Specifications

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RFC 5102, Information Model for IP Flow Information Export
Subscriber Management Access Network Guide
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The LAC Tunnel Selection Overview, Configuring Weighted Load Balancing for LAC Tunnel
Sessions and weighted-load-balancing (L2TP LAC) topics in the Junos OS Broadband
Subscriber Management and Services Library incorrectly describe how weighted load
balancing works on an L2TP LAC. The topics state that the tunnel with the highest
weight (highest session limit) within a preference level is selected until it has reached
its maximum sessions limit, and then the tunnel with the next higher weight is selected,
and so on.
In fact, when weighted load balancing is configured, tunnels are selected randomly
within a preference level, but the distribution of selected tunnels is related to their
weight. The LAC generates a random number within a range equal to the aggregate
total of all session limits for all tunnels in the preference level. Portions of the
range—pools of numbers—are associated with the tunnels according to their weight;
a higher weight results in a larger pool. The random number is more likely to be in a
larger pool, so a tunnel with a higher weight (larger pool) is more likely to be selected
than a tunnel with a lower weight (smaller pool).
For example, consider a level that has only two tunnels, A and B. Tunnel A has a
maximum sessions limit of 1000 and tunnel B has a limit of 2000 sessions, resulting
in an aggregate total of 3000 sessions. The LAC generates a random number in the
range from 0 through 2999. A pool of 1000 numbers, the portion of the range from 0
through 999, is associated with tunnel A. A pool of 2000 numbers, the portion of the
range from 1000 through 2999, is associated with tunnel B. If the generated number
is less than 1000, then tunnel A is selected, even though it has a lower weight than
tunnel B. If the generated number is 1000 or larger, then tunnel B is selected. Because
the pool of possible generated numbers for tunnel B (2000) is twice that for tunnel A
(1000), tunnel B is, on average, selected twice as often as tunnel A.
Subscriber Management Feature Guide
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In the Junos OS Subscriber Management Feature Guide, the fail-over-within-preference
statement at the [edit services l2tp] hierarchy level is incorrectly spelled. The correct
spelling for this statement is failover-within-preference.
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The Junos OS Release 13.3 Subscriber Management Feature Guide fails to include the
new user@domain option for filtering AAA, L2TP, and PPP traces by subscriber. See
the feature description in these Release Notes titled Support for filtering trace results
by subscribers for AAA, L2TP, and PPP for information about using this option.
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The “Example: HTTP Service Within a Service Set” topic in the Subscriber Management
Feature Guide erroneously describes how to configure captive portal content delivery
rules in service sets.
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Documentation Updates