Unified Link Layer API

ULLA Query Language (UQL)

Basically, the UQL is a subset of the Structured Query Language (SQL). Additionally, there is a fixed set a of tables (alias classes) describing the set of available attributes for that table. Hence, different Link Layer Adapters, or device drivers supporting ULLA, would support different tables. However, there is the mandatory ullaLink table, supporting the most generic and common attributes.

An example for a simple valid UQL statement is:

"SELECT rxBandwidth, linkId FROM ullaLink;"

Joined queries

In order to support also queries spanning over multiple tables this implementation supports joined-queries using multiple tables in the from_clause of the select_statement. Please refer to the man-page for further details.

A single LLA can support multiple tables The LLA registers its tables with ULLA at load time, which enables ULLA to support also future technologies with the need for new attributes. For instance, rxBandwidth is an attribute of the ullaLink table, whereas rtsThreshold is an IEEE 802.11 specific attribute and contained in the p80211Link table.

An example for a simple joined-query UQL statement is:

"SELECT ullaLink.linkId, p80211Link.SNIR, p80211Link.rtsThreshold
FROM p80211Link, ullaLink
WHERE ullaLink.state = 2 AND ullaLink.rxBandwidth < 1000000;"

Note, that "state = 2" maps to the connected state. The list of defines is included in the ulla/lu.h header file.

Link Model

The LLA will register a new link to the ullaLink table if a new peer is visible via its card in use.

This ULLA implementation supports composition and aggregated links to show inter-dependencies between links: Each link has an attribute parentId. If the parentId is set, this link is a physical link. If the parentId is equal to the linkId there will be no associated aggregated link. Otherwise the parentId indicates the associated aggregated Link by its linkId.

Lexical and Grammar Specification

The lexical and grammar spcification of the UQL is available in the Backus Naur Form (BNF) as used by LEX and YACC. Please refer to the man pages for further details.