Part 2 Converged networks and services 4 Convergence

Part 2. Converged networks and services 4. Convergence of fixed networks 4. 1. Network characteristics # PSTN/ISDN # Data networks 4. 2. PSTN/Internet convergence for data services # Internet access 4. 3. PSTN/Internet convergence for voice services # Vo. IP and IP Telephony 4. 4. Qo. S issues and Reliability 4. 5. Estimation of Call Quality

4. 1. Network characteristics • PSTN – more then 100 years history • Basic principals – circuit switching, connection-oriented • Three phases on the session • Reservation of network resources: # analog voice channel – 4 k. Hz # digital voice channel – 64 kbps • Guaranteed level of Qo. S (delay/loss) • Very high availability – outage is less then 5 min/year (Bellcore – 3 min/year)

PSTN LE LE PBX PSTN PBX Branch office PBX HQ office

4. 1. Network characteristics (Cntd) • Data networks – 60 s, ARPA • Basic principals – packet switching, connectionlessoriented (IP) • No resource reservation for the transmission • No guarantee for delay and loss – it’s not critical for data, but critical for other possible apps

Data network Server App server Router Public/private network Modem/router Branch office Res. house HQ office

Web Browser, MS Outlook, LOTUS H. 323, SIP, RTP, RSVP, MGCP, MEGACO/H. 248 HTTP, FTP TCP UDP IP Ethernet, ATM, FR, PPP Physical layer

4. 1. Network characteristics (Cntd) Characteristics of PSTN and IP networks PSTN IP Network Bandwidth Fixed Variable Technology Circuit-switched Packet-switched Call handling Connection-oriented Connectionless-oriented Quality Guaranteed limit No guarantee on delay, jitter and loss on transmission quality

4. 2. PSTN/Internet convergence for data services: Narrowband Internet access trunk (ISDN PRI) (local area) LEX Access Po. P ISP trunk (SS 7) LEX Central Po. P (local area) Access Po. P LEX LEX (local area) LEX PSTN LEX Access Po. P LEX - Local Exchange Po. P – Point-of-Presence ISP – Internet Service Provider

Internet access methods Narrowband dial-in access Access Devices ISP Po. P Corporate Po. P POTS/ISDN POTS ISDN PSTN x. DSL cable modem Broadband access X X access server / router CATV PSTN X Broadband access ISP backbone ISP modem bank/ access server/ router ATM/FR/LL Virtual Po. P (VPOP) Narrowband dial-in access with virtual POP FR/ATM/LL Home Network Corporate leased line access Intermediate Network FR - Frame Relay LL – Leased line

4. 3. PSTN/Internet convergence for voice services A. Converged network App server Server Router IP-based public/private network Gateway LAN Modem/Router PC Gateway LAN PBX Branch office Res. house HQ office

B. Network scenarios for Vo. IP Internet Voice POP RAS Voice IWU (Gateway) MGCP Voice IWU (Gateway) Gatekeeper Call Processing Name’s Server OAM Server S 64 kbit/s speech Voice over IP Message interface to central server PSTN/ISDN POP 0 u r c e Destination PC to PC Phone to PC PC to Phone

C. Vo. IP protocols • IP is designed to be media-independent transport mechanism (different transport technologies can be use) • Call control or call processing technique maps telephone numbers or user names into IP source/destination addresses • Call control is implemented by call-control software running on servers (gatekeepers) • Gatekeepers communicate with voice gateways, end-user handsets or PCs using call-control protocols.

Vo. IP protocols: 1. H. 323, ITU-T • H. 323 - first call control standard for multimedia networks. Was adopted for Vo. IP by the ITU in 1996 • H. 323 is actually a set of recommendations that define how voice, data and video are transmitted over IP-based networks • The H. 323 recommendation is made up of multiple call control protocols. The audio streams are transacted using the RTP/RTCP • In general, H. 323 was too broad standard without sufficient efficiency. It also does not guarantee business voice quality

H. 323 call setup process

Vo. IP protocols: 2. SIP - Session Initiation Protocol, IETF (Internet Engineering Task Force) • SIP - standard protocol for initiating an interactive user session that involves multimedia elements such as video, voice, chat, gaming, and virtual reality. Protocol claims to deliver faster callestablishment times. • SIP works in the Session layer of IETF/OSI model. SIP can establish multimedia sessions or Internet telephony calls. SIP can also invite participants to unicast or multicast sessions. • SIP supports name mapping and redirection services. It makes it possible for users to initiate and receive communications and services from any location, and for networks to identify the users wherever they are.

