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.

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Load Balancing UDP traffic transparently

Are there any products (preferably open source) that can load balance UDP packets transparently? We need to scale our syslog servers and require the original source IP be kept intact. Alternatively ...
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681 views

Solaris doesn't know which MAC address to use to send an UDP multicast message

I have a pair of Solaris 10 boxes which are supposed to send multicast UDP packets to a group of hosts. One of them works just fine, whereas the other one does not. The problem with the second ...
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271 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 ...
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494 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 ...
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227 views

Can heavy UDP traffic create network congestion?

I have three IP addresses using the same gateway. Two of them are configured as a cluster with multicast address setup. If there is a heavy UDP traffic between those two, can that affect the network ...
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1answer
436 views

UDP Packet Size.. max, ping failing to 3G.. Recalcitrant software vendor

We have a network of 330 clients (Service Vans) connected via 3G to our central office. Currently these clients are connected via a small ruggedized 3G router that establishes the 3G connection and ...
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1answer
709 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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1answer
48 views

Redirect packet that matches a pattern?

How can I route an incoming udp packet with iptables that matches a pattern like: 53 41 4D 50 5B 79 95 DB 61 1E 69 from public interface (vmbr0) and port 7777 to 192.168.0.1:7777?
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1answer
93 views

Debian 7.4 drops UDP traffic randomly

I'm running Debian 7.4, KVM VPS with the latest updates. I'm getting UDP ports randomly closed for 2-10 minutes for no reason. I'm running gaming servers and the port tester shows the ports are ...
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1k views

UDP port appears to be in use but is not shown in netstat or TCPView

I've encountered some strange behavior I don't understand. I'm installing software on a Windows 2003 Server. This software needs to bind to a specific UDP port an all TCP addresses in order to listen ...
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452 views

UDP maximum segment size

Environment: I am writing a UDP client-server application. the path MTU between client and server is 1500 bytes (with only a wireless link between them, so this value is pretty much stable). My system ...
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1answer
404 views

Serious Packet Loss on UDP using Amazon EC2

I am using ec2 to host a udp TURN server for SIP purpose. Anyway I get a lot of packet loss during voice call, so I did a udp performance test using iperf util. Result: [ ID] Interval Transfer ...
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337 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 ...
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1answer
240 views

port forwarding to access services on servers behind NAT

I have some security camera systems in different locations, each location does have internet, the ISP is NATing all the IPs so theres no way to open ports to my systems. My solution was to rent a VPS ...
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1answer
545 views

Does hole punching require a UDP rendezvous server Or could it be a TCP one?

I'm trying to get my head wrap around this issue... I would like to connect two users... Those users are already connected to a TCP server, which is aware of both public ip and connection TCP port. ...
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1answer
847 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 ...
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1answer
766 views

lots of UDP_IN Blocked errors

Since I have reinstalled my OS, I'm getting lots of UDP_IN Blocked errors in my messages log. Can anyone kindly explain what the error say exactly and what I can do to get rid of this error. Aug 8 ...
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1answer
157 views

UDP packet loss cause

I have two machines connected to the same LAN and multicasting UDP streams at rate of about 30Mbps. Analyzers often show packet losses on one machine, but never on another. What could be the reasons ...
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1answer
286 views

Set udp packet size limit

I have a CentOS server with a JAVA application that receive UDP data packets, it works all OK until the packet is bigger than 584 bytes, I read something about and seems to be a limit of UDP protocol. ...
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205 views

forward snmptraps with snmptrapd to second host

I have a setup with snmptrapd listening on udp:162 to receive snmp traps. They are then processed on this host with snmptt. I am now in the need that I need to forward those traps additionally to ...
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365 views

OpenVPN client opens a random UDP port?

We are noticing this on a number of our openvpn clients: [root@box ~]# netstat -tulpn | grep openvpn udp 0 0 0.0.0.0:53950 0.0.0.0:* ...
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1answer
172 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 ...
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1answer
296 views

Is there a method to send UDP output to one logical NIC such that it gets sent out two physical NICs on different subnets?

I have an application that needs to send UDP multicast data "from" either one or two physical NICs on a single Windows Server 2008 machine. In the two NIC configuration, every datagram needs to be ...
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145 views

Altq limits not being applied to UDP transfers

I have a OpenBSD server acting as a router/firewall with yhr packet filter ruleset shown below, a linux server, and a linux client. When transferring files (using netcat) by TCP, the limits are ...
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443 views

UDP Overflow / UDP Drops on Standby Postgres Service

I am stumped trying to prevent an overflowing UDP buffer on a standby Postgres service. Any help would be most appreciated. Essentially a UDP buffer associated with the pg_standby process on my ...
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191 views

Why is qemu issuing a DHCP discover after it receives a DHCP offer

I'm having some trouble seting up network on qemu. I'm trying the easy option (user). The qemu command I run is this: ./qemu-xilinx/arm-softmmu/qemu-system-arm \ -M xilinx-zynq-a9 -m 1024 ...
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Forwarding udp ports iptables packets “lost”?

I have a Linux router (Debian 6.x) where i forward some ports to internal services. Some tcp ports (like 80, 22...) are OK. I have one Application listening on port 54277udp. No return is coming from ...
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155 views

Firewall rejecting UDP “connections”?

