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Questions tagged [udp]

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

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conntrack expectation on directed broadcast [closed]

I'm testing out a setup that I would reproduce in a production environment if I get it work. What I have: A wireless network 192.168.88.0/24 An IoT device X in the wireless network A Teltonika router ...
path's user avatar
  • 3
0 votes
1 answer
80 views

In wireshark, why following a TCP or UDP stream does not remove ICMP packets?

In Wireshark, when I follow a TCP or UDP stream using right click -> Follow -> UDP Stream, if there are some ICMP packets from same endpoints, wireshark will keep them in the stream. Why? Since ...
Sourav Kannantha B's user avatar
0 votes
0 answers
18 views

how to calculate the udp checksum when the udp payload is and odd number e.g 45 bytes payload [duplicate]

I am new to networking and was learning about the UDP Protocol and i came through the term UDP checksum. I searched the internet spent so much time finding the correct way to calculate the UDP ...
Immad's user avatar
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0 votes
1 answer
60 views

Why my high speed UDP transmitter send package to all devices after being disconnected from the server?

Here is my network configuration: My Embedded board(192.168.124.249) sends a 16-byte UDP packet to my PC2(192.168.124.10) each 1ms. Here is my PC2 received data: Everything works fine until I ...
John Jin's user avatar
  • 103
0 votes
1 answer
330 views

What is the maximum size of an application-layer message for UDP?

TCP is capable of segmentation, i.e. even if the application layer creates an arbitrarily large message, the transport layer under TCP will split it into segments. Now, as per this answer, UDP doesn't ...
Kushagr Jaiswal's user avatar
1 vote
0 answers
129 views

How to forward UDP unicast messages to multiple destinations [closed]

I am trying to forward a UDP Unicast message so that it cant be received by multiple computers. Can anyone point me in the right direction for how to accomplish this? Here are the details: There are ...
James Duvall's user avatar
0 votes
1 answer
25 views

OVS pop_mpls action returning invalid ethernet frames

I am currently running into walls when trying to pop an mpls label with ovs. I currently have two interfaces on one ovs instance connected to ports eth0 and eth1. I define a flow on eth0 to pop an ...
Friwi's user avatar
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1 answer
104 views

does port 8080 need port_forwarding?

is port 8080 open (auto forwarded) in all devices? i used it without PortForwarding and UDP packets transferred successfully! i expected the NAT to block this but public ip address worked simply! i ...
n12y's user avatar
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2 votes
1 answer
663 views

Does UDP work with NAT

I'm learning the TCP and UDP protocols and I have a question about UDP. I used C to develop a UDP server and a UDP client in my LAN and it works as expected. The server and the client could ...
Yves's user avatar
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2 answers
112 views

Why does I2P use UDP? [closed]

UDP is unreliable, why does I2P (garlic routing, an alternative to Tor) use UDP instead of reliable alternative: TCP? Won't I2P become unreliable due to UDP?
Flan1335's user avatar
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2 answers
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UDP fragmented packets not reassembled

I have been working with a device that sends me UDP packets heavily. I'm trying to capture those packets in my Linux machine (Ubuntu 22.04.2 LTS) with Python programming language. But, most of the ...
mustaphos's user avatar
1 vote
3 answers
310 views

UDP encrypted packets

I am analysing a Wireshark capture as part of understanding UDP/TCP, DNS and HTTP concepts and how packets are sent. I found an interesting sequence of messages in the Wireshark file, but I am not ...
Tita's user avatar
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1 vote
1 answer
43 views

Running 2 or more applications PPP

I had a doubt regarding point-to-point protocol. Is it possible for a single PPP link to enable running of 2 or more simultaneous applications between two hosts? Thanks!
ikben's user avatar
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0 votes
2 answers
94 views

Are UDP packets "retransmitted" when dropped by an edge router inside an SSH Tunnel?

A network architect was recently asking about enabling DSCP on tunnels that I create for a VPN-like solution I maintain using ssh to maintain tunnels on linux devices. I thought this was odd because I ...
Peter Turner's user avatar
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0 answers
401 views

Monitor UDP packet in wireshark

I am trying to monitor udp packets from server to client in Wireshark at both end. Can I get any clue in Wireshark with which I find out that ok this specific udp packet is what I sent and received at ...
Nifty's user avatar
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1 answer
119 views

Will the UDP packets reach its destination?

I am trying to send UDP Packets using Linux Socket. Working inside a Linux VM. Server IP = 172.16.x.x Client IP = 172.21.x.x Both are connected via a Ethernet switch. Doing a broadcast on company's ...
shrishri's user avatar
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1 answer
34 views

Is There a Max Number of In-Transit UDP Packets? [closed]

I am sending some data over UDP from client to server using sendto. I noticed all the data was not being received. I began logging (printing) each packet sent on the client, and just the act of doing ...
Pepsi Pimp's user avatar
3 votes
2 answers
2k views

How is congestion avoided when using UDP?

