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Analyze RFC $0 and produce a structured summary for protocol dissector implementation.

Workflow

Step 1: Check for RFC updates

1. Use WebFetch to retrieve https://www.rfc-editor.org/info/rfc$0
2. Look for "Updated by" and "Obsoleted by" fields
3. If an obsoleting RFC exists, analyze that RFC instead
4. If updating RFCs exist, also fetch their txt versions in Step 2

Step 2: Fetch all relevant RFC texts

IMPORTANT: Always use the plain-text version.

1. Fetch https://www.rfc-editor.org/rfc/rfc$0.txt using WebFetch
2. Also fetch each updating RFC's txt version found in Step 1
3. Do NOT use the HTML version. The txt version preserves ASCII art header format diagrams exactly, which is critical for accurate bit-level field extraction.

Step 3: Extract and analyze

Analyze the base RFC and all updating RFCs together to produce a single unified field table:

1. Locate the header format diagram (ASCII art with bit positions) in the base RFC
2. For fields that have been redefined by updating RFCs, use the updated definition (e.g., RFC 791 "Type of Service" was replaced by RFC 2474 "DSCP" + RFC 3168 "ECN")
3. Extract every field: name, bit offset, bit width, byte offset, byte width
4. For each field: valid ranges, default values, reserved bits, behavioral notes
5. Identify the dispatch key (how this protocol indicates the next layer)
6. Identify error conditions: minimum header size, invalid values, truncation points

Every field MUST have an RFC section citation. When a field is redefined by an updating RFC, cite the updating RFC, not the original. Bit-level precision required.