I have a server that is aggregating logs from various other servers. It mostly works great, however from time-to-time (right after a reboot, but not all reboots) it will decide that various UDP ...
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79 views

Internal IP leaked to the public network

I am a programmer and I have made a production server that resides on public IP and listens for UDP packets. The purpose of this server is to collect UDP packets from a huge sensor network. And also ...
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86 views

UDP sends 6 additional packets in Wireshark

I am sending UDP packets using ttcp to another machine which is connected via a Cisco router. However, when I analyze the packets sent in Wireshark, there is a UDP packet sent before the payload ...
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53 views

Nat Traversal, peers unable to communicate

I'm currently working on a project that requires NAT traversal but I seem to be running into difficulty. I have the following setup running for testing: R1, Verizon Fios router connected to the ...
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325 views

UDP socket receive buffer size change on RHEL6.3

Our system used to work on RHEL5.3 And the socket receive buffer size is 64k. And that works fine. We can get message size up to 64k on UDP socket. But after system upgrade, it is running on RHEL6.3 ...
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UDP Multicast not working without promisc. Already tried rp_filter=0

I'm having issues with multicast traffic in Ubuntu Maverick. It only appears to work when the card is in promisc mode (i.e. if I set it manually, or use a tool such as tcpdump). Adding multicast ...
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83 views

tcpdump strange udp line

I've found a strange line in the tcpdump output. Normally UDP packets are dumped in the following form: timestamp IP srcaddress.port > dstaddress.port: UDP, length packetlength but this is just: ...
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41 views

Piping device file over UDP with netcat

Hopefully this is the best Stack Exchange site for this - I think it's primarily a netcat question. I'm developing a custom data acquisition device. It can probably be best thought of as a fancy ...
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33 views

Troubleshooting multicast on Ubuntu 14.04 server

I am troubleshooting an issue with multicast on an Ubuntu 14.04.1 LTS server. I have a simple client that subscribes to a multicast group and waits for data. The subscription is successful and shows ...
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35 views

Does Ubuntu with Linux 3.5 having TX RX ring buffers or BQL

My linux uname -a command outputs: Linux Davinci001 3.5.0-23-generic #35~precise1-Ubuntu SMP Fri Jan 25 17:13:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux So, does NICs with this Ubuntu machine is ...
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26 views

Cannot query UDP services

I run a couple UDP services, one including Teamspeak 3. Unfortunately, I am unable to query either of these UDP services (I cannot connect to the Teamspeak 3 server) besides the TCP based stuff, ...
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191 views

Linux: Reduce UDP Packets Error

I'm facing UDP packet receive errors (under Linux 'netstat -su' command). I have 10 x UDP processes running on Machine-A (RHEL 5.2) and each of them send 290-byte packet at 50 times per second to ...
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41 views

UDP multicast stream on win server 2k8 R2

so i have 3 mega PCs with win 2k8 installed on them having: 1st) 1 internal NIC and 1 external 2nd) 2 internal NIC and 2 external 3rd) 2 internal NIC and 4 external same stream put on any NIC on 1st ...
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66 views

How can I log and maybe even block IPs that send lots of incoming UDP traffic?

we run a voice / teamspeak server which receives legitmate traffic on port 9987 from many ips. Sometimes we get DDoSed. So people use single Servers and send 1-3 Gbits of UDP Floods to that port. This ...
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61 views

How to turn a UDP feed on and off?

I have a linux application that is sending a stream of UDP packets to a particular ip and port. I need a way of suppressing this packet stream so the packets never reach the network, with the ability ...
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30 views

Bonding connection or other techniques to improve UDP delivery

I have several VOIP servers linked by heavily loaded connections, and the voice quality gets pretty spotty at times. I have setup QoS to ensure upstream bandwidth is allocated favorably for VOIP, ...
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19 views

udp expected behaviour not responding to test result

I have a local network topology that is structured as follows: three hosts and a switch in the middle. I am using a switch that supports 10,100,1000 Mbit/s full/half duplex connection. I have ...
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394 views

UDP packets are not reaching iptables NAT table

I'm trying to redirect UDP incoming packets to port 4000 to another IP with iptables: iptables -t nat -A PREROUTING -p udp --dport 4000 -j DNAT --to-destination 192.168.100.20 Unfortunately they ...
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94 views

Why are my multicast packet discarded?

I have two boxes and I have some issues when tcpreplaying a pcap full of multicast from one machine to the other. I see the packet incoming on the destination machine thanks to a tcpdump instance. ...
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48 views

tcpdump, display the data section

i am trying to display only the data section of an udp packet using tcpdump. In some other words, is it any way to filter the header section of the udp package? The below command sudo tcpdump ...
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101 views

opensips sever running fine and UDP connection cannot register but TCP connections works fine

Im a newbie to opensips and Centos/Linux. Recently installed opensips sever which running smoothly on TCP connections, but users cannot register on UDP connections. here my Log, have a look. Feb 26 ...
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268 views

How to forward UDP and TCP traffic from one IP to another

I have a server with two LAN cards installed. I have one server in U.S and one in India. I have created a GRE tunnel to route all traffic from the U.S Server to my Indian Server. My traffic has ...
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107 views

Cannot see an EC2 VPN server from another EC2 instance

I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it. ...