The entire world has always specified bandwidth as the one-way capacity, that is, 1 Gigabit per second ethernet connection is 1 Gigabit in the outbound direction, AND 1 Gigabit in the inbound direction. Of course, you will only ever experience 1 Gigabit of bandwidth since either direction sets the maximum possible bandwidth.
But for Cisco Marketing, that is actually TWO GIGABITS. One out, and one in makes two. Because two must be better than one. Right ?
To ensure that no one knows what is going on, Marketing Math only applies to certain technologies. The most common application of the marketing math is backplane capacity for ethernet switches. For example, the Catalyst 6500-E (using Supervisor 720) has 720 Marketing Gigabits per second of capacity. The REAL bandwidth is 360 Gigabits for the entire chassis, and actually breaks down to 40 Real Gigabit/s per slot (well, for a nine slot 6500 chassis anyway, thirteen slots chassis can’t do 40Gb/s on every slot).
“The FWSM is connected to the backplane of the 6500 or 7600 through a full-duplex 6-gigabit EtherChannel (GEC), totaling 12 gigabits of bandwidth using marketing math.”
Chapter 2, Hardware Architecture, Cisco Secure Firewall Services Module – Cisco Press.
So when reading a brochure or white paper, make sure you check whether the marketing department are lying or not – its often vague and hard to tell which version of “bandwidth” is in use. Find an engineer to tell you the truth.
Other vendors, notably Nortel, have called this Cisco Math. Well, at least Doug Gourlay is having a go, I don’t expect much success.