RE:(2) Multipath (was: Re: Re-chartering for extension work)

[Madhan Raj Kanagarathinam <[e-mail]>]

I Second that. Multipathing in QUIC would be of greater advantage. Mainly for wireless mobile devices and 5G ecosystem.

Multipath TCP had quite a few hiccups and short comes. However, (MP)QUIC, by its design overcomes, the common disadvantages of (MP)TCP.

 

 

Regards,

Madhan Raj K

Chief Engineer - Samsung R&D Institute India Bangalore.

 

--------- Original Message ---------

Sender : Olivier Bonaventure <[e-mail]>

Date : 2019-12-19 00:10 (GMT+5:30)

Title : Re: Multipath (was: Re: Re-chartering for extension work)

 

Jana,

> On 18 Dec 2019, at 07:26, Jana Iyengar <[e-mail]> wrote:
> 
> 
> I'm not sure that this is the time for this conversation, but I'll share my thoughts since the question has been raised.
> 
> There will be quite some heavy lifting to do if we go down the path of designing a multipath extension for QUIC. We've seen this before. I worked on multipath for SCTP, which was quite some work. I remember when we started work on MPTCP at the IETF in 2009, and it was a lot more effort than most people anticipated. When we started work on connection migration for QUIC, we thought it might get done relatively quickly, but it was a feature that kept on giving.

For Multipath TCP, I would argue that most of the difficulty was caused by middleboxes.
> 
> None of this is to say that we shouldn't take on a hard problem, but before we start sliding into it, I would like to be convinced of its importance.. We already have connection migration in the core drafts, and I'd like to see an articulation of the problems that multipath would solve in addition to basic migration. I would also like to see implementations that are keen to build it if an extension were to be developed, and applications that will use it. Without those, we would be putting the cart before the horse.
> 

I think that there are two clear use cases for a multipath transport. The first use case is ressource pooling as already mentioned by Lars. There are various situations where being able to use different paths simultaneously gives improved performance, in terms of delay or throughput. A common scenario is a dual-stack IPv4/IPv6 client that interacts with a dual-stack server through paths of different qualities. 

A second use case is for mobile devices that need to preserve connectivity while switching from one wireless network to another. When such a device detects another wireless network, it needs to bet whether migrating the connection to the new network would improve performance. With a multipath transport, there is no need to bet as the transport will automatically select the best performing network. Apple’s deployment of Multipath TCP is a good example of the benefits of such a multipath strategy.

Multipath was included in the QUIC charter to address such use cases.

Olivier


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