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IOC Hardware Properties

On SRX 5600 and SRX 5800 devices, two IOCs (40x1GE IOC and 4x10GE IOC) are supported on which you can configure schedulers and queues. You can configure 15 VLAN sets per Gigabit Ethernet (40x1GE IOC) port and 255 VLAN sets per 10 Gigabit Ethernet (4x10GE IOC) port. The IOC performs priority propagation from one hierarchy level to another, and drop statistics are available on the IOC per color per queue instead of just per queue.

SRX 5600 and SRX 5800 devices with IOCs have Packet Forwarding Engines that can support up to 512 MB of frame memory, and packets are stored in 512–byte frames. Table 221 compares the major properties of the the Packet Forwarding Engine within the IOC.

Table 221: Forwarding Engine Properties within 40x1GE IOC and 4x10GE IOC

Feature	PFE Within 40x1GE IOC and 4x10GE IOC
Number of usable queues	16,000
Number of shaped logical interfaces	2,000 with 8 queues each, or 4,000 with 4 queues each.
Number of hardware priorities	4
Priority propagation	Yes
Dynamic mapping	Yes: schedulers/port are not fixed.
Drop statistics	Per queue per color (PLP high, low)

Additionally, the IOC features also support hierarchical weighted random early detection (WRED).

The IOC supports the following hierarchical scheduler characteristics:

Shaping at the physical interface level
Shaping and scheduling at the service VLAN interface set level
Shaping and scheduling at the customer VLAN logical interface level
Scheduling at the queue level

The IOC supports the following features for scalability:

16,000 queues per PFE
4 Packet Forwarding Engines per IOC
- 4000 schedulers at logical interface level (level 3) with 4 queues each
- 2000 schedulers at logical interface level (level 3) with 8 queues each
255 schedulers at the interface set level (level 2) per 1-port PFE on a 10-Gigabit Ethernet IOC (4x10GE IOC )
15 schedulers at the interface set level (level 2) per 10-port PFE on a 1-Gigabit Ethernet IOC (40x1GE IOC )
About 400 milliseconds of buffer delay (this varies by packet size and if large buffers are enabled)
4 levels of priority (strict-high, high, medium, and low)

Note: The exact option for a transmit-rate (transmit-rate rate exact) is not supported on the IOCs on SRX-series devices.

The manner in which the IOC maps a queue to a scheduler depends on whether 8 queues or 4 queues are configured. By default, a scheduler at level 3 has 4 queues. Level 3 scheduler X controls queue X*4 to X*4+3, so that scheduler 100 (for example) controls queues 400 to 403. However, when 8 queues per scheduler are enabled, the odd-numbered schedulers are disabled, allowing twice the number of queues per subscriber as before. With 8 queues, level 3 scheduler X controls queue X*4 to X*4+7, so that scheduler 100 (for example) now controls queues 400 to 407.

You configure the max-queues-per-interface statement to set the number of queues at 4 or 8 at the FPC level of the hierarchy. Changing this statement will result in a restart of the FPC. For more information about the max-queues-per-interface statement, see Example: Configuring Up to Eight Forwarding Classes and the JUNOS Software CLI Reference.

The IOC maps level 3 (customer VLAN) schedulers in groups to level 2 (service VLAN) schedulers. Sixteen contiguous level 3 schedulers are mapped to level 2 when 4 queues are enabled, and 8 contiguous level 3 schedulers are mapped to level 2 when 8 queues are enabled. All the schedulers in the group should use the same queue priority mapping. For example, if the queue priorities of one scheduler are high, medium, low, and low, all members of the group should have the same queue priority.

Groups at level 3 to level 2 can be mapped at any time. However, a group at level 3 can only be unmapped from a level 2 scheduler, and only if all the schedulers in the group are free. Once unmapped, a level 3 group can be remapped to any level 2 scheduler. There is no restriction on the number of level 3 groups that can be mapped to a particular level 2 scheduler. There can be 256 level 3 groups, but fragmentation of the scheduler space can reduce the number of schedulers available. In other words, there are scheduler allocation patterns that might fail even though there are free schedulers.

In contrast to level 3 to level 2 mapping, the IOC maps level 2 (service VLAN) schedulers in a fixed mode to level 1 (physical interface) schedulers. On 40-port Gigabit Ethernet IOCs, there are 16 level 1 schedulers, and 10 of these are used for the physical interfaces. There are 256 level 2 schedulers, or 16 per level 1 scheduler. A level 1 scheduler uses level schedulers X*16 through X*16+15. Therefore level 1 scheduler 0 uses level 2 schedulers 0 through 15, level 1 scheduler 1 uses level 2 schedulers 16 through 31, and so on. On 4-port 10 Gigabit Ethernet PICs, there is one level 1 scheduler for the physical interface, and 256 level 2 schedulers are mapped to the single level 1 scheduler.

The maximum number of level 3 (customer VLAN) schedulers that can be used is 4076 (4 queues) or 2028 (8 queues) for the 10-port Gigabit Ethernet Packet Forwarding Engine and 4094 (4 queues) or 2046 (8 queues) for the 10 Gigabit Ethernet Packet Forwarding Engine.

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