常見(jiàn)報(bào)文格式幀結(jié)構(gòu)

1、常見(jiàn)報(bào)文格式匯總1.1Ethernet數(shù)據(jù)包格式(RFC894)VLAN幀格式:EthernetII幀格式:目的MAC地址源MAC地址Type/LengthPayloadFCS(CRC)6bytes6bytes2bytes46-1500bytes4bytes1、目的Mac的最高字節(jié)的第8位如果為1,表明此包是以太網(wǎng)組播/廣播包，送給CPU處理。2、將目的Mac和本端口的MAC進(jìn)行比較，如果不一致就丟棄。3、獲取以太網(wǎng)類型字段lype/Length。0 x0800IP繼續(xù)進(jìn)行3層的IP包處理。0 x0806-ARP送給CPU處理。0 x8035-RARP送給CPU處理。0 x8863-*PPPo

2、Ediscoverystage送給CPU處理。0 x8864-PPPoEsessionstage繼續(xù)進(jìn)行PPP的2層包處理。0 x8100-VLAN其它值當(dāng)作未識(shí)別包類型而丟棄。4、Tag幀。Type：長(zhǎng)度為2字節(jié)，取值為0 x8100,表示此幀的類型為802.1QTag幀。PRI：長(zhǎng)度為3比特，可取07之間的值，表示幀的優(yōu)先級(jí)，值越大優(yōu)先級(jí)越高。該優(yōu)先級(jí)主要為QoS差分服務(wù)提供參考依據(jù)(COS)。VDD(VlanID):長(zhǎng)度12bits,可配置的VLANID取值范圍為14094。通常vlan0和vlan4095預(yù)留，vlanl為缺省vlan,一般用于網(wǎng)管。1、獲取PPP包類型字段。0 x00

3、21-IP0 x8021-IPCP0XC021-LCP0 xc023fPAP0 xc025LQR0 xc223-CHAP0 x8023-OSICP0 x0023-0SI其它值當(dāng)作未識(shí)別包類型而丟棄。繼續(xù)進(jìn)行3層的IP包處理送給CPU處理。送給CPU處理。送給CPU處理。送給CPU處理。送給CPU處理。送給CPU處理。送給CPU處理。1.2PPP數(shù)據(jù)包格式標(biāo)志7E地址FF控制03協(xié)議PayloadCRC標(biāo)志7ElbytelbytelbyteZbytes最多1500bytesZbyteslbyte13ARP報(bào)文格式(RFC826)以太網(wǎng)目的地址6bytes以太網(wǎng)源地址6bytes幀類型2bytes

4、硬件類型2bytes協(xié)議類型2bytES硬件地址長(zhǎng)度lbyt已s協(xié)議地址長(zhǎng)度lbytesOP2bytes發(fā)送端以太網(wǎng)地址6bytes/JA,*yli友送瑞IP地址4bytes目的以太網(wǎng)地址6bytES目的IP地址4by|-28字節(jié)ARP請(qǐng)求/應(yīng)答硬件類型：1表示以太網(wǎng)協(xié)議類型：和Ethernet數(shù)據(jù)幀中類型字段相同0P操作字段：1表示ARP請(qǐng)求2表示ARP應(yīng)答3表示RARP請(qǐng)求4表示RARP應(yīng)答1.4IP報(bào)文格式(RFC791)(20bytes)版本首部長(zhǎng)度dbits4bits服務(wù)類型TOS8bits總長(zhǎng)度16bits標(biāo)識(shí)Ident16bits標(biāo)志Flag3bits片偏移13bitsTTL8b

5、its協(xié)議號(hào)8bits首部檢驗(yàn)和16bits源IP地址32bits目的IP地址32bits選項(xiàng)(可選)TOS12345678PrecedenceDelayThroughoutReliablityIP首部20bytesICMP報(bào)文15PING報(bào)文格式(需IP封裝)(8bytes)IP首部ICMP報(bào)文20bytes類型(0或8)代碼(0)檢驗(yàn)和8bits8bits16bits標(biāo)志符Identi序號(hào)16bits16bits選項(xiàng)數(shù)據(jù)(可選)1.6TCP報(bào)文格式(需IP封裝)(20bytes)IP首部20bytesTCP20bytesTCP數(shù)據(jù)源端口號(hào)目的端口號(hào)16bits16bits序列號(hào)32bits

6、確認(rèn)序列號(hào)32bits首部長(zhǎng)度保留UAPRSF窗口大小4bits6bitsRCSSYI16bitsGKHTNN檢驗(yàn)和緊急指針16bits16bitsURG緊急指針有效ACK確認(rèn)序號(hào)有效PSH接收方應(yīng)該盡快將這個(gè)報(bào)文交給應(yīng)用層RST重建連接SYN同步序號(hào)用來(lái)發(fā)起一個(gè)連接FIN發(fā)端完成發(fā)送認(rèn)務(wù)1.7UDP報(bào)文格式（需IP封裝）（8bytes）IP首部20bytesUDP8bytesUDP數(shù)據(jù)源端1目的端口16bits16bitsUDP長(zhǎng)度UDP檢驗(yàn)和16bits16bits1.8MPLS報(bào)文格式MPLS報(bào)文類型：以太網(wǎng)中0 x8847（單播）0 x8848（組播）PPP類型上0 x8281（MPL

7、SCP）1.9ATM報(bào)文格式信元格式：UNIGFCVPIVPIVCIVCIVCIPTCLPHECData(653bytES)8421NNIVPIVPIVCIVCIVCIPTCLPHECData(653bytES)8421使用AAL-5frame封裝PDU的方法：RFC2684LLCAAL-5ATMPDU/LLC0 xFE-FE-03HLPID1octetAAL-5trailerPayload48octetsA0 x00NullNetworkLayer(notusedwithATMencapsulation)0 x80SNAP(aSNAPheaderfollowstoidentifythePDU

8、type)OxSl-ISOCLNPOx82-ISOESISOK83-ISOIS-IS0 x8EInternetIPv6朱OxCC-InternetIPv4*OkCF-PPPLLC/SNAPPDULLC0 xAA.AA.03SWAPAAL-5trailerOUI0 x00-00-00PID0 x08-00*Payloadi48octets!AAL-5ATM0 x00-00-00thePIDisanEthertypeOUISOWC22bridgedPDUisencapsulatedPID0 x08-00IPv4packetOxO8-06-ARP/InARPpacket0 x88-47MPLSpac

9、ketPossiblevaluesforbridmdPDUsare:0 x00-01802.3Ethernet(withpreservedFCS)0 x00-02802.4Ethernet(withpreservedFCS)0 x00-03802.5Ethernet(withpreservedFCS)0 x00-04FDDI(withpreservedFCS)0 x00-07802.3Ethernet(withoutpreservedFCS)0 x00-08802.4Ethernet(withoutpreservedFCS)0 x00-09802.5Ethernet(withoutpreser

10、vedFCS)0 x00-0AFDDI(withoutpreservedFCS)OxOO-OB802.6Ethernet(FCSpreservationindicatedbyCIBbit)OxOO-OE-BPDUOxOO-OFSourceRoutingBPDUVCMux(NULL)AAL-5幀格式:DataPadCPC8UUCPLengthCRC-32A、Payload48octetsoctets1-65,535ATMAAL-5CSbits0-471116321.10常見(jiàn)的協(xié)議類型協(xié)議名稱協(xié)議號(hào)ICMP1TCP6UDP17OSPF891.11MTU網(wǎng)絡(luò)MTU字節(jié)超通道6553516Mb/s令牌環(huán)(IBM)179144Mb/s令牌環(huán)(IEEE802.5)