network interface in Windows to have a static address, I have to go to TCP/IP settings. In this TCP/IP settings dialog I can set IP, subnet and gateway, which are IP- and route-...
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25 views

Are different clock rates affecting the transfer-rate? [closed]

I have to kinds of IoT-devices, which should communicate over TCP and sharing files with each others. IoT-device of type 1 has 240 MHz. IoT-device of type 2 has 160 MHz. Now I have observed the ...
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1answer
66 views

value EstimatedRTT at first time?

What is the value of EstimatedRTT at first time? EstimatedRTT = (1-α) EstimatedRTT + α*SampleRTT Is it the average of all sampleRTT ? For example i have following SampleRTTs: 120 ms, 140 ms, 160 ms ...
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1answer
172 views

How can I plot the TCP RTT graph in Wireshark?

I'm suspecting one of our Host is not performing well in the TCP protocol Level.I have tried to plot the TCP RTT graph using tcp.analysis option in the IO graph.However,I'm not finding the right ...
2
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1answer
184 views

TCP DUP ACKs occurring on a seemingly regular basis

I noticed this while checking the performance of our Teamviewer connections. If i start a download test, the following pattern can be observed in the TCP stream graph provided by Wireshark: The red ...
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1answer
48 views

Can i measure trip time with TCP timestamps?

I'm trying to understand TCP timestamps and their uses. Suppose I have a TCP session between two hosts, and one of them sends a packet to the other. When the receiver receives the packet, is it ...
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37 views

delay and Jitter and packet rates?

I am running some experiments using a topology of OpenFlow switches and D-ITG packet generator on mininet hosts. I noticed that the average delay and jitter decreases as I increase the packet ...
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1answer
60 views

TCP close 2-way handshake with tcpdump package

Well, I got a pcap package that uses the tcpdump command. In this pcap, the TCP closes in 2-way handshake! Questions: In this picture, can anyone determine who initiated the signal to close the ...
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3answers
117 views

How does TCP client know the destination port at the beginning of the handshake?

I know that at the beginning of the handshake, the client should fill in the Destination IP (For IP Layer) and Destination Port numbers for the segment to be correctly delivered to the server. A ...
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2answers
349 views

Error control in Transport Layer vs Data Link Layer

I understand that under the TCP/IP Protocol Suite, error control, flow control and other such services are provided by both, the Transport Layer and the Data Link Layer. My doubt is specific to error ...
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2answers
654 views

TCP's three-way handshake and Denial of Service attack

Hi I'm a newbie in networking, still confused with the relationship between three-way handshake and Denial of Service attack. As we know that if the client does not send an ACK to complete the third ...
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2answers
152 views

TCP Fast Retransmit and duplicated acknowledgements Ask

Hi I read an Textbook(Computer Networking : a top-down approach / James F. Kurose, Keith W. Ross.) describes the process of TCP's Fast Retransmit, basically TCP retransmits the lost paclet when it ...
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1answer
85 views

Function of Internet layer protocols

I was reading about the Internet Layer and protocols in the CCNA book by Todd Lammle, I am not able to understand the following text: One of the function of Internet layer is to provide a single ...
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71 views

TCP SYN packet to change port during established connection

I am looking a wireshark log, and i can see that while data is being transfered from the server, the client is sending a SYN request. Data continues to come in (probably because the SYN packet has not ...
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1answer
40 views

Delayed Ack every 3 segments

I was studying some wireshark captures. I noticed that though Ack's are sent every other packet like i was expecting due to delayed TCP ack, i noticed that at some times it is acking every 3 segments. ...