Notes - LPTS (IOS-XR)
Last updated
Last updated
LPTS (Local Packet Transport Service) is a process running on each line card that is responsible for transporting “for_us” traffic to the correct destination (typically either the linecard CPU or RP).
LPTS uses a pre internal FIB table (pifib) table that determines where to send each flow. For example, ARP, BFD, ICMP, and OAM traffic is sent to the line card CPU. LDP, BGP, OSPF, etc. traffic is sent to the RP CPU. LPTS also plays a role in NSR by punting traffic to both RPs at the same time.
LPTS comes with default policing values so that traffic cannot overwhelm the CPUs on the router. We can tune these individually per flow type using:
The values can be confirmed using show lpts pifib hardware police
Let’s examine the default values for LDP traffic:
LDP has four different flow types: TCP for a known peer, a configured peer, and the default TCP rate, as well as a UDP rate. A known peer is an established TCP session. A configured peer is a TCP session that is not established, but a flow that matches a configured peer.
We can set these rates individually using:
The average rate type changes to global because we configured these rates globally in the CLI.
Remember that only control plane traffic is subjected to these policing values, because only for_us traffic will be inspected by the LPTS. Data plane traffic passes through the interfaces without inspection from LPTS.
