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Extended Attributes

Extended Attributes. RADEXT - Interim. Alan DeKok FreeRADIUS. Requirements. More RADIUS Attribute Types 256 is too limited Standard support for “long” attributes > 253 octets Better grouping RFC 2868 tags are inadequate. Un-Requirements. Systems which were discussed and rejected

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Extended Attributes

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  1. Extended Attributes • RADEXT - Interim Alan DeKok FreeRADIUS

  2. Requirements • More RADIUS Attribute Types • 256 is too limited • Standard support for “long” attributes • > 253 octets • Better grouping • RFC 2868 tags are inadequate

  3. Un-Requirements • Systems which were discussed and rejected • too complex • too limited • which can’t be applied to existing RFCs

  4. Current Attributes

  5. Extended Attributes

  6. That’s pretty much it. • “Steal” one octet of “value” for extended types • Allocate 4 attributes of this format • 241, 242, 243, 244 • Solves the “need more attributes” problem • Allows for ~1K new attributes

  7. Naming • We need to name the new attributes types. • Use SNMP / IP Address style “dotted number” • 241.{1-255} • 241.1 “This-Is-A-New-attr” • Versus • 1 “User-Name” • Naming applies only for the IANA registry

  8. Grouping • Better grouping by defining a TLV data type • Already in WiMAX, 3GPP2, and other SDOs / vendors.

  9. TLV Data Type

  10. TLV in Ext-Attribute

  11. TLVs in Ext-Attribute

  12. TLV Properties • Can carry any existing or future data type • Including TLVs. • Multiple TLVs can be on in one Ext-Attr • Nested or concatenated • Nesting is limited only by TLV-Length field • 253 / 3 =~ 80 • Practicalities show a depth of 5 is sufficient

  13. TLV Naming • Leverage the same “dotted number” notation! • 241.1.2 • RADIUS Attr 241, of type “ext-attr” • Extended Attr 1, data type “tlv” • TLV 2, data type “integer” • Allows for ~250 fields in a struct • Extends type space past 1K attributes

  14. “Long” Attributes • Leverage the Ext-Type format • Allocate 2 attributes of this type • 245, 246 • Add another field: “flags” • Standard way to say “more than 253 octets of data”

  15. Long Ext Attributes

  16. Flags • 1 bit of “M” for More (or continuation) • Same meaning as existing ext-attrs / WiMAX • 7 bits of “reserved” • We have no idea what to do with these • It’s likely that these will never be used

  17. Additional notes • 24{1-6}.26 are VSAs • Allows for many more VSAs • 24{1-6}.{241-255} are reserved • No “experimental” or “implementation-specific” • They have not been useful • Detail instructions for IANA are included

  18. Motivation • RADEXT discussions have been long • We need a solution soon (i.e. within 2-3 years) • All other solutions are more complex • Attribute audit shows the needs to be simple

  19. Attribute Audit • Public dictionaries • ~100 vendors • 55% or more are “short” (<20 bytes) • ~20 “long” attributes

  20. Summary • > 1K of new attribute space • With TLVs, potentially 10’s of 1000’s • Grouping via TLVs • Proven to work in SDO VSAs • Standard way to have “long” attrs • No more “ad hoc method”

  21. Implementations • In FreeRADIUS “stable” branch • http://git.freeradius.org • Implements TLVs, basic type • No support for “long attrs”

  22. Questions?

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