Cisco 10000 Series Configuration Manual page 230

Data Included in the Policing Rate
Table 6-2
Media
ATM
(UBR)
ATM
(CBR)
1. The router does not account for flags or Frame Check Sequence (FCS) that the hardware adds or removes.
Table 6-3
Table 6-3
Media
Frame Relay
Ethernet
ATM variable bit rate (VBR)
ATM unspecified bit rate (UBR)
ATM constant bit rate (CBR)
1. For Frame Relay networks with link fragmentation and interleaving (LFI) enabled.
Be sure to take into account the framing and cell overhead when specifying a minimum bandwidth for a
class. For example, if you need to commit a rate of 1000 64-byte packets per second and each packet has
4 bytes of framing overhead, instead of using 512 kbps in the bandwidth or police command, use
544 kbps, calculated as follows:
1000 * (64 + 4) * 8 /1000 = 544
A similar scenario for ATM requires 848 kbps because each 64-byte packet requires two cells of
53 bytes.
1000 * 2 * 53 * 8 / 1000 = 848
Cisco 10000 Series Router Quality of Service Configuration Guide
6-24
Policing Rate Data
Data Included
Layer 2 framing
Cell overhead
Layer 2 framing
Cell overhead
describes what bandwidth is based on for each media type.
Basis for Bandwidth
Data Excluded
Class-Based Shaping
No ATM cell overhead
No AAL Common Part Convergence
Sublayer (CPCS) pad
Class-Based Shaping
No ATM cell overhead
No AAL Common Part Convergence
Sublayer (CPCS) pad
Bandwidth Based On
1
Fragments
Bits
Sustained cell rate (SCR)
Peak cell rate (PCR)
Peak cell rate (PCR)
Chapter 6 Policing Traffic
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