Subject: Re: MPLS and Optical network!!

From: "J. Noel Chiappa" <[email-masked]>
Date: Fri, 28 Jan 2000 22:37:17 -0500

> From: Jeremy Lawrence <[email-masked]>

    >> And the number of wavelength is also a problem.

    > Well, 80 wavelengths is enough for one router to connect to 80
    > others across an OXC network (subject to a valid route being available
    > for each lightpath), so this isn't too much of a problem. There are
    > rumours of OXCs coming which support 1000+ wavelengths.

Yes, but to connect each of 80 routers to each of 80 others takes (if I
remember the equation right) (N * (N-1))/2 total connections, or over 3000
virtual links. And the number gets much bigger very quickly (e.g. 100 takes
almost 5000 - it *is* an exponential).

Now, depending on the exact topology of the connectivity mesh of fibers and
OXC switches between them, some of those virtual links can be carried on the
same wavelength, since no parts of the paths of the two (or more) of them will
be congruent (and exactly how many depends on the topology). So that will
reduce the total number of wavelength you need to provide all N^2 (roughly)
virtual links. Still, it's going to be a significant number.

In other words, modelling (at the internetwork layer) an OXC substrate as a
giant Ethernet, where every device connected to it can talk directl to every
other device connected to it, doesn't really work as the OXC substrate gets
larger.

(Which is sort of related to one of my favourite rants, about why you really
want to have route selection at the internetwork layer only, but let's skip
that rathole.)

What exactly will work? Hmm, good question....

	Noel

---

From: "Alexander Marhold" <[email-masked]>
Date: Sat, 29 Jan 2000 13:44:51 +0100

> almost 5000 - it *is* an exponential).

Well that was also my first thought and I also wanted to immediately
answer,BUT

Label merge --- which is done in MPLs and 80 wavelengths (labels) PER
INTERFACE in the OXC means
that every router can have up to 80 LSP´s reachable via each of its
interfaces.

MPLS overcomes the underlying any-to-any-connectivity a normal Layer 2 has.

And the wavelength is only the outer most label, i.e. labels designating
forwarding to a certain interface which is done in MPLS-VPN do not need to
be included in that calculation.

So IMHO with 80 labels you can build up quite a usable optical Core

with best regards

Alexander

__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/__/
     __/
    __/   Dipl.Ing. Alexander Marhold MBA
   __/   CCIE #3324, CCNP, CCNA, CCDP, CCDA, CCSI #20642
  __/   PRO IN <Senior Consultant, PM and Trainer>
 __/   Mobile: ++43-(0)664-16 28 234
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---

From: Juha Heinanen <[email-masked]>
Date: Sat, 29 Jan 2000 16:30:38 +0200 (EET)

> that every router can have up to 80 LSP´s reachable via each of its

how do you merge wavelenghts?

-- juha

---

From: "Loa Andersson" <[email-masked]>
Date: Sat, 29 Jan 2000 15:19:47 +0100

Alexander Marhold wrote:
[... snip ...]

> MPLS overcomes the underlying any-to-any-connectivity a normal Layer 2 has.

True enough, if you can make it happen. Can you give a hint on how you
do
the label mergining - OEO, swapping the labels in optics, ... ?

> So IMHO with 80 labels you can build up quite a usable optical Core

Yes, a useful optical core given that you have a couple of "minor"
problems solved.

> Alexander

/Loa
-- 

Loa Andersson
Regional Director, EMEA
St Eriksgatan 115A, PO Box 6701
113 85 Stockholm, Sweden
phone: +46 8 50 88 36 34,   mobile + 46 70 522 78 34
e-mail: [email-masked]

---

From: "Alexander Marhold" <[email-masked]>
Date: Sat, 29 Jan 2000 16:13:44 +0100

> the label mergining - OEO, swapping the labels in optics, ... ?
my point of view is the following

start:
- the labelled packet enters the optical core with label A and thus
wavelength l1
on each switch:
- the optical packet will be forwarded according to outgoing interface and a
wavelength l2
(note that in these intermediate hops the wavelength and the labelheader
within the transported frame does not match)
optical egress:
- the packet arrives with a wavelength of l5:
as the egress knows the label correspondent to the wavelength l5
the packets will be forwarded with a new label given by the optical egress
router

It is very clear that no label Push or Pop can be done in the optical core

So for me the operation is pretty similar to MPLS over ATM

But if I missed something important pls let me know

regards
Alexander

---

From: "Loa Andersson" <[email-masked]>
Date: Sat, 29 Jan 2000 16:38:00 +0100

Alexander,

in what you describe everything sent on wavelength l1 at the ingress
will show up on wavelength l5 at the egress. You are back at the 
original problem (N*N "connections" to connect N egress point to 
N ingress points). And you haven't done any wavelength merging.

/Loa

Alexander Marhold wrote:

-- 

Loa Andersson
Regional Director, EMEA

---

From: Yangguang Xu <[email-masked]>
Date: Sat, 29 Jan 2000 11:06:26 -0500

Yes, you can't merge with pure analog wavelengths, However with O-E-O, think of
four OC48 multiplexed into one OC192.

Yangguang

---

From: "Alexander Marhold" <[email-masked]>
Date: Sat, 29 Jan 2000 17:46:46 +0100

> N ingress points). And you haven't done any wavelength merging.
No, what I meant but did not describe well is that at every hop labels for
the specific egress will be merged as is done in ATM with vc-merge
 prerequiste is a per interface label-space (wavelength space))
so l5 is the wavelength (label) for all packets going to that egress
independent of where it came from, as I assume that to be a pure destination
based core.

so what the OXC would have to do:
Step 1:  get a packet with wavelength l4 on interface 1
Step 2:  he knows that this will be forwarded as l5 on interface 2
step 3:  convert wavelength of packet to l5
Step 4a: if outgoing interface and wavelength is free ---> send
Step 4b: if outgoing interface is used, mirror packet in an optical queue
and goto Step 3a

But what seems to be my wrong assumption is that currently there is no OXC
which can convert wavelengths on the fly between input and output interface,
whereas delaying an optical packet until the output interface and wavelength
is free seems to be possible at least in an engineering state.

