TCP is just one communications protocol on the web. Others include: User Datagram Protocol (UDP) udp Internet Control Message Protocol (ICMP) icmp Hypertext Transfer Protocol (HTTP) http Post Office Protocol (POP3) pop3 File Transfer Protocol (FTP) ftp Internet Message Access Protocol (IMAP) imap ...
4
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4answers
25 views
Multicast over TCP or UDP or whatever else
My Server and Client run both on Linux.
The Server broadcasts multicast, the Client listens multicast.
My Client has to migrate to another site,
and unfortunately multicast is not allowed between the ...
1
vote
0answers
33 views
A tool to measure overhead of establishing TCP connections
I need a tool which would while doing port forwarding measure how much time was spent establishing TCP connections vs total time passed. Charles debugging proxy has the port forwarding feature and ...
9
votes
2answers
99 views
How to find process which uses most bandwidth
How can I find the process which uses most bandwidth on a Linux PC?
With iftop it's possible to find which connections produce most bandwidth, but how to find the process?
0
votes
2answers
56 views
Routing traffic so that it appears to originate from a single (static) IP address
We have three sets of computers: clients, a single proxy and multiple servers.
The clients (many) want to connect to the servers (many) using TCP on a specific and consistent port. Currently they do ...
0
votes
1answer
34 views
Benchmarking TCP Server
I've written a very basic TCP-Server based on libevent. Now I would like to test the Server.
Is there a tool which generates a lot of connections so that I can check how much concurrent connections ...
0
votes
0answers
26 views
Is a retransmitted SYN *EXACTLY* the same as the original?
If I have a client trying to connect to a TCP server, and the client sends a couple of retransmits trying to establish a connection, is there ANY difference in the SYNs it will send? If the server ...
2
votes
1answer
55 views
apache webserver unresponsible with server-status showing all child processes waiting for connection
My setup:
i have 3 nearly identical webserver machines serving the same high loaded dynamic website with simple load balancing over dns. The service has been working for over two ears with the same ...
0
votes
0answers
11 views
Incoming Connections on Satellite-Connected Server Failing
I am running a Master-Master replication setup, with one server being on a satellite internet connection. I have used this setup before to successfully offer more responsive applications on laggy ...
0
votes
1answer
34 views
socat: Show incoming connections
I am slightly going mad. Even if I call socat like this:
socat -vvvv tcp4-listen:9000 tcp4-listen:9001
it works perfectly, but doesn't inform me about incoming TCP connections! Is there an ...
0
votes
2answers
37 views
SYN cookies on internal machines
Our system uses Cassandra running on Ubuntu 10.04 and during last spike in traffic we observed the following message in logs:
possible SYN flooding on port 9160. Sending cookies.
These machines are ...
2
votes
3answers
182 views
how to check connectivity to server by windows tools?
I need to check if client can connect to server on specific TCP port. Server is listening on it. Tried "telnet server_IP port" but telnet is stuck when I see that it's connected to the server. Seems ...
0
votes
1answer
86 views
Finding short-lived TCP connections owner process
Running tcpdump on local connections to an apache server, I found TCP connections being established and closed immediately every 2 seconds. How do I find which process is responsible for these? ...
3
votes
2answers
135 views
Exhausting Linux machine TCP socket limit (~70k)?
I am the founder of torservers.net, a non-profit that runs Tor exit nodes. We have a number of machines on Gbit connectivity and multiple IPs, and we seem to be hitting a limit of open TCP sockets ...
1
vote
2answers
59 views
Https tunnel for carrying TCP and UDP packets
I had an issue with running Openvpn over UDP in my college network. The firewall was dropping UDP connections. As http and https were working fine and assuming that the firewall was inspecting packet ...
0
votes
0answers
34 views
How to route all internet traffic via a virtual tap device and a public server
We want to route all traffic from one pc to a local virtual device (TAP-Win32 Adapter which is also used by OpenVPN) and then from there to another tap device on a public server. after that all ...
0
votes
1answer
56 views
Clustering TCP servers, so can send data to all clients
I'm developing a real-time mobile app by setting up a TCP connection between the app and server backend. Each user can send messages to all other users.
(I'm making the TCP server in Python with ...
