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Questions tagged [udp]

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.

Because UDP doesn't rely on handshaking to guarantee that packets arrive and in order it can be seen as an unreliable protocol, but for real time systems where acting on the data immediately is the most important consideration not having to wait for delayed packets is a distinct advantage.

UDP is just one communications protocol on the web. Others include:

  • Transmission Control Protocol (TCP)
  • Internet Control Message Protocol (ICMP)
  • Hypertext Transfer Protocol (HTTP)
  • Post Office Protocol (POP3)
  • File Transfer Protocol (FTP)
  • Internet Message Access Protocol (IMAP)

UDP on Wikipedia

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Linux block udp on low-level against DDOS

My server is currently under DDOS attack with nearly 500k UDP packets per second. UDP is blocked in iptables but the processor is still overloaded. Any way to block UDP on a lower level to not pass the packet through all iptables chains/modules but…
Vilial
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Application receiving boradcast from different subnet

I've 2 Linux boxes with following description Box A: Kernel: Linux 2.6 IP: 172.19.1.99/24 Box B: Kernel: Linux 3.14 IP: 192.168.200.100/24 Connected with Layer 2 switch Both boxes run a UDP broadcast service and a UDP Receiver service. Whatever…
Vasudev
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Slow windows DNS server

I have a microsoft DNS server for a local domain, running Windows server 2016STD. This computer is also a domain controller. It's configured to forward to fast public DNS servers. From any computer in the network, directly configuring these same…
Meijer
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TFTP requests Not being serviced

This may look like a duplicate question but I did my share of searching, but could not find any solution. I have created a tftp server, this server when accessed from a local tftp client, over a loopback gets and puts the file just fine. When I try…
ArunMKumar
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Debugging dropped UDP messages on Linux

Here's my setup: I have 1 host that has a 1 Gbit Ethernet connection and 2 hosts with 100 mbit connections (connected to the 1Gbit host through different switches). In a test, I send 1000 1kb messages from the 1Gbit host to the 100 mbit hosts (with…
gnr
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Is there a non-invasive test of uPnP enabled network?

I'm trying to figure out if there is a way to do a non-invasive test on different networks to see if Universal Plug'n'Play (nPnP) is enabled at the router. i.e. Is Internet Gateway Device Profile implemented at the router? I'm thinking of a webpage…
zipzit
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Receiving broadcast UDP packets under Linux

I'm having a similar problem to Linux Kernel not passing through multicast UDP packets only broadcast rather than multicast, and nothing I've tried has helped. I've got a device at 192.168.0.1 spewing out broadcast UDP packets, connected directly to…
Rgaddi
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UDP Server behind Gcloud load balancer: receive ok, reply fails

I have a UDP server set up (on a VM) behind the Google Cloud network load balancer. The server is bound to 0.0.0.0. The UDP server can receive messages that were sent to the balancer, but replies do not go back to the client. There are no errors…
Caleb Hattingh
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how to run memcached on UDP ports only

How can i configure memcached to run on udp ports only on centos box ? Right now it is listening on TCP ports by default. Here is my memcached configuration file. cat…
Aun
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How to resolve UDP packets being dropped given netstat reporting SndbufErrors

I have a server instance on an OpenStack that at a pretty high load starts loosing UDP packets. I captured all outgoing packets using tcpdump and some of them are missing, even though application logs imply that they should have been sent. Usual…
eddyP23
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rx_queue value in /proc/net/udp grows to twice the SO_RCVBUF value

When using an SO_RCVBUF of 10485760 (which is also the current limit as stipulated by sysctl's net.core.rmem_max setting, and sending UDP packets faster than the receiving side is able to handle, the rx_queue column in /proc/net/udp always grows to…
Evgeniy Berezovsky
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How to use an IPv6 Edge router in an IPv4 network?

Background I have the following set-up: I use 6LOWPAN (IPv6 implementation in IEEE 802.15.4) on my sensor link that have IPv6 addresses (stateless) as aaaa::xx/64 It uses RaspberryPi (RPI) as an edge router (called 6lbr) that is both connected to…
Angs
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Can IP spoofed traffic get above the transport layer?

I'd like to know whether you could get packets with a spoofed IP address above the transport layer. My thoughts are: TCP: No, as acknowledgements would never get to the original sender if their IP was spoofed. A session couldn't be set up so…
Ray2k
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difference between local port range & UDP sending port using dig on Debian nameserver resolver

When i go to my local port range on Debian 7, i can see that my ephemeral port range is: cat /proc/sys/net/ipv4/ip_local_port_range 32768 61000 My /etc/sysctl.conf is empty. Normally that would mean that all requests coming out from this…
Nicolas Guérinet
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I need to REJECT first incoming UDP packet by srcip

Im currently under attack by spoofed udp packets. Every spoofed ip trying to send just 1 udp packet in 30sec. But there is tons of ip. I need to drop first packet. But if same srcip in 30sec sends another packet i want to accept it. -A INPUT -d…
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