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Junos OS Syntax

Junos OS Evolved Syntax

Junos OS Hierarchy Level

Junos OS Evolved Hierarchy Level


Enable the Two-Way Active Measurement Protocol (TWAMP) server for light control on the UDP port that reflects the test packets. If you want the default IANA port for TWAMP (862), you do not need to configure the port option. To complete the configuration for light control, you also need to configure the control-type light statement at either the Junos OS [edit services rpm twamp client control-connection control-connection-name] hierarchy level or the Junos OS Evolved [edit services monitoring twamp client control-connection control-connection-name] hierarchy level.

You configure the light statement because you want a stateless version of TWAMP where test parameters are predefined instead of negotiated. All test packets received by the server on a test port are reflected back and forgotten right away. If you want to have a stateful TWAMP server for Junos OS Evolved, you should configure the managed statement at the [edit services monitoring twamp server] hierarchy level instead. For Junos OS, if you want to have a stateful TWAMP server, do not configure the light statement for the TWAMP server, because managed mode is the default. Because TWAMP light servers are stateless, information about them is not included in the output of the show services rpm twamp server connection (Junos OS) or the show services monitoring twamp server control-info (Junos OS Evolved) operational mode command; only information about managed servers is included.


offload-type (none | inline-timestamp | pfe-timestamp)

Enable timestamping of TWAMP probe messages in the Routing Engine, inline in the hardware, or Packet Forwarding Engine host processor. Prior to Junos OS Evolved 22.3R1, for IPv6 traffic, you must configure none, as only Routing Engine timestamping is supported. Starting in Junos OS Evolved 22.3R1, you can configure the pfe-timestamping option for IPv6 traffic.

  • none—Timestamping in the Routing Engine.

  • inline-timestamping—Timestamping inline, in the hardware at the generator, and reflection in the hardware at the reflector. When this option is configured for an ACX router, the ACX can act as either a server or client, but not both. Also for an ACX router, inline-timestamping is not supported on PM50 ports if FEC74 is enabled on that port. You can configure the inline-timestamping option for up to 256 test sessions.

  • pfe-timestamping—Timestamping in the Packet Forwarding Engine.

  • Default: pfe-timestamp

port number

Specify the UDP port that reflects the TWAMP test packets.

  • Range: You can specify any port from 862 through 65535.

  • Default: 862 (IANA port for TWAMP)

stateful-sequence cache-size number-of-entries

Configure stateful sequencing to generate the sequence number in the reflected payload independently, instead of copying the sequence number from the client frame. With independently generated sequence numbers, the software is able to detect in which direction drops have occurred. Unidirectional drop values are inferred minimum values, and are not guaranteed to be exact. The software relies on an actual packet to be reflected successfully to be able to compute differences. If such a packet does not occur, then the software is unable to tell whether the drop happened in the egress or ingress direction.

Because TWAMP light (just like STAMP) is by nature stateless, stateful sequencing can only be done using a cache system. Currently, the software uses a FIFO system to manage the cache; the entry without an update for the longest time is the first one out to make space for a new entry.

  • Range:1000-1000000 entries (number of client sessions kept in the cache)

  • Default: 10000 entries

Required Privilege Level

system—To view this statement in the configuration.

system-control—To add this statement to the configuration.

Release Information

Statement introduced in Junos OS Evolved 20.3R1.

Support added in Junos OS Release 21.1R1.

offload-type and stateful-sequence options introduced in Junos OS Evolved Release 23.4R1.