TCP stands for Transmission Control Protocol and is one of the core protocols of the Internet Protocol Suite. TCP complements the Internet Protocol (IP), and therefore the entire suite is commonly referred to as TCP/IP.

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Why does TCP Reno cut the congestion window in half when I get duplicate ACKs?

I'm having a hard time understanding this conceptually. Why does TCP Reno cut its congestion window in half when it detects triple duplicate ACKs and cuts its window to 1 segment when it times out? ...
8
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3answers
8k views

What are the ramifications of setting tcp_tw_recycle/reuse to 1?

I set both tcp_tw_recycle/reuse to 1 in my configuration file. What are the ramifications of doing this? If a tcp socket is re-used, does that pose a security risk? i.e. 2 different connections both ...
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1answer
95 views

Packets being routed to the wrong IP

Looked around, can't find a similar issue anywhere... I have been having some very strange and hard to explain problems on my network lately, and in my efforts to find the cause, I came across an ...
85
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7answers
126k views

How to forcibly close a socket in TIME_WAIT?

I run a particular program on linux which sometimes crashes. If you open it quickly after that, it listens on socket 49201 instead of 49200 as it did the first time. netstat reveals that 49200 is in ...
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1answer
38 views

Send proper UUID over tcp

I have a small ingest TCP server that should accept a device UUID as a first message, which is only 16 bytes. I'd like to test this manually from terminal, but sending a string won't work, since it ...
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1answer
76 views

Is “keeping alive connections” the smartest approach to access devices behind a router? [closed]

The problem I'm developing an IOT device that will connect to a common Wifi router. As you know in order to make this device publicly accessible from WAN you'll have to do some ports forwarding or ...
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2answers
225 views

Keeping TCP connections alive to track which clients are online

I am developing an application where a server needs to stay in touch with lots of simple IoT devices. Nearly no information exchange is needed between the server and each device, but devices need to ...
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0answers
153 views

Inconsistency in TCP and HTTP connection management

I observe following scenario in WireShark: The problem I see here is that after receiving [FIN, ACK] from server (4090) and acknowledging it (4092), http client attempts to send another HTTP ...
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0answers
78 views

What exactly constitutes a bad TCP segment?

What constitutes a bad segment as in bad segments received in the netstat output below? I would think a TCP header's checksum could do it, but are there other things? If a segment arrives after its ...
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2answers
1k views

How to edit TCP window size from iptables?

There is TCPMSS target to edit MSS value of connections (including forwarded). How to edit window size (for example, cap to some maximum value) by iptables rule? Expecting something like iptables -...
2
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1answer
152 views

(Completely) randomize IP addresses in PCAP file

I have several PCAP files which contain network traffic. To perform some experiments for a network experiment, I need real data with completely randomized IP addresses. I am well aware about the ...
2
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2answers
2k views

Troubleshooting High TCP Retransmit Rate

I've been attempting to troubleshoot a network issue that presents with very high rate of TCP retransmits. 36 samples (taken with Wireshark 1.10.8 running on 32-bit Windows 7) totaling a little over ...
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1answer
438 views

SynProxy can not return syn ack packets with asymmetric dual bridge topology

I have a asymmetric dual bridge topology as shown below when i connect from 172.16.11.5 and 172.16.10.6 with ssh but i can not connect because of SynProxy. ------- ...
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1answer
402 views

Nginx Configuration:504 Gateway Time-out error

We are using Nginx as a Load balancer. Nginx having IP address of :10.110.0.200 and address of host machines are 10.110.3.20|10.110.3.21 this is the configuration file: upstream test1 { server 10....
2
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3answers
4k views

Monitor loopback traffic (monitor MS TCP Loopback inteface traffic) with Microsoft Network Monitor 3.4 - possible?

