[c-nsp] How to configure a STM-1c

[Tim Franklin]

Hi Victor,

> Please could anyone point me out a good link for 
> understanding on how to configure a STM-1C interface?

Firstly, what the config and the diagram in your second link are all about,
are treating a channelised STM-1 as a series of nested boxes.

What you have in your example config is:

The STM-1 contains a single AU-4 (1).
The AU-4 contains 3 TUG-3s (1-3).
The TUG-3s each contain 7 TUG-2s (1-7).
The TUG-2s each contain 3 E1s (1-3).
The E1s each contain one channel-group (0) with 31 timeslots (1-31).

If you just want to use the STM-1 to receive 63 E1s (or some combination of
sub-E1 / N x 64K services, but let's ignore that for the minute), you don't
need to know too much about why SDH groups these things the way it does,
just how to work out which channel a given service is on.

Your provider may give you the information in one of two ways:

- K/L/M or J/K/L/M values.  J is the AU-4 number (always 1 for your STM-1),
K is the TUG-3 number, L is the TUG-2 number and M is the E1 number.  This
is easy, as it matches to your config.

- Channel number 1-63.  In this case you have to convert, but you can treat
the nested boxes like a nested 'for' loop (if you have any programming
background).  Each channel number increments 'M' until they're all used,
then reset 'M' and increment 'L', and so on.

So channel 1 is J/K/L/M 1/1/1/1, 2 is 1/1/1/2, 3 is 1/1/1/3, 4 is 1/1/2/1,
and so on up to 63 at 1/3/7/3.

If you use the config you've included below, you've got one channel group
for each E1, framed, and using all the timeslots, so your correspoding
serial interface becomes 'Serial 0/1/0.1/K/L/M:0'.  Once you've built these
interfaces, you can treat them pretty much like any regular E1 serial
interface.

> Can I configure Link aggregation with this Canalized 
> interfaces? (MLPPP perhaps?)

Yes.

> How do I know to witch channel my ISP is giving me the service?

You need to ask them for either the channel number or the (J/)K/L/M
reference.

They should also confirm that they are using AU-4 for their AUG mapping.
(There are other options, which give you a similar principle, but the
details of the set of nested boxes are different, and so is the channel /
interface numbering.)

> Can I configure a line to be an E3?

This is dependent on the card.  If you actually have the STM-1 SPA you
reference in your first link, it seems that you can set each TUG-3 to either
contain 7 TUG-2s, an E3, or a T3 (I haven't done this - no direct experience
with the STM-1 SPA).  For some of the older cards, such as PA-MC-STM1, you
can't do this, only E1s (and sub-E1s).

And of course, your provider will have to agree to configure an E3 to be
transmitted over one of your TUG-3 'boxes'.

> What means exactly this figure representation?

This is the 'nested boxes'.

> What are the needed parameters that my ISP should give me?

Really, to get the transmission layer up, just the channel number and the
framing (you have 'no-crc4' in your sample config, this may or may not be
correct).  You'll need to do all the normal config on the serial interface,
of course, but these are just like regular serial interfaces you'd get from
plugging in a single E1 card.


One last point though - are you *sure* channelised service is what you're
getting?  'STM-1c' is normally 'STM-1 concatenated' - that is to say just a
high-speed data bitstream, without any of the 'nested boxed'.  This is the
*opposite* of a channelised service!

Regards,
Tim.

-- 
____________   Tim Franklin                 e: tim.franklin at colt.net 
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