[Asterisk-Users] Systems Admin; Telecom Newbie - What do I ne ed?

[Marcelo Pacheco]

Having worked with LAN/WAN/Frame Relay/Internet for 20 years ...

I can't possibly understand what QOS requirements exists on a switched 100mbps 
network for VOIP. Even if packet scheduling issues generate a 1-2 ms delay, 
jitter bufffers and echo cancellors take care of it without breaking a sweat.

It looks like you're trying to kill a fly with a cannon, unless you have a 
fast ethernet switch operating close to full packet switching capability, 
delay should never be a problem within a LAN. If that is the problem, then 
what's necessary is a switch upgrade, to a switch that can handle more 
traffic, not defining QOS within the switch.

I remember reading about a study from MCI or Sprint, where they arrived at the 
conclusion that no QOS was required within their backbones, even for VOIP, 
that the only place QOS was required was on T1 links with their customers. At 
100mbps, data flows awfully fast... A full size Ethernet packet takes 120 
micro seconds (0.12ms) to be sent, so even 100 packets take only 12 ms to be 
sent, if they get queued somewhere, ahead of a VOIP packet. If that becomes 
an issue, better get those interfaces up to Gigabit.

Just my 2 cents.

Marcelo Pacheco

Em Qui 14 Jul 2005 13:32, Wiley Siler escreveu:
> Let me expand on the bandwidth point HTH made and maybe shed light on
> your requirements....
>
> A 100baseT switched (no hubs) network has a lot of bandwidth when you
> think in terms of VoIP.  The uLaw stream (uncompressed) from an IP500
> phone to the Asterisk box is not going to take more than 80K of bandwith
> from the bandwidth pool.  That means 60 phones ALL in a single call
> would only be using around 5 megs of throughput.  At that point packet
> scheduling becomes far more important than bandwidth.  Gigabit is nice
> but the value of QoS in comparison is very evident.  If cost becomes a
> driving factor, you may want to focus on upgrading port count and remain
> at 100baseT instead of going to Gigabit.  A properly configured 100baseT
> network with good QoS rules will yield great performance over an
> unregulated 100baseT network.  Do you know your real traffic needs?  I
> would check how much traffic is via user download, www browsing,
> streaming, email, etc, etc...  You may find that some simple rules save
> you quite a bit of cash.  Just a thought and alternative... Gigabit is
> also very tempting so that whole spiel may have been for not.  8)
>
> Also, pay heed to the PoE stuff you are hearing about.  I may be wrong
> but I am pretty sure you want to be careful what you connect to a PoE
> port.  Otherwise you wind up with fried PoE injectors and end devices.
> I believe PoE ports would only be used for a PoE phone in essence.  Just
> as a reminder and warning.
>
> Cheers,
> Wiley
>
>
>
>
>
> -----Original Message-----
> From: asterisk-users-bounces at lists.digium.com
> [mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Colin
> Anderson
> Sent: Thursday, July 14, 2005 8:47 AM
> To: 'Asterisk Users Mailing List - Non-Commercial Discussion'
> Subject: RE: [Asterisk-Users] Systems Admin; Telecom Newbie - What do I
> ne ed?
>
> >But currently, I only have one ethernet jack per office. Routing
> >another 60 or so ports would add a very substantial expense in both
> >cabling and backbone expansion (what category ethernet is required,
> >BTW?).
>
> Most decent phones have an ethernet passthrough (2 port) so you can plug
> in
> your PC. As long as your LAN is decent (Cat5 100baseT switched) the
> overhead
> using VoIP is negligible.
>
> I have used the 3Com NJ wall jacks with good success:
>
> http://www.3com.com/products/en_US/detail.jsp?tab=features&pathtype=purc
> hase
> &sku=3CNJ90
>
> It's basically a 4 port switch that you replace your wall jack with. I
> used
> the NJ200, it allows you to set priority per port, although I think they
> are
> discontinued now. In combination with a 3Com power over Ethernet
> injector, I
> was able to expand a 24 port LAN to a 96 port LAN with a per-port cost
> of
> $62 Cdn. And, 24 ports of those 96 are PoE, so I can plug my phones
> right in
> to port 1 and they power up, no external power supply needed.
>
> hth
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users at lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users
> _______________________________________________
> Asterisk-Users mailing list
> Asterisk-Users at lists.digium.com
> http://lists.digium.com/mailman/listinfo/asterisk-users
> To UNSUBSCRIBE or update options visit:
>    http://lists.digium.com/mailman/listinfo/asterisk-users