Vo. IP protocols : 2. SIP - Session Initiation Protocol, IETF (Internet Engineering Task Force) (Cntd) • SIP – client-server protocol, Rq from clients, Rs from servers. Participants are identified by SIP URLs. Requests can be sent through any transport protocol, such as UDP, or TCP. • SIP defines the end system to be used for the session, the communication media and media parameters, and the called party's desire to participate in the communication. • Once these are assured, SIP establishes call parameters at either end of the communication, and handles call transfer and termination. • The Session Initiation Protocol is specified in IETF Request for Comments (RFC) 2543.

SIP Proxy operation

SIP Redirect Server

Vo. IP protocols : 3. MGCP/Megaco/H. 248 • MGCP - Media Gateway Control Protocol, IETF [Telcordia (formerly Bellcore)/Level 3/Cisco] • MGCP – control protocol that specifically addresses the control of media gateways • Megaco/H. 248 (IETF, ITU) - standard that combines elements of the MGCP and the H. 323, ITU (H. 248) • The main features of Megaco - scaling (H. 323) and multimedia conferencing (MGCP)

How MGCP coordinates the Media Gateways

Which Standard? 1. H. 323, with its roots in ISDN-based video-conferencing, has served its purpose of helping to transition the industry to IP telephony. Today, however, its circuit switched heritage makes H. 323 complex to implement, resource intensive, and difficult to scale. Vendors and service providers are now de-emphasizing H. 323’s role in their IP voice communications strategies.

Which Standard? (Cntd. ) 2. SIP is ideal for IP voice and will play an important role for next generation service providers and distributed enterprise architectures. SIP suffers from some of the limitations of H. 323 in that it has become a collection of IETF specifications, some of which are still under definition. The other similarity with H. 323 is that SIP defines intelligent end points and vendors have found this approach to be more costly and less reliable.

Which Standard? (Cntd. ) MGCP/MEGACO/H. 248 In contrast to SIP, the MGCP/MEGACO standards both centralize the control of simple telephones. This is popular in environments where both cost and control are important issues, which is certainly the case in the enterprise environment where the PC can be used to augment features and functionality.

H. 323 vs. SIP

Vo. IP components Gatekeeper Intranet/ Internet (IP Network) Vo. IP Terminals Router Vo. IP Terminals Gateway (Voice IWU) PSTN/ ISDN Gateway (Voice IWU) ATM PBX

Vo. IP components and their functions IP Gateway • Packetizes voice • Supports telephone signaling • Applies audio compression • Provides connection control (mapping signaling protocols and addresses: E. 164 IP address) • Tags voice packets using Qo. S mechanisms (Diff. Serv, Priority, …) Router • Recognizes voice packet and tags it accordingly • • • Prioritizes packets as needed Manages bandwidth allocation Provides queuing of traffic overflow Gatekeeper - media gateway controller • MGC acts as the master controller of a media gateway • • • Supervises terminals attached to a network Provides a registration of new terminals Manages E. 164 addresses among terminals

D. Vo. IP scenarios: Phone-to-Phone Voice (a) A PSTN/ISDN POP Voice B POP RAS (b) Voice IWU (Gateway A) MGCP Voice IWU (Gateway B) PSTN/ISDN A Internet (a) Vo. IP Server (Gatekeeper) Basic Call "Phone-to-Phone" ð A-Subscriber dials IWU E. 164 number ð Normal Call Setup (a) between A-Subscriber and A-IWU ð Announcement from A-IWU to user ð Input of A-Subscriber E. 164 Number, PIN and B-Subscriber E. 164 Number (via multifrequency code) ð (SP) Call setup (b) within the Internet between A-IWU and B-IWU (routing functions are in gatekeeper) ð Normal Call Setup (a) between B-IWU and B-Subscriber. B

