Dear BESS experts,

The authors would like to introduce you to the concept of Private Line 
Emulation Emulation (PLE) and the two related drafts 
draft-schmutzer-bess-ple<https://tools.ietf.org/html/draft-schmutzer-bess-ple-02>
 and 
draft-schmutzer-bess-ple-vpws-signalling.<https://tools.ietf.org/html/draft-schmutzer-bess-ple-vpws-signalling-01>

Even though ethernet became the de facto WAN interface technology and pretty 
much all traffic has converged to IP, service providers are still required to 
provide “transparent circuits” to their customers which can not be addressed by 
frame/packet based approaches such as ethernet PWs 
(RFC4448<https://tools.ietf.org/html/rfc4448>) or EVPN-VPWS 
(RFC8214<https://tools.ietf.org/html/rfc8214>). While in the past those were 
mostly DS1s/E1s or DS3/E3s or 10/100Mbps ethernet over PDH/SONET/SDH (GFP/VCAT) 
“leased lines” nowadays customers are requesting larger pipes (private lines) 
and a wider variety of interfaces types. Examples are 1GE, 10GE, OC48/STM16, 
OC192/STM64, various rates of Fibre-channel and even 100GE.

Optical transport technology has evolved to 200-800Gbps capacity per 
wavelength. In order to stay efficient at the optical transport layer, service 
providers require a multiplexing/switching layer to carry 10Gbps or 100Gbps 
private lines over those large capacity wavelengths. Advances in packet 
switching ASIC/NPU technology make IP/MPLS technology a very efficient choice 
for that layer. This is where PLE being an “emulation concept” does come into 
picture. It allows for delivering 100% (bit) transparent “circuits” over a 
packet switching (transport) layer that is completely independent from the 
client layer signal/traffic it is carrying. PLE is also inline with the 
considerations of RFC3916 section 
1<https://tools.ietf.org/html/rfc3916#section-1>.

Granted this idea is not entirely new, you somewhat can see PLE as the expanded 
scope of SAToP (RFC4553<https://tools.ietf.org/html/rfc4553>) that defined the 
transparent transport of low rate DS1/E1/DS3/E3 TDM signals in the past.

While we already had some discussion (in PALS) on rev -00 and -01 of 
draft-schmutzer-bess-ple<https://tools.ietf.org/html/draft-schmutzer-bess-ple-02>
 we kindly request your review and feedback also on the latest rev -02. Changes 
that went in so far:
* explicitly specify payload fill order
* increased default payload size
* change “ODUk aligned” mode to “byte aligned” mode
* correct use of FRG in control word
* increased timestamp frequency
* clarify use of common clock and differential clock recovery (including 
quality targets)
* improve defect and performance monitoring section

Furthermore we would also appreciate your feedback on 
draft-schmutzer-bess-ple-vpws-signalling<https://tools.ietf.org/html/draft-schmutzer-bess-ple-vpws-signalling-01>
 which right now is in rev -01. During recent deployments of SATOP/CESOP/CEP, 
service providers indicated interest in adopting EVPN-VPWS as a signalling 
mechanism. Hence we propose to use EVPN-VPWS for signalling PLE VPWS and 
consider a broader scope to also define how EVPN-VPWS can be used for 
signalling TDM pseudo wires defined in 
RFC4553<https://tools.ietf.org/html/rfc4553>, 
RFC5086<https://tools.ietf.org/html/rfc5086> and 
RFC4842<https://tools.ietf.org/html/rfc4842>.

Looking forward to your suggestions and discussion

Thank you,
Christian
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