I understand how TCP goes about this - through various methods such as Congestion Window (CWND), Sliding Window, Slow Start and Fast Recovery - it's basically built into the protocol. I understand ...
Inquisitive's user avatar
1 vote
0 answers
762 views

How I can filter only quic packets with `tcpdump` command?

I want to capture only QUIC UDP datagrams on 443 port. With following command tcpdump reports all udp packets that arrive to the host on port 443. tcpdump -n udp -SX -i any port 443 How I can set it ...
raiym's user avatar
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2 answers
450 views

IP packet expired by TTL generate an ICMP response in any case?

Acording to Wikipedia IPv4 article for TTL header field: An eight-bit time to live field limits a datagram's lifetime to prevent network failure in the event of a routing loop. It is specified in ...
rfmoz's user avatar
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0 answers
16 views

What is the maximum safe UDP payload size over IPv6? [duplicate]

I am developing a networking library (that uses exclusively UDP) and I want to support both IPv4 and IPv6 by using a dual-mode socket. I want to limit the size of the packet user can send to a value ...
FICHEKK's user avatar
  • 101
0 votes
1 answer
115 views

Why are External NAT ports different when both NATs are restricted cone? [duplicate]

I'm in the progress of implementing my own Signaling server with UDP hole punching, everything have been smooth up until both hosts were behind Restricted Cone NAT, then the ports for P2P ...
Blip's user avatar
  • 1
0 votes
2 answers
923 views

UDP supports multicasting and broadcasting in transport layer or application layer?

We know that UDP does supports multicasting and broadcasting. My question is which layer "UDP supports multicasting and broadcasting"? Is it transport layer or application layer? We know ...
S. M.'s user avatar
  • 398
21 votes
5 answers
6k views

Why is Packet Size Limited?

I was reading: this answer to "Maximum packet size for a TCP connection", where it says: The absolute limitation on TCP packet size is 64K (65535 bytes), but in practicality this is far ...
Algo's user avatar
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-1 votes
2 answers
436 views

What will happen if a sender use TCP and receiver uses UDP?

I am new to networking and was studying about TCP and UDP. One question came to my mind that what will happen if a sender uses TCP and receiver uses UDP for the communication.
MD Sulaiman's user avatar
0 votes
1 answer
793 views

Can UDP traffic be transmitted over TCP ports on OpenVpn to avoid the TCP meltdown

I understand the TCP meltdown problem is associated with overcompensation from errors and incorrect sequencing when arriving the the receiver end. OpenVpn connections are recommended to use the UDP ...
Mervyn Heng's user avatar
1 vote
0 answers
109 views

Optimize Network For UDP Broadcast Traffic?

I have a computer that creates an AP which multiple microcontrollers connect to. The computer sends out UDP Broadcast packets that tell the microcontrollers to do different things. I have an issue ...
Noah's user avatar
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0 votes
2 answers
706 views

Do segments at the transport layer contain IP information?

I have few questions about how UDP segments at the transport layer works. I read that The transport layer encapsulates the application layer data along with destination IP and destination port ...
Pablo's user avatar
  • 103
2 votes
1 answer
4k views

Which one is right, UDP has 508 or 512 bytes payload limits?

We know the size guarantees the datagram won't be fragmented in IPv4 is maximum 576 bytes. But the size when use UDP header 8 bytes and if we take UDP payload 512 bytes and choose maximum header size ...
S. M.'s user avatar
  • 398
-1 votes
1 answer
568 views

Why the pseudo-header is not transmitted with the UDP datagram?

I have read from E. Comer - Internetworking with TCP/IP 4th edition that "The purpose of using a pseudo-header is to verify that the UDP datagram has reached its correct destination. The key to ...
S. M.'s user avatar
  • 398
1 vote
1 answer
2k views

UDP checksum calculation for checksum results in the value zero

I read UDP checksum from Wikipedia that "If the checksum calculation results in the value zero (all 16 bits 0) it should be sent as the one's complement (all 1s) as a zero-value checksum ...
S. M.'s user avatar
  • 398
0 votes
1 answer
1k views

Why UDP checksum is optional for IPv4?

We know that IPv4 header has checksum for header not for data .Therefore for checking data error we need checksum in transport layer. Suppose we're using UDP in layer 4. So if I remove the checksum ...
S. M.'s user avatar
  • 398
1 vote
1 answer
333 views

How UDP checksum get IP address to make pseudo header in transport layer?

