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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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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6k views

How do I increase UDP Recv-Q

I have a gigabit connection that is not fully utilized but I am getting packet receiving loss. When I do netstat, it shows the Recv-Q sometimes maxes out at 262656 during heavy traffic. Proto Recv-Q ...
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189 views

What is the lowest udp source port for puppet dns queries?

On CentOS 6.4 and 6.3 I have seen puppet regularly use ports below 32768. This is contrary to the setting for kernel-assigned ports according to: cat /proc/sys/net/ipv4/ip_local_port_range 32768 ...
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524 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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74 views

Trouble with VPN Tunnel

How to direct a UDP Packet through a VPN tunnel? The router in question dose not have any features that would allow a UDP flooding or broadcasting, so for this project I am shooting in the dark, any ...
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1k 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 ...
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1answer
148 views

Is multicast appropriate for sending a copy of a video chat to a server?

I am creating a p2p video chat app using the libjingle/WebRTC code. I would like to collect a copy of these video conversations on our server for users to watch later - but I don't want to suck up too ...
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407 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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4k views

Is it possible to duplicate a UDP unicast stream with iptables?

I have a proprietary system which transmit a udp video stream from unit #1 (192.168.1.1) to unit #2 (.1.2). I can't make changes to this system, and I'm trying to clone this udp stream so I can access ...
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2answers
940 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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2answers
415 views

Countermeasures versus incoming DNS reflection attack

i am currently experiencing a DNS reflection attack towards my server. I am getting a massive amount of answers via UDP from Port 53 that my server has never asked for: 02:53:57.626156 IP (tos 0x0,...
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4k views

Tool for forwarding UDP packets Windows

Windows Server 2008 I use portproxy interface to forward traffic , but I looked into the msdn page and I noticed it doesn't support udp protocol . protocol Specifies the protocol to use. ...
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2answers
918 views

How does SSL VPN (openvpn) connect via UDP?

I need to test whether an OpenVPN Service (ssl-vpn) is listening on a specific IP address and port from a linux box. I'd like to do that with a bash script or some code in python or c/c++ but that's ...
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1answer
316 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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3answers
198 views

DDOS protection from ISP side, UDP protocol, whitelist

Is it possible to ignore packets from ISP side which are incoming to my server? Is possible this kind of situation ? : I have white list of IP addresses. I continually update white list and sends it ...
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2k views

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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863 views

UDP packets to IP addresses other than specific ones not arriving and not shown in Wireshark

I'm writing a service using UDP, but I can't manage to reply to the client. When sending to the client via the DHCP-assigned IP (192.168.1.143) Wireshark shows no sent packets. The server receives ...
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2answers
678 views

nmap scan only state of port

Is it possible with nmap to check only the state of a port whether- open, closed or filtered and NOT the services behind it? The aim is to speed up scan results. Since UDP scan is also involved it is ...
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566 views

possible UDP attack on BIND?

hello everyone, i was surprised last month when my EC2 instance (ubuntu precise server), that is supposed to be under the free tier still, accumulated lots of traffic... today, while checking my ...
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2answers
6k views

Problems with MDNS flooding on port 5353 UDP

I am running into a big issue at a small network i manage. This network is an Apple network, with airport extremes, expresses, mac book pro's, imac's, ipads, iphones etc... I went to add something to ...
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2answers
2k views

iptables rules for botnet (UDP flood) protection

I'm currently experiencing a massive UDP attack on my server. I host a couple of gameservers, mainly Tf2, CS:GO, CS 1.6 and CS:Source, and my 1.6 server is being flooded. I tried different rules in ...
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581 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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1k views

Multicast in private LAN with different subnets

after i read Multicast IP Addresses and Multicast accross the subnets I am confused. Configuration: I have two devices in the same network. They may not be in the same Subnet, but ...
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Two-way UDP on varying-IP networks

I've heard that on some corporate networks, outbound traffic from the same user can hop around different "from" IPs. Does that break two-way UDP, or do the networks only act that way for TCP? If it ...
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1answer
8k views

Why does VPN IPSec client use UDP?

The VPN I use on my home Windows computer to connect to my company's servers is a Cisco client. The client is configured to use "IPSec over UDP (NAT/PAT)". Why would you use UDP, an "unreliable" ...
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3answers
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Why is UDP slower than TCP on Ubuntu Server?

I transfer data between two Ubuntu Servers (12.04) via iperf on 1Gb LAN. iperf -s <-> iperf -c <addr> -n2G TCP speed = 925 Mbits/sec iperf -su <-> iperf -uc<addr>...
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152 views

UDP flooding multiple servers [duplicate]

Possible Duplicate: What are the best techniques for preventing denial of service attacks? What do you suggest? Being UDP flooded as I write to multiple servers in different data centers in ...
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1answer
253 views

Can NAT port change dynamically in an active session?

I am facing an issue, having client server application where client application is sending UDP data frequently to server and server redirecting back to the client. But in a few cases I am not getting ...
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2k views

HTTP, TCP, UDP and connectionless

I am a bit confused with HTTP lately. Some facts are that TCP can operate connection orientated or connectionless, this I understand. TCP though is connection-oriented while UDP is connectionless ...
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1answer
1k views

Tunnel only one program (UDP & TCP) through another server

I have a windows machine at home and a server with debian installed. I want to tunnel the UDP traffic from one (any only this) program on my windows machine through my server. For tcp traffic this ...
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1answer
1k views

Too much traffic on UDP suspecting bind miss-configuration

A server generates over 600GB of monthly traffic on UDP port (while http is under 1GB), so I ran tcpdump command and I see many (over 10/second or so) fast dns related commands/traffic that looks like ...
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4answers
123 views

Just one client bound to address and port: does it make a difference broadcast versus unicast in terms of overhead?

Scenario: I am implementing failed over for a network node, so my idea is to make the master node listens on a broadcast ip address and port. If the master node fails, another failover node will ...
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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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4answers
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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 ...
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1answer
1k 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! :(...
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2answers
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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 ...
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1answer
3k 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 192.168.0.1:...
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946 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 ...
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2k 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 ...
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6answers
52k 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 ...
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3answers
560 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 ...
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385 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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2answers
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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 ...
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1answer
954 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. ...
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1answer
196 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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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 ...
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375 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. ...
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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 mydom....
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1answer
181 views

Interactive shell based on SSH and UDP [closed]

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 ...
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1answer
768 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 ...