Vo. IP scenarios: PC-to-Phone Voice (b) A PSTN/ISDN (a) Internet POP RAS Voice IWU (Gateway) B POP RAS (b) Voice IWU (Gateway) PSTN/ISDN A Voice Vo. IP Server (Gatekeeper) Basic Call "PC-to-Phone" ð PC needs Vo. IP software (support on of Signaling Protocols) ð Normal Internet login (a) of A-Subscriber ð Access to Vo. IP Server ð Input PIN and B-Subscriber E. 164 Number ð (SP) Call setup (b) within the Internet between A-subscriber and B-IWU (routing functions are in gatekeeper) ð Normal Call Setup (a) between B-IWU and B-Subscriber. (a) B

Vo. IP scenarios: Phone-to-PC Voice (a) A PSTN/ISDN POP (b) POP RAS B RAS (b) Voice IWU (Gateway) MGCP Voice IWU (Gateway) (a) PSTN/ISDN A Internet Vo. IP Server (Gatekeeper) Basic Call "Phone to PC" ð PC needs Vo. IP software (support on of Signaling Protocols) ð Normal Internet login (a) of B-Subscriber and registration at gatekeeper (E. 164 to IP address mapping) ð A-Subscriber dials IWU E. 164 number ð Normal Call Setup (a) between A-Subscriber and A-IWU ð Input of A-Subscriber E. 164 Number, PIN and B-Subscriber E. 164 Number ð (SP) call setup (b) within the Internet between A-IWU and B-subscriber PC (routing setup functions and address mapping are in gatekeeper) B

E. Difference between Vo. IP and IP-T • Voice over IP (Vo. IP) indicates that an analog voice signal has been digitized and converted into the packet format used by IP. This is done in order to allow telephony and other audio signals to be transported over the same network as regular data traffic. Thus, Vo. IP refers to a conversion and transportation process. • IP-Telephony is a service and it refers to Vo. IP over the public Internet. Although technically feasible, the call quality is considered to be too variable for serious use by business professionals. This comes from the fact that voice traffic has to be given priority over data. However, Vo. IP is employed over managed IP infrastructures, e. g. corporate intranets and the backbone networks of carriers. • Unfortunately, the terms Vo. IP and IP-Telephony are often used interchangeably.

Business Vo. IP and IP-T • Business Vo. IP service is defined as a high quality, reliable service capable of sustaining mission-critical communications. High quality is defined as clear audio with the absence of echo. A reliable service connection provides an error free transmission with no service interruptions. • IP-Telephony uses IP as the transport mechanism but it uses the public data network (i. e. , the Internet) to transmit voice packets. Because the Internet is an unmanaged, non-voice engineered conglomerate of many networks, it cannot guarantee bandwidth and timely delivery of voice packets, resulting in unacceptable voice quality for business communications. • By transmitting voice over a private managed IP data network, you can control all of the network characteristics required to ensure high-quality, reliable voice communications over a data network.

Tele. Geography Vo. IP market predictions for 2005 In 2005 the international Vo. IP traffic will exceed 40 billion minutes with more than 30% annual growth.

Roadblocks to Convergence Quality of Service (Qo. S): The converged network must deliver the same Qo. S as the traditional Public Switched Telephone Network (PSTN); without it, video- and voiceover-IP are simply not viable. In an IP-based network, this requires handling data packets - to reduce loss, latency and jitter - with a Qo. S significantly higher than most data transmission networks are designed to support. Reliability and Availability: The converged network must provide redundancy and fault-tolerance with "five nines" (99. 999%) availability. While this is the standard level for most voice systems, many data networks lack the infrastructure to deliver such high availability across the entire system. Bandwidth: The converged network must provide the necessary bandwidth to accommodate voice and video applications, which can demand considerably more than most data applications. While some efficiency schemes have proved useful in lowering the required bandwidth, most have been unable to effectively balance transmission speeds with voice and video quality. Security: In traditional IP networks, packets are transmitted across shared segments, where the possibility exists that someone could decode packets and access secure information. A converged network must provide a new measure of encryption and security for voice traffic.

