Hi Fred,
I'm somewhat confused and it would be good to clearly formulate which
problem you are trying to solve (Hi Radia!).
Requiring to turn off checksumming of Ethernet Frames may be useful
for the particular _solution_ you propose, but this usually does not
apply to all links in the Internet. For instance, in data center
networks link-local retransmissions could actually improve the
performance (e.g., see https://doi.org/10.1145/3603269.3604853).
Long-delay links (e.g. interplanetary) are (always) special and it is
not clear that they should use Ethernet Frame format at all, i.e., you
could exactly design their link-layer differently w.r.t. checksumming.
Moreover, I think there are DTN solutions out there like the Bundle
Protocol
https://www.rfc-editor.org/rfc/rfc9171.html that can readily be used
for these kind of special links.
Regards,
Roland
On 13.11.23 at 20:58 Templin (US), Fred L wrote:
Here is something everyone should read and become familiar with taken from
Section 5 of the latest
version of "IP Parcels and Advanced Jumbos":
https://datatracker.ietf.org/doc/draft-templin-intarea-parcels/
A new link service model is offered that will be essential for supporting
air/land/sea/space mobile
Internetworking. IP Parcels and Advanced Jumbos are the vehicles that support
end-to-end as
opposed to hop-by-hop link error detection in the new model.
This is a truly transformational concept for the Internet - many may already
know about it, but
everyone should become aware of it.
Fred
---
5. IP Parcel and Advanced Jumbo Link Service Model
The classical Internetworking link service model requires each link
in the path to apply a link-layer packet integrity check often termed
a "Cyclic Redundancy Check (CRC)". The link near-end calculates and
appends a CRC code value (often 4 octets) to each packet pending
transmission, and the link far-end verifies the CRC upon packet
receipt. If the CRC is incorrect, the link far-end unconditionally
discards the packet. This process is repeated for each link in the
path so that only packets that pass all link-layer CRC checks are
delivered to the final destination.
While this link service model has contributed to the unparalleled
success of terrestrial Internetworks (including the global public
Internet), new uses in which significant delays or disruptions can
occur are not as well supported. For example, a path that contains
links with significant bit errors may be challenged to pass a
majority percentage of packets since loss due to CRC failures can
occur at any hop while each packet lost must be retransmitted. With
the advent of space-domain Internetworking, the long delays
associated with interplanetary signal propagation can also often
render any retransmissions useless especially when communications
latency is critical.
IP parcels and advanced jumbos now offer a new link service model;
instead of requiring an independent CRC at each intermediate link
hop, IP parcels and advanced jumbos include a CRC code with each
segment that is calculated and inserted by the original source and
verified by the final destination. Each intermediate hop must
therefore pass IP parcels and advanced jumbos without applying
traditional link layer CRC checks and/or discarding packets that
contain errors. This relaxes the burden on intermediate systems and
delivers all data that transits the path to the destination end
system which is uniquely positioned to coordinate recovery of any
data that was either lost or corrupted in transit.
Each IP parcel and/or advanced jumbo-capable hop along the path from
the original source to the final destination must therefore provide
an API primitive to inform the link ingress to disable link-layer
integrity checks for the current IP parcel or advanced jumbo payload.
The parcel/advanced jumbo may therefore collect cumulative link
errors along the path, but these will be detected by the per segment
CRC checks performed by the final destination. The final destination
in turn delivers each segment to the local transport layer along with
a "CRC error" flag that is set if a CRC error was detected or clear
otherwise. The CRC indication is then taken under advisement by the
transport layer, which should consult any transport or higher-layer
integrity checks to pursue corrective actions.
IP parcels and advanced jumbos therefore provide a revolutionary
advancement for delay/disruption tolerance in air/land/sea/space
mobile Internetworking applications. As the Internet continues to
evolve from its more stable fixed terrestrial network origins to one
where more and more nodes operate in the mobile edge, this new link
service model relocates error detection and correction
responsibilities from intermediate systems to the end systems that
are best positioned to take corrective actions.
Note: To be verified, IP parcels and advanced jumbos may be realized
through simple software updates for widely-deployed link types such
as 1/10/100-Gbps Ethernet. If the network driver API provides a
primitive allowing the IP layer to disable link layer integrity
checks on a per-"packet" basis, even very large IP parcels and
advanced jumbos should be capable of transiting the link since
Ethernet link transmission unit sizes are bounded by software and not
hardware constraints.
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