CoA, RADIUS DM, and Session Redirection (Hotlining)
Session Redirection (Hotlining) ▀
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
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Important:
Changing ACL and rulebase together in a single CoA is not supported. For this, two separate CoA
requests can be sent through AAA server requesting for one attribute change per request.
Session Limits On Redirection
To limit the amount of memory consumed by a session manager a limit of 2000 redirected session entries per session
manager is allocated. This limit is equally shared by the set of subscribers who are currently being redirected. Whenever
a redirected session entry is subject to revocation from a subscriber due to an insufficient number of available session
entries, the least recently used entry is revoked.
Stopping Redirection
The redirected session entries for a subscriber remain active until a CoA message issued from the RADIUS server
specifies a filter that does not contain the readdress server ACL rule. When this happens, the redirected session entries
for the subscriber are deleted.
All redirected session entries are also deleted when the subscriber disconnects.
Handling IP Fragments
Since TCP/UDP port numbers are part of the redirection mechanism, fragmented IP datagrams must be reassembled
before being redirected. Reassembly is particularly necessary when fragments are sent out of order. The session
manager performs reassembly of datagrams and reassembly is attempted only when a datagram matches the redirect
server ACL rule. To limit memory usage, only up to 10 different datagrams may be concurrently reassembled for a
subscriber. Any additional requests cause the oldest datagram being reassembled to be discarded. The reassembly
timeout is set to 2 seconds. In addition, the limit on the total number of fragments being reassembled by a session
manager is set to 1000. If this limit is reached, the oldest datagram being reassembled in the session manager and its
fragment list are discarded. These limits are not configurable.
Recovery
When a session manager dies, the ACL rules are recovered. The session redirect entries have to be re-created when the
MN initiates new traffic for the session. Therefore when a crash occurs, traffic from the Internet side is not redirected to
the MN.
AAA Accounting
Where destination-based accounting is implemented, traffic from the subscriber is accounted for using the original
destination address and not the redirected address.
Viewing the Redirected Session Entries for a Subscriber
View the redirected session entries for a subscriber by entering the following command:
show subscribers debug-info { callid
<id>
| msid
<id>
| username
<name>
}
The following command displays debug information for a subscriber with the MSID 0000012345:
