Twamp Active Test Session - ADTRAN Total Access 5000 Deployment Manual

If the sender and receiver addresses are set to 0, then the IP addresses used in the IP packet
that encapsulates the request‐session command shall be used in the test packets.
The timeout in the request‐session command shall be used by the session‐reflector as the
amount of time that the reflector must wait after receiving a stop‐sessions message. The
reflector shall keep reflecting packets until this amount of time passes. After this, the reflector
stops reflecting packets.
The type‐P descriptor was used to set the DSCP or PHB in the message from the sender. The
reflector should use these same values in the reflected packet.
The send schedule for test packets is NOT used in TWAMP. The sender should autonomously
decide the send schedule.

TWAMP Active Test Session

At this point, a switch is made from using TCP to using the UDP protocol. With TWAMP, the
session‐reflector sends out test packets in response to each test packet it receives.
The send schedule is not communicated to the session‐reflector. As such, there is no need for
a standardized computation of packet timing. The sender, though, should have its best
approximation of its real time placed into the departure timestamp field.
The TWAMP session‐reflector timestamps the received packet, copies the packet sequence
number in the corresponding reflected packet field, transmits the reflected packet, and ignores
packets received after the ʺstop‐session command + timeoutʺ.
The TWAMP test packet from the reflector consists of the following parameters:
• Sequence number ‐ is the sequence number of the test packet according to its arrival time
• Timestamp ‐ the session reflectorʹs transmit timestamp. Format is same as used in
• Error estimate ‐ the time error estimate in the session reflectorʹs transmit timestamp.
• Receive timestamp ‐ the session reflectorʹs receive timestamp. Format is same as used in
• ʺSender Sequence Number ‐ an exact copy of the sequence number from the session
• Sender Timestamp ‐ an exact copy of the timestamp from the session‐sender test packet
• Sender Error Estimate ‐ an exact copy of the error estimate from the session‐sender test
• Packet padding ‐ an exact copy of the packet padding from the session‐sender test packet
65K510DEP08-1A
at the session‐reflector. This value should start with zero and increment by one for each
subsequent packet. This is independent from the sequence number of the arriving
packets.
OWAMP.
Format is the same as used in OWAMP.
OWAMP. The difference between timestamp and receive timestamp is the amount of
time the packet was in transition at the session‐reflector. The error estimate associated
with timestamp also applies here.
sender test packet.
packet
Appendix D, TWAMP Provisioning - TWAMP Provisioning
D-3