Subject: Ethernet interface in a TDM device: FSC, TDM, or L2SC?

From: Freek Dijkstra <[email-masked]>
Date: Mon, 17 Jul 2006 11:25:09 +0200

Hi,

Another question.

I have a SONET cross connect. That is, a TDM device.
Most of the interfaces are TDM switch capable interfaces, which known
only about TDM encoding.

However, one of the interfaces of this devices knows about Ethernet
encoding, and is capable of taking the Ethernet packets and embed them
in a couple of STS channels (e.g. STC-24c or STS-3c-7v).

My question: what is the switching capability of this device?

It's not a L2SC, since it does not make decisions based on the MAC
addresses. I'm inclined to think it is also not a TDM switch capable
interface, since it does not switch based on time slots. All it does is
embed all data it encounters on the fiber. So it seems to me that this
interface is a Fiber-Switch capable (FSC) interface with Ethernet
encoding, despite that it is in a "TDM device".

Am I correct here?

Regards,
Freek

---

From: [email-masked]
Date: Mon, 17 Jul 2006 11:40:33 +0200

hi - 

it can't be FSC as you don't switch in the spatial domain (FSC is for 
inst. used in the case of fiber distribution frames)

in your case your interface knows about processing payload of the TDM LSP, 
hence the point is if you put such i/f  back to back 

o) do you switch the STS -> TDM LSP with TDM encoding and TDM ST 

o) do you switch the whole Ethernet packet flow from port-to-port (no 
granularity from the Ethernet header info) -> Ethernet LSP with TDM 
Encoding and L2SC 

ps: if you take such flow from another interface and have limited capacity 
i suggest you take a look at the mln/mln solution doc where you can link 
such capacities

much thanks,
- dimitri.

Freek Dijkstra <[email-masked]>
Sent by: [email-masked]
17/07/2006 11:25
 
        To:     [email-masked]
        cc: 
        Subject:        Ethernet interface in a TDM device: FSC, TDM, or 
L2SC?

Hi,

Another question.

Am I correct here?

Regards,
Freek

---

From: Freek Dijkstra <[email-masked]>
Date: Mon, 17 Jul 2006 12:05:37 +0200

Hi Dimitri,

Thanks for your insights.

> granularity from the Ethernet header info) -> Ethernet LSP with TDM 

Neither. The link between two of these kind of interfaces will be pure
Ethernet, no TDM encoding.

Let me make a drawing here.

    Gigabit     +------------+     Gigabit
   Ethernet     |            |     Ethernet in
 ---------------o TDM switch o----------------------
     in UTP   A |            | B   STS-24c in OC-192
                +------------+

My question concerned interface A in the above drawing. It seems that
your descriptions concern interface B instead.

In this case all bytes from interface A are adapted in 24 STS channels,
which are then adapted to the OC-192 of interface B. I can imagine three
lines of reasoning:

* Interface A announces LSC with Ethernet encoding. After all, it does
not look into the headers, and also does no do the TDM encoding (that
happens at interface B)

* Interface A announces TDM ST with Ethernet encoding. After all, it
will embed the Ethernet packets in STS, so it knows about TDM switching.

* Interface A announces L2SC with Ethernet encoding. That seems
incorrect; while the interfaces will probably know about frame
bounderies, it does not process the header.

I assume the first or second is correct.

> i suggest you take a look at the mln/mln solution doc where you can link 

Do you have a reference?

Regards,
Freek

---

From: [email-masked]
Date: Mon, 17 Jul 2006 12:20:12 +0200

hi -

from your drawing, i/f B: TDM and i/f A: L2SC with Ethernet port mode - 
not frame mode - in the port mode case for i/f A the Max = Min LSP 
bandwidth = port capacity 

note: your device is combining the two interfaces i initially describes

the reference i provided allows to link capacities between interfaces (i/f 
A with i/f B) see IACD sub-TLV section

<http://www.ietf.org/internet-drafts/draft-papadimitriou-ccamp-gmpls-mrn-extensions-02.txt>

thanks,
- d.

17/07/2006 12:05
 
        To:     Dimitri PAPADIMITRIOU/BE/ALCATEL@ALCATEL
        cc:     [email-masked]
        Subject:        Re: Ethernet interface in a TDM device: FSC, TDM, 
or L2SC?

Hi Dimitri,

 ---------------o TDM switch o----------------------

Do you have a reference?

Regards,
Freek