Can eventually someone more knowledgeable on optical tell me how far (in
months or years) my "vision" of an OXC with above described steps and
capabilities is away

so I apologize for the possible confusion on the discussion

regards

Alexander

---

From: Jacques Caron <[email-masked]>
Date: Sat, 29 Jan 2000 17:55:49 +0100

Hi,

In my opinion, what you are describing is a frame/packet switch that 
supports multiple wavelengths, not an OXC. The former buffers 
packets/frames before (queuing and) resending them (like a router or a FR 
switch or an ATM switch doing VC-merge). The latter just changes wavelength 
of the signal, so there is no latency, and very minimal "intelligence". And 
probably better scalability to higher speeds and/or number of wavelengths.

Jacques.

>so I apologize for the possible confusion on the discussion

--- Jacques Caron
     PSINetworks Europe Network Engineer
     PSINet Europe Regional Peering Coordinator
     Planete.net IT Manager
     Mail:   8/10 rue Nieuport - 78140 Velizy - France
     Phone:  +33 (0)1 34 63 19 71 - Fax: +33 (0)1 34 63 19 51

---

From: Yangguang Xu <[email-masked]>
Date: Sat, 29 Jan 2000 12:10:02 -0500

> is free seems to be possible at least in an engineering state.

Optical packet? do you mean checking, buffering packets in analog domain? There
are some research going on this path. However, for commercial usage, I think at
least 5-10 years away.

OXC is still the old circuit switch idea. So far, no packet forwarding look-up
is done on fly for each packet. I surely hope it will do.

Yangguang

---

From: "Loa Andersson" <[email-masked]>
Date: Sun, 30 Jan 2000 00:28:34 +0100

All,

I thought that what Alexander wanted to do was to get away from the 
OEO, if for no other reason because it is expensive.

/Loa

-- 

Loa Andersson
Regional Director, EMEA

---

From: "Bill St. Arnaud" <[email-masked]>
Date: Sun, 30 Jan 2000 13:30:05 -0500

Optical burst switching will probably be the best solution for addressing
your requirements.

The MPLS packet label is carried out of band in a separate wavelength.
Packet switching to different wavelengths and wavelength merging is done at
the optical level.  The OXC decodes in the optical domain the burst label.
The main data channels are put through a small time delay fiber so that
burst label can be decoded and OXC wavelength switch can be set up.

Lots of development in the labs in this area - see OFC conference in
Baltimore.

But I don't know if it is still the right approach to MPLS optical
networking.

Bill

Bill St. Arnaud
Senior Director Network Projects
CANARIE
[email-masked]
+1 613 785-0426

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]On Behalf Of Yangguang
> Xu
> Sent: January 29, 2000 12:10 PM
> To: [email-masked]
> Cc: 'Loa Andersson'; [email-masked]
> Subject: Re: MPLS and Optical network!!
>
>
>

---

From: Curtis Villamizar <[email-masked]>
Date: Sun, 30 Jan 2000 18:43:40 -0500

In message <[email-masked]>, "Alexander Marh
> that every router can have up to 80 LSP´s reachable via each of its

I don't think label merge will work very well at the optical layer.
It might be possible to do TDM and merge lightsources.  You'd have to
very carefully sync clocks at the senders, know the propogation delays
very exactly.  A mismatch in clocks and both signals are gone.  The
lasers would have to be shut off completely when not sending.  Optical
switching times are still too slow for TDM where the optical switch
participates.  Is anyone actually taking such an approach?  I doubt it
but if so, I a may have blown a patent by publishing first (this
email).  It is an obvious idea though.  :-)

You still have the issue of efficiently multiplexing (spacial reuse)
without going to electrical to accomplish color conversions.  There
was a recent article in one of the journals (Nov or Dec in an IEEE or
ACM journal, don't recall, and don't have it here) in which the
placement of these devices was discussed.  Without these the
efficiency with which wavelengths are used drops rapidly beyond 3-4
optical hops.

As soon as you find yourself needing to go to O-E-O you might want put
some intellegnece there to improve network protocol scaling and to
allow packet buffering and more efficient use of the available
lambdas.  The majority of the cost of going O-E-O is the conversion.
The additional cost is not very high.  That more intellegent device
would very likely be a router.

Unless I'm totally out of it, we're quite a long way from all optical
wavelegth conversion and buffering light packets.

Curtis

---

From: Tony Li <[email-masked]>
Date: Sun, 30 Jan 2000 17:56:12 -0800

> wavelegth conversion and buffering light packets.

I concur.

Where we should be going is to extend our signaling protocol so that we can
automate traffic engineering for both the MPLS and optical planes.  This implies
that the OXCs participate (possibly through a proxy) in the signaling protocols,
that optical plane configuration information is carried in our IGPs, and that
traffic engineering path computation also consider optical path establishment as
well as LSP establishment.

My $.02,
Tony

---

From: "dave o'leary" <[email-masked]>
Date: Mon, 31 Jan 2000 07:23:18 -0800

> > wavelegth conversion and buffering light packets.

Curtis and Tony agree on something!   :-)

>well as LSP establishment.

indeed, exactly.

of course, given the optical networking hype, it is time to start loading
the next B Ark.

Are you going to stop by NANOG, or do you have real work to do?

                                         dave