Multi lane optics

joel jaeggli joelja at
Tue Dec 19 17:13:11 CST 2017

On 12/19/17 08:45, Tyler Conrad wrote:
> This blog has a pretty good runthrough -
> Scroll down to "100G PROTOCOLS".
> On Tue, Dec 19, 2017 at 8:38 AM, Baldur Norddahl <baldur.norddahl at>
> wrote:
>> Hello,
>> Some optics are implemented with multiple lasers such as QSFP+ with 4x 10G
>> = 40G or QSFP28 with 4x 25G = 100G. How is the ethernet traffic load
>> balanced between those lanes? Is it bit by bit or more like LACP (packet by
>> packet)?
>> I need to make sure my solution will handle 10G streams correctly. We have
>> a problem with N x 10G and LACP because our L2VPN MPLS endpoints are
>> lacking the flow label support. If I sell a 10G circuit to a customer and
>> uses a L2VPN to transport his port, everything may go on the same sub
>> channel. LACP will not load balance correctly, because it only sees the
>> outer MAC address for hashing, which is the same for all packets.
>> Now we are worried that multi lane optics might have the exact same
>> problem.

100G frames are striped across the 4 x 25G lanes either with or without
fec. That operates as one link from the vantage point of the ethernet frame.

The fec (reed solomon coding generally) offers protection against bit
errors at the expense of some latency.

>> Regards,
>> Baldur

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