Hello,
I’m new to this mailing list. I hope I’ve understood the scope correctly!
I’ve posted this question to ResearchGate but I haven’t had any response. I’m hoping for some guidance from here.
The question is:
“I’m trying to identify trends in adoption of transport technology in the metro-area. If legacy is SDH/SONET and its successor in circuit transport is OTN, what are network providers implementing and planning to implement as transport technology in the metro area? For example, are packet transport technologies being considered as a replacement? As a complementary technology? By packet transport technologies, I am thinking of PBB-TE and MPLS-TP but ultimately, the problem regards how network providers are balancing circuit-transport and packet-transport technologies in current and planned deployments.”
Ethernet has been ruling the Metro for some time now. The control and forwarding planes that drive that are a decision left to the operator. There is a healthy sharing of the pie between DWDM and packet to drive these Ethernet Metro’s, depending on use-case, the operators’ business model, whether it’s an ISP or a content network, e.t.c. In all, SDH/SONET Metro networks, while not completely gone, are certainly on the decline. As far as OTN goes, I’ve always heard more talk than actual biting by customers. In our market, every time a customer has shown interest in OTN, they end up going for EoDWDM, all the time. Mark.
And just to add that I think that as part of the future, 5G is likely to play a big part as well, somewhere between the Metro and the Access.
Mark.
Mark, when you write "There is a healthy sharing of the pie between DWDM and packet to drive these Ethernet Metro’s ", can you elaborate a little? Are you referring specifically to EoDWDM, or do you have something else in mind?
Etienne
EoDWDM.
Ethernet is very widely used, regardless of the Transport technology.
In other markets, you will find SDH Transports delivering Ethernet as
well (EoSDH), although that is dying in favour of EoDWDM or just
Ethernet over (dark) fibre.
Mark.
Bear with me one more time as I drill down a little and spell things out. I’ve realized that there may be more than one interpretation of “EoDWDM”. Are you referring to:
(a) Ethernet packets in OTU frames - thereby implying an underlying OTN?
(b) Ethernet optical SFP+ transceivers with a cable connection into a transponder plugging into a DWDM Mux or DWDM OADM? (no circuit transport)
Either one would count as EoDWDM, in my book.
The general use-case for OTN is to have SDH/SONET-like OAM
characteristics, but over the DWDM network.
In basic deployments, there was a time when folk argued about whether
they take LAN-PHY or WAN-PHY EoDWDM services from providers. The OTN vs.
DWDM discussion kind of falls around there, in my opinion. Considering
that almost all use-cases for EoDWDM are into router ports, where basic
day-to-day Ethernet is the cheapest and simplest option, I haven't heard
of any customers asking for WAN-PHY or OTN in the last 3 years. Not on
our network at least, anyway...
I think the costs of WAN-PHY/OTN re: OAM have been outweighed by making
the right choice in choosing an operator that is able to deliver an SLA,
back it up, and have a NOC that works well.
Now, the next step in all this that is starting to gain a bit of
traction is "spectrum", i.e., rather than take a normal grey service
from a Transport operator, have them deliver you a portion of the DWDM
spectrum so that you can run as much bandwidth as you want over their
network. Think of it as dark fibre, but lit...
Mark.
How are they handling optical power balancing across amplifiers and such? Do they just trust the customer to provide light at the power levels agreed upon? Bulk attenuate the entire "spectrum" automatically? Monitor and drop the whole lot if something is out of whack and causing saturation or gain balance problems for others?
Or is this something you're only seeing at metro distances where separate amplifiers are superfluous? I've inquired with a few metro operators in my area about something like this, albeit a few years ago, and I got a pretty hard "no way we'd ever do that" out of them presumably for the reasons above.
How are they handling optical power balancing across amplifiers and
such? Do they just trust the customer to provide light at the power
levels agreed upon? Bulk attenuate the entire "spectrum"
automatically? Monitor and drop the whole lot if something is out of
whack and causing saturation or gain balance problems for others?
Or is this something you're only seeing at metro distances where
separate amplifiers are superfluous?
The details about this are very vendor-specific, and each vendor has
some way in which they implement this. Spectrum would be a very
customized product between the vendor and operator, and also between the
operator and customer. So no BCP for this, as of yet, that I know of.
I've inquired with a few metro operators in my area about something
like this, albeit a few years ago, and I got a pretty hard "no way
we'd ever do that" out of them presumably for the reasons above.
We are seeing requests from as low as 600km, up to 1,600km, all the way
to 7,000km.
Mark.
I'm having a hard time seeing any of those distances as being "metro" as
opposed to long-haul.. or did they change the definitions again while I wasn't
paying attention?
I was answering Brandon's query re: spectrum over distance.
The OP's question on Metro still stands.
Mark.
Those are definitely longer distances than I was inquiring about. I was asking for distances in the range of more like 100km.
Those distances are firmly into the amplified territory and getting into territory were you're likely to need full RRR stops in at least a couple places. Maybe not with coherent optics especially on NZDS fiber...maybe.
For shorter runs, I think it's cheaper to find dark fibre and do
something yourself.
Mark.
A friend of mine whom I rely upon took it upon himself to put my question to a reliable contact of his. In the hope of adding some value to this thread, I’m reproducing this exchange with their names removed, in descending chronological order (latest first, earliest last).
Academic in the US:It’s almost all packet over OTN. SONET has been on its way out (at least in what I’ve seen) since the mid 2000’s. The last SONET I touched was like 2008, and that was to tear it out and replace it with Ethernet over OTN.
My contact: What you’re seeing pretty much matches what I’m seeing (from the outside). What I think Etienne is wondering is “how is that magic sauce delivered inside the SP network” - are they still using SONET/SDH, did they move to OTN, or is it pure packet-switched technology. The few networks I saw from the inside recently were all using packet-based technology (mostly MPLS) over lambdas. Would you have more data points?
Academic in the US: Almost everything I have seen in the US and parts of western Europe are either spectrum sharing (rare, but definitely a thing), wavelength as a managed service, or - more commonly - “managed ethernet” where the product is basically a L2 managed path with a hard bandwidth cap. This is far more common, especially in metro areas as it’s basically part of pretty much all of the MetroE platforms. In the US, MPLS is still pretty heavy but MPLS-SR is likely going to take over that space. Carriers are selling waves at a premium, they’d much rather oversell a frame service.
This was a bit of an unusual situation. One end it rather rural. The only fiber within miles was one semi-independent operator, the area RBOC, and Comcast. The semi-independent operator is on an old cable with very limited fiber count and apparently has basically every strand lit with DWDM at this point. They had no dark fiber to give.