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.
Thanks
shawn
There's no reason to use frame-relay encapsulation unless you're actually going
through a frame network.
For point-to-point circuits, from Cisco to Cisco, HDLC is the best choice, but
it's proprietary (although Juniper has a Cisco HDLC mode). For
anything else, I'd recommend PPP.
-C
There's no reason to use frame-relay encapsulation unless you're actually going
through a frame network.
For point-to-point circuits, from Cisco to Cisco, HDLC is the best choice, but
it's proprietary (although Juniper has a Cisco HDLC mode). For
anything else, I'd recommend PPP.
From what I recall, once LCP is established, PPP and HDLC have about the
same amount of overhead. I could be wrong. PPP's finite-state machine is
substantially more complex than HDLC's to account for PPP multilink,
encryption, etc, but that would mostly be in the part of the machine that
gets executed prior to or as a part of establishing LCP.
The PPP vs HDLC topic flares up every once in awhile on comp.dcom.sys.cisco.
A Google search should turn up lots of reading on the subject.
jms
If you are running frame-relay now, unless you have an asymmetrical
configuration (which cisco CAN do) where one end is configured to look
like a f/r switch, you probably have your carrier's f/r switch in the
middle.
Whoever configured it that way in the router did it because that is the
king of circuit that was ordered.
It may well be that there was a much better price especially if there
was a lot of mileage and the cir was set low.
f/r can look good sometimes.
If it is a real point to point t3, don't use f/r
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.
S
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.
I'd second that reasoning. FWIW, MLPPP is one of the main reasons that
PPP seems to get used now, the ability to bond multiple DS1s together, or
even multiple DS3s, potentially, although there's little market force to
do that. The main reason for running frame relay on a single
point-to-point would probably be preservation of VLANs across a bridged
link in a controlled way. Not saying that's a particularly good use, just
that that's the most common reason I've seen it deployed on otherwise
simple point-to-points. The idea behind frame relay is that it gives you
a multipoint layer-2 protocol to use on a more complicated network of
circuits.
-Bill
[Replies redirected to cisco-nsp, where this is slightly more on-topic]
* ssprunk@cisco.com (Stephen Sprunk) [Fri 22 Feb 2002, 18:49 CET]:
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.
Also, PPP supports authentication and you have to be careful with
specifying that it's not needed for serial links towards customers,
otherwise you suddenly find yourself or your customer locked out;
with HDLC the risks of this are lower.
Of course, you only run into this sort of trouble if your provisioning
system isn't too well-thought-out, IMNSHO, or if you decide to move from
basic plain password authentication to something TACACS+-based...
Regards,
-- Niels.
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
We allways use PPP, the primary reasons being:
- The line protocol goes down when the line is looped.
int Serial0
encap hdlc
down-when-looped
- It's easier to debug than HDLC
/Jesper
/-----------------------+-----------------------\
Mike Joseph | Netaxs, Inc. |
Network Engineering | ~~~~~~~~~~~~ |
~~~~~~~~~~~~~~~~~~~ | (610)825-9800 |
mjoseph@netaxs.com | www.netaxs.com |
\-----------------------+-----------------------/
> We allways use PPP, the primary reasons being:
>
> - The line protocol goes down when the line is looped.
int Serial0
encap hdlc
down-when-looped
I know, but that needs to be configued in both ends, and as it's not the
default, it's likely not to be configured on the CPE device ...
And when using static routing, it's very nice that the line protocol
goes down.
> - It's easier to debug than HDLC
>
> /Jesper
/Jesper
The customer will never get the link up if he/she doesn't
configure PPP, he/she will get link up if the link is configured
for HDLC but they havn't configured 'down-when-looped'
/Jesper
Jesper Skriver <jesper@skriver.dk> writes:
Jesper Skriver <jesper@skriver.dk> writes:
> >
> >
> > > > int Serial0
> > > > encap hdlc
> > > > down-when-looped
> > >
> > >I know, but that needs to be configued in both ends, and as it's not the
> > >default, it's likely not to be configured on the CPE device ...
> >
> > Neither is PPP.
>
> The customer will never get the link up if he/she doesn't
> configure PPP, he/she will get link up if the link is configured
> for HDLC but they havn't configured 'down-when-looped'
The customer's failure to configure "down-when-looped" on his end will
not adversely affect the behavior of "down-when-looped" on your end.
No, but the service will fail, as the traffic will not fallover
to the backup link.
But this argument is really pedantic and silly. Can we call it quits?
Please?
Ok - but I wanted to correct the above mistake.
/Jesper