UDP stands for User Datagram Protocol. With UDP applications can send messages (datagrams) to other hosts on a network without requiring prior communications to set up special transmission channels or data paths.
15
votes
2answers
2k views
What is the “in-the-wire” size of a ethernet frame? 1518 or 1542?
According to the table here, it says that MTU = 1500 bytes and that the payload part is 1500 - 42 bytes or 1458 bytes (<- this is actually wrong!). Now on top of that you have to add IPv4 and UDP ...
2
votes
1answer
424 views
How to add a broadcast address to loopback with ifconfig on a OS/X?
I am trying to use ifconfig to turn on broadcast on my loopback interface. It currently reads:
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
As you can see, no broadcast address! ...
2
votes
2answers
624 views
Can I test broadcast packets on a single machine?
I want to have a server sending broadcast UDP packets and two other clients, in the same machine, receiving them. Can I do that somehow? What IP address would I use?
@gravyface gave me hope but I ...
1
vote
1answer
371 views
iptables port forwarding for active UDP connections
I am trying to set up port forwarding on UDP from port 12345 to port 54321 using the following:
iptables -t nat -A PREROUTING -p udp -i eth0 -d 192.168.0.1 --dport 12345 -j DNAT --to ...
0
votes
1answer
163 views
Server flooding udp packets on cod 4 port [closed]
I have running a Call of Duty 4 Server on my Debian Squeeze server, but this Port (28960) is flooding UDP Packets like an DDoS attack to a other server.
I checked with iftop the traffic, nothing ...
0
votes
2answers
285 views
Sonicwall IPS blocking Simple Help direct connection
We host a remote access tool called Simple Help. It allows us to access our clients computers and assist them with problems. I can log into it from my remote workstation, and connect to a clients ...
1
vote
1answer
464 views
Many clients on a wireless AP for UDP broadcast packets
I asked this question on StackOverflow and was directed over here, so I'd appreciate any advice.
I'm deploying a smartphone application as part of a live music performance that depends on receiving ...
6
votes
4answers
2k views
Testing UDP port connectivity
I am trying to test whether I can get to a particular port on a remote server (both of which I have access to) through UDP.
Both servers are internet facing.
I am using netcat to have a certain port ...
0
votes
1answer
29 views
Corba Naming_Service creates so many UDP connections
The Corba Naming_Service creates so many UDP connections and they are still remained even when the clients are disconnected. It goes up to 60K connections.
AIX 5.3, TAO Version 1.5a_p22 and ACE ...
0
votes
3answers
243 views
SNMP (UDP) Proxy
I'm Working in a mid-sized telco, and I'm in charge of network monitoring solutions. We have a custom monitoring system, that is using mostly SNMP to communicate with devices. The problem is that ...
1
vote
2answers
148 views
Block packets based on length
Can I block packets (Specifically UDP) that are > X length? I am getting attacked exclusively by UDP packets that are very large in size from a large number of IP Addresses. I have a legitimate use ...
1
vote
1answer
986 views
Higher rmem_max value leading to more packet loss
The rmem_max Linux setting defines the size of the buffer that receives UDP packets.
When traffic becomes too busy, packet loss starts occurring.
I made a graph showing how packet loss increases ...
3
votes
1answer
340 views
Does Windows XP automatically reassemble UDP fragments?
I've got a Windows application that receives and processes XML messages transmitted via UDP. The application collects the data using Windows "raw" sockets, so the entire layer 3 packet is visible.
...
0
votes
1answer
120 views
Confused! php-cgi opened (and didn't close) a UDP “connection” …but isn't UDP connectionless?
This question is more for my own education than to solve any problem.
I am running a VPS at linode w/ lighttpd and PHP 5.3.13 via fast-cgi.
When I list internet connections, I get this strange ...
0
votes
0answers
66 views
UDP load balancing for Windows
I have a several windows clients processing some data which is sent over UDP. For load balancing DNS round robin mechanism is used. But it has one drawback it doesn`t take into account if a client is ...
6
votes
3answers
556 views
telnet counterpart for UDP
Is there anything that enables a "telnet-like" functionality for UDP? I know the difference between TCP and UDP, and why telnet itself won't work - but I'm wondering if there is something similar to ...
