Re: [bfcpbis] TCP/TLS: Who is TLS server when the connection goes down and is re-established?

[Paul Kyzivat <[e-mail]>]

On 1/20/14 8:44 PM, Christer Holmberg wrote:
> Hi,
>
>>> Some initial text proposal:
>>>
>>> "If the TCP connection is lost, the "active" endpoint is responsible for re-establishing the TCP connection.
>>>
>>> Unless a new TLS session is negotiated, subsequent SDP Offers and Answers will not impact the previously negotiated TLS roles."
>>
>> Is the passive endpoint expected to listen for the connection attempt at all times, or when it has noticed that the old connection is lost, or only when
>> there has been a new O/A? (It is kind of a waste to maintain a listener when you have an active connection and aren't expecting more.
>> And it is asking for trouble, since you might get a new connection when you think the old one is still functional.)
>
> If a TCP connection has been established, I think it is enough to listen for the connection when it has noticed that the old connection is lost. I assume both endpoints would detect that more or less at the same time, or?
>
> If a TCP connection has NOT been established, one would listen only when there has been a O/A used to negotiate the TCP connection.

WFM.

>> I realize this is old stuff, but I'm surprised that it didn't follow comedia about all of this, including who is active.
>
> I am not sure I understand. Comedia IS used to indicate who is active. However, comedia is NOT used to indicate who is TLS client/server.

OK.

> Regards,
>
> Christer
>
>
>
>
>> -----Alkuperäinen viesti-----
>> Lähettäjä: bfcpbis [mailto:[e-mail]] Puolesta Christer
>> Holmberg
>> Lähetetty: 16. tammikuuta 2014 21:36
>> Vastaanottaja: Tom Kristensen
>> Kopio: [e-mail]
>> Aihe: Re: [bfcpbis] TCP/TLS: Who is TLS server when the connection goes down and is re-established?
>>
>>
>> Hi Tom,
>>
>>>> I realize the following comes late in the process, and I apologize
>>>> if it has been discussed, but it is related to something which just
>>>> has recently popped up in 3GPP, and it's not addressed in the draft.
>>>
>>> Not too late, since we are still not finished! Anyway, the TCP/TLS
>>> connection reuse is not altered while extending BFCP to support
>>> unreliable transport. Any fixes now must be backwards compatible in
>>> some way.
>>>
>>> That said and based on what I have seen from different vendors, most
>>> of them still use TCP (without TLS) :)
>>>
>>> So, at least if we are changing anything to solve these issues, we
>>> should add an informational note indicating this is a change where
>>> legacy, pure RFC 4582 implementations might differ in behaviour...
>>
>> I am not suggesting to change anything - I am suggesting to specify
>> something which is currently unspecified :)
>>
>>> By the way: How these issues was solved in 3GPP are along the lines of what you propose below?
>>
>> We have had some discussions in 3GPP, and there are some text suggestions for the upcoming meeting next week.
>>
>> However, the discussions so far have been mostly about Q2. Q1 came up on a mailing list just this week, and whill be discussed at the 3GPP meeting next week.
>>
>>>> Section 7 says the following:
>>>>
>>>> "For a TCP/TLS connection established using an SDP
>>>>
>>>> offer/answer exchange [7], the answerer (which may be the client or
>>>>
>>>> the floor control server) always acts as the TLS server."
>>>>
>>>> Q1:
>>>>
>>>> Assume the TCP/TLS connection, for whatever reason, goes down.
>>>>
>>>> Now, I assume that whoever endpoint is "active" will most likely try
>>>> to re-establish the TCP connection.
>>>>
>>>> But, if the "active" endpoint doesn't send an Offer (i.e. it simply
>>>> tries to re-establish the TCP connection based on the previously
>>>> negotiated SDP information), who will act as TLS server? There is no
>>>> Answerer.
>>>>
>>>> One alternative would be to mandate the sending of an Offer when the
>>>> TCP/TLS connection is re-established. Then it would be clear who is
>>>> Offerer, and who is Answerer.
>>>>
>>>> Another alternative would be to say that whoever was previously
>>>> Answerer will act as TLS server.
>>>
>>> I'm not too fond of yet another re-INVITE being mandated, so if we
>>> will fix this issue mandating the previous answerer to be the TLS
>>> server would be my preference.
>>
>> Assuming that, then my follow-up question is:
>>
>> When you say "previous answerer", do you refer to the answerer in the latest Offer/Answer transaction, OR the answerer in the last Offer/Answer transaction that established/re-established the TCP/TLS connection (those Offer/Answer transactions may, or may not, be the same).
>>
>>
>>>> Q2:
>>>>
>>>> Assume there is an Offer/Answer transaction during the session. Now,
>>>> the TCP/TLS connection is not affected by that, but the TLS roles
>>>> may change (if whoever was Offerer in the previous O/A transaction is now Answerer).
>>>>
>>>> I think some wording would be needed about that also.
>>>>
>>>> One alternative is to say that the TLS roles may change, but that
>>>> doesn't affect the TCP/TLS connection.
>>>
>>> A healthy TCP/TLS connection shouldn't be affected at all, should it?
>>
>> Correct. The question is whether such Offer/Answer can affect the TCP/TLS roles - even if the TCP/TLS connection itself if not affected. That could have impact on the case in Q1, where the TCP/TLC connection goes down, and it needs to be determined who is TLS server.
>>
>>> However, any potential connection re-establishment will need to
>>> monitor who was the last answerer to do the TLS initiation correctly.
>>>
>>> Hopefully I did understand the issue here, and added my 2 zlotys or
>>> pence or whatever,
>>
>> I think you did understand the issue :)
>>
>> Regards,
>>
>> Christer
>>
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