[j-nsp] Ethernet Preamble and FCS on EoMPLS

Phil Bedard philxor at gmail.com
Fri Sep 25 16:50:30 EDT 2009

The FCS is part of the frame... RFC4720 specifies a FCS retention  
indicator TLV, but I don't think it's ever been adopted by a vendor.
Some saw the lack of transparency in delivering the FCS untouched as a  
security issue.  A valid original FCS on the remote end means the  
payload arrived unaltered through the transport network.


On Sep 25, 2009, at 3:11 PM, Richard A Steenbergen wrote:

> On Fri, Sep 25, 2009 at 09:10:41AM -0300, Ruter Guike wrote:
>> Hi List.
>> Is Juniper able to include Ethernet "preamble" and "FCS" within the  
>> mpls
>> packet, on EoMPLS? Is it configurable?
>> AFAIK, these fields are removed, by default, before encapsulating...
> Preamble and FCS are layer 1 overhead, they aren't part of the frame  
> and
> can't be transported across MPLS or anything else. Not that there  
> would
> be any point in doing so, they carry no information of value and  
> will be
> recreated on the other side when transmitted again.
> -- 
> Richard A Steenbergen <ras at e-gerbil.net>       http://www.e-gerbil.net/ras
> GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1  
> 2CBC)
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