Will quic become a disruptor of Internet transmission?

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translate ：Alex Technical review ： Liu Lianxiang This article is from Compira Labs, The author is Ravid Hadar.

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QUIC

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When computer scientists notice TCP Because of its limitations, it can no longer support new 、 More advanced Internet services , They are for QUIC Your interest grows with each passing day . As a transport protocol ,QUIC Is an alternative TCP The most important “ The candidate ”, It will be possible to open up a new situation for Internet data transmission .

stay Yesterday's article in , We discussed what is QUIC、 Its purpose and working principle . Now we have a slightly different question to answer ： Is it really worth adopting ？ Next , This article will explore the use of QUIC Advantages and disadvantages of .

QUIC The advantages of QUIC Its supporters point out that it can make the Internet more efficient 、 Fast 、 Safe and evolving . 1∕ Extensibility change TCP Not easy , Because the middleware resists updating , and TCP 40 The optional bits of bytes are almost completely filled （ More information , Please read QUIC And the future of Internet transmission ）. TCP There is no version negotiation （version negotiation） Extension bit , by comparison ,QUIC Yes 32 position , So it has a lot of room to deploy new versions , Manufacturers can also use these spaces to define their own proprietary versions . 2∕ User space implementation QUIC It can be implemented in the application layer , And implemented in the operating system kernel TCP comparison , It can be updated faster . This further improves QUIC extensibility , Enables services to evolve very quickly , So new features can be deployed every day . At the same time, it can achieve higher response capability by calling less overhead during context switching . 3∕ Connect faster Web Browsing requires a quick connection , Because users usually open multiple 、 A short connection . When using HTTPS when ,TCP Before establishing a connection , need “ Three handshakes ” And subsequent TLS Protocol settings . QUIC（ be based on UDP） It doesn't take three handshakes , Plus it will exchange security keys at the first handshake , Thus, the speed of establishing encrypted connection is doubled . 4∕ Reduce the sensitivity to packet loss Use TCP when , If you lose a packet , Next, all packets will stop transmitting , Until the lost packet is sent , This phenomenon is called “ Team head jam ”, It can lead to a significant increase in latency . by comparison ,QUIC Similar to HTTP/2 Multiplexing mode of , It can support multiple data streams at the same time . If a data stream is sent incorrectly , Cause packet loss , Then other data streams will continue to send packets , Without blocking the transmission . The following example shows a connection with a congestion window containing three packets , among 0 Packet number is discarded . Where there is only a single data stream TCP Connecting , Subsequent packets are blocked .QUIC The multiplex connection of has three data streams , Each can operate independently . therefore ,2 Number and 3 No. 1 data stream is still transmitting normally , Only 1 Subsequent packets in stream No. 1 are blocked .

5∕ Performance improvement when switching networks When switching networks ,QUIC A smooth transition can be achieved . such as , If you use your home wifi Watch videos on your mobile phone , Then you go out of the house , Home wifi Then switch to LTE, Or when you've been busy watching videos , When moving between different mobile base stations . In these scenarios ,TCP The connection will be disconnected , And create new connections through the new network , And then affect your viewing experience . and QUIC Can realize seamless connection . 6∕ Improved security and privacy QUIC The encryption function is built in the transport layer , To verify the entire load （ Include header）.TCP stay header Does not contain encryption , Make it very vulnerable .QUIC Secure is supported by default TLS, This means that end-to-end security is complete .

QUIC The limitations of

TCP At the time of invention , The network is wired , And quite reliable . But apparently , Things have changed .QUIC For unreliable 、 Unpredictable wireless connections have been improved , But it has not changed the nature of Internet transmission , Due to its limitations, it can only change some specific usage scenarios . Here are some additional QUIC limitations ：

1∕ transfer app Facing a huge challenge

take app from HTTP/2 Migrate to HTTP/3（ Or from TCP Migrate to UDP） It takes a lot of effort . The whole process needs to transfer the entire application layer implementation and transport layer implementation to UDP, And build new solutions on the server and client .

This is undoubtedly challenging for small manufacturers with relatively limited resources in the streaming media field , It also explains that technology giants like Google and Microsoft can take the lead in adopting QUIC The reason for the agreement .

2∕ Limited adoption

QUIC The biggest problem is that its adoption is still limited . Almost every browser accepts the use of QUIC Simple web browsing , But in addition to chromium, No browser has set it as the default option .

besides , In the field of streaming media , Except Google and Facebook（ Renamed now Meta） outside , Few companies use QUIC. Only a few CDN Provider support QUIC, And some of them just verified QUIC The implementation of the , Not ready for large-scale deployment . This raises the question ： If you introduce the use multi-CDN And based on QUIC New services for , Then there will be only 20% Access using QUIC, Because you can't prove to users that it has a significant impact on the user experience .

3∕QUIC contain TCP Back off

QUIC Is built on UDP above , Part of the reason is that there are very few middleware and network devices to intercept UDP. But there is a real risk of being intercepted , So based on the QUIC Of app Must be designed to fall back to TCP, In case of a one thousand .

