Filtering and route lookup in a switching device

1. A network device comprising:

an input interface to receive a plurality of packets; and

a load balancer to:

determine that a first packet, of the plurality of packets, is an out-of-profile packet,

set a packet loss priority (PLP) bit in a packet notification record to mark the first packet as out-of-profile, and

assign a first drop precedence, to the first packet, that differs from a second drop precedence associated with a second packet, of the plurality of packets, where the second packet is an in-profile packet.

2. The network device of claim 1 , where a difference between the first drop precedence and the second drop precedence is operative only when a state of congestion exists in a network downstream from the network device.

3. The network device of claim 1 , where the load balancer is to determine that the first packet is an out-of-profile packet when the first packet exceeds one or more subscriber or application requirements identified in a service level agreement that is associated with transmission of the first packet.

4. The network device of claim 1 , where the load balancer is to use a random early detection algorithm for queue management associated with an accepted packet based on the first drop precedence or the second drop precedence.

5. The network device of claim 1 , further comprising:

a packet classifier to separate the plurality of packets into policing equivalence classes (PECs) based on a set of rules defined by a plurality of parameters for each PEC.

6. The network device of claim 5 , where the packet classifier is to assign a particular PEC, of the PECs, to each of the plurality of packets meeting each of the plurality of parameters.

7. The network device of claim 5 , further comprising:

a flow monitor to determine an average bandwidth and a maximum burst associated with each of the PECs.

8. The network device of claim 7 , where the flow monitor is to determine that the first packet is an out-of-profile packet and the second packet is an in-profile packet.

9. The network device of claim 5 , where the PLP bit, set by the load balancer, causes a downstream router to select a particular random early detection drop profile.

10. The network device of claim 5 , where the first packet and the second packet belong to a particular transmission control protocol (TCP) session, and

where the load balancer is to assign the first packet and the second packet to a same transmission queue of the network device.

11. The network device of claim 10 , where assigning the first packet and the second packet to the same transmission queue preserves packet ordering of the first packet and the second packet downstream from the network device.

12. A method performed by a network device, the method comprising:

receiving, by one or more devices of the network device, a packet flow associated with a particular transmission control protocol (TCP) session;

marking, by one or more devices of the network device, a first packet, of the packet flow, as an out-of-profile packet by:

changing a drop precedence associated with the first packet, and

writing a packet loss priority bit to defer selection, of a particular random early detection drop profile, to another network device downstream of the network device; and

determining, by one or more devices of the network device, that a second packet of the packet flow is an in-profile packet.

13. The method of claim 12 , where marking the first packet further comprises:

setting Internet Protocol precedence bits in the first packet.

14. The method of claim 12 , where marking the first packet preserves an ordering, of the first packet and the second packet in the packet flow, in a transmission of the first packet and the second packet from the network device.

15. The method of claim 12 , further comprising:

monitoring output queues of the network device for congestion, where changing the drop precedence associated with the first packet causes the first packet to be discarded only when congestion is detected for a queue associated with the first packet.

16. The method of claim 12 , where changing the drop precedence associated with the first packet allows the first packet to be transmitted, when network congestion does not exist in a transmission path, even though the first packet exceeds at least one parameter defined by a service level agreement associated with the first packet.

17. The method of claim 12 , where changing a drop precedence associated with the first packet allows the first packet to be transmitted, when sufficient network bandwidth exists, even though the first packet exceeds at least one parameter defined by a service level agreement associated with the first packet.

18. A method performed by a network device, the method comprising:

receiving, by one or more devices of the network device, a packet flow associated with a particular transmission control protocol (TCP) session;

marking, by one or more devices of the network device, a first packet, of the packet flow, as an out-of-profile packet, where marking the first packet includes:

changing a drop precedence associated with the first packet, and

rewriting Internet Protocol precedence bits in the first packet, before transmitting the first packet, to instruct downstream routers to use a particular random early detection drop profile for the first packet; and

determining, by one or more devices of the network device, that a second packet of the packet flow is an in-profile packet.

19. The method of claim 18 , further comprising:

rewriting Internet Protocol precedence bits in the second packet, prior to transmitting the second packet, to instruct downstream routers to use a different particular random early detection drop profile for the second packet.