IPv6是下一代IP协议，其基本报头中的(61)字段指明了一个特定的信源向某个特定信宿发送的分组序列，各个中间路由器要对该分组序列进行特殊处理以满足应用程序的特殊传输需求。

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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.

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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.