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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3answers
34 views
Max client TCP connections through a router
I've just been thinking about what the maximum number of client connections would be out of my home LAN to a single server on the internet. My home router is also NAT'ing the connections to convert ...
0
votes
1answer
24 views
Socket based byte counts
I see a lot of tools to get the RX and TX byte counts for transmission on interfaces, is there any tool/program that I can use to get a total transmitted byte count for a single specified socket?
I'm ...
2
votes
2answers
65 views
Reduce firewall rules by half - one iptables rule for tcp and udp
I have a number of iptables rules on my firewall that look like this:
iptables -A zone_lan_forward -p tcp -d 1.2.3.0/24 -j ACCEPT
iptables -A zone_lan_forward -p udp -d 1.2.3.0/24 -j ACCEPT
Is ...
6
votes
1answer
124 views
Lower TCP throughput from 1Gbps server than 100Mbps server over large RTT
We've got infrastructure distributed in a few major locations around the world - Singapore, London and Los Angeles. The RTT between any two locations is over >150ms.
We've recently upgraded all of ...
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votes
2answers
34 views
Can I find out what certificate revocation server an application is contacting?
I'm trying to install an application on a machine running Windows XP Pro.
There are two different servers being contacted, both using the same wildcard certificate (GoDaddy). One via https, one ...
0
votes
1answer
43 views
Minimal handshaking necessary before establishing TCP connection
I have a Windows PC that is running a TCP server on port 9000. I also have an FPGA which is directly connected to the PC via a 10G port. The FPGA can send ethernet frames to establish and maintain a ...
1
vote
4answers
47 views
Rsyslog not logging from remote server
I am trying to set up a centralized log server. I have central server (A) receiving logs via a remote server (B) on port 514. I know it is receiving these. Here are a few entries from a tcpdump on ...
2
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0answers
33 views
How to force use of tcp instead of udp for rpcbind?
I'm trying to use tcp/111 for rpcbind under Debian Wheezy instead of udp/111. The portmap in Squeeze uses tcp/111 without any special configuration, but Wheezy fails.
Even numerous sites (as well as ...
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0answers
31 views
How to solve 3 way handshake [closed]
18:19:21.543368 IP (tos 0x0, ttl 117, id 766, offset 0, flags [DF],
proto: TCP (6), length: 48) 103.84.236.14.27937 > 198.27.85.103.6010:
S, cksum 0xb8c2 (correct), 1102345511:1102345511(0) win ...
-2
votes
4answers
166 views
Why is the TCP checksum inverted?
From the Wikipedia page:
The checksum field is the 16 bit one's complement of the one's complement sum of all 16-bit words in the header and text.
Why, after summing the 16-bits in the header ...
1
vote
2answers
46 views
TCP vs UDP Error-Checking
I've bounced upon two articles that describe in-depth on how TCP and UDP connections work. However there is some kind of inconsistency. Where one article tells me that UDP does no Error-Checking at ...
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0answers
43 views
tcp recycle and retransmission
TCP recycle reduces TIME WAIT by reusing sockets. It avoids collision with older packets by storing timestamp and receives packets with greater TCP timestamp. What happens when the client retransmits ...
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1answer
21 views
What process does 'own' socket in 'Time Wait' state?
Main question
I see following line in netstat. Does it means this socket doesn't belong to any process?
#>netstat -tpn|grep TIME_WAIT| head -1
tcp 0 0 ::ffff:127.0.0.1:5555 ...
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votes
0answers
27 views
Networking with Python: No response from IP Phone [migrated]
I'm an Automation Developer and lately I've taken it upon myself to control an IP Phone on my desk (Cisco 7940).
I have a third party application that can control the IP phone with SCCP (Skinny) ...
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votes
0answers
28 views
TCP connection termination
Say I have a App Server & DB Server. When I check the TCP connection to DB Server from App Server(using netstat), it shows like 120 connections, all with status 'ESTABLISHED'. However, when I ...
1
vote
1answer
70 views
TCP RWIN, MSS and MTU [closed]
I have been doing some reading into TCP Receive Window (RWIN), Maximum Segment Size (MSS) and Maximum Transmission Unit (MTU). Right off the bat I have some questions and I need a power user's help!
...
