1. 148 Sidevõrgud IRT 0020 loeng 1215. nov. 2005 Avo Ots telekommunikatsiooni õppetool, TTÜ raadio- ja sidetehnika inst. avo.ots@ttu.ee

2. 149 Digital Phone IP Phone SIP Presence Services Soft-phone IM Client PC w/ USB Camera Converged Presence- Based Client Mobile Phone Collaborative Applications SIP and Presence

3. 150 How Do I Contact Someone? –How can I contact them? IM, voice, cell, e-mail, video? Can my system talk to their system? –Are they available? Are they on the phone or in a meeting? –Are they the right person for the inquiry? –How do I arrange a conference call? What if they don’t dial into the teleconference? –How do I share information? The Communications Detective

4. 151 The Big Picture Goal: a single communications infrastructure unifying collaboration, real-time communications, and presence –Convergence not of voice & data, but rather convergence all forms of real-time communications into a unified application Combined with collaboration tools Integrated into business applications & processes Extensible beyond organizational boundaries Delivering measurable business benefit by streamlining and improving the ability for individuals and groups to communicate Converge non-real time communications (e-mail) –Voice but just one component of a converged communications & collaboration infrastructure

5. 152 What is SIP? Session Initiation Protocol  protocol that establishes, manages (multimedia) sessions –also used for IM, presence & event notification –uses SDP to describe multimedia sessions Standardized by IETF, 3GPP (for 3G wireless), PacketCable

6. 153 Building Applications On Sip Applications for example instant messaging can be built on SIP. Such applications are quick to write with any SIP toolkit and are easily extensible. User agent Proxy server Proxy server User agent ACK OK invite OK ACK invite OK ACK LDAP server LDAP server lmn@tech.net--lmn@tech.net--> 138.47.19.103

7. 154 Basic SIP message flow

8. 155 SIP trapezoid outbound proxy a@foo.com: 128.59.16.1 registrar

9. 156 SIP event notification Named events Typically, used for events within conferences (“Alice joined”) and call legs (e.g., call transfer) Supports arbitrary notification bodies, typically XML SUBSCRIBE sip:alice@vmail.example.com SIP/2.0 To: From: ;tag=78923 Call-Id: 1349882@alice-phone.example.com Contact: NOTIFY sip:alice@alice-phone.example.com SIP/2.0 … Event: message-summary Subscription-State: active Messages-Waiting: yes Message-Account: sip:alice@vmail.example.com Voice-Message: 2/8 (0/2)

10. 157 SIP event architecture Does not try to route notifications (“application layer multicast”) as in SIENA –Filtering at PA under discussion (for low-bandwidth devices) rate content But most ubicomp notification groups are probably small –and message volume not likely to provide much bandwidth saving via network-based filtering Greatly simplifies trust model: no intermediaries that need to inspect content –can encrypt via S/MIME However, can build redistribution “exploders” and list subscriptions (“subscribe to engineering@hp.com”)

11. 158 SIP presence architecture PA a@foo.com: 128.59.16.1 watcher PUAs Alice Bob PUBLISH REGISTER SUBSCRIBE NOTIFY <p:presence xmlns:p="urn:…" entity="pres:alice@example.com"> open tel:09012345678

12. 159 Session mobility Walk into office, switch from cell phone to desk phone –call transfer problem  SIP REFER related problem: split session across end devices –e.g., wall display + desk phone + PC for collaborative application –assume devices (or stand- ins) are SIP-enabled –third-party call control

13. 160 Why Phone NUMBERS? Users should not be burdened with device addresses, when it’s people they really care about Addresses should be mnemonic and empower enterprises to manage the identities of their users sip:dbaron@mit.edu It’s time to put E.164 phone numbers behind us! A.G. Bell did not say: “+1-617-252-1232, come here. I need you!”

14. 161 SIP Proxy DNS SIP-PBX Gateway PBX INVITE (sip:bob@bigu.edu) INVITE (sip:12345@gw.bigu.edu) DNS SRV query sip.udp.bigu.edu telephoneNumber where mail=”bob” PRI / CAS bigu.edu Campus Directory SIP User Agent Bob's Phone SIP.edu Architecture (Phase 1)

15. 162 DNS INVITE (sip:bob@bigu.edu) DNS SRV query sip.udp.bigu.edu bigu.edu SIP User Agent SIP.edu Architecture (Phase 2) location DB If Bob has registered, ring his SIP phone; Else, call his extension through the PBX. REGISTER (Contact: 207.75.164.131) INVITE (sip:bob@207.75.164.131) SIP Proxy SIP Registrar Bob's SIP Phone

16. 163 SIP.edu Call Flow Example SIP DNS lookup for MIT.EDU points to SIP proxy –Sends INVITE to bob@mit.edu to proxybob@mit.edu SIP proxy checks MIT directory –Maps call to PBX extension – eg. 37669@mit.edu37669@mit.edu SIP proxy checks dial plan –Routes call to PBX gateway PBX rings phone

17. 164 PBXPSTN SIP/PRI Gateway SIP.edu Configuration SIP Server Campus Network Internet DNS Server LDAP Server

18. 165 PBXPSTN SIP/PRI Gateway DNS SRV Lookup SIP Server Internet DNS Server DNS SRV LDAP Server Campus Network

19. 166 PBXPSTN SIP/PRI Gateway SIP INVITE SIP Server Internet DNS Server SIP LDAP Server Campus Network

20. 167 PBXPSTN SIP/PRI Gateway LDAP Lookup SIP Server Internet DNS Server LDAP LDAP Server Campus Network

21. 168 PBXPSTN SIP/PRI Gateway Call Sent to PBX Gateway SIP Server Internet DNS Server SIP LDAP Server Campus Network

22. 169 PBXPSTN SIP/PRI Gateway Media Stream via Gateway to PBX SIP Server Internet DNS Server RTP LDAP Server Campus Network

23. 170 PBXPSTN SIP/PRI Gateway SIP.edu Configuration SIP Server Internet DNS Server LDAP Server Campus Network

24. 171 PBXPSTN SIP/PRI Gateway SIP to PBX and PSTN Calling SIP Server Internet DNS Server LDAP Server Campus Network

25. 172 PBXPSTN SIP/PRI Gateway PBX and PSTN to SIP Calling SIP Server Internet DNS Server LDAP Server Campus Network

26. 173 SIP Trunking Example IP-PBX Enterprise Location Provider Network SIP Provider Gateway NY New York PBX Customer Location Los Angels SIP Provider Gateway LA PSTN PRI