非廣播-多路訪問網路（Non-Broadcast Multiple Access，NBMA）是OSPF通信協定中定義的四種網路類型的其中一種。 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路。其他OSPF定義的網路類型有：廣播網路、點對點網路和點對多點網路。OSPF鄰居狀態關係表示，只有Attempt會出現在NBMA協定中。
基本介紹
- 中文名：非廣播-多路訪問網路
- 外文名：Non-Broadcast Multiple Access,NBMA
- 簡介：OSPF定義的四種網路類型其中一種
- 套用：網路通訊
在配置NBMA的情況下，OSPF在同一時刻向每一個路由器只會傳送一個Hello包（Hello包周期性傳送，用於建立和確定路由間的鄰居關係）而不是進行多播。Hello包的傳送周期間隔的範圍為10s~30s，而判斷鄰居失效(dead)的時間範圍為40s~120s（4倍於Hello包傳送間隔）。
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.