I've downloaded NM 3.4 from microsoft.com and it appears that the software doesn't capture traffic on MS TCP Loopback interface. When I ping 127.0.0.1 address, NM shows no packets flowing. I've tried ...
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3answers
5k views

Configuring keepalives with TOAD client communication

I have a scenario where long-idle sessions of TOADSoft client communication with the Oracle server seem to be torn down as they timeout on an intermediate state-full firewall. These sessions could ...
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4answers
42k views
1
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1answer
238 views

Millions of TCP FIN-ACK retransmissions blocking traffic on my desktop machine

In a few minutes I have received about 7 millions(!) FIN-ACK packets from IP address that belongs to Google 74.125.133.188 what totally blocked network traffic on my desktop(!) machine. Other ...
3
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0answers
79 views

Does Fast Retransmit and Retransmission Timer work at the same time?

When Fast Retransmit is implemented, if I received packet 1, then I will send an ACK that says I need packet 2, and then if I received packet 3, I will send a duplicate ACK that says that I need ...
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0answers
27 views

Why is server refusing new connections?

One of our proprietary closed source server applications sometimes stops accepting new connection from remote nodes on its server port. Remote nodes that are already connected work fine. Any new ...
2
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1answer
958 views

Disable kernel processing of TCP packets for raw socket

I'm working on a TCP/IP implementation, for an embedded device, that I want to test from a Linux user space process using raw sockets. raw(7) says that Raw sockets may tap all IP protocols in ...
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3answers
2k views

Windows Server 2008 - unable to bind any TCP port

OS: Win Server 2008 RC2 Windows firewall on (no effect when off) I have suddenly been plagued by an issue in which I cannot find any similar ones with a search. I am running about 20 game servers ...
0
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0answers
80 views

Can I use MS Host Integration Server to connect to an IBM without using SNA

I'm sorry, this will represent a lot of information, but I'd like to avoid some of the back and forth I'm having with various forums trying to resolve this issue. So please, bear with me. I've taken ...
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0answers
28 views

What technology do data center use to guarantee low RTT?

I was reading about data-center-tcp DCTCP and the paper was talking about the low retransmission timer (RTT) of about 250µs, but didn't state how that is being done. Somewhere else I read that DCTCP ...
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1answer
156 views

Does ColdFusion use TCP Ports?

I am trying to access a link on our network. Whenever I try, the page times out. I have discovered that this link is a Adobe ColdFusion web page. Does ColdFusion use a TCP port other than port 80? I ...
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1answer
103 views

How to prevent TCP network flood triggered by KVM VPS clients?

How to to protect nodes/ detect and block KVM VPS clients that TCP flood the network ? I use SolusVM VPS management system. Recently one abuser toke several VPSs and flood it the datacenter network. ...
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0answers
188 views

How to fix the amount of bandwidth of iperf in tcp mode?

I'm working on some experiments about my master's degree project. I'm studying some load-balancers (I'm not supposed to cite them here) and the aim is to get for each bandwidth the cpu % usage of a ...
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2answers
781 views

TCP sequence number randomization

In a recent interview, my friend was asked about firewalls’ TCP sequence number randomization feature. The interviewer mentioned that we know that a firewall randomizes the TCP sequence number, but an ...
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0answers
98 views

what is the significance of URGENT POINTER in TCP Header?

Urgent Pointer: Used in conjunction with the URG control bit for priority data transfer. This field contains the sequence number of the last byte of urgent data. It is possible to identify the urgent ...
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1answer
552 views

Openvpn: no response from server in tcp handshake

I am attempting to connect to an openVPN server that I created on pfSense 2.2.3 by using tunnelblick on my Macbook. Whenever I attempt to connect using either OpenVPN version 2.3.6 or 2.3.7 (all that ...
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0answers
44 views

TCP traffic redirection

I am using an open source program called revinetd: revinetd.sourceforge.net On server side, revinet listens for incoming connections on a defined port to act as a relay server. Now, The server ...
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1answer
88 views

Tcp connection breaking, too fast for serial?

I've been having real difficulties getting a tcp connection to work with my web server. I think the issue might have something to do with the speed or ordering of the packets as the connection seems ...
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0answers
96 views

Why would Windows 7 not complete this TCP handshake?