0
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0answers
23 views
Nagios connection reset (RST) “Misplaced TCP option (SACK)” - No data was received from host
This issue is a strange one. I have a Nagios server running for quite a while now, and all of a sudden I can't get data from 2 hosts...
The hosts are located in a different subnet:
Nagios: ...
3
votes
1answer
29 views
How to disable Xvfb using TCP ports when using pyvirtualdisplay (Python)?
Trying to use pyvirtualdisplay for Python to start some applications with a virtual Xvfb X terminal. However, we've seen port clashes and would like to disable Xvfb from using TCP ports. I have ...
2
votes
0answers
15 views
TCP Reno Window Size drops to 0
I'm working on a task on comparing TCP Tahoe and Reno.
Tahoe drops the window size to 0 every time it detects packet loss, that is clear. However, when I plot my window size for Reno, it does fast ...
0
votes
1answer
34 views
TCP/IP routing: accessing a LAN device with wrong static IP configuration
I forgot to change the static IP of a network device before moving it from my datacenter network to my home LAN. Since it isn't configured properly for my LAN network, I'm not sure how to access it.
...
0
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0answers
40 views
Cant connect to mysql server
I'm trying to configure a freshly installed mysql server to listen on port 3306.
I've removed skip_networking, I have changed bind-address=172.20.33.1 (which is my server ip) and it completely ...
0
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1answer
38 views
How do I get my ubuntu server to listen for database connections?
I am having a problems connecting to my database outside of phpmyadmin.
Im pretty sure this is because my server isn't listening on port 3306.
When I type:
sudo netstat -ntlp
on my OTHER working ...
0
votes
1answer
22 views
Three Duplicate acknowledgements
I understand the process of congestion avoidance where you trying to control the level of congestion in a network, and avoid loss of packets. But how can there be three acknowledgements, even if one ...
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0answers
26 views
PDU for Automatic repeat request protocols [closed]
Which PDU should be used when talking about the automatic repeat request protocols? i understand:
Data (Application Layer 7)
Segment (Transport layer 4)
Packet (Network layer 3)
Frame (Link layer 2)
...
0
votes
0answers
31 views
Acknowledgements in TCP [closed]
When a packet is sent in the three-way-handshake which includes Syn(synchronise) open connection and a packet is sent, this must be ack'ed(acknowledged) which i think is the sequence number of the ...
0
votes
1answer
37 views
svnserve -d child process spawning and svn connections under netstat
I see many svnserve -d processes running on my CentOS 6 box, one with the PID 400 and PPID 1 and the rest with PPID 400. I take this to mean the first one is started by init scripts (i know it is) ...
0
votes
2answers
66 views
Traceroute, ICMP, UDP and TCP
When does traceroute use TCP? Or does it just use UDP, also why does Traceroute use UDP on MacX and ICMP on windows? I thought ICMP just contains a message saying what caused the error of a packet and ...
0
votes
0answers
17 views
Can't connect to SSH over VPN when using 3G only [migrated]
I'm having a bit of a strange problem that I'm not sure how to debug/fix. I have a Raspberry Pi connected to a Windows VPN via either a wired interface or 3G dongle. With the wired interface I can ...
0
votes
0answers
38 views
How to interpret findings on TCP Send/Recv Buffers
I have an application running on a CentOS machine that connects to a remote DB server on another CentOS machine. Every once in a while, without any discernable warning signs, the application seems to ...
0
votes
0answers
35 views
reset packet sent when receiving big TCP traffic
A client receives chunks of TCP segments from a server, which total 20MB or more. Sometimes the client will send RST segments to the server before terminating the TCP connection. Before sending RST ...
2
votes
2answers
30 views
Is TCP RWIN set by application or OS?
I have a situation where an application is listening on a TCP port and every once in a while, as seen in tcp dumps, gets its Receiving Window (RWIN) set to zero. When this happens, its Recv-Q stops ...
1
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0answers
44 views
TCP 443 Connection goes into server but never reaches Apache2 (Passenger)
We have some weird problems, when external servers try to connect to our Website on Port 443(TCP) which is an Apache2+Passenger and a Rails Application.
The problem only happens rarely. I started to ...
1
vote
1answer
20 views
How to diagnose why a port is broadcasting a “ZeroWindow” status
I have two CentOS servers (one is an app server, the other is a DB) communicating over a port. Every once in a while, the application server starts broadcasting that the port connected to the DB has a ...
