[TLS] Re: 【Reply to the comments after the presentation in Montreal】RE: Re: FW: New Version Notification for draft-wang-tls-service-affinity-00.txt

[Aijun Wang <[e-mail]>]

Hi, Eric:

 

What we want to is similar with “Resumption and Pre-Shared Key(PSK)” that is described in https://datatracker.ietf.org/doc/html/rfc8446#section-2.2

>From this section, we can know the application layer will not aware such session resumption, TLS layer handles all the procedure. Right?

 

What you described in previous examples can all happen in the resumption process, and the application layer should have their own additional confirmation/retry logic.

 

For the mentioned draft(https://datatracker.ietf.org/doc/draft-wang-tls-service-affinity/), the additional exchange signals are to transfer the new server address securely after the initial connection.

What’s the client and server need do is to correlate the corresponding cryptographic context to the new underlying TCP connection.

 

Do you have any suggestions to make the above intension more clearly in https://datatracker.ietf.org/doc/draft-wang-tls-service-affinity/?

 

 

 

From: [e-mail] [mailto:[e-mail]] On Behalf Of 【外部账号】 Eric Rescorla
Sent: Tuesday, December 30, 2025 10:41 PM
To: Aijun Wang <[e-mail]>
Cc: [e-mail]; [e-mail]; Mohit Sahni <[e-mail]>; Aijun Wang <[e-mail]>
Subject: Re: [TLS] Re: 【Reply to the comments after the presentation in Montreal】RE: Re: FW: New Version Notification for draft-wang-tls-service-affinity-00.txt

 

 

 

On Tue, Dec 30, 2025 at 2:10 AM Aijun Wang <[e-mail] <mailto:[e-mail]> > wrote:

Hi, Eric:

 

Contrary to your conclusions, I think the application layer and TLS/TCP layer should(already) have their own mechanisms to assure the data integrity,

 

Yes, which might or might not work correctly, because they are rarely tested.

 

there is no necessary to consider them again at the protocol layer, we need just some guidance for the implementation of client/server sides themselves.

If there is data arrival during the switchover, the internal implementation logic is the application layer will call the api of TLS/TCP to send some data, with the same session identifier.

 

I don't know what you mean by "The same session identifier". There is no concept in TLS that two different TCP connections are somehow the same conceptual flow of data. PSK identifiers solely identify keys.

 

 


In this case, the client doesn't know what has happened. You need
mechanisms either at the HTTP layer--or more typically at the REST API
layer--to do the right thing, which might be an idempotency layer
combined with client-side retransmit.  This is all just a
straightforward application of the end-to-end argument, and there's no
real way around it as long as systems might asynchronously fail, but
it's also a source of defects (think about how many times sites tell
you not to press the submit button twice) because these mechanisms may
not have been exercised or tested. For instance, if the server is high
reliability and the client just assumes that anything it sent works,
that will be good enough a very large fraction of the time, but not if
the server has a high failure rate.

 

[WAJ] From the example, we can know each application has its own confirmation mechanism, because most of them are asynchronous. 

The application knows there will be possibilities that the server crash, or the underlay connection broken.

 

Yes. I said exactly this, but again, they're not always going to be

implemented correctly, and that's largely OK because most

connections don't fail. You're talking about making an exceptional

condition routine.

 

 

Unfortunately, these transaction semantics only exist at the HTTP
layer, not the TLS layer, so the TLS layer has no way of knowing to
wait for the 200 OK, it just knows that the client sent some data, but
not whether that reflects an outstanding request or something else;
recall that TLS doesn't even know about the HTTP request/response
semantics, because it's just a dumb pipe.

[WAJ] TLS needn’t aware the 200 OK signal, it is the job of application layer.

TLS/TCP needs only transmit the data from the application layer correctly to other side.

 

So you're saying that in the example above, the TLS layer ought to inform

the HTTP layer that the connection has failed and trust the HTTP layer

to retry in a safe fashion? 

 

  

In your email, you suggest that the client ought to:

1. Wait for the server's TCP ACK of all transmitted data, with the
implied semantics being that once the message is ACKed it will be
reliably delivered to the server, not just to the TCP stack.

[WAJ] No. I emphasize only the TCP ACK and the TCP stack. Not the application stack. That is to say, receiving the TCP ACK doesn’t represent the application layer ACK.


2. Buffer any data it receives form the cleint while waiting for the
ACK and retransmit it on the new connections.

[WAJ] Buffer any data it receives, but can’t transmit immediately during the switchover process, not waiting for the application ACK.

 

I don't understand what you're saying here. Can you please provide:

 

1. A concrete description of what you believe the rules that the

TLS stack should be following.

2. New versions of my ladder diagrams that show what you believe the correct

behavior is.

 

-Ekr