Configuring The Sa Cache Mechanism - HP A5500 SI Switch Series Configuration Manual

By configuring a filtering rule for receiving or forwarding SA messages, you can enable the switch to
filter the (S, G) forwarding entries to be advertised when receiving or forwarding an SA message, so
that the propagation of multicast source information is controlled at SA message reception or
forwarding.
By configuring a TTL threshold for multicast data packet encapsulation in SA messages, you can control
the multicast data packet encapsulation in SA messages and limit the propagation range of SA
messages.
Before creating an SA message with an encapsulated multicast data packet, the switch checks the
•
TTL value of the multicast data packet. If the TTL value is less than the threshold, the switch does not
create an SA message. If the TTL value is greater than or equal to the threshold, the switch
encapsulates the multicast data in an SA message and sends the SA message out.
After receiving an SA message with an encapsulated multicast data packet, the switch decreases
•
the TTL value of the multicast packet by 1 and then checks the TTL value. If the TTL value is less than
the threshold, the switch does not forward the SA message to the designated MSDP peer. If the TTL
value is greater than or equal to the threshold, the switch re-encapsulates the multicast data in an
SA message and sends the SA message out.
Follow these steps to configure a filtering rule for receiving or forwarding SA messages:
To do...
Enter system view
Enter public network MSDP view
or VPN instance MSDP view
Configure an SA message
creation rule
Configure a filtering rule for
receiving or forwarding SA
messages
Configure the TTL threshold for
multicast data packet
encapsulation in SA messages

Configuring the SA cache mechanism

To reduce the time spent in obtaining the multicast information, you can enable the SA cache mechanism
to cache (S, G) entries contained in SA messages locally on the switch. However, caching (S, G) entries
uses memory space on the switch.
When the SA cache mechanism is enabled and the switch receives a new (*, G) join message, the
switch searches its SA cache first.
If the corresponding (S, G) entry does not exist in the cache, the switch waits for the SA message
•
that its MSDP peer will send in the next cycle;
If the corresponding (S, G) entry exists in the cache, the switch joins the corresponding SPT rooted
•
at S.
To protect the switch against denial of service (DoS) attacks, you can set a limit on the number of (S, G)
entries that the switch can cache.
Follow these steps to configure the SA message cache:
Use the command...
system-view
msdp [ vpn-instance vpn-instance-
name ]
import-source [ acl acl-number ]
peer peer-address sa-policy {
import | export } [ acl acl-number
]
peer peer-address minimum-ttl ttl-
value
201
Remarks
—
—
Required
No restrictions on (S, G) entries
by default
Required
No filtering rule by default
Optional
0 by default