Understanding SIP Architecture

SIP Architecture
Raghunath M D
Sub Divisional Engineer (EB)
BSNL Ernakulam
Ph: +91-9446076060
E-mail: mdraghunath@bsnl.co.in

SIP Architecture
 The Session Initiation Protocol (SIP) is a signaling
protocol used for initiating, maintaining, and
terminating real-time sessions that include
voice, video and messaging applications.SIP is
used for signaling and controlling multimedia
communication sessions in applications of
Internet telephony for voice and video calls, in
private IP telephone systems, in instant
messaging over Internet Protocol (IP) networks as
well as mobile phone calling over LTE (VoLTE).
 SIP uses and takes advantage of the Internet
architecture and TCP/IP protocol suite.
2
SIP: Session Initiation Protocol
7/12/2020 Raghunath M D | SDE EB |Ernakulam | KL | 9446076060

SIP Architecture
 Is SIP a different way of doing what we have
always done with traditional Telephony ?
 No….
 SIP can offer far more
3
Why SIP ?
7/12/2020 Raghunath M D | SDE EB | 9446076060

SIP Architecture
 Worldwide, carriers and TSPs have switched to
SIP in their core network, keeping SS7 and legacy
POTS over last mile and SIP for switching across
core network
4
Why SIP ?
SIP
SIP
SIP
SIP
SS7 SS7

SIP Architecture
 Till 1990s TSPs where depending on Telecom
Equipment Vendors for deploying their network
 They were very expensive and proprietary
solutions
 TSPs became locked-in with a particular Vendor
 New features needed time consuming and
expensive R&D by Vendor and once finished
development, It should’ve been physically
installed/distributed all over the TSP network
5
Why SIP ?

SIP Architecture
 Enhancements and new services/features where
happening too slowly.
 They were much costly too
 Eg. The “Call Waiting” took more than one year to
develop and deploy by most of the vendors
 TAPI (Telephony Application Programming
Interface) also was very expensive
6
Why SIP ?

SIP Architecture
 SIP was originally designed by Mark Handley,
Henning Schulzrinne, Eve Schooler and
Jonathan Rosenberg in 1996 in Columbia
University, USA
 The protocol was standardized as RFC 2543 in
1999. In November 2000, SIP was accepted as a
3GPP signaling protocol and permanent element
of the IP Multimedia Subsystem (IMS) architecture
for IP-based streaming multimedia services in
cellular networks.
 In June 2002 the specification was revised in RFC
3261
7
SIP: History

SIP Architecture
 SIP was originally designed to provide a signaling
and call setup protocol for IP-based
communications supporting the call processing
functions and features present in the public
switched telephone network (PSTN) with a vision
of supporting new multimedia applications
 It has been extended for video conferencing,
streaming media distribution, instant messaging,
presence information, file transfer, Internet fax
and online games
8
SIP: History

SIP Architecture
 SIP is distinguished by its proponents for having
roots in the Internet community rather than in
the telecommunications industry
 SIP has been standardised primarily by the IETF,
while other protocols, such as H.323, have
traditionally been associated with the
International Telecommunication Union (ITU)
9
SIP: History

SIP Architecture
 SIP is fully implemented in Software
 SIP works on Generic Servers rather than on
Proprietary, Vendor supplied Telecom Equipment
Hardware
 Easy to upgrade and implement new features
 No need to design new hardware and
manufacture
 Just modify the code and download to the Server
 It works !
10
SIP: General Features

SIP Architecture
 SIP is an ‘Open Protocol’
 Feely available to everyone
 SIP is very simple, easy to understand and exploit
 Anyone having interest and ability to build
software applications can use it to create
compatible and interoperable communication
products and services
11

SIP Architecture
 SIP is highly Flexible and Extensible
 Hundreds of extensions have been added to SIP
during the last years
 All SIP Extensions are also feely available
 SIP is easy to integrate with Desktop applications
and Web Interfaces
12

SIP Architecture
 SIP Works along with other Protocols
 TCP
 UDP
 TLS
 SDP
 RTP
 RSVP
 LDAP
13

SIP Architecture
 SIP is independent of the underlying media
 SIP doesn’t have dependency on any particular
Codec
 New Codecs can be added
14

SIP Architecture
 SIP is…
 Cost Effective
 Simple
 Open
 Accessible
 Extensible
 Hence SIP is very Flexible
15

SIP Architecture
 SIP address also called a SIP URI (Uniform
Resource Identifier) is written in user@domain.
The format in a similar fashion to an email
address
 Eg. sip:alice@work.com, sip:bob@elsewhere.com
 sips: is also used in Secure (TLS) SIP
Communication
 Using ENUM (IETF standard, RFC 2916)
telephone numbers in E.164 format can be
translated to SIP URI
16
SIP: Addressing

