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Steps towards an 802.1ad draft. Style of specification : A recommendation Mick Seaman. What is a bridge?. A miscellaneous collection of learning and forwarding functions, more or less? Equipment conforming to 802.1D or 802.1Q? Definitely the latter!. A pure standalone standard.
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Steps towards an 802.1ad draft Style of specification : A recommendation Mick Seaman
What is a bridge? • A miscellaneous collection of learning and forwarding functions, more or less? • Equipment conforming to 802.1D or 802.1Q? • Definitely the latter!
A pure standalone standard • Related to 802.1Q as 802.1Q is to 802.1D • Restatement of service, network operation, addressing, bridge operation and mgmt. • Extensive freedom of specification • Not just a possibility but a certainty of reinvention (we can reinvent bridging too!) • A ton of work, especially in alignment
A profiling standard • Option selection from 802.1Q and 802.1D • Forces examination and use of existing standard mechanisms • No chance of accidental reinvention and misalignment • Short standard, and not much work • Over constraining for this application
Profiling with extensions • Extensions limited to expanding functionality of known architectural entities • Very powerful style but effective against reinvention • Forces in depth understanding of what is specified already • Short mandatory part • May have extensive explanation, scene setting
Example 802.1ad specification • Not a proposal for final text! • Known to be not what is wanted by some at least • However easily extensible with not much additional text to be what at least two people appear to want today • A specification of the wart without the facial disfigurement
What the example does (1) • Specifies provider bridges • For construction of secured P-networks • Provides multiple service instances to different customers by encapsulation • Uses controls already defined in .1Q • Uses protocols already defined in .1Q • No new top level entities
What the example does (2) • Provides a very rapid way to specify Q-in-Q • Aligns closely with the way existing real bridges have been deployed in provider networks
What the example does not do (1) • Multiple service instance selection on a single UNI • Two quite different approaches possible, one just varying existing control, other expands the existing VLAN classification process • Define provider-provider interfaces • Improve performance of L2 protocols over lossy and reordering links
What the example does not do (2) • Provide any supporting tutorial information • Sift through every L2 protocol to see where it terminates etc. etc. (this is a necessary study activity) • Prevent different provider tag styles being standardised (actually makes it easy) • Prevent extensions to user priority classification
Recommendation • Adopt the profile with extension/expansion methodology as a guide to what we are attempting to mandate in this standard • Focus discussion and proposals from the start! • Consider the proposed standard as an amendment to 802.1Q (and possibly as a future extension to the MAC Service Definition)