148 Sidevõrgud IRT 0020 loeng 1215. nov. 2005 Avo Ots telekommunikatsiooni õppetool, TTÜ raadio- ja sidetehnika inst. [email protected].

1

SidevõrgudIRT 0020

loeng 12 15. nov. 2005

Avo Otstelekommunikatsiooni õppetool,

TTÜ raadio- ja sidetehnika [email protected]

2

Digital

PhoneIP Phone

SIP

Presence

Services

Soft-phone IM Client PC w/ USBCamera

Converged Presence-

Based Client

Mobile

Phone

Collaborative

Applications

SIP and Presence

3

• 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

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

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

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.

Useragent

Proxyserver

Proxyserver

User agentACK

OK

invite invite

OK

ACK

invite

OK

ACK

LDAPserver

LDAP server

[email protected]> 138.47.19.103

7

Basic SIP message flow

8

SIP trapezoid

SIP trapezoid

outbound proxy

[email protected]: 128.59.16.1

registrar

9

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:[email protected] SIP/2.0To: <sip:[email protected]>From: <sip:[email protected]>;tag=78923Call-Id: [email protected]: <sip:[email protected]>

NOTIFY sip:[email protected] SIP/2.0…Event: message-summarySubscription-State: active

Messages-Waiting: yesMessage-Account: sip:[email protected]: 2/8 (0/2)

10

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 [email protected]”)

11

SIP presence architecture

PA

[email protected]: 128.59.16.1

watcher

PUAs

Alice Bob

PUBLISH

REGISTERSUBSCRIBE

NOTIFY

<?xml version="1.0" encoding="UTF-8"?><p:presence xmlns:p="urn:…" entity="pres:[email protected]"><p:tuple id="sg89ae"> <p:status> <p:basic>open</p:basic> </p:status> <p:contact>tel:09012345678</p:contact></p:tuple></p:presence>

12

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

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 userssip:[email protected]

• It’s time to put E.164 phonenumbers behind us!

• A.G. Bell did not say:

“+1-617-252-1232, come here. I need you!”

14

SIPProxy

DNSSIP-PBXGateway

PBX

INVITE (sip:[email protected])

INVITE(sip:[email protected])

DNS SRV query sip.udp.bigu.edu

telephoneNumberwhere mail=”bob”

PRI / CASbigu.edu

CampusDirectory

SIP User Agent

Bob's Phone

SIP.edu Architecture (Phase 1)

15

DNS

INVITE (sip:[email protected])DNS SRV query

sip.udp.bigu.edu

bigu.edu

SIP User Agent

SIP.edu Architecture (Phase 2)

locationDB

If Bob has registered, ring his SIP phone; Else, call his extension through the PBX.

REGISTER(Contact: 207.75.164.131)

INVITE (sip:[email protected])

SIPProxy

SIPRegistrar

Bob's SIP Phone

16

SIP.edu Call Flow Example

• SIP DNS lookup for MIT.EDU points to SIP proxy– Sends INVITE to [email protected] to proxy

• SIP proxy checks MIT directory– Maps call to PBX extension – eg. [email protected]

• SIP proxy checks dial plan– Routes call to PBX gateway

• PBX rings phone

17

PBX PSTN

SIP/PRIGateway

SIP.edu Configuration

SIP Server

Campus Network

Internet

DNS Server

LDAP Server

18

PBX PSTN

SIP/PRIGateway

DNS SRV Lookup

SIP Server

Internet

DNS Server

DNS SRV

LDAP Server

Campus Network

19

PBX PSTN

SIP/PRIGateway

SIP INVITE

SIP Server

Internet

DNS Server

SIP

LDAP Server

Campus Network

20

PBX PSTN

SIP/PRIGateway

LDAP Lookup

SIP Server

Internet

DNS Server

LDAP

LDAP Server

Campus Network

21

PBX PSTN

SIP/PRIGateway

Call Sent to PBX Gateway

SIP Server

Internet

DNS Server

SIP

LDAP Server

Campus Network

22

PBX PSTN

SIP/PRIGateway

Media Stream via Gateway to PBX

SIP Server

Internet

DNS Server

RTP

LDAP Server

Campus Network

23

PBX PSTN

SIP/PRIGateway

SIP.edu Configuration

SIP Server

Internet

DNS Server

LDAP Server

Campus Network

24

PBX PSTN

SIP/PRIGateway

SIP to PBX and PSTN Calling

SIP Server

Internet

DNS Server

LDAP Server

Campus Network

25

PBX PSTN

SIP/PRIGateway

PBX and PSTN to SIP Calling

SIP Server

Internet

DNS Server

LDAP Server

Campus Network

26

SIP Trunking Example

IP-PBX

Enterprise Location

Provider Network

SIPProvider Gateway

NY

New YorkPBX

Customer Location

Los Angels

SIP

Provider Gateway

LA

PSTN

PRI

PRI