For J-series Services Routers, you can configure virtual channels, which allow you to limit traffic sent from a corporate headquarters to branch offices. Virtual channels might be required when the headquarters site has an expected aggregate bandwidth higher than that of the individual branch offices. The router at the headquarters site must limit the traffic sent to each of the branch office routers to avoid oversubscribing their links. For instance, if branch 1 has a 1.5-megabits per second (Mbps) link and the headquarters router attempts to send 6 Mbps to branch 1, all of the traffic in excess of 1.5 Mbps is dropped in the ISP network.
To limit the traffic the headquarters router sends to each branch, you can configure virtual channels on a logical interface. Each virtual channel has a set of eight queues with a scheduler and an optional shaper. You can use an output firewall filter to direct traffic to a particular virtual channel. For example, a filter can direct all traffic with a destination address for branch office 1 to virtual channel 1, and all traffic with a destination address for branch office 2 to virtual channel 2.
When you configure virtual channels on an interface, the virtual channel group uses the same scheduler and shaper you configure at the [edit interfaces interface-name unit logical-unit-number] hierarchy level. In this way, virtual channels are an extension of regular scheduling and shaping and not an independent entity.
Although a virtual channel group is assigned to a logical interface, a virtual channel is not the same as a logical interface. The only features supported on a virtual channel are queuing, packet scheduling, and accounting. Rewrite rules and routing protocols apply to the entire logical interface.
To configure virtual channels, you can include the following statements at the [edit class-of-service], [edit firewall], and [edit interfaces] hierarchy levels of the configuration:
- [edit class-of-service]
-
virtual-channels {
-
virtual-channel-name;
- }
-
virtual-channel-groups {
-
-
virtual-channel-group-name {
-
-
virtual-channel-name {
-
scheduler-map map-name;
-
shaping-rate (percent percentage | rate);
-
default;
- }
- }
- }
-
interfaces {
-
-
interface-name {
-
-
unit logical-unit-number {
-
virtual-channel-group virtual-channel-group-name;
- }
- }
- }
-
- [edit firewall]
- family family-name {
-
- filter filter-name {
-
- term term-name {
-
- then {
-
virtual-channel virtual-channel-name;
- }
- }
- }
- }
-
- [edit interfaces]
-
interface-name {
-
per-unit-scheduler;
- }
This chapter discusses the following topics: