dot1Q

詞語(yǔ)解釋

dot1Q是IEEE 802.1Q標(biāo)準(zhǔn)的簡(jiǎn)稱(chēng)，是一種用于解決以太網(wǎng)VLAN（虛擬局域網(wǎng)）分層的技術(shù)。IEEE 802.1Q協(xié)議在數(shù)據(jù)幀中添加一個(gè)4字節(jié)的標(biāo)簽，用于標(biāo)識(shí)VLAN，這4字節(jié)的標(biāo)簽稱(chēng)為802.1Q標(biāo)簽，也叫dot1Q標(biāo)簽，所以dot1Q也是IEEE 802.1Q標(biāo)準(zhǔn)的簡(jiǎn)稱(chēng)。 dot1Q標(biāo)簽的格式如下： | 優(yōu)先級(jí) | CFI | VLAN ID | | :----: | :-: | :-----: | | 3 bits | 1 bit | 12 bits | 其中，優(yōu)先級(jí)用于指定VLAN的優(yōu)先級(jí)，CFI（Canonical Format Indicator）用于標(biāo)識(shí)幀的格式，VLAN ID用于標(biāo)識(shí)VLAN的ID號(hào)。 dot1Q技術(shù)的應(yīng)用主要是用于以太網(wǎng)VLAN的分層，以太網(wǎng)VLAN的分層可以使網(wǎng)絡(luò)拓?fù)浣Y(jié)構(gòu)更加清晰，可以更好地控制網(wǎng)絡(luò)中的流量，減少網(wǎng)絡(luò)擁塞，提高網(wǎng)絡(luò)的安全性。 dot1Q技術(shù)的應(yīng)用非常廣泛，可以用于實(shí)現(xiàn)網(wǎng)絡(luò)的細(xì)分，實(shí)現(xiàn)網(wǎng)絡(luò)的隔離，可以把一個(gè)物理網(wǎng)絡(luò)分成多個(gè)虛擬網(wǎng)絡(luò)，每個(gè)虛擬網(wǎng)絡(luò)都有自己的VLAN ID，不同的VLAN ID可以實(shí)現(xiàn)不同網(wǎng)絡(luò)之間的隔離。 dot1Q技術(shù)還可以用于實(shí)現(xiàn)網(wǎng)絡(luò)的劃分，可以把一個(gè)物理網(wǎng)絡(luò)分成多個(gè)虛擬網(wǎng)絡(luò)，每個(gè)虛擬網(wǎng)絡(luò)都有自己的VLAN ID，不同的VLAN ID可以實(shí)現(xiàn)不同網(wǎng)絡(luò)之間的劃分。 dot1Q技術(shù)還可以用于實(shí)現(xiàn)網(wǎng)絡(luò)的負(fù)載均衡，可以把一個(gè)物理網(wǎng)絡(luò)分成多個(gè)虛擬網(wǎng)絡(luò)，每個(gè)虛擬網(wǎng)絡(luò)都有自己的VLAN ID，不同的VLAN ID可以實(shí)現(xiàn)不同網(wǎng)絡(luò)之間的負(fù)載均衡。總之，dot1Q技術(shù)是一種用于解決以太網(wǎng)VLAN（虛擬局域網(wǎng)）分層的技術(shù)，它可以用于實(shí)現(xiàn)網(wǎng)絡(luò)的細(xì)分、實(shí)現(xiàn)網(wǎng)絡(luò)的隔離、實(shí)現(xiàn)網(wǎng)絡(luò)的劃分、實(shí)現(xiàn)網(wǎng)絡(luò)的負(fù)載均衡等功能，是網(wǎng)絡(luò)管理中非常重要的技術(shù)。

   802.1Q- -

802.1Q

An IEEE standard for providing VLAN identification and quality of service (QoS) levels. Four bytes are added to an Ethernet frame, increasing the maximum frame size from 1518 to 1522 bytes. Three bits are used to allow eight priority levels (QoS) and 12 bits are used to identify up to 4096 VLANs. 802.1q is the IEEE specification for implementation of VLANs (Virtual Local Area Networks) in Layer 2 LAN switches, with emphasis on Ethernet. Similar to 802.1P, prioritization of traffic is accomplished through an additional four bytes of data in the frame header. Most data fields in this addition to the header are specific to VLAN operation. Also included is a field which provides the same 3-bit priority flag specified in 802.1P&＃039;s priority-mapping scheme. In addition to conventional data traffic, 802.1Q supports voice and video transmission through Ethernet switches. In short, the 802.1Q specification provides a 32-bit header for VLAN frame tagging. Each 802.1Q tag sits in an Ethernet frame between the source address field and the media access control (MAC) client type/length field. An important feature of 802.1Q is the ability to share multiple subnets across a high-speed link. This capability not only reduced the number of lower speed links needed for physical separation, but it also allowed for asymmetrical traffic management so that different speed links could be managed more easily. With IEEE 802.1p and 802.1Q, we saw the introduction of some important concepts that have been carried forward for further QoS (Quality of Service) development. These 802.1 features also can be mapped into higher layer protocols like IP and ATM.

