[c-nsp] Re: Cisco 7301 w/ PA-A3 Max VC or Sessions

[Dennis Peng]

Steve Wright [steve.wright at visp.me.uk] wrote:
> Hi all,
> 
> We use a 7301 with a PA-A3, and 1Gb memory which acts as an LNS for about
> 3500 PPPoA sessions.
> 
> I've heard that the PA-A3 can only deal with about 4000 sessions, and have
> been looking into this, and it appears that it can only deal with 4096 VC's.
> 
> However, for our L2TP Termination, we have 2 VC's setup.. and I am unsure of
> how this terminates the sessions onto the PA-A3, and whether each session is
> taking up 1 VC, or whether their is another figure somewhere that can tell
> me how many sessions I can terminate, or whether I am just limited by the
> amount of bandwidth the router can push/ is available?

For most architectures, you only need to worry about the VC limit on
the LAC side (if you are aggregating PPPoA or PPPoEoA sessions). The
LNS receives the sessions over L2TP/UDP/IP and even if you are using
ATM as the interconnect, it's generally muxed over one or a few VC's,
so no worries there.

As for the number of session you can terminate, the forwarding
performance of the box is usually the limiting factor, especially if
you are aggregating broadband sessions. Control plane scalability is
more of a factor when you are aggregating narrowband (dial) sessions
where there is not as much traffic per user.

Dennis
 
> However, I have been unable to determine a final answer to how many sessions
> we can terminate, and am wondering if anyone can help?
> 
> TIA,
> 
> Cheers,
> Steve Wright
> 
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