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<p class="MsoNormal">Dear SEA-SA SCCS-ARD interest group,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">We held a Webex on 6 Mar 23 to discuss the status of SCCS-ARD edits. The focus was primarily on Section 5, Physical View, which is all about the kinds of Nodes that we define, where they are typically deployed, and what sorts of functions
they are expected to implement. We explicitly associate those functions with the protocols that are used, but the protocols, and the specific protocol stacks, are really described in depth in Chap 6, the Protocols View.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Attendees: Faramaz Davarian, Karl Vaden, Shelbun Cheng, Costin Radulescu, Robert Rovetto, Peter Shames<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><u>Chap 5, Planetary Space Link Terminal (PSTL) SSI section</u><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">The SSI PSLT was a [Future] element in the original Magenta Book, largely because only SSI Stage 1 was supported by standards at that point and there is no PSLT role in Stage 1.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">For Stage 2 (a and/or b) there is the possibility of a PSLT, which may be deployed on the surface of the Moon or Mars as a comm relay asset. The various Lunar Comm architecture diagrams
that are floating around show such elements, that we would call a PSLT, in the form of a “Cell Tower”, or a Habitat, that provide relay functions. See attached LunaNet Security diagram, especially pg 4.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">We discussed the allocated functions in a PSLT, which include all of the standard link layer functions (and protocols), and also the potential inclusion of the SOIS Wireless protocols,
WiFi and 3GPP.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">As you can see from the diagram these PSLTs potentially have to include long haul protocols back to Earth (USLP, AOS) and Proximity (Prox-1) to Orbiters and relay spacecraft (or user
spacecraft). And they have to include a variety of “proximate” communications, including Prox-1 (out to 100K Km), 3GPP (out to 10 Km), and WiFi (out to 300 M). These are all link layer protocols.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">The PSLT must also include either DTN protocols (including store and forward Bundle Agent functions), or IP protocols (only provides a real time routing function).<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">The original [Future] PSLT requirement, which aligned with the understanding of the protocols documented prior to May 2015, suggested that both IP and DTN could be handled in the same
infrastructure, with the addition of a weakly specified integration approach, as shown in the following requirements:<o:p></o:p></li></ul>
<p style="margin-left:1.0in"><b><span style="font-size:12.0pt;font-family:"TimesNewRomanPS",serif">5.3.3.2.3
</span></b><span style="font-size:12.0pt;font-family:"TimesNewRomanPSMT",serif">[Future] SSI PSLT nodes shall implement one or more CCSDS-compliant space internetworking functions (reference [IPS] or [DTN]) to process, store, and route IP or DTN data in the
space link terminal. </span><o:p></o:p></p>
<p style="margin-left:1.0in"><b><span style="font-size:12.0pt;font-family:"TimesNewRomanPS",serif">5.3.3.2.9
</span></b><span style="font-size:12.0pt;font-family:"TimesNewRomanPSMT",serif">SSI PSLT nodes shall implement CCSDS-compliant LTP PDU, DTN or IP encapsulation (references [9], [10], [14], [31], [46]) in the space link terminal.
</span><o:p></o:p></p>
<p style="margin-left:1.0in"><b><span style="font-size:12.0pt;font-family:"TimesNewRomanPS",serif">5.3.3.2.14
</span></b><span style="font-size:12.0pt;font-family:"TimesNewRomanPSMT",serif">[Future] SSI PSLT shall implement protocol and PDU conversion and bridging functions in the relay asset (reference [D7], [D24]).
</span><o:p></o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">In working our way through these drafty SSI (IP and/or DTN) requirements, and the currently understood PSLT functions, it has become clear that we really need to treat IP and DTN as
separate kinds of networks, with separate semantics, and with specific “bridging functions” in the PSLT.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">We had a lengthy discussion of the very real differences in the semantics of the “Internet Protocol Suite” (IPS) vs the DTN Protocol Suite (DPS).<o:p></o:p></li><ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">IPS assumes continuous, end-to-end connectivity. TCP provides once only, in order, without omission, delivery of streams of IP datagrams in a low latency environment. Low round trip
light-time delays (RTLT < 1 sec) are assumed and are “baked into” the protocols. <o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">The core structural element of IPS is an IP router that operates in real time to route IP Datagrams.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">IPS also depends upon a core set of ancillary protocols that are often not mentioned (Domain Name Service (DNS), routing protocols, inter-system routing protocols, management protocols,
security and key management protocols, are among the key ones). <o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">IPS supports use of chatty protocols like HTTPS and SMTP, as well as streaming protocols that we all rely upon, such as voice, video, and streaming movies from NetFlix.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">The Internet is composed of a set of Autonomous Systems.<o:p></o:p></li><ul style="margin-top:0in" type="square">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1"><a href="https://www.cloudflare.com/learning/network-layer/how-does-the-internet-work/">The Internet</a> is a network of networks, and Autonomous Systems are the big networks that
make up the Internet. More specifically, an autonomous system (AS) is a large network or group of networks that has a unified
<a href="https://www.cloudflare.com/learning/network-layer/what-is-routing/">routing</a> policy. Every computer or device that connects to the Internet is connected to an AS.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Every AS controls a specific set of IP addresses, just as every town's post office is responsible for delivering mail to all the addresses within that town. The range of IP addresses
that a given AS has control over is called their "IP address space."<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">All of the Address Spaces for all of the interconnected AS are managed locally, but coordinated globally.<o:p></o:p></li></ul>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">DPS assumes dis-continuous, end-to-end (hop by hop) connectivity. BP provides delivery of streams of DTN Bundles in a high latency, disconnected, environment. High round trip light-time
delays are assumed and are “baked into” the protocols, as is the ability to handle disruption.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">The core structural element of DPS is a Bundle Agent that operates a store and forward bundle delivery service.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">DPS also depends upon a core set of ancillary protocols that are often not mentioned, and are largely not yet standardized (a “DTN Domain Name Service (DDNS)” and node/endpoint identities),
