Subject: RE: [Tsvwg] EndPoint and Association Address conflict

From: Tuexen Michael <[email-masked]>
Date: Mon, 29 Apr 2002 15:35:15 +0200

Brian,

see my comment below.

Best regards
Michael

Michael Tuexen    Tel.:   +49 89 722 47210
Siemens AG        Fax:    +49 89 722 48212
ICN WN CC SE 7    E-mail: [email-masked]

> -----Original Message-----
> From:	Brian F. G. Bidulock [SMTP:[email-masked]]
> Sent:	Monday, April 29, 2002 3:33 PM
> To:	Tuexen Michael
> Cc:	Jacob Heitz; Khan, Mohammad; [email-masked]'; Pillai, Hari
> Subject:	Re: [Tsvwg] EndPoint and Association Address conflict
> 
> Michael,
> 
> Please see comments below...
> 
> On Mon, 29 Apr 2002, Tuexen Michael wrote:
> 
> > Brian,
> > see my comments below.
> > Best regards
> > Michael
> > 
> > Michael Tuexen    Tel.:   +49 89 722 47210
> > Siemens AG        Fax:    +49 89 722 48212
> > ICN WN CC SE 7    E-mail: [email-masked]
> > 
> > > -----Original Message-----
> > > From:	Brian F. G. Bidulock [SMTP:[email-masked]]
> > > Sent:	Monday, April 29, 2002 2:37 PM
> > > To:	Tuexen Michael
> > > Cc:	Jacob Heitz; Khan, Mohammad; [email-masked]'; Pillai, Hari
> > > Subject:	Re: [Tsvwg] EndPoint and Association Address conflict
> > > 
> > > Tuexen,
> > > 
> > > It is absurd, because it is an artificial restriction without merit
> > > and without parallel in TCP.  Removing (ignoring) this sentence causes
> > > no problems for the protocol.  Also, the peer has no way of detecting
> > > or enforcing this restriction, making it even more absurd.
> > > 
> > 	[Tuexen Michael]  It is just a technical term
> > 	to talk about SCTP related stuff. There is no 
> > 	'higher' meaning.
> > > The other way of looking at it is to say that E1 and E1' *are* the
> > > same "SCTP Endpoint", but are different communications endpoints (i.e.,
> > > they are engaged in different associations).  Then even this absurd
> > > statement is not violated (E1 and E1' are the same "SCTP Endpoint")
> > > yet IP addresses can be added on a per-association basis.
> > > 
> > 	[Tuexen Michael]  E1 and E1' are not the same 
> > 	end point. They have changes. One end point of association
> > 	A1 has changed. AddIp, DelIP is about modification of
> > 	end points.
> 
> They are the same endpoint, because by definition a transport
> address is unique to an endpoint.
> 
	[Tuexen Michael]  No they are not the same, because they have not
	the same list of IP addresses. They have on in common. This is not a 
	violation to page 13 of RFC 2960, because they do not exist at the same
	time. When E1' exists, E1 does not exist anymore.
> --brian
> 
> 
> > 
> > 
> > > --brian
> > > 
> > > On Mon, 29 Apr 2002, Tuexen Michael wrote:
> > > 
> > > > Brian,
> > > > 
> > > > see my comments below.
> > > > 
> > > > Best regards
> > > > Michael
> > > > 
> > > > Michael Tuexen    Tel.:   +49 89 722 47210
> > > > Siemens AG        Fax:    +49 89 722 48212
> > > > ICN WN CC SE 7    E-mail: [email-masked]
> > > > 
> > > > > -----Original Message-----
> > > > > From:	Brian F. G. Bidulock [SMTP:[email-masked]]
> > > > > Sent:	Monday, April 29, 2002 2:15 PM
> > > > > To:	Tuexen Michael
> > > > > Cc:	Jacob Heitz; Khan, Mohammad; [email-masked]'; Pillai, Hari
> > > > > Subject:	Re: [Tsvwg] EndPoint and Association Address conflict
> > > > > 
> > > > > Tuexen,
> > > > > 
> > > > > On Mon, 29 Apr 2002, Tuexen Michael wrote:
> > > > > > > 
> > > > > > > Why restrict Add-IP to an endpoint basis?
> > > > > > > 
> > > > > > 	[Tuexen Michael]  Consider E1 = ({IP'}, Port), E2 = ({IP'''}, Port),
> > > > > > 	E3 = ({IP''''}, Port) with pairwise different IP', IP''', IP'''' and two associations
> > > > > > 	A1: E1 <-> E2
> > > > > > 	A2: E1 <-> E3
> > > > > > 
> > > > > > 	Now if we add IP'' to the association A1 we get
> > > > > > 	A1 : E1' <-> E2
> > > > > > 	with E1' = ({IP', IP''}, Port).
> > > > > > 	E1' and E2 share one transport address which is in violation to RFC> 
> > > > > > 	2960, page 13.
> > > > > 
> > > > > There is only one MUST on page 13: "Two SCTP endpoints MUST NOT have more
> > > > > than one SCTP association between them at any given time."
> > > > > 
> > > > > How does this violate anything on page 13?
> > > > 	[Tuexen Michael]  I did not mean this sentence. 
> > > > > E1' and E2 only have one association between them.  E1 and E3 only have one
> > > > > association between them.  Everthing appears ok as far as page 13 is
> > > > > concerned.
> > > > > 
> > > > > Did you mean another page?
> > > > > 
> > > > > Or, did you mean the statement: "A transport address used by an
> > > > > SCTP endpoint must not be used by another SCTP endpoint.  In other
> > > > > words, a transport address is unique to an SCTP endpoint."  ...which
> > > > > is absurd, particularly as it is done in TCP all the time, and when
> > > > > you consider that non-multihomed SCTP associations need to reuse
> > > > > dynamic port numbers for connection to other hosts.
> > > > 	[Tuexen Michael]  I mean this sentence. This sentence
> > > > 	is NOT absurd, at least if you use the definition of
> > > > 	SCTP end-point I have given earlier. This is one of the reasons
> > > > 	I'm quite sure that the RFC authors had the defintion I gave
> > > > 	in mind.
> > > > 
> > > > > --brian
> > > > > 
> > > > > > 
> > > > > > 	Please note that an association has two SCTP end points and these end> 
> > > > > > 	points have the IP addresses. So changing IP addresses means modifying
> > > > > > 	the end points.
> > > > > > 
> > > > > > 	Best regards
> > > > > > 	Michael  
> > > > > 
> > > > > -- 
> > > > > Brian F. G. Bidulock    > ¦ The reasonable man adapts himself to the ¦
> > > > > [email-masked]    ¦ world; the unreasonable one persists in  ¦
> > > > > http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
> > > > >                         ¦ Therefore  all  progress  depends on the ¦
> > > > >                         ¦ unreasonable man. -- George Bernard Shaw ¦
> > > 
> > > -- 
> > > Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
> > > [email-masked]    ¦ world; the unreasonable one persists in  ¦
> > > http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
> > >                         ¦ Therefore  all  progress  depends on the ¦
> > >                         ¦ unreasonable man. -- George Bernard Shaw ¦
> 
> -- 
> Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
> [email-masked]    ¦ world; the unreasonable one persists in  ¦
> http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
>                         ¦ Therefore  all  progress  depends on the ¦
>                         ¦ unreasonable man. -- George Bernard Shaw ¦

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