Common use of Network Path Measurement Clause in Contracts

Network Path Measurement. To enable accurate measurements of the network path between peers, TIP specifies the RTCP APP packet extension “ECHO”. This packet is similar in function to an ICMP ECHO, but has some significant advantages. By performing the echo function in-band, the same network path and most importantly the same QoS is applied to the measurement packets as the media packets. Also ICMP ECHO packets are frequently filtered by intermediate systems such as firewalls. The in-band RTCP messages are less likely to suffer this fate. TIP devices can use these RTCP APP ECHO packets to measure network path latency. Indirectly this also serves as aliveness test of the network and the remote peer. The current best practice is to transmit an ECHO packet once per second during a call on each UDP channel, and measure averages over 10 second periods. RTCP APP ECHO packet format +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V=2|P|subtype=4| PT=APP=204 | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | name=xcts | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit NTP timestamp, most significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit NTP timestamp, least significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive NTP timestamp, most significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive NTP timestamp, least significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RTCP APP Packet field definitions should follow [4] and: subtype: 5 bits MUST be set to ‘4’ to designate the ECHO packet type.

Network Path Measurement. To enable accurate measurements of the network path between peers, TIP specifies the RTCP APP packet extension “ECHO”. This packet is similar in function to an ICMP ECHO, but has some significant advantages. By performing the echo function in-band, the same network path and most importantly the same QoS is are applied to the measurement packets as and the media packets. Also ICMP ECHO packets are frequently filtered by intermediate systems such as firewalls. The firewalls and the in-band RTCP messages are less likely to suffer this fatebe filtered. . TIP devices can use these RTCP APP ECHO packets to measure network path latency. Indirectly this also serves as aliveness provides a keepalive test of for the network and the remote peer. The current best practice is to transmit an ECHO packet once per second during a call on each UDP channel, and measure averages over 10 second periods. RTCP APP ECHO packet format +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |V=2|P|subtype=4| PT=APP=204 | length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SSRC | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | name=xcts | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit NTP timestamp, most significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Transmit NTP timestamp, least significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive NTP timestamp, most significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Receive NTP timestamp, least significant word | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ RTCP APP Packet field definitions should follow [4] and: subtype: 5 bits MUST be set to ‘4’ to designate the ECHO packet type.