Rate Shaping on MIC and MPC Interfaces
This topic covers the following information:
Granularity of Rate Shaping on MIC and MPC Interfaces
Interfaces hosted on MIC and MPC line cards have a certain granularity in the application of configured shaping rates. In other words, the observed hardware value might not exactly match the user-configured value. Nevertheless, the derived values are as close to the configured values as allowed.
Table 1 lists the shaping granularity for each MPC port type. The derived shaping rate granularity ranges from 250 Kbps for coarse-grained queuing on the basic hardware up to 1.5 Kbps for fine-grained queuing on the enhanced queuing hardware.
MIC or MPC Port in an MX Series Router |
Shaping Rate Granularity |
||
|---|---|---|---|
Line Card Type |
Port Speed |
Port Level, Queue Level |
Logical Interface Level, Interface Set Level |
Non-Queuing MPC |
1 Gbps / 10 Gbps |
250 Kbps |
n/a |
Queuing MIC or MPC |
1 Gbps |
2.4 Kbps |
9.6 Kbps |
10 Gbps |
9.6 Kbps |
38.4 Kbps |
|
Enhanced Queuing MPCs |
1 Gbps |
1.5 Kbps |
6 Kbps |
10 Gbps |
6 Kbps |
24 Kbps |
|
The shaping rate granularity for MX Series routers with the MPC3E and MPC4E is approximately 293-300 Kbps. For routers with other MPCs (Trio-based FPCs), the shaping rate granularity is 250 Kbps. The predefined shaping rates for these MPCs are the next multiple of these shaping rate granularity values. The expected deviation from the predefined shaping rates is 5 to 10 percent.
Accounting for Layer 1 and Layer 2 Overhead in Egress Rate-Shaping Statistics
In calculating egress rate-shaping statistics for shaped-session packets on the egress side of MIC and MPC interfaces, the system adds 20 bytes per packet by default.
To configure an explicit overhead value to use for calculating
egress rate-shaping statistics, include the egress-shaping-overhead statement
at the [edit chassis fpc slot-number pic pic-number traffic-manager] hierarchy level. You can specify an offset value from –63 bytes
through 192 bytes per egress packet.