SIP Architecture
17
SIP: Basic Call Flow

SIP Architecture
 1. SIP User Agents
 SIP User Agents are endpoint clients users use to
communicate each other.
 A SIP User Agent can be an application on a PC, an App
on a mobile phone, a SIP Phone, an IP PBX..etc
 Functions of User Agents are
 Manage Signaling
 Capture ,encode and send media
 Receive, decode and deliver the media
 If there are two SIP User Agents connected to same
network and their IP addresses are known to each
other, they can communicate with SIP Protocol
18
SIP: Network Elements

SIP Architecture
 SIP Registrar Service, SIP Location Service, SIP
Registry
 In practical scenario, the IP addresses of users may not
be known to each other.
 SIP Location service is used to find out the IP address
of User Agent
 To accomplish this all User Agents must update their IP
addresses to SIP Registrar Service.
 SIP Registrar Service will store this information in SIP
Registry Database
19

SIP Architecture
 2. SIP Proxy Server
 SIP Proxy Server is the Network Element which provides
the SIP Registrar Service, SIP Location Service
 Additionally SIP Proxy Server is responsible for
receiving and forwarding SIP Messages between SIP
User Agents
20

SIP Architecture
 3. SIP Feature Servers
 SIP can support all features available in PSTN
 Eg. Call Waiting, Call Hold, Call Divert, Voice Mail..Etc
 All of these features are implemented in separate
Servers which are called SIP Feature Sever and can
seamlessly work along with SIP Proxy Server
21

SIP Architecture
 4. SIP Media Server
 It is another SIP Endpoint User Agent
 It can record inbound media
 It can play recorded outbound media
 It can collect DTMF input for IVRS Applications
 It can act as a Media Bridge by mixing Audio/Video
streams from multiple User Agents for Audio/Video
conferencing
22

SIP Architecture
 5. DNS Server
 DNS is required when the Called Part and Calling Party
are in different domains
 The SIP Proxy Server queries the DNS Server to get the
IP address of Called Party’s Domain
23

SIP Architecture
 6. SIP Redirect Server
 SIP Redirect Service is for forwarding SIP Calls when the
user has moved to another domain
24

SIP Architecture
 7. SBC Session Boarder Controller
 SBC act as a Gatekeeper or Firewall to protect the SIP
Domain from malicious use and intruders from outside
 It controls incoming and outgoing traffic
 Changes sensitive message contents like internal
addresses like what is done in NATing
25

SIP Architecture
 8. SIP Gateways to Communicate with non-SIP
Users
 Signaling Gateway
 To translate SS7 signaling to SIP Messages and back
 Media Gateway
 To transcode media streams between PSTN and SIP
26

SIP Architecture
27

SIP Architecture
 BSNL has deployed state-of-art IMS based Next Generation
Network System with eight cores at Bengaluru, Hyderabad,
Pune,Ahmedabad, Chandigarh, Lucknow, Kolkata and
Bhubaneshwar
 Hence, for monetization and optimal utilization of NGN Core, SIP
Trunk service is offered by BSNL which supports Voice over IP
(VoIP) bundled with Data that can be seen as a substitute of ISDN
PRI and Analog Trunk
 SIP Trunk is widely deployed by communications service
providers across the globe, and it is being sold as a replacement
for PRI
 SIP Trunks are delivered over existing Ethernet(FTTH) or Multi
Protocol Label Switching (MPLS) network infrastructure, this
reduces the cost and management complexity associated with
legacy digital platforms, while also provisioning additional
features
28
BSNL SIP Trunk

SIP Architecture
29
BSNL SIP Trunk Vs ISDN PRI
PRI SIP
Distribution
PRI is sold per circuit, each circuit
consist of 30 channels
SIP is sold per channel, it can be offered in
multiples of 10 channels
Scalability
To increase the number of
channels, additional PRI Circuit
must be offered. Delivery of PRI
Circuit takes time.
To increase concurrent channels, additional
bandwidth and channels can be upgraded at
back end on the same link within few hours
without delivering any physical circuit.
Hardware
PRI requires each circuit to be
physically connected via cables and
termination hardware
SIP requires no additional hardware
Call Quality Good Superior
Cost Of
Delivery
High Low
Maintenance
Physical Maintenance is required,
which increases cost of
maintenance
Virtually, no physical maintenance is
required, low cost of maintenance. Can be
monitored and maintained from back end.
Data Service
For Data Service separate link is
required
Data Service can be delivered on the same
link delivered for Voice.

SIP Architecture
Thank You…

Understanding SIP Architecture

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Understanding SIP Architecture

Similar to Understanding SIP Architecture (20)

Recently uploaded

Recently uploaded (20)

Understanding SIP Architecture