Subject: Re: [Fwd: Re: IPSP proposed text (1st approach)]]

From: Dennis Niermann <[email-masked]>
Date: Thu, 01 Nov 2001 07:57:57 -0600

Hi Brian,
Your example of RC value assignments was a
very clear explanation of how you see things.
So, in that sense it helped a lot. Thanks.

But, I have two points.

First, I think that the RC values given for the double
ended case are not accurate. I believe that in the double
ended case there would always be a particular RC value used for a 
particular AS (1-1 mapping from AS to RC) and so then values 
would be as such:

                                      RC Values
                                 ==========    ======
                                   Double      Single
     IPSP/    Remote    Local      Ended        Ended
      Assoc     AS       AS      R->L  L->R     L<->R
     -------  -------   -----    ----  ----     -----
        1      100:4     200      1     4         1
        1      100:4     201      2     4         2
        1      100:3     200      1     3         3
        1      100:3     201      2     3         4
        2      100:3     200      1     3         1
        2      100:3     201      2     3         2
        2      100:5     200      1     5         3
        2      100:5     201      2     5         4

Second, I do not believe that the single ended case
has half the RC values to keep track of. In terms of
"values" the single ended case uses from 1-4 and the 
double ended case uses from 1-5. But, that is not
important. What is important if the number of "meanings"
of RC values to keep track of.  In the double ended case
there is 5 (same as the total number of ASs). Whereas in 
the single ended case there is 8. This is because in the 
single case an RC has meaning only in the context of a 
particular association (the second RC 1 is unrelated 
to the first RC 1).

At a given node, in the double ended case the number of 
RCs to keep track of equals the number of ASs in the entire 
network (known at that node).  Whereas in the single ended
case the number of RCs to keep track of is equal to the 
number of associations times the number of ASs per association.   
one particular node). 

So, if we were to extend the example to include the 
associations for IPSP4,
the double ended would have exactly 6 RCs with unique
meanings and single ended would have 16 RCs with unique
meanings.

Regards,  Dennis 

"Brian F. G. Bidulock" wrote:
> 
> Dennis,
> 
> Your example does not highlight any differences
> between the single-ended and double-ended approaches.
> 
>       +------+                                  +------+
>       |      |                                  |      |
>       | AS   |                                  | AS   |
>       | 100:4|                                  | 201  |
>       |      | \                              / |      |
>       +------+   \  +-----+   IP   +-----+  /   +------+
>                    /       \------/       \
>       +------+     | IPSP1 |      | IPSP3 |     +------+
>       |      +- - -\       /-+   /\       /- - -+      |
>       | AS   |      +-----+   \ /  +-----+      | AS   |
>       | 100:3|                 \                | 200  |
>       |      |      +-----+   / \  +-----+      |      |
>       |      +- - -/       \-+   \/       \- - -+      |
>       +------+     | IPSP2 |      | IPSP4 |     +------+
>                    \       /------\       /
>       +------+   /  +---- +        +-----+  \   +------+
>       |      | /                              \ |      |
>       | AS   |                                  | AS   |
>       | 100:5|                                  | 202  |
>       |      |                                  |      |
>       +------+                                  +------+
> 
> Consider example RC assignment for both the
> single-ended and double ended cases at IPSP3
> in the following table:
> 
>                                      RC Values
>                                 ==========    ======
>                                   Double      Single
>     IPSP/    Remote    Local      Ended        Ended
>      Assoc     AS       AS      R->L  L->R     L<->R
>     -------  -------   -----    ----  ----     -----
>        1      100:4     200      4     1         1
>        1      100:4     201      3     2         2
>        1      100:3     200      2     3         3
>        1      100:3     201      1     4         4
>        2      100:3     200      4     1         1
>        2      100:3     201      3     2         2
>        2      100:5     200      2     3         3
>        2      100:5     201      1     4         4
> 
> As you can see, the same AS pairings occur for both
> cases.  With the single-ended approach, IPSP3 has half
> the RC values to keep track of.  That's it.
> 
> When IPSP1 loses activation of AS100:3 in the double-
> ended case it would send ASPIA RC=4 (from the table)
> to IPSP3.  If IPSP3 loses activation of AS200 it would
> send ASPIA (RC=1,3) to IPSP1.
> 
> When IPSP1 loses activation of AS100:3 in the single-
> ended case it would send ASPIA RC=1 (from the table)
> to IPSP3.  If IPSP3 loses activation of AS200 it would
> send ASPIA (RC=1,3) to IPSP1.
> 
> The same information is conferred, but in the single-
> ended case you need half the RC values and do not have
> to worry about half-duplex relationships between AS.
> 
> Does this make things perfectly clear to you?
> 
> There is absolutely no point in a double-ended
> procedure.  Double-ended procedures add overhead and
> complexity where not required.
> 
> --brian
> 
> Dennis Niermann wrote:                                     (Wed, 31 Oct 2001 10:11:03)
> >
> > Brian,
> >
> > I don't think that what you suggest is workable.
> > If one RC value is used that identifies both
> > ASs in a pair then problems arise.
> >
> > If IPSP1 sends an ASPIA to IPSP3 using RC=3 to
> > indicate that it is no longer serving AS100:3,
> > which of the ASs that IPSP3 is serving need to
> > also use RC3 on that association?
> > Both AS200 and AS201?
> > Or, just one of them?
> > If both AS200 and AS201 use RC3 then there is no way
> > distinguish between them.
> > If just one of them use RC3, then it breaks your rule
> > that the same RC value should be used by the ASs on
> > each side of the association.
> >
> > /Dennis
> >
> 
> --
> Brian F. G. Bidulock
> [email-masked]
> http://www.openss7.org/
> 
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-- 
---------------------------------------------------------------
 Dennis Niermann              [email-masked]
 Ericsson Network Systems   
 Richardson, Tx 75081

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