Tagged Questions
0
votes
0answers
42 views
What could be the possible reasons for bad performance of TCP over Wireless or Sate-lite networks ?
I am running a wireless network having Linux(fedora 17) at sender end.We decided TCP_veno is most useful for my network,so we are using it as default congestion control algorithm.Still, We are not ...
0
votes
1answer
95 views
How to display TCP handshake in Linux [closed]
Hi is there a way to display TCP handshake in Linux? Like for example this WIKI - TCP handshake
Not exactly like the illustration but at least it would show client has sent SYN, ACK, FIN etc
and the ...
0
votes
1answer
28 views
What are the other congestion control algorithms specially designed for lossy Wireless Networks like LTE and WiMax?
I am trying different congestion control algorithms for getting maximum throughput and minimum delay across my setup for TCP flow.Please suggest other available algorithms apart from
Veno, ...
1
vote
3answers
221 views
rsh runs perfectly in normal user but not in root, very strange, why?
When I run command, rsh localhost pwd as a root
It shows below output.
connect to address 127.0.0.1 port 544: Connection refused
Trying krb4 rsh...
connect to address 127.0.0.1 port 544: Connection ...
1
vote
2answers
227 views
Why TCP TIME-WAIT State is present at both ends after a connection termination?
I am reading how the TCP states work and especially the connection termination part.
All of the books or online material I read, shows that for the termination procedure these states are followed ...
3
votes
2answers
226 views
Meaning of log entries from an iptables configuration
My router has Linux as its OS. The system log has a lot of rows about iptable and klogd that I don't understand, could someone explain them to me?
The iptables setup:
iptables -t nat -A PREROUTING ...
2
votes
1answer
242 views
Memory ussage for TCP or named pipe message buffers?
I have a group of programs that I was stress testing today. I drastically shot up the input load to the program and it worked at first, but I had an apparent memory leak sucking up memory. The only ...
3
votes
0answers
98 views
Socksifying a qemu-kvm using tsocks
I'm trying to socksify a qemu-kvm using tsocks, but I have no success.
I don't know if qemu access directly the hardware, skipping the OS or something like that, but I wasn't able to do this feat.
...
3
votes
3answers
236 views
How to measure the time when a packet arrives?
When the packet arrives the NIC generates an interrupt and the kernel then takes over. I want to measure the time at which a packet of a particular TCP flow arrives.
How do I do this in Linux? This ...
3
votes
2answers
4k views
Linux Networking routing to virtual ip addresses from a different subnet
New to linux networking, had a question about routing to virtual ip addresses from a different subnet.
I have three servers (they can all ping each other):
A 10.10.51.182 (connected to router ...
0
votes
2answers
157 views
Why my Http Proxy doesn't reply [SYN,ACK] after received a [SYN] packet from the client?
I have a http proxy running on Linux (RHEL 5.5), intermittently it doesn't reply [SYN,ACK] packet after received a [SYN] packet from the client. This issue can be recovered by restarting the proxy. I ...
3
votes
1answer
1k views
Kill TIME_WAIT sockets immediately?
Is there anyway to kill those TIME_WAIT sockets immediately ? e.g output of netstat:
tcp 0 0 127.0.0.1:8080 127.0.0.1:41500 TIME_WAIT -
tcp 0 ...
15
votes
1answer
2k views
Why doesn't Linux use the IANA Ephemeral port range?
According to Wikipedia
The Internet Assigned Numbers Authority (IANA) suggests the range 49152 to 65535 for dynamic or private ports. Many Linux kernels use the port range 32768 to 61000.
Even ...
2
votes
1answer
664 views
/dev/tcp not present in Linux
I am porting C/pro*c code from UNIX to Linux. The code is:
#define __NFDBIT (8 * sizeof(unsigned long))
#define __FD_SETSIZ 1024
#define __FDSET_LONG (__FD_SETSIZ/__NFDBIT)
typedef struct ...
3
votes
1answer
223 views
Route incoming network requests for a given port to different applications
I have an application that listens for connections on a port, but I occasionally take it down for updates and the like. I'd like a way to configure the system such that if that program is running, ...
1
vote
1answer
280 views
How to limit all tcp traffic to the network interface the session was initiated on?
