[CCAMP] Questions/comments on OTN signaling

["Gruman, Fred" <[e-mail]>]

Hello Fatai,

 

I have some comments/questions on
draft-zhang-ccamp-gmpls-evolving-g709-09.

 

1) I think the draft should discuss the Generalized Label Request
object.  Will this object use the new OTN switching capability
(Switching Type = 101)?

 

2)  How is ODUflex(GFP) signaled? In general, the draft seems to lack
detail on ODUflex(GFP).

 

More specifically, the draft states "In case of ODUflex(CBR), the
Bit_Rate and Tolerance fields MUST be used together to represent the
actual bandwidth of ODUflex" and later "In case of other ODUk signal
types, the Bit_Rate and Tolerance fields are not necessary and MUST be
set to 0."  It is not clear if this implies that ODUflex(GFP) should set
Bit_rate and Tolerance to zero.  I would assume ODUflex(GFP) would need
Bit_Rate, but unsure if tolerance is needed.

 

3) G.709 Amendment 2 (2011-04) Table 7-9 has a row to cover the generic
ODUflex(CBR) with notes to the formulas to calculate the number of
tributary slots.  Additionally, this table has specific rows to cover
ODUflex(CBR) IB SDR, IB DDR, IB QDR, FC-400, and FC-800 and specifies
the explicit number of tributary slot assignments when mapped into
ODUflex into HO-OPUk).   

 

It seems that the generic formula for ODUflex(CBR) does not result in
the same number of tributary slots for some of these client signals.
For example, IB SDR over HO-OPU3 has nominal bit rate of 2,500,000
kbits/s and bit rate tolerance of +/-100ppm (from G.709 Amend2 Table
17-14).  Using the generic ODUflex(CBR) formula, you get:

 

N = ceiling [(2500000 * (1+100/1e6)) / ( 1254703.729 * (1-20/1e6)) ]

    = ceiling [2500250 / 1254678.635]

    = ceiling [1.99274135]

    = 2

  

Table 7-9 shows that IB SDR mapped into ODUflex over HO-OPU3 would use 3
tributary slots, not 2.

 

Please verify my math but if the generic ODUflex formula does not apply
to the IB or FC clients, then we may need to have explicit signal types
for these clients.

 

I found that the IB clients do not match the generic formula for some
HO-OPUk but the FC clients do match.  This may mean we only would need
explicit signal types for:

- ODUflex(CBR)-IB-SDR

- ODUflex(CBR)-IB-DDR

- ODUflex(CBR)-IB-QDR

 

Please let me know what you think.

 

Thanks,

Fred