Questions tagged [udp]

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

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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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UDP Broadcast Packets Lag On Receiving End ESP8266 and Raspberry Pi [closed]

I'm working on a cool lighting project where each person in a group will be wearing string lights that are controlled using an ESP8266 WiFi microcontroller. All of the ESPs connect to an AP created by ...
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2answers
30 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 ...
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1answer
519 views

Which one 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 ...
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1answer
62 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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1answer
69 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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1answer
44 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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1answer
41 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 ...
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2answers
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 ...
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5answers
435k 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 results someone says ICMP uses Port 7, someone ...
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1answer
38 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 ...
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1answer
28 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 ...
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1answer
54 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" ...
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1answer
42 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 ...
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1answer
49 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?
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1answer
28 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&...
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0answers
15 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 ...
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1answer
66 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 ...
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0answers
173 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
63 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 ...
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1answer
44 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 ...
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3answers
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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8answers
22k views

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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4answers
11k 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
25 views

Resegment incoming TCP/UDP packet

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 ...
4
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1answer
8k 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 ...
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2answers
1k views

How are UDP source ports mapped on a NAT?

Here is an example use case; I am curious to see how this is suppose to work and why: Someone has a NAT router from their ISP. Behind the router are 2 PCs running Linux and using ntpd. ntpd sends ...
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1answer
15 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 ...
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3answers
59 views

Understanding the ways of communication in IP networks

I am trying to check my understanding about the ways of communication in IP networks. I would classify the ways of communication in IP networks into three generic types: The source requests name ...
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3answers
2k views

Does the OSI model support connectionless communication in the transport layer?

In section 7.4.4.1.2 of ISO/IEC 7498-1:1994(E) it begins with: In connectionless-mode, the Transport Layer provides the following functions to support connectionless-mode transmission: But many web ...
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2answers
126 views

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

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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2answers
8k 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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2answers
2k views

NAT Translation Table Port Number

I had a practice question about a NAT-enabled router with outside address 24.34.112.235 and inside network 192.168.1/24 and three inside hosts .1, .2 and .3. The three hosts all open two connections ...
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2answers
3k views

Why traffic shape/police ingress traffic?

Pardon me for my ignorance. I have not tried QoS nor traffic shaping/policing before. I have been pondering on whether can/why would we want to shape/police ingress traffic if you have no control ...
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3answers
2k views

port numbers for TCP and UDP

Why do we need both source and destination port numbers in transport layer protocols such as TCP or UDP? What is the purpose for having both?
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2answers
3k 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 ...
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2answers
5k views

How does a layer-2 switch work with UDP?

If UDP and/or TCP send packets via IP to an Internet Protocol Address, how can a layer-2 switch forward these? Is this possible or do you need a layer-3 switch?
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2answers
220 views

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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1answer
42 views

Pros and cons of the idea of parallell data transmission

I am learning the basics of internet protocols and related principles. I recently performed experiments comparing UDP and TCP. But when I did that (using the ttcp program) it was only one process and ...
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6answers
5k views

Could IPv6 make NAT / port numbers redundant?

From what I can tell, each process could get its own IP address, with loads of IP's to spare. What would the drawbacks be? Essentially, your host would become a router and each process is a host (in ...
44
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7answers
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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1answer
64 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
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1answer
19 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 ...
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1answer
728 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
40 views

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 ...
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2answers
196 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 ...
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3answers
78 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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2answers
424 views

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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6answers
41k views

Is a DHCP offer packet a broadcast or unicast?

DHCP OFFER is a layer3 broadcast because the server don't know client Ip, but server knows the client mac address. So how it would be the broadcast? If anyone ask me about this? how should I answer? ...
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1answer
550 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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