Re: [core] #409 (block): CoAP over TCP: Multiple Simultaneous TCP Connections

["weigengyu" <[e-mail]>]

Hi Hannes,

Ciao Hannes wrote:
> Hi Gengyu,
> thanks for your input.

> In the issue I added to the tracker I raised two issues, namely
> 1) "What should the CoAP over TCP state regarding the use of multiple TCP 
> connections?"
> It seems you are arguing that nothing should be said about that topic.

My suggestion is that CoAP does not need to touch the issure using mutliple 
TCP connections.
The reason is to refer P2P software in which it is the application software 
to do this.

> 2) "Should we recommend the use of Block-wise Transfer for large file
> transfers and incorporate BERT into the CoAP over TCP draft?"

Yes. The draft should give statements for this. CoAP over TCP should support 
CoAP Block-wise Transfer related to RFC7252.

> You didn't directly answer that question and I am curious what your 
> thoughts are.

When doing CoAP over TCP, RFC7252 should be considered firstly.

If an application tranfers a large data by CoAP/UDP, it should concern the 
limit of UDP datagram, i.e less than 64KB.
Then the data may be delivered by CoAP Block-wise Tranfer.
If the size of data is greadter than 64KB, the application should do 
multiple invocations of CoAP/UDP.

If CoAP/TCP is considered, one TCP connection can transfer 64KB data in one 
window, probably with sevreal segments.
The 64KB limitation should be kept for the purpose with consistency to 
RFC7252,  and this limitaion may need clarifying in the draft.

Regards,


Gengyu WEI
Network Technology Center
School of Computer
Beijing University of Posts and Telecommunications
-----原始邮件----- 
From: Hannes Tschofenig
Sent: Thursday, May 05, 2016 4:51 PM
To: weigengyu ; [e-mail] ; 
[e-mail]
Cc: [e-mail]
Subject: Re: [core] #409 (block): CoAP over TCP: Multiple Simultaneous TCP 
Connections