IEEE P802.1 CMde/D2.1:2020 pdf download.Draft Standard for Local and metropolitan area networks-Time-Sensitive Networking for Fronthaul Amendment: Enhancements to Fronthaul Profiles to Support New Fronthaul Interface,Synchronization, and Syntonization Standards.
IEEE P802.1 CMde/D2.1 defines profiles that select features, options. configurations, defaults, protocols and procedures of bridges, stations, and LANs that are necessary to build networks that are capable of transporting fronthaul streams, which are time-sensitive.
NOTE—Stream and flow are used as synonyms in this document.
1.2 Purpose
The purpose of this standard is to specify defaults and profiles that enable the transport of time-sensitive
fronthaul streams in Ethernet bridged networks.
1.3 Introduction
Fronthaul provides connectivity between functional blocks of a cellular base station (BS). The fronthaul flows between these functional blocks have stringent quality of service requirements. The successful support of fronthaul flows in a bridged network requires the selection of specific features and options that are specified in a number of different standards, some developed by IEEE Project 802®, and others (in particular, those that relate to functionality in OSI layer 3 and above; ISO/IEC 7498:1994 [B11]) developed by other standards organizations.
Change the hyphen list as shown:
— Virtual Local Area Network (VLAN) Bridge specification in IEEE Std X02.IQTM.
— MAC service specifications in IEEE Std 802.1ACTM.
— MAC/PHY technology specifications in IEEE Std 802.3.
— Interspersing express traffic specification in IEEE Std 802.3brTM.
—Frame preemption specification in IEEE Std 8O2.1Q.
— Time synchronization and Precision Time Protocol (PTP) specifications in IEEE Std 1588TM.
— Telecom profile specification in ITU-T G.8275.1, which is based on IEEE Std l588.
— Synchronous Ethernet specification in ITU-T G.8261, G.8262, G.8262.I. and G.8264.
7.3 Frame preemption
Frame preemption is the suspension 01 the transmission 01 a preemptabie Irame to allow one or more express frames to be transmitted before the transmission of the preemptable frame is resumed. IEEE Std 802.3br specifies the MAC Merge sublayer. which supports interspersing express traffic with preemptable traffic. The MAC Merge sublayer supports two ways to hold the transmission of preemptable traffic in the presence of express traffic (until subsequent release): the MAC Merge sublayer can preempt (interrupt) preemptable traffic being currently transmitted, and the MAC Merge sublayer can prevent starting the transmission of preemptable traffic (see 99.1 of IEEE Std 802.3br-2O16). The IEEE 802.IQ bridge forwarding process optionally supports frame preemption. The benefits provided by frame preemption decrease as the data rate of a bridge port increases.
Frame preemption takes some time; the express frame cannot be transmitted immediately. If frame preemption is possible, then the express frame can be transmitted only after the transmission of the current fragment of the preemptable framc including the Cyclic Redundancy Check (CRC) of the frame and the Inter Packet Gap (IPG). Preemption occurs only if at least 60 octets of the preemptable frame have been transmitted and at least 64 octets (including the frame CRC) remain to be transmitted. The earliest starting position of preemption is controlled by the addFragSize variable, which is a 2-bit integer value indicating, in units of 64 octets, the minimum number of octets over 64 octets required in non-final fragments by the receiver (sec 99.4.4 and 79.3.7 of IEEE Std 8O2.3br-20l). That is, the worst case is 1240 bit times when addFragSizc =0, which is used for the worst-case calculations in this document.
If PTP messages are carried by express frames or by frames that are smaller than 124 octets, then they are not preempted.IEEE P802.1 CMde/D2.1 pdf download.