LPTS (Local Packet Transport Services)
The IOS-XR product line does not use CoPP, instead it uses LPTS (Local Packet Transport Services) to preform policing of control plane traffic.
LPTS is a process on each line card which is responsible for punting traffic destined to the router to the line card CPU (such as ARP, ICMP, BFD, OAM) or punting traffic to the RP CPU (such as LDP, PIM, BGP, etc). LPTS even plays a role in supporting NSR by punting traffic to both RPs.
LPTS runs by default and comes with default policing values. Generally you should not need to adjust these, and if you do so, you should configure your own values with caution.
LPTS has pre-defined flow rates that are very granular. For example, there is a separate police rate for BGP unestablished traffic, BGP traffic for a configured neighbor, and BGP traffic for a neighbor in an Established state.
On an XRv9000 you can see this with the following command:
RP/0/RP0/CPU0:XR3#show lpts pifib hardware police location 0/0/CPU0 | in "flow_type|BGP|---"
Mon Nov 7 20:05:34.458 UTC
-------------------- -------- ------------ --------------- ---------- ----- -------------- ------------ ----------- --------- ----------
flow_type priority sw_police_id hw_policer_addr Cur. Rate burst static_avgrate avgrate_type AggrAccepts AggrDrops TOS Value
-------------------- -------- ------------ --------------- ---------- ----- -------------- ------------ ----------- --------- ----------
BGP-known high 6 219 2500 1250 2500 Static 0 0 01234567
BGP-cfg-peer medium 7 220 2000 1000 2000 Static 0 0 01234567
BGP-default low 8 221 1500 750 1500 Static 0 0 01234567Known BGP peers can transmit at 2500 pps, configured peers that are not yet Established at 2000 pps, and default 179 traffic at 1500 pps.
Lab
I’ve swapped R3 for an XR9000v, and re-used the CoPP lab topology:
Changing the police rate values on XR is quite simple. You do not need to use ACLs, because LPTS handles classification of the traffic. Instead you simply identify the protocol and set a rate limit in packets-per-second (pps). Let’s change ICMP to 3 pps.
lpts pifib hardware police
flow icmp local rate 3When we ping R3 from R1, only three packets get through per second.
R1#ping 3.3.3.3 repeat 28
Type escape sequence to abort.
Sending 28, 100-byte ICMP Echos to 3.3.3.3, timeout is 2 seconds:
!!!.!!!.!!!.!!!.!!!.!!!.!!!.
Success rate is 75 percent (21/28), round-trip min/avg/max = 3/7/47 msOn the XR router we can verify statistics using the following command:
RP/0/RP0/CPU0:XR3#show lpts pifib hardware police location 0/0/CPU0 | in "flow_type|ICMP|---"
Mon Nov 7 20:16:31.356 UTC
-------------------- -------- ------------ --------------- ---------- ----- -------------- ------------ ----------- --------- ----------
flow_type priority sw_police_id hw_policer_addr Cur. Rate burst static_avgrate avgrate_type AggrAccepts AggrDrops TOS Value
-------------------- -------- ------------ --------------- ---------- ----- -------------- ------------ ----------- --------- ----------
ICMP-local medium 12 225 3 750 1500 Global 21 7 01234567
ICMP-control high 40 253 1000 500 1000 Static 0 0 01234567
ICMP-app low 52 265 1500 750 1500 Static 0 0 01234567
ICMP-default low 53 266 1500 750 1500 Static 0 0 01234567
ICMP-app-default low 90 303 1500 750 1500 Static 0 0 01234567Global under avgrate_type indicates that this value was configured globally using the CLI
The Cur. Rate does not match the static_avgrate for the ICMP-local flow that we changed. The static_avgrate is the default rate. When you globally configure a new rate, it overrides the static (default) rate.
AggrAccepts are packets which matched the flow and were not dropped
AggrDrops are packets which matched the flow and exceeded the pps policier, and were therefore dropped
To clear statistics we can use the following command:
clear lpts pifib hardware statistics location 0/0/CPU0Further Reading
https://xrdocs.io/ncs5500/tutorials/introduction-to-ncs55xx-and-ncs5xx-lpts/
https://www.reddit.com/r/Cisco/comments/lhmx1w/asr9k_dropping_pings_to_interfaces/
Interesting discussion about issue caused by LPTS
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