CISCO 2921 WAN Performance Question

[bc4switch]

Looking at CISCO 2900 series data sheet, there is a sentence under "Benifits"

The Cisco 2900 Series enables deployment in high speed WAN environments with concurrent services enabled up to 75 Mbps

Can someone please explain what does this mean? The interface is 1Gbps, why 2900 is only enabled up 75 Mbps?

[Collin Clark]

What that means is that the router running services (ie Zone-based firewall, NAT, NBAR, etc) can maintain 75Mb of traffic throughput. So why the gig interface? If you don't want to run any services, the throughput is more than 100Mb so a gig interface is necessary.