-1
votes
3answers
66 views
How to troubleshoot network infrastructure issues from computer side (no access to switches/routers) [closed]
I have situations where the first ping is dropped/times out between certain machines, and connections to Windows shares often time out or get dropped. I don't see errors on the NIC for these ...
1
vote
1answer
79 views
UDP packets dropped
A host sends UDP broadcast, but its UDP packets are not received by any other hosts in the same subnet. However, its TCP traffic with others hosts are OK. I observed this using tcpdump.
Could it ...
1
vote
3answers
47 views
RHEL (say 5.6, kernel 2.6.18-238) with dual IP address (IPv4v6)
So I have a SERVER that that utilizes RHEL's (assume 5.6) underlying kernel for setting up TCP connections and other networking aspects. My deployment need requires that the SERVER have dual IP ...
0
votes
2answers
53 views
IP and Port Forwarding on ASA 5505
I have an ASA 5505 with outside network of public ips 95.123.234.64/26 and inside network of private ips 10.22.33.0/24. I would like to redirect any tcp traffic that hits 95.123.234.67:80 to a public ...
3
votes
1answer
57 views
Does a growing number of TIME_WAIT connections affect server performance?
I have 2 servers, both running RHEL 6, one for Apache 2.2 and one for memcached (memcached-1.4.4-3).
I noticed an increase in the number of TIME_WAIT connections on the Apache server
netstat -n | ...
1
vote
3answers
109 views
Send TCP/IP packets down three routes and pick fastest
Does there exist a way to split TCP/IP traffic across three routes and have the first packets to reach the destination be used?
I'm imagining something like multi-homing but with the requirement that ...
0
votes
1answer
55 views
Is tcp_keepalive application dependant on Linux?
According to http://tldp.org/HOWTO/TCP-Keepalive-HOWTO/index.html , the kernel keepalive function occurs at the OS level, and doesn't require an application to explicitly call it. However I also read ...
1
vote
1answer
54 views
Problems with connecting to TCP server
I have two PCs in the same LAN: "A1" and "A2". There is another PC in a different LAN: "B". A TCP server is listening on machine "B", port 80. From machine "A1", I can connect successfully to machine ...
1
vote
1answer
33 views
Is a tcp packet with only FIN flag set valid?
got some packets dropped, but from what looks like legitimate IP
0
votes
0answers
147 views
ffmpeg simple RTMP streaming
I am trying to launch up a rtmp transcoder server using ffmpeg; that receives udp MPEG-TS streams as input, transcodes it; and generates an rtmp output to a URL, that can be accessed by users to ...
-2
votes
1answer
99 views
Telnet Port 23 Not Responding' [closed]
I have an assignment that requires remote access into some Cisco routers. According to Netlab, it uses TCP port 23.
I'm unable to pass the port test. I'm on Windows 7, I've tried all major ...
0
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1answer
54 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?
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3answers
54 views
Which bit represents which TCP flag?
For instance, a WireShark capture filter example I found - tcp[13] & 8 == 8 represents packets with PSH flags.
How do I count the 8 ?
Based on the wikipedia image,
PSH is in the middle of ...
2
votes
1answer
35 views
SVN repo browser does not show an open TCP connection on backend
When I am connected to mysvnserver using the repo browser (TortoiseSVN), I do not see an open connection when I perform a netstat on the mysvnserver box and grep for my computer. What is the ...
0
votes
1answer
112 views
openvpn tcp or udp (specific situation, reliability-layer collisions)
My question is whether to use TCP of UDP for my openVPN connection.
I've set up a simple network for a startup company that allows users from the outside to acces the network via an openvpn server (in ...
3
votes
1answer
132 views
Rotating outgoing IPs using iptables
I am trying to rotate outgoing IPs using iptables. I want to rotate outgoing connections between three IPs, one by one. Here is what I'm doing with iptables:
root@server:~# iptables -t nat -I ...
8
votes
1answer
200 views
Where can I embed proprietary information in a layer 2 or layer 3 packet?
The Citrix Netscaler has an interesting property that embeds information in the TCP packet that gets sent to the host. This property is echoed back to the Netscaler in such a way that the Netscaler ...
