[Sis-dtn] HPRP Orange Book - Draft A for Comments

[Sipos, Brian J.]

Felix and Jeremy,

This is a good definition of this protocol so far. I have a few feedback
comments to clarify some things.

 

One aspect of the HPRP that doesn't seem to be discussed is the technical
relationship between HPRP and LTP in the sense that the two protocols can be
disambiguated over the same (datagram) channel. They put the version code in
the same starting spot in each datagram and use disjoint code points that an
endpoint or a middlebox can use to distinguish them. This could be
explicitly not a requirement for interoperation between LTP and HPRP over
the same paths, but just to mention that it could happen and there is no
problem in doing so.

 

In Section 3.6 I think the need from the underlying layer are not just to
send and receive segment data, but when sending there must be either a
notion of a destination (parameterized by engine ID perhaps) or a discussion
that this parameterization assumes that the underlying layer is assumed to
be point-to-point with a single peer engine (and if there are actual link
addresses required those addresses need to be handled outside of the HPRP
engine/layer).

 

In Section 3.6 it would be helpful to have an explicit statement that this
protocol does not rely on there being any relation between the forward and
return path taken by segments between two HPRP engines. They could involve
completely separate underlying transport, framing, or link layers.

 

Generally about the integer fields: I don't see any statements about the
endianness of multi-octet integers. It would be good to be explicit about
this, maybe at the start of Section 4.

Is there an expected use/need/benefit from non-power-of-two encoded sizes?
Is there any requirement for minimum-length encodings? Can an engine choose
to just use 4-octet (or whatever other fixed length) encodings for
everything (assuming it fits all needed values)?

 

One other nit: The "session length" field may be less confusingly called the
"block length" to use the term "block" consistently with other parts of the
document.

 

From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org> On Behalf Of Felix Flentge
via SIS-DTN
Sent: Tuesday, March 5, 2024 8:10 AM
To: Dr. Keith L Scott via SIS-DTN <sis-dtn at mailman.ccsds.org>
Subject: [EXT] [Sis-dtn] HPRP Orange Book - Draft A for Comments

 


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Dear All,

 

Jeremy and myself produced a new draft for the HPRP Orange Book.

 

Please note that there are still some open questions which also may lead to
some updates of the data formats. In addition, we certainly need to work on
the specification of the protocol behaviour.

 

The document is available in Google Docs. Please add any comment you may
have directly to the document.

 

https://docs.google.com/document/d/1WsxgHSiG7UQNiHNHXtPOv9Dd98fK_ZKN/edit?us
p=sharing
<https://docs.google.com/document/d/1WsxgHSiG7UQNiHNHXtPOv9Dd98fK_ZKN/edit?u
sp=sharing&ouid=113258250953253070571&rtpof=true&sd=true>
&ouid=113258250953253070571&rtpof=true&sd=true

 

Regards,

Felix

 

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