Tunnel Services PICs and Multicast

On Juniper Networks routers, data packets are encapsulated and de-encapsulated into tunnels by means of hardware and not the software running on the router's processor. The hardware used to create tunnel interfaces on M-series and T-series routers is a Tunnel Services PIC. If M-series and T-series routers are configured as rendezvous points or IP version 4 (IPv4) PIM sparse-mode DRs connected to a source, a Tunnel Services PIC is required. MX-series routers do not require Tunnel Services PICs.

In PIM sparse mode, the source DR takes the initial multicast packets and encapsulates them in PIM register messages. It then unicasts them to the PIM sparse-mode RP router, where the PIM register message is de-encapsulated.

When a router is configured as a PIM sparse-mode RP router (by specifying an address using the address statement at the [edit protocols pim rp local] hierarchy level) and a Tunnel PIC is present on the router, a PIM register de-encapsulation interface, or pd interface, is automatically created. The pd interface receives PIM register messages and de-encapsulates them by means of the hardware.

If PIM sparse mode is enabled on any router (potentially a PIM sparse-mode source DR) and a Tunnel Services PIC is present on the router, a PIM register encapsulation interface, or pe interface, is automatically created for each RP address that is used to encapsulate source data packets and send them to respective RP addresses on the PIM DR as well as the PIM RP. The pe interface receives PIM register messages and encapsulates them by means of the hardware.

Note: Do not confuse the configurable pe and pd hardware interfaces with the nonconfigurable pime and pimd software interfaces. Both pairs encapsulate and de-encapsulate multicast packets, and are created automatically; however, the pe and pd interfaces only appear if a Tunnel Services PIC is present. The pime and pimd interfaces are not useful in situations requiring the pe and pd interfaces.

If the source DR is the RP, then there is no need for PIM register messages and consequently no need for a Tunnel Services PIC to be present.

When PIM sparse mode is used with IP version 6 (IPv6), a Tunnel PIC is required on the RP, but not on the IPv6 PIM DR. The lack of a Tunnel PIC requirement on the IPv6 DR applies only to IPv6 PIM sparse mode and should not be confused with IPv4 PIM sparse-mode requirements.

Table 11 shows the complete matrix of IPv4 and IPv6 PIM Tunnel PIC requirements.

Table 11: Tunnel PIC Requirements for IPv4 and IPv6 Multicast

Copyright © 2009, Juniper Networks, Inc. All rights reserved. Trademark Notice.