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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457 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
3k 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
1k 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 ...
3
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1answer
404 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
470 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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3answers
69 views

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 ...
2
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1answer
3k 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
5k views

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 ...
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1answer
140 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 ...
0
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1answer
184 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 ...
4
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1answer
810 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 ...
2
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1answer
766 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
722 views

Broadcasts from guest machine not reached host machine

I have an application that sends UDP broadcasts to some port, for example 11000 (BROADCAST_APP) and another application that listens the 11000 UDP port(LISTENER_APP). The apps works well on the ...
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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
112 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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1answer
469 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. ...
17
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2answers
8k 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 ...
3
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1answer
906 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
2k 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 ...
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1answer
2k 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
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2answers
633 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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2answers
1k 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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4answers
18k 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
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1answer
39 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 ...
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3answers
404 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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2answers
243 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 ...
3
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1answer
5k 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 ...
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1answer
676 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
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1answer
168 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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3answers
2k 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
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1answer
280 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. ...
5
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1answer
6k 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 ...
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1answer
160 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
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1answer
488 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
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1answer
359 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 ...
2
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2answers
3k 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
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1answer
625 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 ...
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1answer
166 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
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1answer
551 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
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2answers
1k 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
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1answer
139 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
145 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
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2answers
1k 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 : ...
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2answers
1k 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 ...
3
votes
1answer
2k 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? ...
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2answers
12k 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 ...
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1answer
239 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 ...
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1answer
783 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
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2answers
424 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 ...
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3answers
1k 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?