Questions tagged [udp]

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

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I can receive a Ping Reply from a device but not an UDP Broadcast message? [closed]

I have a simple Setup which consists of a Windows PC-Ethernet Switch (10/100M)-Embedded Device. I can ping the Embedded Device, no problem at this stage. The Embedded device is UDP Broadcasting (SRC ...
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1answer
36 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
18k 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
9k 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
20 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
55 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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5answers
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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
43 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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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
114 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
7k 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
1k 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
2k 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
156 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
41 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
4k 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 ...
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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
60 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
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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 ...
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1answer
699 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
30 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
162 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
39 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
146 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
37k 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
389 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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1answer
32 views

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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2answers
36 views

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 ...
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2answers
596 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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2answers
7k 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?
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1answer
2k 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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1answer
28 views

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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2answers
5k views

Why No Source and Destination IPs in UDP Datagram?

In literature, I see UDP datagram format as following: I cannot understand why it does not include source and destination IP addresses?
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1answer
45 views

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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1answer
76 views

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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3answers
88k views

How to verify that a UDP port is open? [closed]

I have here a dilemma. I have a device that communicates to another remote device but there is a firewall between them. It's a UDP connection, so TCP utilities don't work to test if the specific port ...
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2answers
2k views

What is the reason for the different order of the Source and Destination in a L2 header?

A TCP/UDP header (Layer 4) lists the Source Port, then the Destination Port: An IP header (Layer 3) lists the Source IP, then the Destination IP: An Ethernet header (L2) and a WiFi Header (L2) lists ...
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1answer
103 views

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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2answers
63 views

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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4answers
6k 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
448 views

UDP in wifi getting excessively buffered [closed]

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
205 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
56 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 ...