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=64657&t=64362 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