An IEEE standard for providing VLAN identification and quality of service (QoS) levels. Four bytes are added to an Ethernet frame, increasing the maximum frame size from 1518 to 1522 bytes. Three bits are used to allow eight priority levels (QoS) and 12 bits are used to identify up to 4096 VLANs. 802.1q is the IEEE specification for implementation of VLANs (Virtual Local Area Networks) in Layer 2 LAN switches, with emphasis on Ethernet. Similar to 802.1P, prioritization of traffic is accomplished through an additional four bytes of data in the frame header. Most data fields in this addition to the header are specific to VLAN operation. Also included is a field which provides the same 3-bit priority flag specified in 802.1P&＃039;s priority-mapping scheme. In addition to conventional data traffic, 802.1Q supports voice and video transmission through Ethernet switches. In short, the 802.1Q specification provides a 32-bit header for VLAN frame tagging. Each 802.1Q tag sits in an Ethernet frame between the source address field and the media access control (MAC) client type/length field. An important feature of 802.1Q is the ability to share multiple subnets across a high-speed link. This capability not only reduced the number of lower speed links needed for physical separation, but it also allowed for asymmetrical traffic management so that different speed links could be managed more easily. With IEEE 802.1p and 802.1Q, we saw the introduction of some important concepts that have been carried forward for further QoS (Quality of Service) development. These 802.1 features also can be mapped into higher layer protocols like IP and ATM.

IEEE關(guān)于提供VLAN（虛擬局域網(wǎng)）識(shí)別和服務(wù)質(zhì)量（QoS）等級(jí)的標(biāo)準(zhǔn)。在以太網(wǎng)一個(gè)幀當(dāng)中加入4個(gè)字節(jié)，將一幀的最大長(zhǎng)度從1518字節(jié)提高到1522字節(jié)。4個(gè)字節(jié)中的3比特提供8種優(yōu)先等級(jí)，12比特用于最多識(shí)別4096種虛擬以太網(wǎng)。在第二層局域網(wǎng)交換，尤其是以太網(wǎng)中，802.1q成為IEEE虛擬以太網(wǎng)實(shí)施的技術(shù)規(guī)范。與802.1P相類(lèi)似，通信業(yè)務(wù)優(yōu)先權(quán)的確定是通過(guò)在幀標(biāo)題中額外加入一個(gè)4字節(jié)數(shù)據(jù)來(lái)完成的。在幀標(biāo)題中額外加入的大多數(shù)數(shù)據(jù)段僅限于虛擬以太網(wǎng)操作。幀標(biāo)題中還包括一個(gè)數(shù)據(jù)段，提供802.1P優(yōu)先權(quán)設(shè)定方案中給出的相同的3比特優(yōu)先標(biāo)記。除了一般的數(shù)據(jù)通信業(yè)務(wù)，802.1Q還通過(guò)以太網(wǎng)交換支持話音和視頻傳輸。簡(jiǎn)而言之，802.1Q技術(shù)規(guī)范為虛擬以太網(wǎng)幀標(biāo)簽提供一個(gè)32位標(biāo)題。每一個(gè)802.1Q標(biāo)簽位于以太網(wǎng)幀源地址字段和介質(zhì)訪問(wèn)控制（MAC）客戶類(lèi)型/長(zhǎng)度字段之間。802.1Q的一個(gè)重要特點(diǎn)是能夠通過(guò)一個(gè)高速鏈路共享多重子網(wǎng)。這一功能不僅減少了物理分離所需的低速鏈路數(shù)量，而且還允許進(jìn)行非對(duì)稱(chēng)通信業(yè)務(wù)管理，這樣能夠更容易對(duì)不同速度的鏈路進(jìn)行管理。通過(guò)IEEE 802.1p和802.1Q，我們可以看到一些已經(jīng)為服務(wù)質(zhì)量（QoS）進(jìn)一步開(kāi)發(fā)所采納的重要理念。這些802.1特性還可以被引入更高一層的協(xié)議，如IP和ATM。

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dot1Q

dot1Q

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