[Sois-sig1] Proposed method for discussion

[Takahiro Yamada]

Dear sig1 members,

In this message I'd like to propose a method for discussing networking 
issues so that we can exchange opinions in a systematic way and reach 
agreements efficiently by the face-to-face meeting scheduled for 
October 29.

I'd appreciate it if you could give me any comments and/or suggestions 
on this method. Alternative proposals for a method of discussion are 
also welcome.

(A) Proposed method

This method consists of three steps.

Step 1: Identify requirements

We have already discussed requirements we have for onboard networking 
and protocols in the mailing list, but I think we should re-state our 
requirements with a common set of terms in order to make sure that 
everybody understands the requirements in the same way. A proposed 
template for expressing requirements is shown in (B) of this message.

Step 2: Evaluate candidate protocols

Based on the identified requirements, we should evaluate candidate 
protocols to see how they meet the requirements. We may discover areas 
where no existing protocols meet the requirements. In the latter case, 
we should formulate requirements for new protocols.

Step 3: Synthesize a network architecture

Based on the findings of step 2, we should synthesize an architecture 
to show how the protocols are to be used in real systems. This 
architecture should basically be based on the Open Systems 
Interconnection Basic Reference Model (OSI-BRM) and the Reference 
Architecture for Space Data Systems (RASDS), but we may need to add 
some things to them to accommodate special protocol configurations we 
need for our spacecraft.

References on the RASDS are found at:
http://www.ccsds.org/docu/dscgi/ds.py/View/Collection-279

(B) Standard template for expressing requirements

For each type of system or mission, a set of requirements should be 
identified using the following categorization. This is just an example 
and any suggestions are welcome.

1. Application driven requirements

Service Types
- File transfer,
- Message transfer, or
- Application dependent.

QOS
- Time critical (synchronous), or
- Delay tolerant (asynchronous).

Reliability
- Reliable (errors should be detected and/or corrected in a timely
   manner), or
- Error tolerant.

2. Topology driven requirements

Routing and relay
- Routing and relay among multiple subnetworks required, or
- Routing and relay among multiple subnetworks not required,

Addressing
- What kind of address space or spaces are required

Extent of routing/addressing
- Within a single spacecraft,
- Within a set of spacecraft,
- Between a spacecraft or a set of spacecraft and its corresponding
   ground system, or
- Between many spacecraft and many ground systems.

3. Implementation driven requirements

Onboard Bus
- Spacewire,
- Firewire,
- Ethernet,
- MIL 1553B, or
- Others.

Space-to-Ground link
- Proximity link,
- Near earth link, or
- Deep space link.


That's it.

I will distribute an example of a set requirements and an example of 
protocol evaluation next week.

Have a good weekend!

Best regards,
Takahiro Yamada, ISAS.