SIP.edu by Numbers: SIP.edu by Numbers Ben Teitelbaum SIP.edu Working Group Call June 23rd, 2005


Big Problem: Big Problem How to SIP from a 12-key phone?


Big Question: Big Question Use E.164 or Not?


Use E.164 Numbers: Use E.164 Numbers Pros Seamless interoperability with PSTN No need to change numbers Cons Not our numbers Finite resource Regulatory implications “If it walks like a duck…” Seamless interoperability with PSTN (i.e. users should notice that something has changed!)


Use Non-E.164 Numbers: Use Non-E.164 Numbers Pros Our numbers Numbers could be more mnemonic Users will notice that something has changed Lighter regulatory touch (maybe) Could fit into E.164 down the road (+87810…) Cons Calling from PSTN would require two-stage dialing Calling from a legacy campus environment would require an escape code


E.164: E.164 Cons out-weigh pros Various implementation options Dial plan distribution ENUM DUNDi Private ENUM or SIP redirect server Not discussed further here


Non-E.1641/2: Non-E.1641/2 Pros out-weigh cons Some design considerations Numbers derived from SIP.edu addresses, derived from existing extensions, or completely new? Address structure Flat or hierarchical? Fixed length or variable-length? Escape codes


Non-E.1642/2: Non-E.1642/2 Various implementation options IVR Gateway Hash Registrar Domain Redirect Others? Let’s discuss them… First, though, a few words on… Address Structure Escape Codes


Address Structure*: Address Structure* (prefix)(hash) Requires central authority to resolve hash (prefix)(user)(domain) Like email Perhaps “00” could be used as separator (prefix)(domain)(user) Maps to DNS (e.g. non-E.164 ENUM) (user) part could be interpreted locally * Thanks to Ed Guy for this taxonomy.


Escape Codes: Escape Codes Campus dialing plans must designate some escape code to indicate that a “SIP.edu number” follows E.g. **EDU (**338) Local conventions will vary Will variable-length numbers be a problem?


IVR Gateway: IVR Gateway Two-stage dialing through central GW Gateway generates SIP.edu INVITE dbaron@mit.edu = **338 then… Speak “dbaron at MIT dot e-d-u” (voice recognition) Type 3122217363620614381 (two-tap DTMF codes) T9® predictive text—probably not (proprietary technology; dictionary too big) Voice only (“I-IM-R”?)


Hash Registrar1/3: Hash Registrar1/3 Each campus forwards UA registrations to a central registrar Hash SIP.edu address to 8-10 digits dbaron@mit.edu = **338xxxxxxxxx md5(‘dbaron@mit.edu’) % 109


Hash Registrar2/3: Hash Registrar2/3 Hash collisions Make ‘em rare Resolve through an IVR (“Press one for dbaron@mit.edu; two for alice@wonderland.edu.” ) Or (maybe) don’t resolve (“Bad luck, you will have to get a new email address if you want to be SIP-able by numbers.”)


Hash Registrar3/3: Hash Registrar3/3 Pros Knowing an email address  knowing the number Simplifies identity management Users don’t get explicit numbers CGI “white page” can compute hash and produce number Cons Only registered UAs reachable by number Collisions Requires campus proxy / registrar to pass REGISTERs


Domain Redirect1/4: Domain Redirect1/4 Mnemonic campus prefixes Central redirect server interprets prefixes and redirects to campus proxy dbaron@mit.edu = **338648xxxxx = **338xxxxx00648 “MIT” Locally interpreted by MIT (could be extension or username hash)


Domain Redirect2/4: Domain Redirect2/4 Default Campus Prefixes


Domain Redirect3/4: Domain Redirect3/4 Some defaults collide mit = niu = 648 Others have colliding prefixes 28 (bu) 282 (cua) 282875 (auburn) Suggested policy First come, first served Can’t have a default unless its yours Resolve conflicts Different lengths mit + 5-digits niu + 6-digits Numbering knowledge mit + [2357][0-9]{4} niu + [468][0-9]{4} Use a non-default prefix 645 (nil)


Domain Redirect4/4: Domain Redirect4/4 Pros Each campus can number its own way Existing extensions Username hash New numbers Reaches all campus phones Prefix gold rush Cons Prefix gold rush Prefix collision resolution could get tricky I like this option! Full Disclosure…


SIP.edu Reachability: Present and Future: SIP.edu Reachability: Present and Future To: From:


SIP.edu Reachability: Present and Future: SIP.edu Reachability: Present and Future To: From:


SIP.edu Reachability: Present and Future: SIP.edu Reachability: Present and Future To: From: