[Sls-slp] Re: Encapsulation Service

Greg Kazz greg.j.kazz at jpl.nasa.gov
Fri Mar 24 18:28:10 UTC 2006


Thanks for your comments. They have helped make the Encapsulation Service a 
better specification.  My answers to your comments are in ** ** below.



At 03:05 PM 3/23/2006, Thomas Gannett wrote:
>FYI:  The CESG poll on encapsulation serve has received at least one 
>"Approve with Conditions" vote (from Durst).  The conditions are below.
>APPROVE WITH CONDITIONS:  1 (33.33%) (Durst)
>In section 2.2, it is unclear what the conformance requirements 
>are.  There are two protocols (Space Packet and Encapsulation Packet) 
>under a single service interface.  Are both required for conformance?

**Both protocols can be used to encapsulate other protocols. For example, 
CFDP can be encapsulated into space packets by using APID=2045 or into an 
Encapsulation packet by using PID = '110'. I need to know more about what 
you are expecting in terms of "conformance requirements". The encapsulation 
service specifies the inputs, what protocols are used to do the 
encapsulating, and references the Space Link Identifiers document, which 
supplies all of the IDs one needs in order to carry out the service.**

>The document requires a SANA Implications section to address registered 
>APIDs and PIDs, and to define procedures to register new APIDs and PIDs.

** All of the IDs used by the Encapsulation Service are defined in the 
Space Link Identifiers spec. This is true for all of the link layer 
protocols. Therefore, it is the Space Link Identifiers book that requires a 
SANA implication section, not Encap. service.  APIDs and PIDs are defined 
in the Space Link Identifiers book which is referenced in section 2.3 **

>The document requires a security implications section.

** I will work with Howie on how to accomplish this **

>Section  It is unclear to me whether and how a user of the 
>service is expected to know the correct GVCID and PVN to use.  Are these 
>statically assigned?  Assigned on a per-mission basis?  What are the 
>implications on interoperability?

** GVCID = SCID + VCID. SCID is statically assigned. VCID is an enterprise 
or project managed parameter. CCSDS recognizes certain PVNs. All of these 
IDs are defined and their values are listed (if not a managed parameter) in 
the Space Link Identifiers spec. For things like PVN it's very static. For 
APIDs, an enterprise has to really manage these across the enterprise in 
order for interoperability to happen. Global enterprise APIDs begin to 
happen in these cases. **

>Section 4.1, item b)  the APID "shall be one of the reserved APIDs" 
>defined in reference [8].  Are there guidelines or further restrictions on 
>how a particular APID is chosen?  Does interoperability depend on this 
>choice?  In Table 5-2 of reference [8], there appear to be two degrees of 
>"reserved" -- reserved and assigned to a particular protocol, and reserved 
>but unassigned.  Are any of these fair game?  Or was it intended that 
>these be drawn from the 2040-2044 range?

** Again APIDs are a managed parameter by an enterprise except for the ones 
defined in the CCSDS Space Link Identifiers book. There are no further 
restrictions except the ones managed by the enterprise. Yes, 
interoperability is an issue for the management of those apids. It is 
intended that 2040-2044 be used for encapsulation by space packets. **

>Section, item g -- this is a poorly worded summary of section 
>  Recommend rewording to "Packet Length (0, 1, 2, or 4 octets) -- 
>See Figure 4-2.

** Agreed. It will be changed to Packet Length (0, 1, 2, or 4 octets). **

>Section -- "The value '110'..." does this require a RID against 
>135.0-B-2 (or whatever)?

** The PID value '110" needs to be added to Space Link Identifiers blue 
book via a new pink sheet **

>Section -- "The extended protocol IDs..."  I didn't see this in 
>reference [8].  Does it require a RID?

** A new table called "Extended Protocol IDs" needs to be added to the 
Space Link Identifiers blue book via the new pink sheet. **

>As a note to the secretariat, I'd suggest that we add an Annex for red 
>books that require modifications to other documents that consolidates 
>and  summarizes those external dependencies. ** I agree **

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