[Sis-dtn] [EXTERNAL] IPN URI Scheme Service Numbers

Wed May 24 09:25:12 UTC 2023

Hmm,

What I would expect missions to come up with is something like:

1 – essential HK TM in packets (e.g., ESA PUS format)
2- TC packets for immediate execution (e.g., ESA PUS)
3 – CFDP Uplink
4 – CFDP house-keeping downlink
5 – CFDP payload downlink
(or some combination of the CFDP stuff but we may have different CFDP entities for uplink/house-keeping/payload)
Human spaceflight might add something for voice and video.

Now the question would be for me whether we consider this private use (I would think so), or if we would standardise e.g, SN 1 = essential housekeeping TM but leave the format open?

I don’t fully understand that for relaying CFDP data we would need to have a standardised service number unless we want to implement network policies based on service numbers (e.g., priorities or convergence layer choices). I am not sure whether this would be a good generic approach (could make sense for limited networks but these could define their own service number assignments within their policies). For a more generic approach, I would prefer having explicit BP extensions for QoS.

Having said this, I believe having standardised service numbers for generic, ‘network-related’ services makes a lot of sense to me, e.g. bpecho (to allow using bping for connectivity testing) and network management related functionalities (e.g., provision of contact information, network management, registries, DNS-like functionalities,  …).

Regards,
Felix

From: SIS-DTN <sis-dtn-bounces at mailman.ccsds.org> On Behalf Of Torgerson, J. Leigh (US 332C) via SIS-DTN
Sent: Tuesday, May 23, 2023 10:40 PM
To: EXTERNAL-Birrane, Edward J (US 9300-Affiliate) <Edward.Birrane at jhuapl.edu>; sis-dtn at mailman.ccsds.org
Subject: Re: [Sis-dtn] [EXTERNAL] IPN URI Scheme Service Numbers

I generally agree with the proposal Ed outlines (though I would like to reserve all 1 or 2 byte SN’s as standards, and leave the private use service numbers for the 3 or 4-byte encodings, much like the convention of the first 1024 IP well-known ports, since everyone should want to be using standard application services like bping, other snmp-like applications, and for deep space use, CDFP at least.. Standard 1 or 2 byte service numbers for the most common applications would be more efficient.

Why not all private? If a program (say, the Mars program) wants all nodes to be able to host a CFDP client that identifies itself as service number 65, then if a mission is launched later, and it wants to relay CFDP data through one of the other Mars nodes, then it will have to use service number 65, or arrange with other nodes to use some other service number, which will take intervention by the operators of the other nodes.

This is the primary operational need to agree on some standard conventions for service numbers. I don’t think you want every DTN node in an IPN network to be able to pick its own service number for each application. (Some underlying convergence layer choices in a relay situation may depend on knowledge of the application so the correct convergence layer may be chosen for the next hop, and if the service numbers aren’t standardized, it will be a crap shoot at any relay node.)

We’re trying to create an easily-interoperable DTN-enabled network, and I don’t see why standardized service numbers are controversial.  Is it a matter of food-fights between “registry organizations”? Is it a matter of how many bytes you use because of the CBOR encoding? IDK, but I do think making service numbers all “private” is a really bad idea – it just kicks the can down the road and leaves room for a lot of chaos as the SSI and DTN scale up.

Leigh

On 5/22/23, 5:49 AM, "SIS-DTN on behalf of Birrane, Edward J. via SIS-DTN" <sis-dtn-bounces at mailman.ccsds.org <mailto:sis-dtn-bounces at mailman.ccsds.org<mailto:sis-dtn-bounces at mailman.ccsds.org%20%3cmailto:sis-dtn-bounces at mailman.ccsds.org>> on behalf of sis-dtn at mailman.ccsds.org<mailto:sis-dtn at mailman.ccsds.org> <mailto:sis-dtn at mailman.ccsds.org>> wrote:

WG,

Last week at the SIS-DTN weekly meeting we had a good discussion on allocation strategies for IPN service numbers.

IIRC, there were three major areas of discussion related to these numbers: encoding size, allocation policy, and registry ownership.

The encoding size discussion noted that the CBOR encoding of service numbers creates a very small allocation of 1-byte encodings (0-23), a small allocation of 2-byte encodings (24-155), a moderate size allocation of 3-byte encodings (256-65,535), and then 4+ byte encodings that give us the remainder of the 64bit service number space.

The allocation policy discussion noted that there was a good case for "private use" service numbers for mission-specific use cases (commanding, telemetry) that do not otherwise map to a standardized protocol. These mission specific service numbers should not be standardized (they are mission specific) and there should be some allowance for them in the small encoding space since they will be used by missions often (perhaps most often).

The registry ownership discussion noted that IANA is creating (updating really..) a registry for service numbers and should there be a SANA allocation in that registry.

At the end of the discussion the following proposal was put forward:

1 byte service numbers (1-23) will be private use .

2 byte service numbers (24-255) will be expert review with a 64-id chunk allocated to SANA.

3 byte service numbers (256-65k) will be cut 1/3 private use, 1/3 IANA managed and 1/3 IANA managed but given to SANA.

4 byte will have a chunk of experimental.

4+bytes is unassigned.

This continues to be an area of active discussion in the IETF mailing list. Some IETF participants are proposing that all service numbers be private-use and there be no standard service numbers since service discovery is better done today independent of port numbers. I disagree with this position - service numbers are not port numbers - but that case needs to be made, for those interested in following the discussion on the IETF mailing list.

-Ed

---

Edward J. Birrane, III, Ph.D. (he/him/his)

Chief Engineer, Space Constellation Networking

Supervisor, Embedded Applications Group

Space Exploration Sector

Johns Hopkins Applied Physics Laboratory

(W) 443-778-7423 / (F) 443-228-3839

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