Changes%20to%20the%20ForCES%20Model

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Changes to the ForCES Model

• 7-March-2005
• Presented by Joel Halpern
• jhalpern_at_megisto.com

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Summary of Changes

• FE Object now an LFB
• Added Element Identifiers
• For LFB Classes, LFB attributes, and structure
  components
• Add Content Keying
• Added Alias starting point
• Added variable length octet sequences

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FE Schema -gt LFB Class

• Class ID 1, Instance ID 1
• Captures all the information that what is in the
  previous FE schema
• Called the FE Object LFB Class
• Probably still could use some additional
  information

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Element Identifiers

• For LFB Classes, added attribute LFBClassID to
  hold the identifier of the class.
• Class IDs must be globally unique, across all
  libraries. Should we introduce a 16 bit library
  ID?
• For attributes, capabilities, and structure
  elements, added elementID attribute
• Provides identifiers for use in paths

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Content Keying

• An array declaration can declare one or more
  combinations of fields as keys.
• Each key is declared with a ltkeygt element.
• Which has a keyID attribute
• And one or more ltkeyFieldgt elements to declare
  the parts of the key
• Should this be called contentKey?
• Should we wrap the multiple ltkeygt occurences in a
  ltkeysgt (or ltcontentKeysgt) element?

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Key Declaration Example

• ltarray typevariable-sizegt
• lttypeRefgtIPneighborlt/typeRefgt
• ltkey keyID1gt
• ltkeyFieldgtIPaddresslt/keyFieldgt
• lt/keygt
• lt/arraygt
• Assuming that IPneighbor has IPaddress

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Alias for sharing between LFBs

• An ltaliasgt declaration declares
• The name of the alias
• The type of the alias
• And has an elementID attribute
• An Alias implicitly creates four pieces
• The LFB Class and LFB instance of the target
• The path to the target attribute
• An element to dereference to the shared value

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Issues and Topics

• Configured Adjacency Description
• Element Meta Information
• Events
• Optional Elements
• Unlimited length strings

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Configured Adjacency

• The current definition reflects configuring
• MAC or IP address of the neighbor
• the port through which the neighbor is reached.
• Suggestion is to replace the address with the
  nrighbors FE ID and port information
• Since this is for the case where the neighbor is
  under control of the same CE

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Element Meta-Information

• Currently, we have capabilities
• Which can carry anything at the LFB level
• No easy way to express consistent capabilities
• No easy way to express structure or array element
  capabilities
• Optional elements, read / write
• Should we create a protocol syntax for working
  with this kind of information?

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Events

• We have to have event reporting
• We have to have a way to define what events an
  LFB may generate
• And what information to include in the report
• We need boolean variables for the CE to set which
  events it wants
• And this has to be understandable. It is way to
  easy to get very complex here