1
vote
1answer
34 views
What's the difference between Send-Q and S-BCNT in FreeBSD netstat -anx?
What's the exact meaning of Send Buffer byte count in the extended netstat statistics, and why is it always bigger than Send-Q?
In other words, what's counted against the S-BCNT that's not counted ...
1
vote
2answers
74 views
When the TCP engine decides to send an ACK?
In my LAN, I have a router that runs a Samba server and my PC connects to the router.
I wiresharked during a uploading to the server and a downloading from the server.
The wireshar results show ...
0
votes
2answers
43 views
Needs help to understand the wireshark results of a data transferring
In my LAN, I have a router that runs a Samba server and my PC connects to the router.
I wiresharked during uploading a file from my PC to the samba server.
Below is a shortcut of the wireshark ...
1
vote
2answers
89 views
Force forwarder DNS requests to TCP mode
I have set up a DNS-server on SLES10 (currently bind 9.6) on a multi-homed server. This server can be queried from all internal networks and delivers answers for all internal networks. We have two ...
2
votes
6answers
195 views
Effect of distance from server on page load speed
I measured the load speed of a static image file severed by nginx from my server (using pingdom service). The server should normally process this request within few seconds. My server is located in ...
-1
votes
1answer
61 views
Congestion Control in TCP
Why is the threshold set to one half of the current congestion window size when the timer expires at the sender?
1
vote
2answers
90 views
why there is a large difference during the 1st and 2nd packet and then a very small difference between the 2nd and 3rd packet in the TCP handshake?
Why there is a big difference in the time elapsed between the SYN and SYN-ACK and then a much lesser difference between the time elapsed from SYN-ACK and the last ACK during the TCP 3-way Handshake?
0
votes
0answers
32 views
pass source port to app server behind haproxy
I have a haproxy configuration run in http mode. I pass requests to backend java servers. I use forwardfor option to get client ip in backend server. I want to get source port in backend server but ...
1
vote
2answers
105 views
What is the simple Linux utility that is like cat but works via TCP (to be used for port knocking)?
For port knocking over at my old job, one of the SAs use to perform something like the following:
echo 'blah' > tcpcat -a 192.168.3.1 -p 2222 && ssh beamin@192.168.3.1
I cannot remember ...
0
votes
1answer
60 views
Is there any way to set PPTP on UDP Protocol? [closed]
In our network,many web site has been filtered ,so we should use VPN or Socks ,They reduce any tcp connection speed by dropping random packet (Than post and get on http),So ssh,pptp and ... are so ...
2
votes
1answer
105 views
TCP initial congestion window (slow-start)
I have noticed that the initial congestion window in my traces is 8920bytes~=6*1448. rfc3390 states the initial cwand should be max 4000 bytes(around 3*1448).
At first i thought it might be because ...
1
vote
1answer
85 views
Server behind DMZ firewall won't respond
I have a DMZ server set up to forward specific ports to a couple of machines. The intended behavior is for me to send a request to the DMZ on a specific port, and have the machine that's inaccessible ...
1
vote
0answers
36 views
TCP Connection Keep-Alive direction
When a connection have not received packets for a certain period of time (default 2 hours), it should send KEEP-ALIVE packets.
My question is, who will start sending KEEP-Alive packets, the client, ...
4
votes
1answer
76 views
droping packet on iptables = wasting bandwidth?
recently I do this on my iptables :
-A INPUT -p tcp --dst 192.168.0.0/16 -m hashlimit --hashlimit-above 32/sec --hashlimit-mode dstip --hashlimit-name hosts -j DROP
it seems that if my client ...
4
votes
1answer
67 views
Collect per-TCP connection statistics on Linux without promiscuous mode (e.g. without tcpdump)
Linux keeps per-interface statistics, ifconfig reports them just fine.
But does Linux keep per-TCP connection statistics, specifically, how many rx/tx bytes this session? If it does, I sure can't ...
1
vote
1answer
73 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 ...
1
vote
1answer
85 views
ICMP destination unreachable
I am working on an arch linux machine with ethernet interface eth1. I have created interface eth1:0 using ifconfig and given it a dummy hw address (00:01:02:03:04:05). When I send a UDP packet to a ...
