A Reverse Address Resolution Protocol RFC903 19991019 RARP
- Slides: 13
A Reverse Address Resolution Protocol RFC#903 指導老師 梁德昭 博士 報告者 曹元良 1999/10/19
RARP 簡介 n n n 位址反解析協定 屬於TCP/IP架構之連線服務Layer 連線服務 將硬體位置(hardware address)映射成IP位 address) 置(protocol address) 32位元IP address ARP RARP 48位元乙太網路Address
RARP封包格式 n 同ARP封包格式 (28 octets) n Field OPERATION specifies an RARP request (3) , or RARP response (4) 8 0 HARDWARE TYPE 6 H LEN 16 1 P LEN 4 24 0 x 0800 PROTOCOL TYPE OPERATION SENDER HA (octets 0 -3) SENDER HA (octets 4 -5) SENDER IP (octets 0 -1) SENDER IP (octets 2 -3) TARGET HA (octets 0 -1) TARGET HA (octets 2 -5) TARGET IP (octets 0 -3) 31 1 - 4
RARP Server 實作 n When the opcode is 3 (‘request reverse’) – – n Sender HA is 發送需求封包介面的硬體位址 Sender PA is undefined. Target HA is ff: ff: ff: ff Target PA is undefined. When the opcode is 4 (‘reply reverse’) – – Sender HA is the responder的硬體位址 Sender PA is the responder的IP address. Target HA is 發送需求封包介面的硬體位址 Target PA is 發送需求封包介面想要詢問的IP address
RARP Server 實作 (Cont. ) n RARP Server 收到request 時會比對該 Client的hardware address 在/etc/ethers中， 所對應的hostname – for example (/etc/ethers) – 2: 60: 8 c: 48: 84: 49 hazel – 0: 0: c 0: a 1: 5 e: 10 hickory – 0: 80: c 7: aa: a 8: 04 herbert – 8: 0: 5 a: 1 d: c 0: 7 e anderson
RARP Server 實作 (Cont. ) n RARP Server 再將對映出的hostname，比 對/etc/hosts檔或是DNS，已找出該 hostname對應的IP address，最後將IP address填入reply的packet 傳送給發送需 求的系統 – for example (/etc/hosts) – hazel 163. 13. 200. 40 – hickory 163. 13. 200. 32 – herbert 163. 13. 200. 193 – anderson 163. 13. 200. 222
The other way to assign IP address - BOOTP n n n BOOTP (啟動協定) RFC#951 使用UDP，通常與TFTP共同運作 BOOTP 的 request and reply封裝在UDP的 datagram 裡 包含IP address、Gataway address 、MAC address、server hostname、Boot file name… 可透過Router(BOOTP Server Proxy)傳遞， 解決了RARP在鏈結層廣播的缺點
The other way to assign IP address - DHCP n n n Dynamic Host Configuration Protocol DHCP 提供Client 來取得所有的網路設定 資訊，包括(IP address、subnet mask、 gateway etc. ) DHCP 提供Client 動態且快速地取得IP address。
