Questions tagged [udp]

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

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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 ...
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What is crypto padding i see when i capture my wifi connection using wireshark? [closed]

I'm worrying that my pc is used for mining from any malware , i opened wireshark and see this in my pc. 12 0.953233 2a10:XX:XX:0:XXX:XX:XX:XX 2a00:XXX:XX:XX::X QUIC 1292 Initial, DCID=...
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1 answer
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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 ...
1 vote
2 answers
128 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 ...
1 vote
0 answers
103 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 ...
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2 answers
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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 ...
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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 ...
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1 answer
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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 ...
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2 answers
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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 ...
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0 answers
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How IP packet's payload bigger than the whole former PDU (segment)? [duplicate]

As far as I know: File is too big ---> Fourth layer (TCP or UDP) divide it to a multiple segments ---> Then each segment encapsulated separately into a packet. What means if I have 10 segments, ...
20 votes
5 answers
4k 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 ...
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-1 votes
2 answers
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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.
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1 answer
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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 ...
1 vote
0 answers
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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 ...
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2 answers
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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 ...
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1 answer
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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 ...
-1 votes
1 answer
181 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 ...
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1 answer
388 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 ...
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1 answer
285 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 ...
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1 answer
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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 ...
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 ...
1 vote
1 answer
51 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 ...
0 votes
1 answer
41 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 ...
2 votes
1 answer
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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" ...
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1 answer
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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 ...
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1 answer
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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?
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1 answer
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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&...
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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 ...
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1 vote
1 answer
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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 ...
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2 votes
1 answer
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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 ...
17 votes
3 answers
3k 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 ...
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1 vote
2 answers
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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 ...
0 votes
1 answer
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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 ...
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1 answer
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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 ...
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1 answer
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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
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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 ...
44 votes
7 answers
15k 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 ...
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1 answer
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How might ARP impact the UDP communication and what is a scenario i can reproduce to check/understand it?

I was wondering which impact the ARP protocoll might have on a UDP communication. I am learning for an exam and trying things out with mininet (linux )/ wireshark to understand the dependencys between ...
1 vote
2 answers
224 views

Is this UDP diagram wrong?

I was just wondering if anyone can tell me why all UDP diagrams I have seen list a request from the server to the client as the first point of communication? Take a look at the following diagram for ...
0 votes
3 answers
215 views

Is the length header used to indicate the end of a segment?

I was reading a textbook which says the need of length header for UDP: The length field specifies the number of bytes in the UDP segment (header plus data). An explicit length value is needed since ...
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How does UDP control the flow of data in file transferring?

I know that transferring files over UDP is possible even though TCP is preferred. My question is how does the server know how much the client can handle or vice versa, or any router in between. TCP ...
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1 answer
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How UDP protocol Number is 0x011?

How UDP protocol number is 0x11 when it's supposed to be 0x17 According to ianna website
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multicast udp streaming dst and src address assignment

If I am streaming on a host using the internet outside my nat, how is multcast addressing work with respect to streaming for example, if the application outside sends to 224.0.0.1 how is the packet ...
-1 votes
1 answer
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Real time video streaming over TCP [closed]

One of the topics I have been following for quite sometime is real-time streaming. Over the course of my research everyone suggested and says WebRTC (based on UDP) is the only solution to achieve real-...
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When port-forwarding, will a port only be listed as OPEN if the service host is actually reachable?

I'm fiddling around in my lab today and attempting to learn more about port-forwarding. I've noticed that when I set up port-forwarding for a given port and run a port scan from outside the network, ...
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2 votes
1 answer
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Does UDP perform packet re-ordering at the destination?

User Datagram Protocol is a simpler message-based connectionless protocol. Connectionless protocols do not set up a dedicated end-to-end connection. Communication is achieved by transmitting ...
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28 votes
8 answers
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Why does DHCP use UDP and not TCP?

DHCP uses UDP as its transport protocol. DHCP messages that a client sends to a server are sent to well-known port 67 (UDP—Bootstrap Protocol and DHCP). DHCP Messages  that a server sends to a client ...
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2 answers
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Which port determines the protocol?

If we have a common protocol port on both ends.. say source point is 443 and destination port is 80 (hypothetical situation, I know this combination of ports probably makes no sense).. how do we ...
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How does UDP provide continuous sound in VOIP even though segments are discrete?

I would like to know how does UDP achieve continuity in VOIP or in any streaming service.
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1 answer
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ports and security

I'm thinking about how the "port" operates for the network connections and tried reading the CCNA cert. guide to understand the details, however, I need to clarify doubts: does occupying all the TCP/...
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