One of our customers is running Windows 7, and cannot reach some of our servers because it seems Windows 7 cannot complete a TCP handshake. Here's a packet trace to one our servers -- note that a SYN ...
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82 views

Spurious retransmission, Dup ACK and HTTP 408

I have a server which serves as sms gateway (using kannel) and have multiple client connecting to it, but recently this one client with their particular IP said that they can't send to my server and ...
18
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4answers
91k views

What causes duplicate ACK records?

We're reviewing Wireshark captures from a few client machines that are showing multiple duplicate ACK records which then triggers retransmit and out-of-sequence packets. These are shown in the ...
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0answers
272 views

Citrix NetScaler sending FIN, ACK for SSL VPN Clients

I realise that it's unlikely anyone here has a definite "Check this box to resolve this" answer, but I'm struggling with this issue and I'm hoping that someone with more knowledge than me can give me ...
0
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1answer
164 views

TCP Keepalive: Why does an idled ESTABLISHED connection end after 60 seconds, instead of tcp_keepalive_time?

I am investigating ways to mitigate a server against DoS-type attacks. In one scenario, I've opened several hundred TCP connections to my webserver. I do not send any data after the initial TCP ...
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0answers
12 views

Route only on output chain?

I have two machines A and B. I want to send iperf traffic from A to B, but first have it route through a userspace program on A. I did this with a tunneling device: therefore, I used the command ip ...
5
votes
1answer
7k views

Unexpectedly shrunk window

I run a major media upload/download site and I noticed these: Is this serious or background noise due to the big file sizes and is there any tweaks I can add to /etc/sysctl.conf to improve and ...
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2answers
185 views

How to run Different congestion control algorithms in FEDORA 17?

I need to use different congestion control algorithms for tcp flow. How can I continue using those flow congestion algorithms from Fedora 11 in Fedora 17?
5
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3answers
696 views

TCP sequence number

I would like to know if two segments of same sequence number arrive at the destination, which segment will get accepted ? For eg: A clients sends a packet to a server and wait for an ...
2
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3answers
4k views

Test a server using MTR through TCP

Is it possible to use MTR over TCP? If not is there an alternative? I have done some research and I am not finding any way to do such a thing, so I'm wondering if anyone has had any experience with ...
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1answer
63 views

ufw status (what does the v6 stand for?)

My ufw status output looks like this: To Action From -- ------ ---- 22 ALLOW Anywhere 80/tcp ...
1
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0answers
94 views

Debian limit number of TCP sockets for a process (especially tor) on OpenVZ

I have a debian 7.8 server, running on OpenVZ. On this server I'm running a tor relay and some other network services (like apache and mysql). However the tor service seems to eat up all my available ...
2
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0answers
56 views

Network sensor for a TCP connection for collecting statistics each second [closed]

I need a Network Sensor capable to gather basic end-to-end statistics (packet loss, jitter and network delay/RTT) of several TCP connections directed to the very same destination (ip-addr:port) on ...
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0answers
100 views

Should I disable the Nagle Algorithm for Outlook / Exchange RPC/HTTP communication?

I'm investigating reasons why several Outlook clients in non-cached mode are having delays communicating... resulting in Outlook hanging. My suspicion is that a Netscaler, or intermediate device (? ...
-1
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1answer
65 views

Can TCP be used like UDP by simply not sending ACK?

Assuming both client & server cooperated, could you emulate the functionality of UDP by not sending ACK packets, and not sending retransmissions? Or would most routers somehow bork the process if ...
0
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0answers
141 views

SSH stalled after a while

I am executing some commands over SSH from a linux client (centos 7) toward a server (wind river linux) and for a reason it always stopped ( not completed ). If i executed a command that take short ...
0
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1answer
123 views

REDSOCKS goes 'out of file descriptors' when trying to redirect all outgoing (TCP) traffic from my Linux machine

I'm trying to redirect all outgoing TCP traffic from my linux box to the remote SOCKS5 proxy server. Currently I'm using the following rule in the OUTPUT chain: sudo iptables -t nat -A OUTPUT -p tcp ...