The flow controls from TCP, although dependable, are unable to recover missing data fast enough to be useful in real-time video communications.
And while data integrity is important, it has to be balanced with speed to ensure the pace of communication remains unhindered. Additionally, Lifesize employs strategies like error concealment, error correction, and rate controls for robust UDP media connections sans lags or latency.
Lifesize strongly recommends our customers enable access via UDP toward our cloud servers, as this can help achieve the best user experience possible. For the highest-quality video conferencing available, Lifesize favors UDP to reduce delays and ensure smooth calls every time. In just a few steps, you can have UDP enabled on Lifesize and be well on your way to better meetings and stronger results.
Open the Lifesize web or desktop app to get started. Lifesize supports a wide range of devices and user preferences, with apps for PC and Mac computers, Android and iOS phones and tablets, and a browser-based web app for any devices unable to download applications. To place calls to other devices through a firewall, you need to configure your firewall to allow incoming and outgoing traffic to the Lifesize system through the reserved TCP or UDP ports.
By default, Lifesize systems communicate through ports in the range — for video, voice, presentations, and camera control. While Lifesize encourages users to stick to this range, you do have the ability to restrict the number of UDP ports that are available.
If the range you choose is not a subset of the default, be sure it begins with a port number greater than Additionally, the range has to start with an even number and end with an odd number to include an even number of total ports.
For example, if a range starts at , set the lower end to and the upper end to to allocate ports the required minimum. Be sure to click Save on your updates. However, in a situation where there is no need to check for errors or correct the data that has been sent, this may not pose a significant problem.
This is one reason why UDP is used in video applications. Getting the video signal to its destination on time is worth the occasional glitches. As data is transferred from one point to another, it is given a header, which tells devices what to do with it.
The UDP header is a simple 8-byte fixed header. With TCP, on the other hand, the header can vary from 20 to 60 bytes. The fields for UDP port numbers are 16 bits long, giving them a range that goes from 0 up to The header consists of a bit source port, a bit destination port, a bit length, and a bit checksum.
This is the information used to send the datagram toward its destination. The sending process does not involve any verification of a connection between the source and the destination. TCP is different in that it requires a handshake between where the data originates and where it is headed.
In the course of a TCP communication, the data can only be sent along after the destination and source have been formally linked. With UDP, because no link is required, the data can be sent right away. Also, TCP provides for the confirmation that the packets arrived as intended. In the event that the packet does not arrive, TCP dictates that it needs to be sent again. UDP does not require any confirmation, checking, or resending. If an application uses UDP, the users assume the risk of errors, the data not reaching its destination, or being duplicated.
The reward for accepting this trade-off is better speed. UDP itself is not necessarily to blame for the data loss. On the other hand, some applications benefit from the addition of a few features to the protocol which a UDP wrapper could handle better than TCP. Show 2 more comments. Jarvis 8, 3 3 gold badges 23 23 silver badges 53 53 bronze badges.
Lott S. Lott k 75 75 gold badges silver badges bronze badges. Highly depends on lower network layers reliability. Mark Wilkins Mark Wilkins What if you'd developed it for TCP only and buy better hardware instead of 5x more coding effort?
Thanks for the concrete numbers! My guess is that the farther it is, the higher the difference is. The result is that UDP can: Achieve higher throughput than TCP as long as the network drop rate is within limits that the application can handle. Deliver packets faster than TCP with less delay. Setup connections faster as there are no initial handshake to setup the connection Transmit multicast packets, whereas TCP have to use multiple connections.
Transmit fixed size packets, whereas TCP transmit data in segments. With TCP, you may feed the sending socket Bytes, but the receiver only reads Bytes, and you have to figure out somehow that there are more Bytes on the way.
This is important if your application transmit fixed size messages, rather than a stream of bytes. Andy Andy 2, 1 1 gold badge 22 22 silver badges 25 25 bronze badges. When networks get sufficiently congested as to cause packet loss, TCP tries to minimize its impact on other users of the network, while many UDP-based implementations don't.
This lets them grab a bigger share of a diminishing pie, but also reduces the total amount of useful bandwidth available period e. First of all, thank you for the great answer, I really learned a lot from it! I'd really appreciate if you could explain it to me. You are right, fragmentation of packets that exceed the MTU of the link layer 2 happens at layer 3-IP. However, TCP is a stream based protocol and it treats data as a stream of bytes. How much data TCP puts in a segment, or much data your socket reads varies by many factors though; it can be 1 byte or MSS bytes.
With UDP, the receiver always gets the exact number of bytes the transmitter sent, if the packet is not lost en route. Arnkrishn Arnkrishn 28k 39 39 gold badges silver badges bronze badges. Shital Shah Shital Shah Video streaming is a perfect example of using UDP. Daniel A. White Daniel A. White k 43 43 gold badges silver badges bronze badges. Please provide some examples.
Consider a live match being streamed over hotstar. TCP does have a delivery guarantee: chunk A will be delivered to an application before chunk B, therefore if an application acknowledges at a application level chunk B you know it got chunk A. But this also happens at the TCP handling level also. In TCP, one can safely delimit chunks of data by simply prefixing each chunk with its length. Not exactly a huge overhead. Such a design would be bad with protocols that don't guarantee in-order delivery without gaps, but when using TCP such a design is just fine.
You are absolutely right. This also means you are adding complexity to your application; complexity which is actually needed in UDP. For this reason, TCP is better for transferring streams, such as files. Network communication for video games is almost always done over UDP.
The key question was related to "what kind of situations would UDP be the better choice [over tcp]" There are many great answers above but what is lacking is any formal, objective assessment of the impact of transport uncertainty upon TCP performance.
Brian M. Hunt Brian M. Hunt It's also appropriate when you want to broadcast the same information to many users. Community Bot 1 1 1 silver badge. Robert S. Barnes Robert S. Barnes A bit more information on that last point, for anyone that comes along.
TCP works for bulk data transfer, but if you don't care that your data arrives in start-to-end order, you can write a protocol over UDP that might be faster - a lot faster in very specific pathological cases. It's not that you can't do bulk transfer in UDP, it's not that it's always a worse performer; it's just such a pain in the arse to implement that it's rarely worth the bother.
Yes, you can use UDP for bulk transfer, and you have to implement your own control mechanism. If its a pain in the arse or not depends on your programming skills, but it's definitely not always a worse performer. You have to know what you are doing; if you don't then yes, you may suffer. We know that the UDP is a connection-less protocol, so it is suitable for process that require simple request-response communication.
Jorgesys Jorgesys k 22 22 gold badges silver badges bronze badges. This is an extremely important property in complex systems, which can be used to overcome unforeseen boot-order dependencies, for example. I've seen this used in various vision systems. I've also seen UDP "syslog sinks", where log data is sent to multiple inward-only systems to create multiple cross-referable logs.
In some sites you can't even ssh to them, you have to go to the machine room and use the console. It is frequently stated that UDP is unreliable, which makes it sound as though it has inherent non-delivery. This is false: what it lacks is an inbuilt retry mechanism, leaving it to the upstairs protocols compare DNS and streaming for approaches. Under some very nasty real-world conditions with very high packet loss, you also find that UDP gets through where TCP often doesn't.
They each do one job well. Because of the separation of comms into discrete tasks, testing and debugging is much easier. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
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