Tim Salo tjs at
Thu Sep 1 21:40:39 UTC 1994

> From: bmanning at ISI.EDU
> Subject: Comments
> To: nanog at, iepg at
> Date: Tue, 30 Aug 1994 03:28:33 -0700 (PDT)
> Cc: nap-info at
>  	[...] 
>   	The difficulties with the RFC 1490 approach were listed in the 
> 	Toronto meeting.  I list them here:
>   		There is no clear migration path from this approach to
>   		a more correct/robust implementation using RFC 1577
>   		encapsulation over native ATM (OC3c).

The migration from RFC 1490 to RFC 1577 is probably straight forward.
Cisco has promised RFC 1577 microcode (for PVCs only) for their HSSI
interface.  Therefore, one [clear] migration path is to upgrade the HSSI
microcode when it is available and stable, and then migrate from RFC 1490
to RFC 1577.

By the way, it should be noted that the Cisco 7000-series router is the
only router that any NSP has indicated that they will use to connect to
an ATM NAP.  Note that the router selection was made by the NSPs, not
the NAP managers.

>   		There are additional points of failure and additional costs
>   		with the requirement for an ADSU.

Compared to what?  There is a strong desire to use existing, released
products which can connect to a DS-3 ATM switch as soon as possible.
This rather limits the options.
>   		The listed approach requires manual configuration.

Again, compared to what?  There will be considerable manual configuration
in the initial ATM NAPs, (e.g., PVCs).
>   		This appears to lock the NAP into a top speed of 45Mbps
>   		or DS3 speeds.

I don't understand your point.  The migration to OC-3c will be straight
forward, (e.g., pull out board A, insert board B), particularly after the
planned 1490/1577 migration.

>   	In addition to these weaknesses, there were a number of assumptions
>   	regarding specific hardware implementations of ATM protocols (use
>   	of a very small selection of vendors and limited interfaces) and 
>   	the ability and/or willingness of the attaching ISPs to work toward
>   	a more elegant, cheaper, robust solution at the possible expense of 
>   	some time while vendors address the implementation gaps.

As I indicated above, the Cisco 7000 was the choice of the NSPs.  There
is also a strong desire among those involved to implement the new NSFNET
architecture as soon as possible, (which implies using existing, released
>   	Questions on the desirability of a native media support with RFC 1577
>   	support were posted to the IP-ATM wg of the IETF and the 
>   	email response was affirmative in recommending an approach with
>  	RFC 1483/1577 over AAL5 with LLC/SNAP coding.
>	[...]

As you know, everyone involved intends to migrate to RFC 1577.  Initial
deployment of RFC 1577, rather than RFC 1490, conflicts with the
objectives of using existing, released products, implementing ATM NAPs
as soon as possible, and supporting DS-3 ATM interfaces.


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