Questions tagged [udp]

For questions about User Datagram Protocol, a Transport Layer protocol.

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why iperf3 UDP throughput is lower than the TCP throughput?

I'm running an iperf3 throughput test from my PC to another one, going through a router. I've tried the same configuration for TCP traffic and for UDP traffic. However, for UDP traffic, I get worse ...
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4answers
66 views

Why ICMP Destination Port Unreachable error messeage is generated for unreliable UDP packets?

My doubt is why an icmp destination port unreachable error message generated for udp. Why we can't simply discard the udp packet if the destination port is not reachable by saying udp is connection-...
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1answer
38 views

UDP in wifi getting excessively buffered

We are using a wifi-enabled device that receives a stream of UDP packets (30 per second). It is very important for us to receive these messages without lag, that's why we are using UDP and not TCP ...
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1answer
46 views

How does a DNS response reach a client behind a NAT?

How does a DNS response reach a client behind a NAT? I'm talking about DNS queries using UDP for transport with a server that is not in the same network as the client. Does the NAT correlate the ...
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2answers
36 views

Forcing UDP traffic from specific ports [closed]

Is it possible that all traffic from computer 1 towards computer 2 go thru udp port D of computer 1 and received at udp port B of computer 2. Similarly all traffic from computer 2 towards computer 1 ...
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1answer
56 views

what is the definition of out degree and in degree in computer networks?

in wikipedia we have a good definition for in degree and out degree in a graph: " The degree of a node is the number of connections or edges the node has to other nodes. in-degree is the number of ...
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10 views

Can a UDP service and TCP service use one port? [duplicate]

When we open a UDP or TCP connection, there will start a port in server. there I have a question, can a UDP service and TCP service use a same port?
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1answer
64 views

If you're behind a firewall and all the ports are blocked, how is your browser able to access the internet?

I'm behind a router and I'm able to run game servers on my home computer after forwarding ports or using the DMZ feature on the router. However, I still don't understand the underlying technology as ...
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1answer
52 views

Is UDP Hole Punching possible if the network of one peer has multiple external IP addresses?

I've developed an implementation for UDP hole punching that works for most use cases that I've come across. However, one of our offices has a network configuration where we have two ISPs providing us ...
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1answer
51 views

Avoid bottleneck in UDP multicast

The question is that a server is serving a multicast group with UDP. Lets say that its a file server and it will be serving big files (~10GB). Now we have a multicast group with multiple clients. Some ...
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7answers
6k views

Why isn't UDP with reliability (implemented at Application layer) a substitute of TCP?

TCP provides reliability at transport layer while UDP does not. So, UDP is fast. But, a protocol at application layer can implement reliable mechanism while using UDP. In this sense, why isn't UDP ...
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1answer
66 views

Collect UDP packets lost during iPerf test

I'm testing my network infrastructure where I'm using iPerf and UDP protocol. I'm using the following: On the server side: ubuntu@ip-172-0-1-11:~$ iperf -s -u and the client side: ubuntu@ip-172-2-...
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2answers
119 views

How to measure max bandwidth with Wireshark?

I'm trying to measure the max bandwidth usage of my LAN with Wireshark. I´ve done several packet captures but I don't know how to obtain the max bandwidth usage. Any Idea? Thank you in advance
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1answer
87 views

Weird Wireshark protocol list (eth:ethertype:ip:data where is the “udp”?)

I am capturing incoming and outgoing WAN to LAN data at a particular host on my LAN (i.e., the one actually receiving/sending the data). Sometimes I get anomalous captured frames that are missing the ...
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0answers
18 views

Are there NATs which will block any further incoming packets from a peer after rejecting first one?

I'm attempting to test udp hole punching. Right now I'm simply testing how my computer reacts behind a router. If I send a udp packet from my computer to a server, it can reply back on the same port ...
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47 views

Unable to get NetFlow flow in Cisco CSR1000v on AWS

I'm trying to use NetFlow Traffic Analyzer of SolarWinds or any NetFlow Monitor in my Cisco CSR1000v routers which are deployed on AWS. I am unable to see any NetFlow flows in the NetFlow Traffic ...
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1answer
99 views

Setting Destination MAC address for RTP/UDP packets

I have a requirement where I have to send the UDP packet to a destination multicast IPv6 address. In addition to that the packets must also have corresponding destination multicast MAC address set. I ...
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1answer
126 views

How to send data from one PC to another PC over internet? [closed]

I'm basically a developer, and this is the first time i'm trying to develop a chat application over internet without any servers in between. It's easy to send data from PC to server and then to ...
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2answers
146 views

How to calculate traffic in bytes from sFlow datagrams?

