Re: [Syslog] Missing dead peer detection in DTLS (Gerhard Muenz)

Hi, Gerhard

Thanks for your comments, I read the proposals, I can see it's a good idea to solve the dtls/udp's flaw.
"time-out" is a solution, but it's disadvantage here is hard to decide an appropriate least round trip times,
A short "time-out" will cost the dtls client large calculation expense. Providing a "heart-beat" solution 
the sender needn't renegotiation at each round trip time of "heart-beat", which may set
a longer resume-session time and renegotiation time according to its strategy. 
I prefer a "heart-beat" solution than a "time-out" solution for this issue.

The only thing left here for syslog-dlts is if we need specific using "heart-beat" in a syslog-dtls proposal?
It's a problem of dtls/udp, which can be fixed in the implementation of dtls and as a part of dtls protocol.
There's anything need syslog-dtls to do to support it? what's your consideration?

Thanks
Linda

----- Original Mail -----
发件人: syslog-request@ietf.org
日期: 2009年 7月 29日, 星期三,  上午3:02
主题: Syslog Digest, Vol 47, Issue 9
收件人: syslog@ietf.org

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>     1. Missing dead peer detection in DTLS (Gerhard Muenz)
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>  ----------------------------------------------------------------------
>  
>  Message: 1
>  Date: Tue, 28 Jul 2009 10:41:31 +0200
>  From: Gerhard Muenz <muenz@net.in.tum.de>
>  Subject: [Syslog] Missing dead peer detection in DTLS
>  To: syslog@ietf.org, "ipfix@ietf.org" <ipfix@ietf.org>
>  Cc: Michael Tuexen <tuexen@fh-muenster.de>,	Robin Seggelmann
>  	<seggelmann@fh-muenster.de>,	Daniel Mentz <mentz@in.tum.de>
>  Message-ID: <4A6EB9BB.9040002@net.in.tum.de>
>  Content-Type: text/plain; charset="iso-8859-1"
>  
>  
>  Hi,
>  
>  This mail goes to the ipfix and syslog mailing lists in order to
>  summarize the common issues regarding DTLS.
>  
>  IPFIX specifies support of DTLS as mandatory for transport over UDP and
>  SCTP in RFC5101. In SYSLOG, it is intended to standardize DTLS for
>  transport over UDP.
>  
>  In IPFIX, we have a first implementation of IPFIX-over-DTLS/UDP, and 
> we
>  will have a first implementation of IPFIX-over-DTLS/SCTP very soon.
>  During this implementation effort, we found that the current
>  specification of DTLS/UDP has a severe flaw when used with
>  unidirectional protocols (like IPFIX): The sender cannot recognize if
>  the receiver has crashed and lost the DTLS state.
>  
>  We discuss this issue in a draft:
>  http://tools.ietf.org/html/draft-mentz-ipfix-dtls-recommendations-00
>  http://www.ietf.org/proceedings/75/slides/ipfix-6.pdf
>  
>  I've had a look at draft-feng-syslog-transport-dtls-01 and
>  draft-petch-gerhards-syslog-transport-dtls-02. It seems that this
>  problem has not yet been covered, although the problem should be the
>  same for SYSLOG.
>  
>  As a solution, the DTLS Heartbeat Extension has been proposed very recently:
>  http://tools.ietf.org/html/draft-seggelmann-tls-dtls-heartbeat-00
>  A feature patch for OpenSSL is available:
>  http://sctp.fh-muenster.de/dtls-patches.html#features
>  
>  So, I think that we should support this standardization initiative as 
> it
>  solves our problem. For IPFIX and SYSLOG over DTLS/UDP, we then can
>  specify that the DTLS Heartbeat Extension MUST be implemented.
>  
>  Dan suggested to have a single document solving the DTLS issues
>  regarding unidirectional protocols. I think that such a document is not
>  needed if we have DTLS Heartbeat Extension.
>  
>  Regards,
>  Gerhard
>  
>  -- 
>  Dipl.-Ing. Gerhard M?nz
>  Chair for Network Architectures and Services (I8)
>  Department of Informatics
>  Technische Universit?t M?nchen
>  Boltzmannstr. 3, 85748 Garching bei M?nchen, Germany
>  Phone:  +49 89 289-18008       Fax: +49 89 289-18033
>  E-mail: muenz@net.in.tum.de    WWW: http://www.net.in.tum.de/~muenz
>  
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