5
votes
1answer
210 views
Hardware/topology recommendations for low latency UDP network
I'm setting up a LAN comprised of 60 end nodes that are receiving a high volume of UPD datagrams from one master server.
The server sends 60 unique datagrams every 100ms, each datagram is 64 bytes. ...
3
votes
1answer
2k views
OpenVPN failing on self-signed certificate over udp, works over tcp
I have the following server.conf:
# OpenVPN 2.x config
proto tcp
port 1194
dev tun-vpn
dev-type tun
server 10.8.0.0 255.255.0.0
push "route 172.16.0.0 255.255.0.0"
push "dhcp-option DOMAIN ...
1
vote
1answer
123 views
Interactive shell based on SSH and UDP
I've heard from a friend about a client-server application which initializes on top of SSH connection but implements interactive shell over UDP protocol. It is specifically designed for bad quality ...
2
votes
1answer
277 views
Tactic to block a UDP spoofing attack
The packets are margin of 200,000 ~ 800,000 per second and UDP spoofed(0 bytes/46bytes)
I have a linux deb 6 and windows server 2003 that is taking a hit.
Current idea:
- Setup a proxy server up ...
0
votes
1answer
176 views
How to block specific UDP packet outgoing from machine using iptables
I want to block specific UDP packet OUTGOING from my machine using iptables. Packet has a string in "hex in RAW"(?) i want to check packet by it.
Like: If UDP packet hex RAW match "test_text" - block ...
1
vote
2answers
1k views
Netcat UDP File Transfer?
Is there any way to send a file (picture or video) using Netcat and UDP. It defaults as TCP, but I would like to send using UDP. I tried simply adding -u to the nc command, but that didn't work. Here ...
2
votes
1answer
348 views
enable large DNS queries on Microsoft 2008 R2 DNS server
When I run the Network analyzer at http://netalyzr.icsi.berkeley.edu/ it reports:
The resolver at could not process the following tested types:
Medium (~1300B) TXT records
Large (~3000B) TXT ...
-1
votes
1answer
106 views
Segments/Processes running on same UDP socket
Suppose a process in Host C has a UDP socket with port number 12345. Suppose both Host A and Host B each sends a UDP segment to Host C with destination port number 12345. Will both of
these segments ...
2
votes
1answer
350 views
Creating a simple UDP listener [closed]
The situation is this: I'd like to make a hole punching server for a game and I need to listen to UDP traffic. It will run on a Debian Squeeze VPS so I'm pretty flexible as far as possibilities go.
...
2
votes
2answers
466 views
need a live UDP echo Server IP and port
I require to test my UDP program using echo server. I have tested this application in LAN but now I require it to test it in Internet.
Is there and globally recognize freely available well known ...
0
votes
1answer
108 views
Is throughput on higher bandwidth networks hindered by smaller UDP packet size?
I recently conducted an experiment on UDP throughput across 802.11g networks, using packet sizes between 100 and 1000 and bandwidths ranging from 6Mbps and 54Mbps.
I have noticed that that higher ...
4
votes
1answer
113 views
Script to find the address udp packets are being sent to?
Here is the scenario.
I have an IP address 1.2.3.4 port 2000 sending udp packets to one unknown IP. I would like to find the unknown IP so I can block it with iptables.
Is there a way to do it with ...
2
votes
2answers
631 views
IPtables: is there a minimum UDP packet size for a DNS lookup?
IPtables for a virtual dedicated server.
I would like to block UDP scans and I was wondering whether there's a minimum packet size for a DNS lookup?
Nmap sends 0-byte UDP packets (source : ...
1
vote
2answers
548 views
Limit UDP connections per IP iptables
I want to limit connections per IP for a specific UDP port. I got it working for TCP, but somehow it doesn't work on UDP. These are my rules:
For TCP (working)
iptables -A INPUT -p tcp --syn ...
1
vote
1answer
357 views
Block all incoming DNS requests EXCEPT from IPs x,y,
I want to block all incoming requests on my two DNS servers APART FROM certain IP addresses e.g. IP of 1.2.3.4 will be allowed to make requests but NOBODY else will.
