RE: [802.3ae] Wan Interface Sublayer
The terms that you are asking about are internal industry terms. SRE and
LRE are industry names for Section Regenerating Equipment and Line
Regenerating Equipment which are specific SONET and SDH equipment. ELTE
is a fictional term that added the word Ethernet to the SONET term LTE
(Line Terminating Equipment). Since an LTE is actually a system that
multiplexes SONET or SDH sub-rate payloads, it does not even apply properly
to Ethernet, which does not have sub-rate payloads. Being part of the
group that when someone came up with the term ELTE, what they were actually
talking about was more like an LRE than an LTE.
At 09:51 AM 8/28/01 -0700, Amir Bar-Niv wrote:
>Can you pls point me to a reference (presentation of the EFM or another
>document) that explain/define the terms SRE, LRE, ELTE.
>From: Roy Bynum [mailto:email@example.com]
>Sent: Monday, August 27, 2001 4:11 PM
>To: Gary Nicholl; Ayers, Mike
>Subject: RE: [802.3ae] Wan Interface Sublayer
>There has been a lot of "talk" about "jitter specifications". In a
>conversation with some of our technology people that have been around a
>long time, I fond out something interesting about why the SONET and SDH
>specifications are what they are. The SONET and SDH specifications are
>based around the requirements for electrical multiplexing of not only
>digital signals but "analog" signals as well. The old T0/T1/T3 signals
>were analog signals that were "bit stuffed" to provide alignment pointers
>within the SONET transmission system. The jitter specifications were real
>tight because of the compounding of the "adjustments" cause reliability
>issues with the "analog" client signals.
>When going through amplifiers the issues of jitter become compounded. When
>going through SREs the clock recovery and regeneration cleans up any
>"jitter". In a service deployment, a service provider that does not at
>least have an SRE as a service demarcation is not going to be very serious
>about their business. In looking at the way DWDM systems will be deployed
>in order to provide service demarcation, I doubt that "jitter" will be a
>real issue. The upper "end" of that service demarcation will be an LRE (in
>the politically correct terminology of 802.3, ELTE) to demark the
>customer's line overhead as well as their section overhead. This is not
>much different than the way it is done between service providers, except
>that the service providers generally use full sub-rate multiplexing LTEs to
>do transmission service handoff.
>At 05:17 PM 8/27/01 -0400, Gary Nicholl wrote:
> >One difference might be that OC-192c POS interfaces are fully compliant to
> >SONET/SDH jitter specifications (in terms of generation, transfer and
> >tolerance). The two parameters that are important with regard to interop
> >with long haul DWDM systems are obviously jitter generation and jitter
> >tolerance. If I understand correctly the 10GbE WAN PHY is not currently
> >aligned with SONET/SDH jitter specs. Any thoughts about the impact of this
> >on the interop with long haul systems ? I guess it was always my
> >understanding that one of the functions of this mysterious ELTE was to
> >convert from WAN PHY jitter specs to SONET/SDH jitter specs?
> >Gary Nicholl .............
> >At 10:29 AM 8/27/2001 -0500, Roy Bynum wrote:
> >>We are currently deploying OC192c POS over long haul systems using only
> >>amplifiers and SREs. The network management of the POS systems at each
> >>end of the SONET span is separate from the SONET span. The POS systems
> >>are "free-running" relative to SONET synchronization. Fault protection
> >>is being handled by the SREs. I do not see any difference in deploying
> >>10GbE WAN PHY in the same way.
> >>Thank you,
> >>Roy Bynum
> >>At 04:56 PM 8/24/01 -0500, Ayers, Mike wrote:
> >>> > From: Roy Bynum [mailto:firstname.lastname@example.org]
> >>> > Sent: Friday, August 24, 2001 01:09 PM
> >>> > Being a SONET transmission service provider with OC192 SREs
> >>> > already in the
> >>> > transmission network. With the WAN PHY at +/-20PPM, your
> >>> > possibility #1 is
> >>> > correct. The SONET SREs (read SONET class B regenerators)
> >>> > can handle the
> >>> > WAN PHY and provide section level performance monitoring and
> >>> > protection.
> >>> > From: James Colin [mailto:email@example.com]
> >>> > Sent: Friday, August 24, 2001 12:14 AM
> >>> > Option (4) is the correct answer. SONET and WIS must
> >>> > stay on their own network. A network device called
> >>> > "ELTE" is doing the bridging between the WIS net and
> >>> > the SONET.
> >>> Hmmm - I think a little more discussion on this is in order, and
> >>>minds greater than mine. My interest is this: if it is possible to
> >>>WIS directly over a SONET network, then the management model for WIS
> >>>much more involved, since it must support management by either the SONET
> >>>model or the traditional ethernet model (two very different models).
> >>>However, if an ELTE is required betrween the two, it effectively
> >>>the networks such that there is no overlap nor need for two management
> >>>models; ethernet being used on one side of the ELTE and SONET on the
> >>>It does not matter, from my perspective, whether an ELTE gets used - what
> >>>matters is whether the ELTE is required. Is it possible that the SRE is
> >>>acting as an ELTE in Roy's scenario?
> >>> Thanks,