I want to approximate network traffic in bytes by writing a sFlow collector that receives sFlow datagrams, parses them, extracts key information only and applies a formula that summarizes the traffic ...
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2answers
69 views

Is it correct to assume that ordering of frames at switch level is not important?

My understanding is that if the payload of the frame contains any data that needs to be reassembled, at least for TCP payload, it can be done at the OS level, once all the packets are received and ...
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1answer
130 views

TCP or UDP for Stop & Wait / Go Back N

I'm creating server/client classes for "Stop & Wait" and "Go Back N" (variant of sliding window) protocols, though I'm unsure on whether I should pursue TCP or UDP. From my current understanding I ...
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2answers
3k views

Why maximum length of IP, TCP, UDP packet is not suit?

From many tutorials, I get follow knowledge(maybe I'm misunderstood) : maximum of an Ethernet packet is about 1500 bytes. maximum of an IP packet is about 65535 bytes. maximum of a UDP packet is ...
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0answers
21 views

Why maximum length of IP、TCP、UDP packet is not suit? [duplicate]

From many tutorials, I get follow knowledge(maybe I'm misunderstood) : maximum of an Ethernet packet is about 1500bytes. maximum of an IP packet is about 65535bytes. maximum of a UDP packet is 65515 ...
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1answer
153 views

How to plot and benchmark UDP response time?

Our application uses UDP protocol in the transport layer. I'm currently filtering the packet trace with the port and then manually checking the RTT by selecting the packet stream and by using " Set ...
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2answers
64 views

How can TCP be used in order to implement DHCP and under which circumstances is this preferable?

I am pretty new to the computer networking studies and was learning about the DHCP protocol. It is implemented based on UDP, as I've gathered, but is there a way for it to be implemented over TCP? ...
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2answers
39 views

How to know difference between 2 devices connected to the same Wi-Fi hotspot in IPV4?

I am working on a small project to make a client server program to make a connectionless implementation & I want to transmit Information between 2 devices which is connected to the same Wi-Fi ...
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1answer
147 views

How does the transport layer tell UDP apart from TCP?

So I'm reading Computer Networking: A top down approach (where these images are from) and I was looking at the Transport layer. A generic segment in the transport layer has a pretty simple structure: ...
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2answers
111 views

Why do UDP connections only require a socket on one endpoint?

I thought for a long time that sockets were defined as an end point of a two way connection, however UDP sockets can be created without the other end making a socket to keep the connection live. What ...
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1answer
76 views

How is a lost DNS query handled [closed]

If a DNS query gets lost along the way to its destination, is nothing done about it? In my networking class, my lecturer said that DNS runs on UDP. I verified this in Wireshark by doing nslookup for a ...
3
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1answer
384 views

How can a UDP Client and a packet sniffer run on the same machine?

In my understanding, if you have a UDP socket client that is bound to a particular port, then a second UDP client on the same machine can't bind to the same port. If this is the case, then how can a ...
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1answer
106 views

Is there any video streaming online service that actually uses UDP?

We usually hear that UDP is used with data with which a few packets loss/out-of-order can be tolerated like video streaming. And the instructor typically goes on saying "so if you lose a few ...
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1answer
30 views

Question about output of 'lsof -i' and UDP being connectionless

I'v got a simple setup: Server (IP 10.0.0.33) listening on port 7770 using the command: $ netcat -lup 7770 And a client (IP 10.0.0.2) that communicates with the server using: $ nc -u 10.0.0.33 ...
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2answers
52 views

How could a response be sent to the requestor without requestor's address?

