Operation Manual – QoSH3C S7500 Series Ethernet Switches Chapter 1 QoS Configuration1-5Byte 1TPID (Tag Protocol Identifier) TCI (Tag Control InfoPriority cfi Vrmation)LAN IDByte 2 Byte 3 Byte 400 0 00 0 000 0 0 00 00 03 27 4 1 06 5 3 27 4 1 06 5 3 27 4 1 06 5 3 27 4 1 06 5rFigure 1-3 The contents of an 802.1Q tag headeIn the figure above, the 3-bit priority field in the TCI filed is 802.1p priority in the range of0 to 7.The 3 bits specify the precedence of the frame.8 classes of precedence are usedto determine which frame is to be sent preferentially when congestion occurs on theswitch.Table 1-3 Description on 802.1p priorityCoS precedence(decimal)CoS precedence(binary) Description0 000 best-effort1 001 background2 010 spare3 011 excellent-effort4 100 controlled-load5 101 video6 110 voice7 111 network-managementThe precedence is called 802.1p priority because the related applications of thisprecedence are defined in detail in the 802.1p specification.3) Local precedenceLocal precedence is the precedence of an outbound queue on a port of the switch. It isin the range of 0 to 7. Each outbound queue has its corresponding local precedence.1.1.4 Priority of Protocol PacketsEach protocol packet carries its own priority. You can perform QoS actions for protocolpackets by setting their priorities.1.1.5 Priority MarkingThe priority marking feature is to use ACL rules for traffic identification and remark thepriority for the packets matching the ACL rules.
