Supported SKUs for Audio Video Bridging All Cisco Catalyst 9300 Series Switches support PTP or AVB on all ports (both uplink and downlink ports) except as listed below: • C9300-48UXM: Supported on 1 to 16 downlink ports only and all uplink ports. • C9300-48UN: Supported on 1 to 36 downlink ports only and all uplink ports. Information About Generalized Precision Time Protocol Generalized Precision Time Protocol (gPTP) is an IEEE 802.1AS standard, which provides a mechanism to synchronize clocks of the bridges and end point devices in an AVB network. It defines the mechanism to elect the grandmaster clock (BMCA) among the time-aware bridges and talker and listener.
The grandmaster is the root of the timing hierarchy that gets established in the time-aware network and distributes time to nodes below to enable synchronization. Time synchronization also requires determining the link delay and switch delays in the network nodes. A gPTP switch is an IEEE 1588 boundary clock, which also determines the link delay using the peer-to-peer delay mechanism. The delays computed are included in the correction field of the PTP messages and relayed to the end-points. The talker and listener use this gPTP time as a shared clock reference, which is used to relay and recover the media clock. gPTP currently defines only domain 0, which is what the switch supports.
The peer to peer delay mechanism runs on STP blocked ports as well. No other PTP messages are sent over blocked ports. In a PTP domain, Best Master Clock (BMC) algorithm organizes Clocks and Ports into a hierarchical fashion, which includes clocks and port states: Clocks • Grandmaster (GM/GMC) • Boundary Clock (BC) Port States • Master (M) • Slave (S) • Passive (P) Information about Multiple Stream Reservation Protocol Multiple Stream Reservation Protocol (MSRP) provides a mechanism for end stations to reserve network resources that guarantee the transmission and reception of data streams across a network with the requested QoS.
It is one of the core protocols that are required on an AVB device (talker, listener, and switches). It allows talkers to advertise streams across a network of AVB switches and listeners to register for receiving the streams. MSRP is the key software protocol module for supporting AVB. It enables stream establishment and teardown. It interfaces with gPTP to update the latency information for the streams. It interfaces with the QoS module to setup the hardware resources that would guarantee requested bandwidth for the streams. It also provides the QoS shaping parameters that are required for the credit based shaper.
Configuring Audio Video Bridging Supported SKUs for Audio Video Bridging Configuring Audio Video Bridging 4