How do you do this with iptables?
...
10
votes
2answers
2k views
Does traceroute use UDP or ICMP or both?
When I do a trace on the www.google.com domain from my laptop, am I using icmp or udp ?
I thought it was icmp type 11 but while searching for something else I came across rules where icmp type 30 was ...
0
votes
1answer
176 views
Very strange localhost connections on linux workstation. Need help identifiying the source
The following is the output of netstat on a Ubuntu machine. Can someone help decrypt the output? I am especially curious what the ::1:43213 connection is.
Also, why are there so many connections ...
1
vote
1answer
337 views
How to measure UDP socket buffer loss on Windows Server 2008 R2?
Is there a way to view/measure UDP socket buffer loss on Windows Server 2008 R2? I've tried 'netstat -s' and looking at available perfmon counters, but nothing jumps out to me as a measure of socket ...
0
votes
2answers
139 views
TCP what's the purpose of the third step of 3-way-handshake [duplicate]
Possible Duplicate:
Why is it 3-way-handshake and not more?
Example: If a client wants to talk to a server, it just tells the server that it wants to establish a connection, then the server ...
2
votes
2answers
512 views
Why is it 3-way-handshake and not more?
TCP uses the 3-way-handshake mechanism. I understand how it works pretty well but I wonder why it's not 4, or even 5-way? Is it because that's too much overhead and is not needed?
1
vote
1answer
916 views
How to create UDP proxy using iptables
I have a server running UDP server on port 50000. This server receives updates from clients, and pings back the clients every 5 seconds to the socket they were connected from.
Now I want to redirect ...
2
votes
2answers
149 views
How can I find out where a UDP connection fails?
I want to setup a VPN server with OpenVPN, so client PCs can access each other like they were in the same physical network.
One problem I encountered is, that I cannot connect via UDP. When I change ...
0
votes
1answer
2k views
Iptables ratelimit UDP DOS attacks
Well, I've been a victim of Ddos attacks and I really can't figure out how to avoid it. On some machines it works, while on some it doesn't or probably I'm doing it wrong in some way,
Attackers are ...
2
votes
1answer
299 views
What is the difference between bind, network (interface) and multicast addresses?
The DatagramSocketImpl in Java has a joinGroup method that takes a socket address (IP and PORT) plus the interface address (IP and PORT). I am trying to understand the difference and purpose of each ...
0
votes
1answer
171 views
How to sniff udp between two windows applications on the same machine
How do I monitor the duplex udp traffic between two apps on my windows machine.
2
votes
1answer
263 views
Block UDP traffic by rate/string-match on Windows 2008
I am administrating a Windows 2008 server (64-bit). It is being subjected to a focused set of DOS attacks where UDP packets are sent to a specific port and contain a specific string.
What I need to ...
3
votes
1answer
703 views
tcpdump udp data capture latency
I am using tcpdump to capture UDP packets and analyze network latency between a UDP broadcaster and my server. To calculate latency I compare the source host timestamps reported in UDP application ...
1
vote
1answer
580 views
Iperf udp test show only 50 % of bandwidth
I test bandwith with iperf. I set up UDP protocol.
I'm trying to setup limit from 10 to 100 megabit/s. Until 90 megabit max speed is correct.
When I write -b 100m or don't write this speed become ...
1
vote
2answers
293 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 ...
1
vote
2answers
471 views
Troubleshooting UDP multicast on Windows
I'm a programmer, not a system adminstrator, so please forgive my administrative naivete. My software, written in C#, relies on UDP multicasting. One machine, the server, streams events to an known ...
0
votes
1answer
351 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 ...
1
vote
1answer
240 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
2answers
214 views
Some questions on UDP send receive buffer, and networking
I have two debian servers located on the same subnet. They are connected by a switch. I am aware the UDP is unreliable.
Question 1: I assume the link layer is ethernet. And MTU from a standard
...
1
vote
1answer
1k views
Filter incoming traffic to UDP port for pci compliance
It had been recommended for PCI compliance that I filter incoming traffic to UDP port 5353 please can someone advise what are the steps to do this?
I am currently using Centos 5.7 64 bit.
