HP MSR4080 Configuration Guide

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connect VPN multicast receivers and multicast sources. When specific network criteria are met, a
switchover from the default-MDT to the data-MDT occurs to forward VPN multicast traffic to
receivers.
The process of default-MDT to data-MDT switchover is as follows:
1. The source-side PE device (PE 1, for example) periodically examines the forwarding rate of the
VPN multicast traffic. The default-MDT switches to the data-MDT only when the following
criteria are both met:
 The VPN multicast data has passed the ACL rule filtering for default-MDT to data-MDT
switchover.
 The traffic rate of the VPN multicast stream has exceeded the switchover threshold and
stayed higher than the threshold for a certain length of time.
2. PE 1 selects a least-used address from the data-group range. Then, it sends an MDT
switchover message to all the other PE devices down the default-MDT. This message contains
the VPN multicast source address, the VPN multicast group address, and the data-group
address.
3. Each PE device that receives this message examines whether it interfaces with a VPN that has
receivers of that VPN multicast stream.
If so, it joins the data-MDT rooted at PE 1. Otherwise, it caches the message and will join the
data-MDT when it has attached receivers.
4. After sending the MDT switchover message, PE 1 starts the data-delay timer. When the timer
expires, PE 1 uses the default-group address to encapsulate the VPN multicast data. The
multicast data is then forwarded down the data-MDT.
5. After the multicast traffic is switched from the default-MDT to the data-MDT, PE 1 continues
sending MDT switchover messages periodically. Subsequent PE devices with attached
receivers can then join the data-MDT. When a downstream PE device no longer has active
receivers attached to it, it leaves the data-MDT.
For a given VPN instance, the default-MDT and the data-MDT are both forwarding tunnels in the
same MD. A default-MDT is uniquely identified by a default-group address, and a data-MDT is
uniquely identified by a data-group address. Each default-group is uniquely associated with a
data-group range.
Backward switching from data-MDT to default-MDT
After the VPN multicast traffic is switched to the data-MDT, the multicast traffic conditions might
change and no longer meet the switchover criterion. In this case, PE 1, as in the preceding example,
initiates a backward MDT switchover process when any of the following criteria are met:
•
The traffic rate of the VPN multicast data has dropped below the switchover threshold. In
addition, the traffic rate has stayed lower than the threshold for a certain length of time (known
as the data-holddown period).
•
The associated data-group range is changed, and the data-group address for encapsulating the
VPN multicast data is out of the new address range.
•
The ACL rule for controlling the switchover from the default-MDT to the data-MDT has changed,
and the VPN multicast data fails to pass the new ACL rule.
Inter-AS MD VPN
In an inter-AS VPN networking scenario, VPN sites are located in multiple ASs. These sites must be
interconnected. Inter-AS VPN provides the following solutions:
•
VRF-to-VRF connections between ASBRs—This solution is also called inter-AS option A.
•
EBGP redistribution of labeled VPN-IPv4 routes between ASBRs—ASBRs advertise
VPN-IPv4 routes to each other through MP-EBGP. This solution is also called inter-AS option B.

HP MSR4080 Specifications

General

Brand	HP
Model	MSR4080
Category	Network Router
Language	English