It means app（ be based on QUIC） The developer of must develop and maintain two different versions at the same time （ because TCP Fallback and restricted adoption ）, They bear a heavy burden .

The good news is , With the latest DEVOPS Structure and HTTP Of Alt-Svc Use of labels , Supporting both protocols is much simpler than before .

4∕ Unable to check packet

Network firewall cannot decrypt QUIC Traffic to check packets , Therefore, the potential malicious traffic is very likely to enter the network without being detected by the standard security function . therefore , CISCO and Palo Alto Networks And other security vendors usually use the port 80（Web The server ） and 443（TSL） Intercept QUIC Data packets （ Think they contain malware ）, Force the client to back out of use HTTP/2 and TCP agreement .

However, the above operations will not significantly affect the content user experience , Because the correctly implemented streaming media service will fall back to by default TCP+TLS, But this kind of operation may prevent the first deployment QUIC Ideas . Only by addressing this challenge ,QUIC Can be widely accepted by major enterprises .

5∕ Do not have some TCP characteristic

People take it for granted that TCP Some features included by default in （ such as Throttling）. But use QUIC, You may need to build these features yourself .

besides ,HTTP/3 Lacking some of the features required to adopt certain protocols . such as ,HTTP/3 Block transfer is still not supported （chunked transfer, The ability to segment video slices into small pieces ）, but HTTP1.1 This feature is supported . This limits the ability to be used based on QUIC Number of video transmission protocols .

therefore , Even though QUIC Support most common transport protocols （ Such as HLS、MPEG-DASH）, But at present it cannot support any more new protocols , These protocols are mainly used to reduce glass-to-glass Delay , For example, those that rely on block transmission LL CMAF（Low Latency Common Media Format）.

glass-to-glass Delay ： Refers to the delay between the display screen and the camera lens , It can also be called “ End to end delay ”, It means to start （ Capture ） And end （ Show ） Delay over the entire transmission pipeline between [1].

6∕ It's easier to be fingerprinting

Malicious actors are likely to sniff the network traffic between Internet users and visited websites , And create different patterns corresponding to a specific website through the discovered packets , This operation is called web fingerprinting. In the early flow connection stage ,TCP+HTTPS It seems more resistant to fingerprinting.

7∕QUIC May need higher CPU Usage rate

Some point of view is that QUIC The required HTTP/3 Both the client and the server take up more CPU resources . However , Google holds the opposite view , Think QUIC Helps extend battery life .

in any case , once QUIC Enter the mainstream technology stack , This problem is not expected to have much impact .

8∕ There are many protocols that need to be implemented

because IETF after 5 It took more than years to release the first edition QUIC, So now there are 60 Kind of QUIC Version implementation , Are developed in QUIC Before standard . therefore , Most of the QUIC Version or does not support complete QUIC standard , Or it only supports the implementation of its own version . Only when different versions of QUIC Consistent with official standards , It can be widely adopted .

9∕ The Internet is still aimed at TCP To optimize

TCP Transmission has existed for decades , Over the years ,TCP Application through the software （ Such as the operating system kernel ） And hardware （ Such as network interface and intelligence NIC） Build offload performance in and get thoroughly optimized . and QUIC But do not have this ability . It's based on UDP, Located in user space , So its endpoint , And some middleware functions have obvious disadvantages at this stage . however , once QUIC Widely adopted , You get this optimization , So it's important for QUIC It is only a temporary problem .

QUIC vs TCP： Impact on quality experience

QUIC Support some unique features and provide more flexibility in the implementation of new features . therefore , contrast TCP, be based on QUIC The application of is expected to be in QoE Bring more advantages .

Here are two QUIC bring QoE Common use cases for advantages ：

• Web Browse ：QUIC Support the built-in TLS, And can quickly establish a connection . In most cases, the connection time is short （ For example, the fast download duration of secure websites ）, It can provide significant performance advantages . Google claims to run on QUIC The download time of the application page on is shortened 10%.
• Video streaming ：QUIC Some supported features are expected to improve the performance of video streaming QoE. So far, , because QUIC The implementation logic and TCP be similar , So the predictable impact has been limited . But in some cases , You can still experience QUIC The benefits , such as ,QUIC The ability to reduce the blocking of the queue head brings to the network with medium and high packet loss rate QoE advantage .

QUIC May be “ Improver ”, No “ The disruptors ”

QUIC It does bring incremental gains to Internet users , But whether it is true “ The disruptors ” This view is still controversial . There are good reasons to adopt QUIC, but QUIC The problems and challenges faced by early adopters are “ encourage ” A wait-and-see attitude .

notes ：

[1]https://cloud.tencent.com/developer/article/1346159

thank ：

This paper has been approved by the author Ravid Hadar Authorized translation and release , Hereby thank .

Link to the original text ：

https://www.compiralabs.com/post/quic-is-it-the-game-changer-for-internet-delivery

Extended reading ：

Chat QUIC The development of the agreement

IETF interview ：HTTP/3 The global share continues to grow ,QUIC The prospect is bright

IETF：QUIC Version 1 (RFC 9000) As a standardized version, it has been released

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