nanog mailing list archives

Re: [nsp] Cisco DS3 Questions..


From: Jesper Skriver <jesper () skriver dk>
Date: Fri, 22 Feb 2002 20:45:31 +0100


On Fri, Feb 22, 2002 at 11:27:16AM -0600, Stephen Sprunk wrote:

Thus spake "Gyorfy, Shawn" <sgyorfy () elinkny com>
Since the topic exploded, what are your opinions on encapsulation of
leased
line DS3s.  We currently use Frame Relay for out Point to Point DS3
connections.  Personally, I don't know why we use FR as our encapsulation,
and so the question to all.  If you are running Cisco to Cisco, would it
be
wise to run HDLC or PPP?  Our DS3s' here are hardly maxed out, 15% or so,
so
I'm not complaining about the few extra bits I can squeeze out them but
maybe that 15% can shrink to 10% with less overhead.  Opinions or examples
of life appreciated.

As you're finding out, this is largely a religious issue.  There are no
significant differences in overhead between HDLC, PPP, and FR.  Any
performance difference can be more easily attributed to vendor
implementation than to protocol efficiency.

In practice, HDLC is the dominant encapsulation, primarily since it's
Cisco's default.  If for no other reason, you should use HDLC because almost
everyone expects you to be using it.  PPP is obviously present in non-Cisco
shops, and anywhere MLPPP or LFI is needed.  FR is only used as a p-t-p
encapsulation in certain cases that require it; almost nobody uses it
without a good reason.

We allways use PPP, the primary reasons being:

- The line protocol goes down when the line is looped.
- It's easier to debug than HDLC

/Jesper

-- 
Jesper Skriver, jesper(at)skriver(dot)dk  -  CCIE #5456
Work:    Network manager   @ AS3292 (Tele Danmark DataNetworks)
Private: FreeBSD committer @ AS2109 (A much smaller network ;-)

One Unix to rule them all, One Resolver to find them,
One IP to bring them all and in the zone to bind them.


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