I have an embedded linux system with two network interfaces (lan0, wlan0) that are configured to the same subnet. A server on this system accepts tcp connections on both interfaces.
How I can assure ...
8
votes
1answer
584 views
Kernel socket structure and TCP_DIAG
I'm working on a software which connects to a Real Time data server (using TCP) and I have some connections dropping. My guess is that the clients do not read the data coming from the server fast ...
6
votes
3answers
1k views
What is the formula to determine how much memory a socket consumes under Linux?
I'm doing some capacity planning and I was wondering if there is a formula that I could use to predict (from a memory standpoint) how many TCP connections I could handle on my server. At the moment, ...
3
votes
2answers
390 views
How to listen to all ports (UDP and TCP) or make them all appear open in Debian
I got an external Debian server. The problem is that my university campus doesn't allow connections to go outside when the port is different than TCP port 22, 80, 443, or UDP port 123. I tested them ...
8
votes
1answer
497 views
what level of the network stack does tcpdump get its info from?
As I was trying in vain to fix a faulty ethernet controller here, one thing I tried was running tcpdump on the machine.
I found it interesting that tcpdump was able to detect that some of the ICMP ...
8
votes
2answers
1k views
minimal TCP MSS in Linux
The TCP MSS in Linux must be at least 88 (include/net/tcp.h):
/* Minimal accepted MSS. It is (60+60+8) - (20+20). */
#define TCP_MIN_MSS 88U
My question is: where did they come up with ...
0
votes
1answer
748 views
How to do “netcat” relays properly so that I have more control?
How to use the netcat to have relays? Like following I tried but not working:
cd /tmp
mknod backpipe p
nc -l -p 7007 0<backpipe | nc 192.168.1.101 9001 | tee backpipe
I want to receive data on ...
0
votes
1answer
491 views
Can't connect remotely to server running redhat (ec2)
I created a RedHat 6.1 VM with EC2. Logged in as root, I installed (unzipped) JDK1.7 in /root/bin/jdk1.7.0 and installed (unzipped) GlassFish 3.1.1 in /root/bin/glassfish3. I set JAVA_HOME and ...
4
votes
1answer
897 views
How long is a TCP local socket address that has been bound unavailable after closing?
On Linux (my live servers are on RHEL 5.5 - the LXR links below are to the kernel version in that), man 7 ip says:
A TCP local socket address that has been bound is unavailable for some time after ...
4
votes
2answers
777 views
What tools do I need to intercept and change an incoming packet on a WP2-Personal wifi hub
Which tools should I research into to intercept a plain text packet, edit it and then continue it on it's way. I am using Ubuntu 11.04 and Backtrack 5; my wifi is WPA2-person encrypted. I need to edit ...
4
votes
1answer
2k views
iptables port-mirroring
I need to be able to get a copy of packets received on port 8001 to port 8002. I have tried the following but I get an error that --tee is undefined.
sudo iptables -t nat -A PREROUTING -p TCP -s ...
14
votes
2answers
5k views
how to check rx ring, max_backlog, and max_syn_backlog size
Quite often in the course of troubleshooting and tuning things I find myself thinking about the following Linux kernel settings:
net.core.netdev_max_backlog
net.ipv4.tcp_max_syn_backlog
...
2
votes
3answers
264 views
Port monitoring on GNU/Linux based NAT router
I am using a Ubuntu machine as a NAT router. How can I find out the following:
the ports on which the LAN machines are listening or communicating (both tcp and udp);
which local machines have ...
13
votes
5answers
8k views
Linux: allowing an user to listen to a port below 1024
I need to allow an user (different from root) to run a server listening on port 80.
Is there any way to do this?
8
votes
2answers
21k views
Orphaned connections in CLOSE_WAIT state
I've got a SLES machine that accumulates TCP connections in a CLOSE_WAIT state for what appears to be forever. These descriptors eventually suck up all available memory. At the moment, I've got 3037 ...
1
vote
1answer
318 views
Select YeAH-TCP like congestion control algorithm to configure kernel
I'm configuring/compiling the 2.6.37 kernel and I want select YeAH-TCP like default congestion control algorithm but, although I enable this option (CONFIG_TCP_CONG_YEAH), it doesn't show in the ...
