660
C
HAPTER
61: Q
O
S C
ONFIGURATION
As shown in the figure above, each host supporting 802.1Q protocol adds a 4-bit
802.1Q tag header after the source address of the former Ethernet frame header
when sending packets.
The 4-bit 802.1Q tag header contains a 2-bit Tag Protocol Identifier (TPID) whose
value is 8100 and a 2-bit Tag Control Information (TCI). TPID is a new class defined
by IEEE to indicate a packet with an 802.1Q tag. Figure 172 describes the detailed
contents of an 802.1Q tag header.
Figure 172
802.1Q tag headers
In the figure above, the 3-bit priority field in TCI is 802.1p priority in the range of 0
to 7. The 3 bits specify the precedence of the frame. 8 classes of precedence are
used to determine which packet is sent preferentially when the switch is
congested.
The precedence is called 802.1p priority because the related applications of this
precedence are defined in detail in the 802.1p specification.
3
Local precedence
Local precedence is the precedence of an outbound queue on a port of the switch.
It is in the range of 0 to 7. Each outbound queue has its own local precedence.
Priority of Protocol
Packets
Protocol packets carry their own priority. You can perform QoS actions on protocol
packets by setting their priorities.
Priority Remark
The priority remark function is to use ACL rules in traffic identification and remark
the priority for the packets matching with the ACL rules.
Packet Filter
Packet filter means filtering the service traffic. For example, in the operation of
dropping packets, the service traffic matching with the traffic classification rule is
Table 530
Description on 802.1p priority
CoS (decimal)
CoS (binary) Description
0 000
best-effort
1 001
background
2 010
spare
3 011
excellent-effort
4 100
controlled-load
5 101
video
6 110
voice
7 111
network-management
Byte 1
TPID (Tag Protocol Identifier)
Priority
VLAN ID
Byte 2
Byte 3
Byte 4
0
0 0 0
0
0 0
0
1
0
0 0
0 1
0 0
3 2
7
4
1 0
6 5
3 2
7
4
1 0
6 5
3 2
7
4
1 0
6 5
3 2
7
4
1 0
6 5
cfi
TCI (Tag Control Information)
Содержание Switch 7754
Страница 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Страница 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Страница 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Страница 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Страница 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Страница 126: ...126 CHAPTER 14 SUPER VLAN ...
Страница 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Страница 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Страница 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Страница 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Страница 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Страница 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Страница 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Страница 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Страница 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Страница 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Страница 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Страница 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Страница 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Страница 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Страница 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Страница 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Страница 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Страница 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Страница 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Страница 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Страница 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Страница 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Страница 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Страница 718: ...718 CHAPTER 63 CLUSTER ...
Страница 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Страница 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Страница 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Страница 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Страница 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Страница 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Страница 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Страница 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Страница 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Страница 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...