DTN routing protocols (SABR exists but no routing update), inter-system routing protocols (non-existent), management protocols (ADM in IETF drafts only), security and key management protocols (BPSec, but not yet key management), are among the key ones.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">DPS does not support use of chatty protocols, it uses bundle protocol (hop-by-hop, store & forward) and also streaming protocol (experimental) for voice & data where a contemporaneous
link exists end-to-end.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">The DPS does not (yet) document the notion of Autonomous Systems nor of separate, managed, Address Spaces, but it is now developing the concepts of DTN namespaces. Since DTN names
(node IDs and endpoint IDs) use URI’s and there are not (yet) registries documenting which specific nodes are assigned, nor where they are, nor how they can be accessed, routing and paths are not (yet) clearly specified.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph" style="margin-left:1.0in"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">IPS can be deployed in any closely connected environment, with short RTLT and low latency. Any such deployment of an “autonomous system” that is sufficiently remote from the Internet
will need its own locally managed address space, its own routing, its own DNS, and its own identity management & policies. And it will need the means to coordinate IP addresses with the terrestrial Internet, even though it is disconnected from it.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">DPS can be deployed in any continuously (or occasionally) connected environment. Any such deployment of a “DTN autonomous system” that is sufficiently remote from the Internet will
a coordinated address space, coordinated routing, coordinated DNS, and coordinated identity management & policies. And it will need the means to coordinate DTN entities, addresses, and identities with the terrestrial Internet, even though it is frequently
disconnected from it.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph" style="margin-left:1.0in"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">After discussion we arrived at this sort of formulation for the different kinds of PSLT that might be needed.<o:p></o:p></li><ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An IP PSLT may be deployed and may service as a routing node for the local IP Internet. It may use only IP within the local network. It (or some ancillary node that is reachable)
will have to support: routing, DNS, identity registration & management, and network management and policies within the local network (AS).<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An IP PSLT will provide support for standard IP services within the local Autonomous System.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">Any node that is not directly reachable by some combination of continuously connected links will only be reachable via a DTN protocol translating gateway, see next…<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An IP PSLT may provide protocol translating gateway services (TBS) for a specific subset of IPS protocols & services that are amenable to such treatment. These protocols and services
are likely to include: email gateway, file delivery gateway, streaming voice and video file delivery gateway, some sort of DNS and identity update service, and possibly some sort of web service bulk update gateway (configured for local AS proxies) … this last
part seems like a stretch.<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">These protocol translating gateway services will have to do something like:<o:p></o:p></li><ul style="margin-top:0in" type="square">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Terminate each of the IP-based services within the remote AS<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Package the protocol PDUs and data into a file<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Add meta-data about the intended destination on Earth<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">And ship the file and meta-data, via DTN, to a paired protocol translating gateway on Earth<o:p></o:p></li></ul>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">The paired protocol translating gateway services on Earth will have to do something like:<o:p></o:p></li><ul style="margin-top:0in" type="square">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Accept the file and meta-data, via DTN, from a paired protocol translating gateway on the remote planet<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Access the meta-data about the intended destination on Earth
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">“Reconstitute” the protocol PDUs and data from the file<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level3 lfo1">Send the data to the specified IP address on Earth using the specified IP-based services within the Earth AS<o:p></o:p></li></ul>
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">Where protocol translating gateway services are in use at a PSLT we assume that a corresponding paired gateway will be available at the servicing ESLT, or at a node that is reachable
by DTN protocols.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph" style="margin-left:1.0in"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An SSI Stage 2 PSLT may be deployed and may service as a routing node for the local DPS Internet. It may use only DTN protocols within the local network and remotely. It (or some
ancillary node that is reachable) will have to support local and off-planet: DTN routing, DTN DNS, DTN identity registration & management, and DTN network management and policies within the local network (AS).<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An SSI Stage 2 PSLT will provide support for standard DTN services within the local Autonomous System and provide support to remote systems, using DTN delay tolerant store & forward
protocols. <o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">Any node that is reachable by some combination of continuous or intermittent links may be reached by DTN protocols.
<o:p></o:p></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An SSI PSLT may also provide protocol translating gateway services (TBS) for a specific subset of IPS protocols & services that are amenable to such treatment. These protocols and
services are likely to include: email gateway, file delivery gateway, streaming voice and video file delivery gateway, some sort of DNS and identity update service, and possibly some sort of web service bulk update gateway (configured for local AS proxies)
… this last part seems like a stretch.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph" style="margin-left:1.0in"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<ul style="margin-top:0in" type="circle">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level2 lfo1">An SSI PSLT may support all of the functions of an IP PSLT as well as all of the functions of an SSI PSLT.<o:p></o:p></li></ul>
</ul>
<p class="MsoListParagraph"><o:p> </o:p></p>
<ul style="margin-top:0in" type="disc">
<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1">We also reviewed, briefly, the IOAG Collaborative Security draft materials (pg 3 in particular) which documents the published (green), not yet fully specced (orange) and missing (red)
DTN security and network management functions. This was relevant to understand the functions needed in an SSI PSLT and to understand what must be added to make DTN Stage 2 a complete interoperable reality.<o:p></o:p></li></ul>
<p class="MsoListParagraph"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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