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NBMA
鎖定
非廣播-多路訪問網絡（Non-Broadcast Multiple Access，NBMA）是OSPF通信協議中定義的四種網絡類型的其中一種。 NBMA用來描述如X.25和幀中繼這類本身並不具有支持廣播和多播能力的多路訪問網絡。其他OSPF定義的網絡類型有：廣播網絡、點對點網絡和點對多點網絡。OSPF鄰居狀態關係表示，只有Attempt會出現在NBMA協議中。
- 中文名
- 非廣播-多路訪問網絡
- 外文名
- Non-Broadcast Multiple Access,NBMA
- 簡 介
- OSPF定義的四種網絡類型其中一種
- 應 用
- 網絡通訊
在配置NBMA的情況下，OSPF在同一時刻向每一個路由器只會發送一個Hello包（Hello包週期性發送，用於建立和確定路由間的鄰居關係）而不是進行多播。Hello包的發送週期間隔的範圍為10s~30s，而判斷鄰居失效(dead)的時間範圍為40s~120s（4倍於Hello包發送間隔）。
NBMA (non-broadcast multiple access)is one of four network types in the OSPF (Open Shortest Path First) communications protocol. NBMA is used to accurately model X.25 and frame relay environments in multiple-access networks where there are no intrinsic broadcast and multicast capabilities. The other OSPF network types are: broadcast, point-to-point, and point-to-multipoint. In an NBMA configuration, OSPF sends HELLO packets (packets sent periodically to establish and confirm neighbor relationships between routers) to each router one at a time rather than multicasting them. The HELLO timer (which tells the router how often to send HELLO packets) is extended from 10 to 30 seconds and the dead router timer (which tells the router how long to wait before it decides that a neighboring router is not functioning) is extended from 40 to 120 seconds.
