[Fwd: Connections to switches]

[Peter Jones <[e-mail]>]

Hi There,

We have found that <draft-ietf-atommib-atm1ng-03.txt> is unclear about
the usage of TX and RX when defining the traffic descriptor usage for
connections via the Proprietary Virtual Interface to the AAL5 entity in
a switch.

I requested clarification from Kaj in the attached mail. His response
was that he thought the directions should be the same as any other
interface to the switch fabric, i.e. case 1) as defined in the mail.

I would like this clarified in the RFC by adding some text like:

	Connections to the Proprietary Virtual Interface are treated
	like a normal (e.g. UNI) interface.

        The TX and RX indexes in the VPL or VCL Entry, 
	(e.g. atmVclReceiveTrafficDescrIndex and 	
	atmVclTransmitTrafficDescrIndex) apply from the point of 
	view of the ATM switching fabric (i.e. the ATM entity in 
	Figure 7), i.e. the atmVclReceiveTrafficDescrIndex 
        defines the traffic parameters that apply to the flow from 
        the AAL5 entity to the ATM Entity, not the traffic flow from 
        ATM Entity to the AAL5 entity.

        RxTrafficDescrIndex     ATM Entity     <---  AAL5 Entity
        TxTrafficDescrIndex     ATM Entity     --->  AAL5 Entity

What this means is that the traffic parameters appear to be normal from
the switch's "switch fabric" point of view, and reversed from the
switch's AAL5 Entity (e.g. Management CPU) point of view.

Regards
Peter Jones

-- 
______________________________________________________________________
 Peter Jones                      Atmosphere Networks
 Project Manager - NMS            GPO Box U 1987
 Direct:[phone]         Perth WA 6845, Australia
 Mobile:                          Tel: [phone]
 Email: [e-mail]      Fax: [phone]     
_______________________________________________________________________

--- Begin Message ---

Hi Kaj,

We have a question about the details of building connections to
switches.

Reference the following picture from atm1ng-03.


                        ___________________________
                        |                         |
                        |     =============       |
                        |     |    AAL5   |       |
                        |     |   Entity  |       |
                        |     =============       |
                        |           |             |
                        |         -----Prop. Virtual Interface
                        |           |             |
                        |     =============       |
                        |     |   ATM     |       |
                        |     |  Entity   |       |
                        |     =============       |
                        |_____|__|__|__|__|_______|
                              |  |  |  |  |
                             ---------------- ATM UNIs
                              |  |  |  |  |
                              |  |  |  |  |
                              v  v  v  v  v

                Figure 7: Model of an AAL5 Entity in a Switch


What is the interpretation of the "direction" on the VCL or VPL table
entries that relate to the "Prop. Virtual Interface"?

There are two possibilities:

1)	Treat the "Prop. Virtual Interface" like a normal UNI 
	interface.

	In this case, the TX and RX indexes, e.g. 
		atmVclReceiveTrafficDescrIndex and 
		atmVclTransmitTrafficDescrIndex
	effectively apply from the point of view of the ATM 
	switching fabric (i.e. the ATM entity in the figure above), 
	i.e. the atmVclReceiveTrafficDescrIndex 
	defines the traffic parameters that apply to the flow from 
	the AAL5 entity to the ATM Entity, not the traffic flow from 
	ATM Entity to the AAL5 entity.

	RxTrafficDescrIndex	ATM Entity     <---  AAL5 Entity
	TxTrafficDescrIndex	ATM Entity     --->  AAL5 Entity

2)	Treat the "Prop. Virtual Interface" as a special case switch 
	interface.
		
	In this case, the TX and RX indexes, e.g. 
		atmVclReceiveTrafficDescrIndex and 
		atmVclTransmitTrafficDescrIndex
	effectively apply from the point of view of the AAL5 Entity, 
	i.e. the atmVclReceiveTrafficDescrIndex 
	defines the traffic parameters that apply to the flow from 
	the ATM Entity to the AAL5 entity, not the traffic flow from 
	AAL5 Entity to the ATM entity.

	RxTrafficDescrIndex	ATM Entity     --->  AAL5 Entity
	TxTrafficDescrIndex	ATM Entity     <---  AAL5 Entity

I can come up with arguments to justify either approach.

What I want to know is what the "standard" approach is (which should be
very clear from the RFC's).

I have had a look at the drafts, but I can't see anywhere where this is
defined.

Regards
Peter Jones

--
______________________________________________________________________
 Peter Jones                      Atmosphere Networks
 Project Manager - NMS            GPO Box U 1987
 Direct:[phone]         Perth WA 6845, Australia
 Mobile:                          Tel: [phone]
 Email: [e-mail]      Fax: [phone]     
_______________________________________________________________________

--- End Message ---