Local and metropolitan area networks— Virtual Bridged Local Area Networks Amendment 12: Forwarding and Queuing Enhancements for Time-Sensitive Streams
|Publication Date:||9 December 2009|
Insert the following text at the end of 1.1, renumbering the list items and NOTEs as necessary:
This standard allows bridges to provide performance guarantees for time-sensitive (i.e., bounded latency and latency variation) loss-sensitive real-time audio video (AV) data stream transmission (AV traffic). It specifies priority regeneration and controlled bandwidth queue draining algorithms. Virtual Local Area Network (VLAN) tag encoded priority values are allocated, in aggregate, to segregate frames among queues that support AV traffic and queues that support non-AV traffic, allowing simultaneous support of both AV traffic and other bridged traffic over and between wired and wireless Local Area Networks (LANs). To this end, it.
a) Defines status parameters that allow the boundaries of a Stream Reservation Protocol (SRP-see Clause 351) domain (6.6.4) to be identified and maintained
b) Specifies how the priority information in frames received at SRP domain boundary ports is regenerated
NOTE 1-The priorities in frames transmitted from outside an SRP domain to a Bridge inside an SRP domain are remapped in order to ensure that traffic that is not associated with a reservation does not disrupt traffic that is associated with a reservation. Hence, traffic entering an SRP domain that uses priority code point values associated with reserved traffic classes will be re-mapped to priority code point values that are not associated with reserved traffic classes.2
c) Specifies how priority information is used to determine the traffic classes to be used for timesensitive streams
d) Defines a credit-based shaper algorithm to shape traffic in accordance with stream reservations
NOTE 2-The credit-based shaper algorithm operates on the outbound queues; the mechanisms specified for the support of time-sensitive AV traffic do not involve any form of ingress metering or policing.
1Clause 35 is defined in IEEE P802.1QatTM [B31] that was a draft standard under development at the time of publication.
2Notes in text, tables, and figures are given for information only and do not contain requirements needed to implement the standard.