I'm reading this talking about the differences between two fire-and-forget message (for example, under UDP) and a request-response communication (for example, under TCP). I came across this: The ...
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1answer
315 views

Packet with wrong source MAC address

When I send a UDP packet with wrong source MAC address but with right source IP address, assuming a reply is sent, will I get the reply because I have right source IP address, or I will not get the ...
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1answer
201 views

Wireshark udp checksum errorI

I sniffing udp communication with 2 instance of wireshark , 1: 2.0.0 2: 2.2.1 . In version 2.0.0 I get valid udp.checksum , but with 2.2.1 I always get udp checksum = 0000 . Why is that? those ...
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2answers
288 views

Why is there a difference on the amount of data transferred during a UDP iperf measurement?

I have the following result from a UDP throughput test as measured by iperf3 $ iperf3 -u -t 10 -c 192.168.1.2 -b 100M -V iperf 3.6+ Linux pi-raspberry1 4.4.38-v7+ #938 SMP Thu Dec 15 15:22:21 GMT ...
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0answers
315 views

How to control unwanted UDP traffic (Broadcast & Multicast) on Cisco Router 2911?

Please suggest, we are getting UDP traffic either broadcast or multicast in router 2911 which cause 95%+ utilisation of the router. And we got error in link and business impact due to this. Company ...
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4answers
3k views

Why is a TCP Socket identified by a 4 tuple?

Newbie to networking here. I'm reading the Computer Networking (3rd edition) book, and in section 3.2 they are discussing multiplexing / demultiplexing for both UDP and TCP. In the UDP protocol, a ...
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2answers
1k views

How does NAT work with incoming UDP packets from unknown IP

Apologies in advance for the relatively noob question and if this is off topic here ( I am not sure...) The situation is that I have a UDP client and server bound to the same port. My understanding ...
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1answer
459 views

How IP datagram know its upper layer protocol?

Hi I'm a newbie in networking, I just want to know how IP datagram know its upper layer protocol is TCP or UDP? I know there is protocol field inside the IP datagram header that can tell the layer ...
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2answers
224 views

How does the server know how to respond to a UDP packet? [closed]

As far as I know, UDP ports and OS sockets are mapped only by the (local port, local address) pair. In other words, the receiver side's OS does not keep a state of (remote port, remote address) pair (...
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1answer
183 views

User Datagram Protocol (UDP) protocol can error control?

UDP can congestion control? UDP can flow control? UDP have some error correction mechanism?
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1answer
98 views

HP MSR2004 router is not processing udp through nat

I set up a new HP MSR2004 router for a corporate network. The network uses an internal private net and has one static public ip address. Surfing the web and all tcp related things seem to work fine. ...
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3answers
642 views

Is UDP Usage in Routing Information Protocol (RIP) a Secure Practice?

I know that UDP is a connectionless transport layer protocol. Since it is easy to fake your source IP and source Port in your headers, what keeps anyone from poisoning routing tables via RIP? It seems ...
3
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1answer
159 views

rate-limit dns queries on HP procurve 8212zl

I had ast week the situation that a user accidentally got our DNS server to its knees by sending over 270K DNS queries to our dnsmasq. I was looking for a reliable method to prevent this Happening in ...
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1answer
169 views

NS2 program specifications questions

I am using the Network Simulator NS2 program (https://www.isi.edu/nsnam/ns/) in order to simulate a simple network topology with 1 UDP agent and 1 CBR Application Traffic sending data from a node over ...
5
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1answer
573 views

How does UDP NAT Know When To Remove The Rule

So say you are a user behind a NAT/router on an internal network. You begin sending UDP data to an internet-facing server. The packet hits your router, it inserts an entry to allow returning packets ...
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1answer
115 views

Udp broadcasting for communicate with a device who has the same IP address , is it possible?

I was thinking about broadcasting in an ad-hoc local area network, then i asked me a question.Assuming that this LAN is made of 2 pc, if this pc have the same IP address, Can i send udp packet from ...
2
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2answers
111 views

UDP packets vs two parallel gateways running NAT

I‘m writing an application that sends information, using UDP packets, to the server on the internet and then receives data same way. It seems to work fine from behind NAT but I’m wondering about more ...
3
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2answers
4k views

NAT and UDP problems

I have a question regarding NAT, UDP and TCP. Given a standard NAT server, is it a problem for it that UDP is connectionless? If so, why? And does TCP or QUIC solve this problem?