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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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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.
Dino
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UDP and NATs - is the timeout bidirectional?

Is the timeout for an UDP connection through a NAT reset every time a packet is sent OR received by the client, or are there any (common) implementations that require the client to actively send something to keep the connection alive? I'm developing…
lxgr
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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 route... user@pc-149:~$ sudo ip route add multicast…
evil_andy
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Unable to receive UDP packets from a link-local address

I have a program which attempts to contact to an embedded device over UDP. The embedded device has a link-local address only (169.254..); the Linux host has a normal (DHCP, RFC1918) address, managed by NetworkManager on ubuntu natty. This local…
bdonlan
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Adding more than one IP to sip.conf tcpbindaddr and udpbindaddr (Asterisk 1.8)

The defaults in the sample sip.conf under Asterisk1.8 contain udpbindaddr=0.0.0.0 and tcpbindaddr=0.0.0.0. I want to bind the incoming [foo] extension to udp:192.168.1.1/255.255.255.0, the outgoing [foo] to tcp:192.168.3.3/255.255.255.0, the…
tarkaköpönyeges csecsfogdosó
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Forward broadcast to fixed IP using IPTables

I need to forward (route) broadcast packets from several wireless clients to a single server in the fixed network. The wireless and fixed network are not bridged for security reasons. With the following lines the packets show up in the INPUT chain…
MightyZen
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Causes of UDP Flood

This is part of a mail that I received The IP 69.89.6.235 is attacking our server at 94.23.204.191 and 87.98.168.239.80 with UDP flood. I have a newsletter scripts that I use to send newsletter to a lot of emails on my site (with IP 69.89.6.235).…
yankitwizzy
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Protecting against UDP flood

One of my servers is being flooded with udp packets on random ports. 12:11:54.190442 IP 182.48.38.227.60173 > localhost.51523: UDP, length 1 12:11:54.190447 IP 182.48.38.227.60173 > localhost.23769: UDP, length 1 12:11:54.190560 IP…
Balon
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Does IRC use UDP for passing text messages client to server?

I have been told that IRC uses UDP for client to server communication and TCP for server to server communication (in the case of linked servers). It seems that TCP is the better transport layer protocol for text chat since you need a ensure the text…
Will
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Netcat, Syslog, UDP, and <134>

Listening with netcat on UDP 514 to syslog data I see that each sent log message is separated by <134>. Does anyone note what <134> is?
Kyle Brandt
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UDP Socket bound to one IP?

Say I have two hosts - Using fictitious IPs for this example, say host A has IP 1.1.1.1. host B has two IPs - 2.2.2.2 and 2.2.2.3. If host B is listening on port 8888, and sees a packet come in from 1.1.1.1, produces a response and sends it out on…
regulatre
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How do you prevent UDP-flood based DDOS attacks on a DNS server?

I'm studying networking at the moment, and it just occurred to me that one can easily forge DNS requests with fake IP addresses (since they use UDP). Since DNS relies on UDP for communication, couldn't a malicious user send millions of forged…
Anne Nonimus
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iptables -m string inspecting udp payload only

This is the rule I'm working with: iptables -A QUERY -p udp -m length --length 24:63 -m udp -m string --algo bm --hex-string '|ffffffff|' --from 12 --to 28 -j QUERYLIMIT Is there a way to inspect only the UDP payload instead of processing the whole…
evcz
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Wireshark won't pick up packets sent from localhost to localhost via network

I'm running on Windows and trying to get Wireshark to pick up my network traffic. It picks up all outbound and inbound traffic fine, except for a client/server I'm running on my local system. As it is, even when I'm sending packets through my LAN…
Rushyo
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Why isn't my ip helper-address helping?

I have a hub site with a Cisco 2811 and several remote sites, running a mixture of Cisco 851 and 871 routers configured for site-to-site VPN. I am in the process of adding DHCP scopes and DNS zones for the remote computers to enable easier…
atroon
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