Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!ames!pasteur!zabriskie!spp
From: spp@zabriskie.uucp (Steve Pope)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Serial TCP/IP - all the same?
Message-ID: <5189@pasteur.Berkeley.EDU>
Date: 23 Aug 88 18:38:06 GMT
References: <759@stcns3.stc.oz> <977@rlgvax.UUCP> <26204@think.UUCP>
Sender: news@pasteur.Berkeley.EDU
Reply-To: spp@zabriskie.UUCP (Steve Pope)
Organization: Postgres Research Group, UC Berkeley
Lines: 19

>The justifications you gave explain why there must be SOME escape
>convention (which should go without saying), but not why that
>particular one was chosen.  Why is this particular escape convention
>better than the old "double the special characters" convention or
>preceding a special character by the escape character?  
>
>Barry Margolin

Let me attempt an answer -- the SLIP frame-escape method has the
property that the only place a FRAME_END character appears in the
SLIP-encoded data is between packets, i.e. FRAME_END doesn't occur
within a packet even in escaped form.  Thus, transmitting SLIP's use
one or more FRAME_ENDs to clear an idle channel, and a receiving slip 
always knows to reset itself if it gets a FRAME_END.  This approach 
might have a slight robustness advantage.  Other escape conventions
might not provide the transmitting SLIP with a definite way of 
resetting the receiver if the receiver is in an unknown state.

steve pope (spp@berkeley.EDU)