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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iperf max udp multicast performance peaking at 10Mbit/s?

I'm trying to test UDP multicast throughput via iperf but it seems like it's not sending more than 10Mbit/s from my dev machine: C:\> iperf -c 224.0.166.111 -u -T 1 -t 100 -i 1 -b 1000000000 ...
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What settings should I modify to tune a Linux server for very small yet very high packet rate UDP receive loads?

I am tuning a server that needs to handle small (average of about 50 bytes) UDP packets. The average packet rate is approximately 100,000 packets/second. The data is very burst and can sometimes burst ...
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Where is the documentation that states TCP and UDP source port should be over 1024 and random?

I am having a hard time to find where it is documented that the source port should be random and in the range 1024-65535. In which RFC is this documented? Edit: First reference for privileged ports ...
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228 views

Strange UDP/TFTP Problem

My TFTP client only seems to be getting responses from the TFTP server to its RRQ (download requests) if I watch the traffic in wireshark. If I shut down wireshark (running on the TFTP server), the ...
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1answer
92 views

tc: packets filter

I need to drop UDP packets with specific UDP port number) on network interface (say eth0). On my setup the interface eth0 is part of the bridge. is it possible to do it using tc command? if yes, how? ...
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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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80 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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191 views

Port Knocking and TCP/IP within the OSI model

I have read that Port Knocking can be subject to false negative (type II error) due to the optimization techniques of TCP/IP. A correct port knock given by the client may be read as incorrect by the ...
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295 views

shell record UDP stream from a specific address

I'm trying to record an incoming UDP stream (stream the sense that it's a stream of consecutive datagrams). I tried netcat but unfortunately multiple sources send data on the same port address and nc ...
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2answers
644 views

Which UDP ports are required to resolve external hosts?

Today I asked my hoster to block all UDP ports except port 53. Due to daily UDP attacks, this was currently the only option to stop flooding my lines. Now since the block is in place, I cannot wget ...
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3answers
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Block All UDP traffic (to prevent ddos) [duplicate]

I have been receiving countless ddos attacks the last couple of weeks. Just now I caught one while I was running iptraf. Normally 99.9% of the packets used on my server are TCP packages, and not UDP. ...
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61 views

UDP Protocol - ICMP Error Generation

I know that UDP has no real error control facilties outside of silent discard of packets failing checksums. Am I correct in thinking that a UDP packet with a TTL=1 reaching a router will generate an ...
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2answers
253 views

(Simple) UDP Protocol - Networking

I know that UDP is an unreliable protocol where things can arrive out of order, fail to arrive completely, etc. I'm also aware that when using UDP for something like traceroute, packets that arrive ...
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4answers
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How can I test Multicast UDP connectivity between two servers?

I have a two servers on the same subnet. I have an application installed which uses Multicast UDP to propagate events between the servers and keep them in sync. This does not seem to be happening, ...
0
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1answer
236 views

(RFC-791) Application Layer PDU size, guaranteed to pass without fragmentation

I am writing a client-server python application, a part of which is using UDP Multicast to communicate. And my current concern is about fragmentation. RFC 791 (page 24) says: Every internet ...
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382 views

Hosting a UDP Server

How do I host a UDP server for free or cheap? I can't afford to actually buy or rent a physical server. I have a prototype server application written in C#, and I can probably rewrite it in any ...
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4answers
722 views

Unable to receive UDP packets from a link-local address [closed]

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 ...
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1answer
618 views

how to enable port 7777

I am initiating file transfer using tcp on openfire server. But I am not able to open the port number 7777, from which I need to send files. I changed the security setting in the admin console panel ...
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1answer
745 views

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 ...
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1answer
129 views

Getting UDP traffic statistic between particular hosts on Linux

I need to gather some network statistic to test my server application. I've tried many linux tools, but nothing I've found suits my needs. Basically I want to gather some UDP statistics ...
2
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2answers
759 views

Rate of UDP packet loss over WLAN

While testing something with TFTP I noticed lots of timeouts (and slow speed as result) when I used my WLAN - and no problems when using a network cable. A quick test program sending/receiving UDP ...
2
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1answer
1k views

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 ...
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3answers
571 views

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 ...
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1answer
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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 > ...
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1answer
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Netcat - Listen for Multiple UDP Connections

I'm trying to use netcat to debug SIP calls, which communicate over UDP. Is there a way to get the same netcat instance to listen to multiple UDP Connections? I've tried connecting to the same netcat ...
3
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1answer
394 views

one particular laptop does not receive UDP broadcast messages

I am trying to debug a problem with a particular laptop which is running Ubuntu. We have a service which uses broadcast UDP messages, and this laptop is not receiving them on its wireless interface, ...
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2answers
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How to connect to a udp port command line?

