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Questions tagged [udp]

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

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2answers
56 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
50 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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1answer
1k views

Does Cisco-IPSLA work with Huawei-NQA?

I want to monitor udp-jitter using IP SLA (Cisco Router). The Destination Router was Huawei Router. I'm not sure whether Huawei Router doesn't support IP SLA responder. Is there anyway to use NQA with ...
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0answers
26 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 ...
2
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1answer
70 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
52 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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4answers
2k 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
55 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 ...
0
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1answer
72 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 ...
4
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2answers
63 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 ...
1
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1answer
77 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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1answer
1k views

How TCP hole punching works?

Is TCP Hole Punching similar to UDP hole punching?How it is established between "Peer A" and "Peer B" when both the peers are behind NAT? You can use Peer A and Peer B as example to make it easy to ...
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2answers
33 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 ...
6
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2answers
2k 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
17 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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2answers
55 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? ...
4
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1answer
94 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
78 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 ...
1
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1answer
382 views

UDP and fragmentation calculation

Assume we have a ethernet link with an MTU of 1300 bytes, while an application want to send 5200 bytes of data. How many fragments do we transmitted ? i would say 5, to send 5200 bytes over a link ...
0
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1answer
39 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 ...
42
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4answers
225k views

PING port number?

Yesterday interviewer ask me what is port number for ping and which protocol ping use TCP/UDP. After interview I search on internet and found different different results someone says ICMP uses Port 7,...
2
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1answer
58 views

Could long sequences of consecutive zeros cause Ethernet link problems?

I am in the process of debugging an Ethernet communication issue. Basically using Wireshark to monitor the source data the stream was intermittent when the cable was removed and subsequently ...
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2answers
677 views

Why do routers (and router firewalls) go through so much effort to make peer-to-peer difficult? [closed]

It is not uncommon for large routers to have unpredictable, random port allocation (which cripples UDP hole punching by making port prediction impossible) and for firewalls (not the software firewall ...
1
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1answer
241 views

Does an EIM-NAT work across both UDP and TCP?

I've read RFC 4787, 5382 and 5128 and I just need a bit of clarification. Assume a NAT has Endpoint Independent Mapping behavior for both UDP and TCP. Although I understand that if a machine would ...
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2answers
1k views

UDP Sessions and Ephemeral Port Selection

I would like to ask community to help me finding answers to the following questions: According to RFC 6056 an operating system should pseudo-randomly select ephemeral ports for each transport layer ...
3
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1answer
7k views

VXLAN: how receiver knows that the received packet is VXLAN-encapsulated?

I'm trying to understand how a receiver knows that the received packet is a VXLAN-encapsulated. Looking at the VXLAN RFC, I can't see anything specific that defines that the packet contains VXLAN ...
1
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1answer
457 views

UDP checksum calculation on improperly padded packets

Suppose I'm receiving IPv4 UDP packets whose payload is less than 18 octets, so when they are transmitted over Ethernet they have some trailing padding. Between the packets' source and my receiver ...
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2answers
934 views

How does the TCP/IP stack handle UDP checksum errors?

RFC 2460, Internet Protocol, Version 6 (IPv6) Specification, Section 8.1 Upper-Layer Checksums, states the UDP checksum is mandatory and any IPv6 receivers must discard UDP packets containing a zero ...
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2answers
167 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 ...
3
votes
1answer
321 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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2answers
2k views

Why does IKE use UDP instead of TCP?

Why does IKE use UDP, and handle any retransmission itself? (Larger IKE packets may cause UDP fragmentation and are dropped by some ISPs: IKE over TCP.
0
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1answer
613 views

Is UDP used in every TCP/IP connection?

I am confused on whether UDP and TCP work together, or are they completely separate protocols. So, UDP is used to allow multiplexing of different services on the same machine. So, essentially, for ...
2
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1answer
99 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 ...
1
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1answer
26 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
46 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 ...
3
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1answer
162 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 ...
0
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1answer
130 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 ...
0
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2answers
174 views

Hardware Implementation of Ports

What is the hardware implementation of a port and/or network socket? I understand that, at the lowest level, x86 uses opcodes such as IN and OUT when the data resulting from the instruction execution ...
1
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1answer
1k views

HPE 1920-8G-PoE+ multicast filtering

I have a switch HPE 1920-8G-PoE+ that is connected to two computers and two access points: Ubiquiti UniFi AP-Pro n450. The access points receive data from many devices. The two computers send UDP ...
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2answers
165 views

The meaning of TCP port in the network context

When talking about ports, sometimes I read articles that state TCP port while others just say port. Are there some features that make TCP port different from other ports in the OS?
7
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0answers
251 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
22k views

How to know whether a protocol uses TCP or UDP

Well I know that might sound a stupid question and I believe that the most proper answer will be like I will be able to tell as my experience builds up and I learn more and more about the protocols. ...
6
votes
5answers
2k views

Is rerouting possible in UDP?

So I am trying to understand routing for TCP and UDP segments. I have a couple of things that I am confused about: In TCP, is there any specification on how many packets would be dropped before a ...
18
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3answers
6k views

What do TCP/UDP add to “raw ip”?

I know that both TCP and UDP are built on top of IP, and I know the differences between TCP & UDP, but I'm confused about what exactly "raw ip" is. Would it be fair to say that TCP & UDP both ...
2
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2answers
665 views

Why do open ports give no response in networking?

Nmap places ports in open|filtered state when it is unable to determine whether a port is open or filtered. This occurs for scan types in which open ports give no response. The lack of response could ...
2
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2answers
96 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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1answer
2k views

Traceroute UDP port question

I know, that traceroute uses UDP, and for destination port it starts with 33434. Then, with each next hop it increments the destination port number by 1. The questions is: why does traceroute need to ...
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2answers
912 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 ...
2
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1answer
383 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 ...