I guess my understaning is limited, so I'm interested in hearing the results of this also.
I've seen the flags left off of various protocols before, but I assumed they were simply being sloppy. I can't understand how any protocol could be transmitted without any flag/preamble at all. scott ""Priscilla Oppenheimer"" wrote in message news:[EMAIL PROTECTED] > s vermill wrote: > >> Cisco HDLC just > > > has this: > > > > > > Address - 1 byte > > > Control - 1 bytes > > > Protocol - 2 bytes > > > > > > It's curious that Cisco HDLC doesn't have the flag fields. > > > Maybe they just aren't mentioned in the only document I have > > on > > > Cisco HDLC?? The 0x7E flag is present in most derivatives of > > > HDLC, including SDLC. It's used to signal the beginning and > > end > > > of a frame and can be sent multiple times and during silence > > to > > > keep the link up, from what I remember. > > > > Every HDLC derivative I've ever worked with uses the ol' 7E7E > > idle pattern. Next time I have an o'scope out, I'll take a > > peek at a Cisco HDLC encapsulated link. > > Oh, yes, do please get your scope out! :-) I'm really curious about Cisco > HDLC and expect the doc I have doesn't tell the whole story. > > I wonder if a scope would strip out the flags, sort of like an Ethernet > analyzer doesn't show the preamble, though. > > THANKS > > Priscilla > > > > > >Howard would know for > > > sure, but I thought it was necessary in order for the other > > end > > > to synch up. > > > > Than's the general idea. You don't want to wait until there's > > data to be transferred before declaring protocol down. Loss > > of, say, three consecutive idles can trigger a protocol down > > condition. Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64736&t=64362 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
