At 10/19/2012 12:40 AM, Dennis Burgess wrote:
Maybe I should take this off-list but this would be a better
question. What RFC or industry standard features are you referring
? Specific items! :)
It's not in RFCs; RFCs are the IETF vehicle, which is really all
about TCP/IP. Carrier Ethernet is not theirs. It's standardized by
the Metro Ethernet Forum, so the standards have MEF numbers. MEF in
turn largely cites IEEE specs from the 802 family, but assembles
them, with its own touches, into its own packages.
inline comments
On Thu, Oct 18, 2012 at 3:05 PM, Fred Goldstein
<<mailto:fgoldst...@ionary.com>fgoldst...@ionary.com> wrote:
At 10/18/2012 02:52 PM, Dennis Burgess wrote:
MPLS does run over a IP backbone, but can use VPLS tunnels to
create what you are doing at layer 2. Not to mention you would get
all of the benefit of Traffic Engineering, and internal routing
giving you the best of both worlds. Why its sometimes called Layer
2.5, as it creates tunnels inside your routed network, giving you
fail over and multiple paths. With TE you can also reserve bandwidth etc. :)
With some implementations of MPLS (TE required) and a whole lot of
fiddling, you can build an MPLS network that does pretty much what
Carrier Ethernet does, given enough skilled labor to keep it
running. But Carrier Ethernet is a big new market, selling like
crazy, and there are thus a lot of CE networks out there. (Cable
companies and ILECs are both competing for it.)
Also, when you leave the "ISP" world and deal with the big-money
"IT" custoemrs, they have their own MPLS networks, and need
something to run them over. CE makes a good substrate for
MPLS. Carrier MPLS does not carry customer MPLS as naturally. In
fact I think it would be fairly hard to configure that. I know of
some real users facing that, where a local fiber network went in
using MPLS as its basic service, thinking that a government with its
own MPLS would be able to use it, when they're different MPLS
domains. CE would be so much cleaner. Unlike RINA, where there's
never a conflict about recursing a layer, TCP/IP protocols tend to
be written with brittle interfaces to others that are expected to be
above and below them.
You can run MPLS tags inside a VPLS circuit. You would simply build
a VPLS circuit on top of your MPLS network, the MPLS network is
really the transport, the VPLS is your private layer2 network (or if
you got VRF or BGP VPLS, you can run in layer3). Thus giving you the
ability to run another MPLS network over your existing MPLS
network. I am not disagreeing that CE could be cleaner, but I am
not versed in all operations of CE, so its like comparing
apples/oranges. The example that you used though was VLANs though.
Yes, you can go through some hoops to stack things, when that's
supported. (I'm not sure everyone who uses single-company MPLS would
know how to do all of that though.) The most extreme case of
unexpected recursion is VoIP, of course, where an entire stack's
application payload is in turn potentially just a layer 1 telephone
call pipe. Which, if good enough, might support a modem and another
stack... (just kidding).
But CE does it all a lot more easily and cheaply, if you're trying to
light a fiber network. The customer can just plug the routers (with
or without MPLS) in to the network (which can do its own tagging) and
the EPL is just a point-to-point link. This btw is essentially the
old "TLS" renamed.
Yeah, I'd like Ethernet ports on RouterOS boxes to be that easy to
use. I think I know how bridges could be set up between them with a
network in between. I just don't know RouterOS well enough yet.
So while you can argue the merits of MPLS vs. CE for a brand-new
metro network, if you are looking for CPE to go onto an existing
network, you don't put an MPLS box on a CE network, or
vice-versa! I'm looking at a (different) real CE network going up
now where there's an open question of what CPE to use. I see a
market opening for a Routerboard-priced SFP box. But it doesn't
matter if it costs $39, runs at 10 Gbps, washes windows and makes
tea, if it doesn't mate with the network and its services.
I just posted another question then, what features with CE
specifically are you looking for in this box?
Basically what's summed up in the MEF specs, and then I think the EPL
(ptp) and EVPL (ptmp) options are more important than the LAN
emulator option. I then want
- tagging (of untagged traffic coming into an EVPL)
- QinQ (carrying tagged traffic)
- CIR and EIR support
- Easy port configuration
- Some OA&M capability
Note that in these two services, MAC address is basically treated as
payload. No traditional bridging takes place. The "VLAN" tag is
really a virtual circuit ID, but for some reason a lot of folks don't
like that term.
These networks typically end at a CPE that's a small switch (if
shared) or router (which is part of the customer network if it's not
public ISP access).
--
Fred Goldstein k1io fgoldstein "at" ionary.com
ionary Consulting http://www.ionary.com/
+1 617 795 2701
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