On a J-series Services Router, CoS queuing enabled for tunnel interfaces allows you to
Each tunnel can be shaped so that a tunnel with low-priority traffic cannot swamp other tunnels that carry high-priority traffic.
Traffic for one tunnel does not impact traffic on other tunnels.
Traffic through various tunnels is limited to not exceed a certain bandwidth.
For example, suppose you have three tunnels to three remote sites through a single WAN interface. You can select CoS parameters for each tunnel such that traffic to some sites gets more bandwidth than traffic to other sites.
You can apply different queuing, scheduling, and shaping policies to different tunnels based on user requirements. Each tunnel can be configured with different scheduler maps, different queue depths, and so on. Customization allows you to configure granular CoS policy providing for better control over tunnel traffic.
For example, CoS queuing avoids having low-priority packets scheduled ahead of high-priority packets when the interface speed is higher than the tunnel traffic speed. This feature is most useful when combined with IPsec. Typically, IPsec processes packets in a FIFO manner. However, with CoS queuing each tunnel can prioritize high-priority packets over low-priority packets. Also, each tunnel can be shaped, so that a tunnel with low-priority traffic does not swamp tunnels carrying high-priority traffic.