We know that UDP checksum's pseudo header contains the most important parts of the IP header, that is, source and destination address, protocol number and data length. I hope that the concept of IP ...
S. M.'s user avatar
  • 398
1 vote
2 answers
1k views

How is UDP used in multimedia system inspite of being connectionless

We know that UDP does not care about segment (packet) in-order and their arrival on the destination.Then how on YouTube or VoIP (skype) are we able to stream videos? If a packets is lost (doesn't ...
S. M.'s user avatar
  • 398
1 vote
1 answer
64 views

Is there any research that tracks fragmentation and drop rates of UDP packets based on size?

I'm designing a P2P system. I need to decide an ideal packet size that maximizes the efficiency of my system. This answer claims a 508 bytes is the maximum safe size, but I believe larger packets ...
MaiaVictor's user avatar
0 votes
1 answer
59 views

Are NAT external:internal mapping types the same for UDP and TCP

Suppose I use a STUN server (UDP) to determine that a client's NAT randomly assigns external port values. Does this imply that the client's NAT will also assign random external port values when using ...
Thomas Braun's user avatar
2 votes
1 answer
102 views

Is the distinction between ports under and above port 1024 exists only in TCP and UDP protocols?

Is the distinction between ports under and above port 1024 exists only in TCP and UDP protocols? I want to know if in other protocols (i.e. not TCP and UDP) such a distinction between "root" ...
puertoportopoio's user avatar
1 vote
1 answer
73 views

Does UDP can be exposed to stateful analysis?

From protocol theory we know that TCP is stateful protocol. Different stateful packet filters do filtration based on connection state. I.e. it can distinguish responses and replies. It's obviously for ...
z0lupka's user avatar
  • 207
1 vote
1 answer
300 views

Is UDP a Transport Layer Protocol in the TCP/IP model?

In some tables explaining the TCP/IP model, both UDP and TCP are set as examples as protocols for the Transport Layer. Does this mean that UDP is part of the TCP/IP protocol suite?
Samuel Martineau's user avatar
0 votes
1 answer
67 views

The origin of the name UDP

I was wondering, UDP being broadly defined as a connection-less, unreliable protocol giving applications control over messages sequencing and flux control, is it correct to say that the "User&...
geauser's user avatar
  • 105
1 vote
0 answers
18 views

How to send 10-20KiB with UDP semantics? [closed]

I have volatile traffic, of 10-20KiB, that I want to send with UDP semantics. I have measured packet loss between several servers across the internet. In testing, I can reliably get 32KiB UDP packets ...
fadedbee's user avatar
  • 113
1 vote
1 answer
270 views

Does UDP's lack of congestion control clog up the Internet?

I'm reading Computer Networking: A Top-Down Approach, and from what I understand, UDP has no widely adopted mechanism for congestion control like TCP does. Isn't this a problem for the Internet as a ...
fpsvogel's user avatar
  • 113
2 votes
1 answer
207 views

What is the equivalent of "ethernet frames" for satellite communications?

I'm currently implementing error-correction for a UDP-based network protocol. We chose to implement error-correction in order to reduce the number of packet re-transmissions. The architecture is very ...
Luca Polito's user avatar
17 votes
3 answers
5k views

Why does one say IP fragmentation is bad and to be avoided when in reality data always needs to be fragmented for MTU compatibility?

Why does one say fragmentation is bad and must be avoided due to performance issues when in reality fragmentation intrinsically occurs within the communication ? Example: User1 wants to send 100 000 ...
Floji's user avatar
  • 319
1 vote
2 answers
56 views

Resegment incoming TCP/UDP packet [closed]

The question is as follows: what is the algorithm to resegment an incoming TCP/UDP packet? So, for example, I have a TCP packet, which size is more than some number, and I want to split this packet ...
Pavel Kotov's user avatar
0 votes
1 answer
24 views

How to ensure packet was created within certain time?

I am creating a custom protocol over UDP and I want to use a low number of bits for the sequence number. This means that the number can wrap relatively fast. Is setting the TTL for the outgoing ...
Daniel's user avatar
  • 101
0 votes
1 answer
124 views

CISCO: Copy one UDP unicast packet to other destination

I have following scenario: host A and host B are sending to each other unicast UDP packet. I need that same message from host A will arrive also to host C - with new DST address. How to configure my ...
user1977050's user avatar
1 vote
1 answer
345 views

Is there any other network protocol than tcp/udp that works with ports?

Do you know at least one protocol (any OSI layer) that, like tcp and udp, works with ports ? Thank you
beauthi's user avatar
  • 13
0 votes
1 answer
46 views

DNS request on google.com. with QTYPE = 0xff returns no entries [closed]

Ive written my own DNS request client but I'm having some interesting behavior. If I send the request with the QTYPE section = 0xff, I get a valid response however with no entries. My Request: 0x70 ...
SwimMaster's user avatar
45 votes
7 answers
16k views

Does UDP do anything at all?

It's my understanding that TCP has logic for ensuring reliable communication, but UDP just naively sends information along the channel set up for it using IP and things in lower layers. Does UDP ...
JacKeown's user avatar
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