This is what I tried,but seems not working : [root@ ~]# netstat -a|grep 48772 udp 0 0 *:48772 *:* [root@ ~]# telnet localhost ...
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2answers
347 views

Multicast IP Addresses

I posted this on StackOverflow and was told it might be more appropriate here. I'm having trouble understanding how multicast addresses work. First off, is it true that if I have N clients or peers ...
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3answers
3k views

Does IRC use UDP for passing text messages client to server? [closed]

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 ...
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2answers
675 views

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?
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644 views

UDP over TCP on vpn connections

For example we have a VPN TCP transport connection through proxy. I wonder how is UDP emulated over this TCP connection? How its unreliable nature is emulated?
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3answers
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How is the MTU is 65535 in UDP but ethernet does not allow frame size more than 1500 bytes

I am using a fast ethernet of 100 Mbps, whose frame size is less than 1500 bytes (1472 bytes for payload as per my textbook). In that, I was able to send and receive a UDP packet of message size 65507 ...
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1answer
119 views

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 ...
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UDP pseudoheader

Is it true that in the UDP header 2 bytes store a checksum for verification purposes by the destination host, and that this checksum is generated from a pseudoheader? If this is true, then why does a ...
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How do you prevent UDP-flood based DDOS attacks on a DNS server? [duplicate]

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, ...
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8answers
694 views

Network monitoring solution [closed]

I have a big distributed system I need to monitor. Background: My system is comprised of two servers, concentrating and controlling the system. Each server is connected to a set of devices (some ...
2
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1answer
727 views

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 ...
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2answers
477 views

Network UDP logger with replay

I need network logger utility with ability to replay the data it collected, for example, I will record incoming data on UDP port 1234 for 10 minutes, record it to file, then replay that data (with ...
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2answers
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How can I reject all incoming UDP packets except for DNS lookups?

I set my server to reject ALL incoming UDP packets, to prevent UDP floods. However, I was told that because I use my own domain and server for my nameservers, this can cause some problems. How can I ...
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2answers
976 views

Why are UDP messages from outside the network received but not delivered?

I have an Ubuntu Server 10.04 application I've developed that receives messages over a UDP port. The ultimate purpose of this application is to receive messages sent from workers' 3G modems out in ...
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4answers
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How does UDP track connections?

If UDP does not establish a connection as TCP does.. it seems the only way it could track connections is source ip/port and destination ip/port. Is this correct? So, I guess there are special packets ...
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6answers
694 views

which applications based on UDP?

I hava installed nginx on my localhost, then I copy test.avi to html directory, then i can watch the video by http://localhost/test.avi in browser, i want to know, is the video traffic based on UDP? ...
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319 views

Can a network interface be configured to have a default gateway for UDP packets?

It is quite possible that my question may not make a lot of sense. I apologize, but I am not a networking guy, and that's my excuse. To elaborate, WikiPedia defines "Default Gateway" as a node on a ...
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539 views

Sending a UDP message to a computer inside a network

Say I have the ip and mac address of a computer inside a network and I wish to send him a UDP message. By initializing the mac and ip addresses of the sent message to the given, when the network ...
0
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1answer
105 views

How to simulate high wire speed ?

I want to test the max speed of my VPN(pptp) server, so I plan to download something from one server by VPN, At first, I think the server need to supply a high speed(30M) for client, who can tell ...
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How to measure and minimize UDP packet loss

I sometimes face voice break when calling through a VOIP application. Since all VOIP applications uses UDP for data transmission, is there any tool in Linux to measure the amount of packet loss and ...
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1answer
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DNS SERVFAIL and Incorrect Flag only via TCP: Broken DNS Servers?

Is it poor configuration to return the root name servers in the additional section for a CNAME lookup that points to another domain? Particularly the one I'm seeing this with is a CNAME hosted by ...
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listen to UDP data on local port with netcat

netcat -ul -p2115 fails with a usage statement. What am I doing wrong? Thanks!
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Wireshark won't pick up packets sent from localhost to localhost via network [duplicate]

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 ...
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3answers
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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 ...