[mrtg] Re: Another MaxBytes Question

[Dan Wentzel]

Chris,

	18.7MB/s * 8 =  149.6Mb/s

	19.4 MB/s * 8 = 155.2Mb/s

An OC-3c on your ATM switch gives a line speed of exactly 155.52Mb/s (3 * OC-1 at 51.84Mb/s)

The SONET overhead is exactly 5.76Mb/s.

	Thus, the first number above (149.6) is APPROXIMATELY the USABLE speed of the OC-3, which
is exactly 149.76Mb/s not including any AAL5, LANE, or HEC overhead for the ATM cells.

	The second number above (155.2) is APPROXIMATELY the FULL line speed of an OC-3 (including
SONET overhead).

	The first number is more accurate IMO, to use for Max Speed, unless you want to just remember 
that you will only reach ~96% of the full line speed.

	I was originally the TCOMM guy, now I'm the Network guy.  :)

DJW

-----Original Message-----
From:	Chris Williams [SMTP:pierce at columbus.rr.com]
Sent:	Monday, February 14, 2000 3:03 PM
To:	MRTG
Subject:	[mrtg] Another MaxBytes Question

This may be a simple question.  I am monitoring OC3 ports on ATM switches as
well as OC3 ports on a Cisco 7505 interface, what could be causing the
following difference?

Max Speed displayed for Fore ATM Switch = Max Speed: 18.7 MBytes/s (Sonet)

Max Speed displayed for Cisco 7505 = Max Speed: 19.4 MBytes/s (sonet)

why am i getting a max speed value of almost a full MByte/s on the Cisco?

Thanks,

cpw

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