1
vote
1answer
72 views
Automatic TCP connection slowering (shaping)
I'd like to automatically shape bandwidth-hungry TCP connections corresponding to the already transmitted data.
A summary would be : "The first Mbit is transferred at full bandwidth, then it ...
1
vote
2answers
121 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 ...
0
votes
2answers
83 views
Can I have TCP timouts up to 10-20 minutes?
It it important to rely on TCP guaranteed delivery even in case of mobile client which could disappear in a tunnel for a long time when TCP with standard settings give up and close the connection. Is ...
0
votes
2answers
41 views
Listing TCP/UDP process from an organically grown application
I've been asked to compile a list of TCP/UDP and ports they use for the collection of application that comprise our product for a client who wants the information for their firewall.
So I fired up ...
4
votes
2answers
89 views
How do I check how many connections are open currently on a specific TCP port?
I'm doing some comet benchmarks and would like to see how many open connections I have.
Actually I use netstat:
netstat -ant | grep 8080 | grep EST | wc -l
But it needs around 4-6 minutes to list ...
0
votes
2answers
153 views
Troubleshoot large number of TCP retransmits / dup ack / segment lost
I have a problem with RDC slowing to a crawl or disconnecting entirely. Client is XP SP3 w/ RDC 6, server is Win 2k8 R2. Both have been scanned thoroughly and found to be virus free.
I downloaded ...
-1
votes
3answers
298 views
Been up for 2 days please help! SYN flooding Error [closed]
I'm having a problem been working on this for 3 weeks been up the past two days trying to fix this.
My server is a busy server
If I run netstat -plan | grep :80 | wc -l I get 22717.
In my logs I ...
1
vote
1answer
48 views
Setting MTU Per Destination Host
I'd like to change the MTU per host as I have a mixed infrastructure where not all devices support the same MTU. I'm on OS X 10.7 and like to set some MTU per destination host and a default one.
-1
votes
2answers
51 views
SSH occasionally (rarely) doesn't connect
I've been running this script for a few days:
while [ true ]; do ssh USER@SERVER echo -n . || date +"%s"; done
Obviously, my terminal is filled with dots, but sometimes (quite rarely) I get this
...
2
votes
1answer
59 views
Testing my Load Balancer
To test my Load Balancer I would need to create several TCP/IP connections (from one host).
Which tool can be used to create this sessions with different source-ip addresses?
(no worries, only in my ...
10
votes
3answers
446 views
Is it possible for a TCP connection to remain open when the client has disconnected?
We have a server application which is facing TCP exhaustion problems at around 4000 connections. This will occur every 3 or 4 weeks (approximately). The vendor, which has created this server ...
1
vote
0answers
79 views
Does TIME_WAIT affect dynamic ports?
I've read a bit about TIME_WAIT connections, and know they should be harmless to my server (connection closed, so no resource connected with this socket).
Recently, my server reached the magic ...
2
votes
1answer
102 views
Kill Tcp Connection
Greeting,
I am testing application on linux, and we have a bug related to the database connection, since the database connection cannnot be restarted and it's on a remote machine, I would like to ...
2
votes
2answers
116 views
When does a browser send HTTP payload separately from the HTTP request?
Under what circumstances would you expect a web browser split an HTTP request into two IP packets, even if the sum of the packet sizes is still less than the maximum segment size? I would assume that ...
0
votes
1answer
78 views
What is responsible for Connect/Send/Wait in a HTTP request?
Services like pingdom and Google speed analyze the time consumed for reading a HTTP file. This includes
DNS: Obviously, DNS management to interpret the namespaces is responsible.
Connect: ???
Send: ...
0
votes
2answers
101 views
how to calculate packet loss from a binary TCPDUMP file
Our connection to just one remote server on port 80 over the internet is not working properly. (From time to time it is working and sometimes not)
It must be some kind of packet loss, because from ...
8
votes
5answers
370 views
In TCP/IP terms, how does a download speed limiter in an office work?
Assume an office of people, they want to limit HTTP downloads to a max of 40% bandwidth of their internet connection speed so that it doesn't block other traffic.
We say "it's not supported in your ...
