1
vote
1answer
35 views

Debian 7.4 drops UDP traffic randomly

I'm running Debian 7.4, KVM VPS with the latest updates. I'm getting UDP ports randomly closed for 2-10 minutes for no reason. I'm running gaming servers and the port tester shows the ports are ...
0
votes
0answers
24 views

tcpdump, display the data section

i am trying to display only the data section of an udp packet using tcpdump. In some other words, is it any way to filter the header section of the udp package? The below command sudo tcpdump ...
0
votes
2answers
30 views

Suspect UDP traffic on lo interface

I'm monitoring the lo interface with iptraf and am getting a lot of movement in the following form: UDP (268 bytes) from 127.0.0.1:49254 to 127.0.0.1:49254 on lo This message appears on average ...
0
votes
1answer
114 views

UDP port appears to be in use but is not shown in netstat or TCPView

I've encountered some strange behavior I don't understand. I'm installing software on a Windows 2003 Server. This software needs to bind to a specific UDP port an all TCP addresses in order to listen ...
1
vote
1answer
100 views

UDP maximum segment size

Environment: I am writing a UDP client-server application. the path MTU between client and server is 1500 bytes (with only a wireless link between them, so this value is pretty much stable). My system ...
0
votes
0answers
68 views

How to forward UDP and TCP traffic from one IP to another

I have a server with two LAN cards installed. I have one server in U.S and one in India. I have created a GRE tunnel to route all traffic from the U.S Server to my Indian Server. My traffic has ...
1
vote
1answer
80 views

Loadbalance UDP traffic with session affinity and way to take servers in & out of rotation [closed]

What is the best way to go about load balancing UDP traffic among a whole bunch of servers, while keeping session affinity based on the users' IP? I need to also be able to take servers in and out of ...
1
vote
1answer
324 views

How do I add a broadcast IP to the loopback interface under os/x using ifconfig when my machine has no network? [duplicate]

I'm new to advanced network administration and I would like to do some testing with UDP broadcasting, so I need a broadcast address on my loopback interface. The machine is offline, in other words, ...
-1
votes
2answers
98 views

What is the equivalent of 127.255.255.255 for OS/X machines so I can test broadcast udp packets without a network? [duplicate]

I am trying to test my program that makes use of broadcast UDP (not multicast!). In Linux, I can use the 127.255.255.255:64651 address and everything works beautifully, in other words, I send a packet ...
21
votes
5answers
1k views

Can TCP and UDP packets be split into pieces?

Can TCP packets arrive to receiver by pieces? For example, if I send 20 bytes using TCP protocol, can I be 100% sure that I will receive exactly 20 bytes at once, not 10 bytes then another 10 bytes ...
3
votes
1answer
260 views

Symmetric NAT and UDP Hole Punching

I've read this question, but the explanation of Symmetric NAT wasn't detailed enough. Please could someone help me to understand the following paragraphs? I read this about Symmetric NAT: Each ...
0
votes
2answers
126 views

Can heavy UDP traffic create network congestion?

I have three IP addresses using the same gateway. Two of them are configured as a cluster with multicast address setup. If there is a heavy UDP traffic between those two, can that affect the network ...
0
votes
2answers
35 views

unicast traffic on windows server

I have three servers with IP addresses (10.15.23.23, 10.15.23.24, 10.15.23.25). Server 1 and Server 2 have Tomcat installed and are configured as a cluster listening on a multicast IP address ...
0
votes
1answer
49 views

LAN has two entry points - how to manage traffic

I asked this question yesterday when I (seemingly) couldn't get traffic across my router. I've spent a lot of time since then with packet capturing, the ASA 5505 cli/ASDM and wireshark. I've ...
1
vote
0answers
40 views

Nat Traversal, peers unable to communicate

I'm currently working on a project that requires NAT traversal but I seem to be running into difficulty. I have the following setup running for testing: R1, Verizon Fios router connected to the ...
2
votes
2answers
136 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 ...
1
vote
1answer
190 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 ...
2
votes
2answers
444 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 ...
0
votes
0answers
94 views

Cannot see an EC2 VPN server from another EC2 instance

I'm using openVPN to connect to one EC2 instance from another. The client cannot see the server, however, despite that servers outside of AWS can see the server and successfully negotiate with it. ...
2
votes
2answers
323 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 ...
1
vote
1answer
202 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 ...
0
votes
1answer
144 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 ...
1
vote
4answers
106 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 ...
17
votes
2answers
5k 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
votes
1answer
698 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! ...
2
votes
2answers
1k 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 ...
1
vote
1answer
775 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
votes
3answers
342 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 ...
5
votes
1answer
244 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. ...
0
votes
1answer
125 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 ...
0
votes
1answer
223 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 ...
1
vote
1answer
511 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
votes
2answers
276 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 ...
2
votes
2answers
257 views

How can I find out where a UDP connection fails?

I want to setup a VPN server with OpenVPN, so client PCs can access each other like they were in the same physical network. One problem I encountered is, that I cannot connect via UDP. When I change ...
2
votes
1answer
369 views

What is the difference between bind, network (interface) and multicast addresses?

The DatagramSocketImpl in Java has a joinGroup method that takes a socket address (IP and PORT) plus the interface address (IP and PORT). I am trying to understand the difference and purpose of each ...
1
vote
1answer
312 views

ICMP destination unreachable

I am working on an arch linux machine with ethernet interface eth1. I have created interface eth1:0 using ifconfig and given it a dummy hw address (00:01:02:03:04:05). When I send a UDP packet to a ...
1
vote
2answers
298 views

Some questions on UDP send receive buffer, and networking

I have two debian servers located on the same subnet. They are connected by a switch. I am aware the UDP is unreliable. Question 1: I assume the link layer is ethernet. And MTU from a standard ...
3
votes
2answers
134 views

Service to temporarily queue UDP packets

I have a service running on a linux box that receives a fairly constant stream of packets via UDP. The occasional loss or corruption of packets associated with using UDP is fine. However, the service ...
4
votes
4answers
2k views

How to list all requests to udp sockets?

I'm operating a couple of server daemons that use udp to communicate with large number of clients. How do I find and list out all the active udp "connections" that are talking to the servers in order ...
0
votes
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 ...
1
vote
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 ...
5
votes
4answers
10k views

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
votes
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 ...
0
votes
4answers
719 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 ...
1
vote
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
votes
1answer
1k views

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 > ...
1
vote
1answer
2k views

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 ...
2
votes
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 ...
1
vote
8answers
690 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 ...
1
vote
4answers
1k views

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 ...