TRIP Transit Network Support draft-walker-iptel-trip-tns-00.txt Dave Walker ( )

03 August 2000 Dave Walker SS8 Networks 2 Background PSTN (usually) offers multiple routes to destination which may traverse different carriers networks Transit Network Selection indicates (ordered sequence of) preferred carriers –Q.931 Setup, ISUP IAM national identification plans –ANSI ISUP: 4 digits (0-9,B,C) administered by NANPA user may presubscribe, or may explicitly dial a Carrier Access Code (including dial-around) networks respect TNS except for local termination

03 August 2000 Dave Walker SS8 Networks 3 Why should this matter to IPTEL? in the near future, have to allow users access to both IP and PSTN based carriers –for IP based carriers, set the Request-URI appropriately... –for PSTN based carriers, IP network must route the call to the specified network could try to route to gateway nearest destination, then local PSTN call, but... –callee's preferred local provider may be inaccessible –not all destination areas may be local to gateways –best (cheapest, shortest,...) may be via PSTN instead of IP want to provide best route into the specified network

03 August 2000 Dave Walker SS8 Networks 4 TRIP based Solutions 1.define a new TRIP Address Family 2.define a new TRIP Attribute

03 August 2000 Dave Walker SS8 Networks 5 Representation encoding of TNS is specific to national plans solution: identify by prefixing country code transit-network = country-code network-identifier country-code = 3DIGIT network-identifier = *network-digit network-digit = DIGIT | 'A' | 'B' | 'C' | 'D' | 'E' | 'F' | Length | TN prefix (variable) | Transit Network is a sequence (size determined by overall length) | transit-network1... | transit-network2... |

03 August 2000 Dave Walker SS8 Networks 6 Proposal 1 - New Address Family route on TN regardless of dialled number (excl. CAC) new database key value (currently POTS, RoutedNumber) –POTS, RN still advertised separately (useful if TN not selected) issue: call signalling may be sub-optimal –correct route may require both E.164 and TN (but same key) –E.164 and TN may have different "best" routes

03 August 2000 Dave Walker SS8 Networks 7 ITAD2 ITAD1 ITAD3 We need both E.164 and TN gateway to TNa (+1408*) gateway to TNa (+1617*) originator INVITE ;TN=a Reachable=TNa

03 August 2000 Dave Walker SS8 Networks 8 Proposal 2 - New Attribute Type TN is an optional attribute of E.164 ReachableRoute –flexible –reaching all E.164s (i.e. "*") equivalent to new address family can use existing TRIP DBs with addition of new key issue: complexity –affects E.164 aggregation and equivalence rules

03 August 2000 Dave Walker SS8 Networks 9 Whats Next? choose best proposal ensure all national plans satisfied clarify intra- & inter-domain behavioural differences –e.g. does carrier prefer internal GW to TN over own external (i.e. different ITAD) GW to E.164? meet requirements of section 5.12 for new attribute specification describe TN usage in sip: and tel: URLs

03 August 2000 Dave Walker SS8 Networks 10