如果分配给子网Y1的网络号为216.28.64.0，分配给子网Y2分配的网络号为216.28.16.0～216.28.31.0。如果连接这两个子网的路由器收到一个目标地址为11011000.00011100.01000011.00100001的IP数据报，则该数据报将(65)。

(143)

(144)

(142)

SDLC was invented by IBM to replace the older Bisynchronous protocol for wide area connections between IBM equipment. A varietion of the(71)protocol called NRM is essentially the same as SDLC.

 SDLC is(72)protocol like HDLC, Frame. Relay or X.25.An SDLC network is made up of(73)that controls all communications, and(74).It is capable of(75).operation, but almost all practical applications are strictly half duplex.

(141)

(139)

(137)

(138)

(136)

Frame. Relay is simplified form. of(66), similar in principle to(67), in which synchronous, frames of data are routed to different destinations depending on header information.

 Packets are routed throught one or more Virtual Circuits known as(68). Most Virtual Circuits are(69), which means that the network provider sets up all DLCI connections at subscription time.(70)are also part of the Frame. Relay specification. They privide a link that only lasts only as long as the session.