Re: [tcpm] I-D Action: draft-ietf-tcpm-converters-01.txt

<mohamed.boucadair@orange.com> Thu, 12 July 2018 12:23 UTC

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From: <mohamed.boucadair@orange.com>
To: "philip.eardley@bt.com" <philip.eardley@bt.com>, "tcpm@ietf.org" <tcpm@ietf.org>
Thread-Topic: [tcpm] I-D Action: draft-ietf-tcpm-converters-01.txt
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Subject: Re: [tcpm] I-D Action: draft-ietf-tcpm-converters-01.txt
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Hi Phil, 

Apologies of the delay to answer. 

Thank you for sharing these comments. 

Please see inline. 

Cheers,
Med

> -----Message d'origine-----
> De : tcpm [mailto:tcpm-bounces@ietf.org] De la part de philip.eardley@bt.com
> Envoyé : jeudi 10 mai 2018 17:51
> À : tcpm@ietf.org
> Objet : Re: [tcpm] I-D Action: draft-ietf-tcpm-converters-01.txt
> 
> Hi,
> 
> I remember in the London discussion there were some comments about things it
> would be good to add to the draft - mainly about more examples. I agree with
> this, it would be useful I think to cover:
> 
> -	The example is for one client. I assume multiple clients each require
> their own Ipv6 address on the converter (ie which is the source address for
> that client's converter-server(s) connections)?

[Med] This is deployment-specific. The converter may behave in address sharing or address preservation modes. A text change is proposed here: https://github.com/obonaventure/draft-tcp-converters/pull/41/commits/de004090c1861f0f8b076285b4119d48f7ab47e8 

"The Converter may behave in address preservation or address sharing modes as discussed in Section 5.4 of {{draft-nam-mptcp-deployment-considerations}}. Which behavior to use by a Converter is deployment-specific. If address sharing mode is enabled, the Converter MUST adhere to REQ-2 of RFC6888 which implies a default "IP address pooling" behavior of "Paired" (as defined in Section 4.1 of [RFC4787]) must be supported. This behavior is meant to avoid breaking applications that depend on the external address remaining constant. Also, maintaining the same external IP address for a client is meant to preserve the validity of the TFO cookie."

> -	How would the client access Ipv4 content?

[Med] We would like to avoid overloading the document with deployment-specific examples. Plenty of those are described in draft-nam-mptcp-deployment-considerations. We may add a pointer if needed. 

> -	I assume the client has to be configured somehow with the converter's
> address

[Med] Yes, we do have the following text in the draft:

   This document assumes that a client is configured with one or a list
   of Converters (e.g., [I-D.boucadair-tcpm-dhc-converter]).
   Configuration means are outside the scope of this document.

> -	What happens if the converter fails? I suppose the client has to
> somehow notice, and (at config time) it gets told the address for a back-up
> converter or a DNS name.

[Med]  I-D.boucadair-tcpm-dhc-converter specifies a procedure to provision one or multiple converters; each identified by a list of IP addresses. The procedure to follow for selecting the address to use will need to be specified. Should we include it in draft-ietf-tcpm-converters or in I-D.boucadair-tcpm-dhc-converter? I do prefer to leave that procedure out of draft-ietf-tcpm-converters because the selection may not only be based on the availability of an address, but based on other criteria.   

> -	What happens if a link fails? I assume if one of the client-converter
> links fails, then MPTCP shifts all the traffic to the other path.

[Med] This is normal MPTCP behavior. Do we really need to say something there? 

 If the
> converter-server connection fails, how does the client discover this?

[Med] This is done by means of the "Network Failure (65)" error code: 

   o  Network Failure (65): This error indicates that the Converter is
      experiencing a network failure to relay the request.

      The Converter MUST send this error code when it experiences
      forwarding issues to relay a connection.

 I
> assume packets build up at the converter and are dropped, and at some point
> the converter informs the client.
> 
> Thanks,
> Best wishes,
> phil
> 
> -----Original Message-----
> From: tcpm [mailto:tcpm-bounces@ietf.org] On Behalf Of internet-
> drafts@ietf.org
> Sent: 05 March 2018 18:17
> To: i-d-announce@ietf.org
> Cc: tcpm@ietf.org
> Subject: [tcpm] I-D Action: draft-ietf-tcpm-converters-01.txt
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the TCP Maintenance and Minor Extensions WG of
> the IETF.
> 
>         Title           : 0-RTT TCP Convert Protocol
>         Authors         : Olivier Bonaventure
>                           Mohamed Boucadair
>                           Bart Peirens
>                           SungHoon Seo
>                           Anandatirtha Nandugudi
> 	Filename        : draft-ietf-tcpm-converters-01.txt
> 	Pages           : 37
> 	Date            : 2018-03-05
> 
> Abstract:
>    This document specifies an application proxy, called Transport
>    Converter, to assist the deployment of TCP extensions such as
>    Multipath TCP.  This proxy is designed to avoid inducing extra delay
>    when involved in a network-assisted connection (that is, 0-RTT).
>    This specification assumes an explicit model, where the proxy is
>    explicitly configured on hosts.
> 
>    -- Editorial Note (To be removed by RFC Editor)
> 
>    Please update these statements with the RFC number to be assigned to
>    this document:
>    [This-RFC]
> 
>    Please update TBA statements with the port number to be assigned to
>    the Converter Protocol.
> 
> 
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-tcpm-converters/
> 
> There are also htmlized versions available at:
> https://tools.ietf.org/html/draft-ietf-tcpm-converters-01
> https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-converters-01
> 
> A diff from the previous version is available at:
> https://www.ietf.org/rfcdiff?url2=draft-ietf-tcpm-converters-01
> 
> 
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
> 
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
> 
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