Weight and Priority usage in the Blueworx Platform

Using Weight and Priority

Some entities in BVR use weight and priority values to determine which of a set of possible resources should be used, as follows:

An entity with a lower priority value will be used in preference to an entity with a higher priority value, for redundancy
If there are two or more entities with the same priority value, then BVR load balances usage of this group of entities in proportion to their weights

Currently the entities in BVR using weight and priority are Call Features and SIP Proxies. The following examples use proxies but the behaviour is also applicable to Call Features.

Weight: A value determining how likely it is for the proxy to be picked, where the likelihood of a given proxy being picked is the proxies weight in relation to the total weight of all proxies that are UP within the same priority group.
Priority: Proxies with the lowest priority number are always used unless all proxies with that priority group are down, at which point proxies with the next level of priority are used. The lower the priority number, the more preferred it is (e.g. a priority of 10 is more preferred than a priority of 20).

Note: It is recommended that you use priority numbers that aren't densely packed (e.g. not 1,2,3 etc) as this makes it more difficult to add new priorities in between. This is why priority numbers of 10 and 20 are used in this documentation; if another proxy was to be added in between proxies with a priority of 10 and 20, the new proxy could have a priority of 15. If the values were 1 and 2, all proxies with a value of 2 would have to be renumbered to insert a new proxy in between.

Examples

Table 1. Optional Parameters
Proxy name	Weight	Priority	Status
Proxy1	50	10	UP
Proxy2	20	10	UP
Proxy3	30	10	UP
Proxy4	1000	20	UP

In this example, Proxy1 has a 50% chance of being picked, Proxy2 has a 20% chance of being picked and Proxy3 has a 30% chance of being picked.

Now assume the status changes and Proxy1 goes down. The status is now:

Table 2. Optional Parameters
Proxy name	Weight	Priority	Status
Proxy1	50	10	DOWN
Proxy2	20	10	UP
Proxy3	30	10	UP
Proxy4	1000	20	UP

In this example, Proxy2 has a 40% chance of being picked and Proxy3 has a 60% chance. This is because Proxy1, which had a weight of 50, is no longer UP. Therefore the total weight of the proxies at priority 1 is 50, so the chance of Proxy2 being picked is 20/50 (40%) and for Proxy3 is 30/50 (60%).

Table 3. Optional Parameters
Proxy name	Weight	Priority	Status
Proxy1	50	10	DOWN
Proxy2	20	10	UP
Proxy3	30	10	DOWN
Proxy4	1000	20	UP

In this example, Proxy2 will ALWAYS be picked. This is because Proxy1, Proxy2 and Proxy3 are all in the most preferred priority group, but Proxy1 and Proxy3 are down so will not be used.

Now, Proxy2 also goes down

Table 4. Optional Parameters
Proxy name	Weight	Priority	Status
Proxy1	50	10	DOWN
Proxy2	20	10	DOWN
Proxy3	30	10	DOWN
Proxy4	1000	20	UP

In this example, Proxy4 will always be used.