Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: [HSSG] Reach Objectives

I fully agree with you. This should never have been a problem because bit transparency of the full physical layer is considerably more than what should be needed for transport of something called Ethernet. What should be important is transparency of the packet payload, characteristic information, traffic units, or whatever you want to call the stuff that is carried over an Ethernet network.
But what we learn from experience is that there isn't a lot of way to avoid that someone uses something in a way that was never intended.
We have discovered at least one router vendor who carries proprietary stuff (I assume OAM) in the preamble and insists that the preamble be carried transparently so as to not break this proprietary use. I understand that there exists a mapping of 10 Gigabit fibre channel into Ethernet that encodes something in the IPG.
I agree that this should never have happened, but we now see a lot of market pressure, resulting in some network operators and equipment vendors caving into the pressure to offer carriage of a 10G Ethernet signal in a fully bit transparent manner - every one of the 10.3125 Gbit/s being carried intact including the 64B/66B coding!
In reaction to a proposal that we now need to change the OTN bitrates in ITU-T to carry the full 10G BASE-R signal with 64B/66B coding over an ODU2-like structure with a higher bitrate, one of the participants quipped that it sounded like someone wants us to change the standard so that we can carry something that isn't Ethernet over something that isn't OTN.
What I am arguing for is that, for the next higher rate, we avoid defining different interfaces with slight difference in data carrying capacity. Doing this leaves open a crack that might be used improperly (or at least WHEN it is used improperly, it breaks something or introduces some unexpected constraint in the network).

From: Geoff Thompson [mailto:gthompso@xxxxxxxxxx]
Sent: Saturday, September 02, 2006 6:57 PM
To: Trowbridge, Stephen J (Steve)
Cc: STDS-802-3-HSSG@xxxxxxxxxxxxxxxxx
Subject: Re: [HSSG] Reach Objectives


There is something that you are talking about here that I don't understand.

At 11:40 AM 9/2/2006 , Trowbridge, Stephen J (Steve) wrote:
David, One of the "mistakes of 10G" was having effectively defined MACs of two slightly different rates - one for LAN PHY and the other for WAN PHY.

While one might assume that one would select the correct interface for the correct purpose, experience has shown that this is not the case. We have way too many examples of cases where someone builds something around a 10G LAN PHY and then expects it to be transported with absolute bit transparency across a wide-area network (e.g., a secure government application where they insist that the service provider not touch the payload).

Here is the part I don't understand. We (Ethernet) provide a packet service, not a SONET service. We should be able, even with speed changes, to be able to provide absolute bit transparency of the data portion of frames for anything going across a network (as long as the preamble, SA, DA and type are not encoded) and absolute bit transparency of the entire data frame if it is going across a point-to-point connection ( i.e. bit-for-bit replication of IPGs and preambles are not guaranteed, everything else should be).

If the customer wants to do encryption across multiple Ethernet packets*, then what they want is not Ethernet. If all they want is integrity of the payload then there shouldn't be a problem.

Preambles are not payload
Interpacket gaps are not payload.

Why are we failing to communicate?

Best regards,


* with encryption algorithms that, for example, encrypt or even count the "bits" (they aren't really bits) between packets.

While some vendors have provided proprietary solutions (e.g., an OTU2 like frame structure at a higher clock rate), there is no standard way to do this. There are a comple of different proprietary mappings that do not interwork with each other. None of them work in other than a point-to-point configuration. Since the operate at a higher bitrate, they don't have the spectral characteristics of G.959.1 interfaces. They don't have the clock accuracy required in G.709 or follow the jitter/wander characteristics of G.8251. And they can't be multiplexed up to standard OTU3 40 Gbit/s interfaces.

I think that it is extremely important to avoid this debacle at the next rate. We can certainly use a variety of different physical interfaces, but to have a variety of slightly different payload bitrates is a disaster.