4. 4. Qo. S issues and Reliability • The number one issue operators have is: guarantee of Quality of Service How to support voice traffic on backbone ? Actually, this is the number two issue • The number one issue is: Reliability of the data network • Why? Qo. S makes only sense if the network is up and running all the time, hence reliable

A. Reliability • Reliability in PSTN networks is already for 10 s of years equal to the famous 99. 999%, also called the 5 nines • Operators are so used to this reliability that they take it for granted • Why is it so important? – – 99% means downtime of 3. 7 days per year 99. 9% means downtime of 9 hours per year 99. 99% means downtime of 53 minutes per year 99. 999% means downtime of 5. 5 minutes per year • Traditional IP data equipment does not offer 5 nines reliability

Nines of availability and corresponding downtime

Reliability is a fundamental philosophy Manufacturer Selection Criteria (Q 61, n-11) Product Reliability moved up the value scale and now rates highest for Tier_1 Service Providers 100 82 Best Price-to-Performance Ratio Financial Stability 73 Leading-Edge Technology 73 Manufacturer’s Products Already Installed 64 Pre-and post-sales service and support 64 Manufacturer reputation 45 Manufacturer’s future product offering 45 Leasing and Financing Options 27 Lowest Price 27 Sales and Marketing Services Source: Contingency Planning Research, a division of Eagle Rock Alliance Ltd Source: Infonetics Research, November 2001 The Tier 1 Service Provider Opportunity, US/Canada 2001 Network Integration and Design Services 18 9 0% 25% 50% 75% 100% Percent of Respondents Rating 6 to 7

Reasons for system unavailability Source: Gartner Group • User Errors and Process: Change management, process inconsistency • Technology: Hardware, network links, environmental issues, natural disasters • Software Application: Software issues, performance and load, scaling On average, computer system reliability is estimated at around 98. 5%. This number includes not only the data networks and their components, but all the core business applications, servers, and mainframes.

Why are traditional IP Routers Unreliable? Unknown 2% Malicious 2% 7% Customer Premises Equipment Congestion 5% t Network Engineering t 36% Router Operations t Software/hardware updates t Configuration errors MPLS traffic engineering t t Software upgrades Hardware upgrades Physical Links 27% t t 21% Router Failures t Hardware fault intolerance t Software quality Diversity of paths Fast Restoration t t Software process isolation and redundancy 99. 999 percent available hardware Source: University of Michigan

Common causes of downtime in IP networks Source: University of Michigan and Sprint study, October 2004 More than half of the problems causing downtime in IP networks - 59% - pertain to routing management issues. More deeply, 36% of these problems are attributable to router misconfigurations, and 23% come from a category broadly described as "IP routing failures. " By contrast, of the remaining 41% of problems, link failures of some form account for 32%, and "other causes" comprise the remaining 9%.

Benefits of network reliability and losses due to failures – Reductions in capital expenditure • eliminates requirement for duplicate hardware configurations to support redundancy – Reductions in ongoing operational costs • lower maintenance due to reduced number of network elements • true non-service-interrupting upgrades • reduced floor space, cooling and power requirements – Revenue opportunities • no data session interruption during control plane switchover will allow customers to achieve 99. 999 percent availability • increased customer retention – Ability to offer low-risk SLAs • Five nines SLA Business Brokerage operations Credit card/sales authorisation Pay-per-view Home shopping (TV) Airline reservations Tele-ticket sales Package shipping Automated teller machines Cost per minute of downtime ($) 107, 333 46, 333 2500 1883 1500 1150 467 242 Source FCA

Commonly used techniques to “solve” reliability • Instead of one reliable router, provide a reservation for each router • Not quite the solution, isn’t it ? – double the price – need for extra interfaces for interconnection – but more importantly in case of failure, it takes time to reroute the traffic from one to the other, in the meantime the ongoing calls are affected • outage time can be quite long