ITNW 1380 COOPERATIVE EDUCATION –ITNW 1380 COOPERATIVE EDUCATION –

NETWORKING NETWORKING

Seminar # 5Seminar # 5VOIP and Wireless Networking SolutionsVOIP and Wireless Networking Solutions

Unified Communications and Collaboration Solution

Unified Communications IP Convergence: Voice, data & video on the same

network. Voice: Voice over IP - VOIP.

Collaboration Solution IM: Yahoo, MSN, Novell, Skype... 3G Wireless: CDMA, UMTS. 4G Wireless: Wireless LAN.

Today's Collaboration Solution

VOIP Wireless LAN

PART I

VOIP

Presenter: Nguyen Chi Thanh

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

VoIP Definition

VoIP (Voice Over Internet Protocol). Voice transmission over packet based network

such as Internet, corporate intranet, LAN, WAN. VoIP known as Internet telephony. Integrate VoIP enabled voice signals with faxes

& data into a unified network. Telephone conversation over Internet.

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

VoIP Service providers

With VoIP you can call PC to PC, PC to VoIP phone, or VoIP phone to ordinary phone over Internet.

VoIP is popular international calling. VoIP enables you to call from virtually anywhere. VoIP provider offer low rates or free service

deals – Free World Dial & Skype...

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

VOIP Benefits Lower long distance rates: requires only Internet

connection. Simplicity: VoIP transmission combines voice &

data. Capacity: VoIP better uses you network for less. Global outsourcing: International call centers rely

on VoIP. Automatic routing: Receive calls automatically to

your VoIP phone. Portability: Travel with your VoIP phones.

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

VoIP Protocols

H.323 Session Initiation Protocol (SIP)

H.323 Published by Telecommunication Standardization

Sector (ITU-T) in November 1996. ITU-T defines H.323 protocols to provide audio-

visual communication sessions on any packet network.

Widely implemented by voice and videoconferencing equipment manufacturers.

Widely deployed worldwide by service providers and enterprises for both voice and video services over Internet Protocol (IP) networks.

H.323 (Cont.)

Suited for transmitting calls across networks using a mixture of IP, PSTN, ISDN, and QSIG over ISDN.

Within the context of H.323, an IP-based PBX might be an H.323 Gatekeeper.

Codecs: Video codec: H.261, H.263, H.264 Audio codec: G.711, G.729 (including G.729a),

G.723.1, G.726 Text codecs: T.140

H.323 (Cont.)

H.323 Architecture: The H.323 system defines several network elements

that work together in order to deliver rich multimedia communication capabilities

Terminals, Multi-point Control Units (MCUs), Gateways, Gatekeepers, and Border Elements.

A complete, sophisticated H.323 protocol stack

VoIP Protocols (Cont.)

H.323 Session Initiation Protocol (SIP)

Session Initiation Protocol (SIP)

Purpose of SIP SIP URI SIP Network Elements SIP Messages Transactions Dialogs Typical SIP Scenarios

Purpose of SIP

Application-layer control protocol which has been developed and designed within the IETF.

The most important one is RFC3261 which contains the core protocol specification.

The protocol is used for creating, modifying, and terminating sessions with one or more participants. By sessions we understand a set of senders and receivers that communicate and state kept those senders and receivers during the communication.

Purpose of SIP (Cont.)

Purpose of SIP is just to make the communication possible, the communication itself must be achieved by another means. Two protocols that are most often used along with SIP are RTP and SDP.

RTP – Real Time Protocol is used to carry the real-time multimedia data (including audio, video, and text), the protocol makes it possible to encode and split the data into packets and transport such packets over the Internet.

Purpose of SIP (Cont.)

SDP – Session Description Protocol, which is used to describe and encode capabilities of session participants. Such a description is then used to negotiate the characteristics of the session so that all the devices can participate (negotiation of codecs used to encode media so all participants will be able to decode it).

SIP is based on HTTP protocol. SIP is used to carry the description of session

parameters, the description is encoded into a document using SDP.

SIP URI

SIP entities are identified using SIP URI (Uniform Resource Identifier).

A SIP URI has form of sip:username@domain, for instance, sip:thanhnc@saigontech.edu.vn.

As we can see, SIP URIs are similar to e-mail addresses, it is, for instance, possible to use the same URI for e-mail and SIP communication, such URIs are easy to remember.

SIP Network Elements Basic SIP elements are: User Agents:

Internet end points that use SIP to find each other and to negotiate a session characteristics are called user agents (cellular phones, PSTN gateways, PDAs)

Proxy Servers: In addition to that SIP allows creation of an

infrastructure of network hosts called proxy servers. User agents can send messages to a proxy server. They perform routing of a session invitations according to invitee's current location, authentication, accounting and many other important functions

SIP Network Elements (Cont.) Registrar:

The registrar is a special SIP entity that receives registrations from users, extracts information about their current location (IP address, port and username in this case) and stores the information into location database.

Purpose of the location database is to map sip:thanhnc@saigontech.edu.vn to sip:thanhnc@1.2.3.4:5060.

The location database is then used by thanhnc's proxy server. When the proxy receives an invitation for sip:thanhnc@saigontech.edu.vn, it will search the location database.

SIP Network Elements (Cont.)

Redirect Server: The entity that receives a request and sends back a

reply containing a list of the current location of a particular user is called redirect server.

A redirect server receives requests and looks up the intended recipient of the request in the location database created by a registra.

SIP Messages

SIP Requests: ACK This message acknowledges receipt of a final

response to INVITE. BYE Bye messages are used to tear down multimedia

sessions. CANCEL Cancel is used to cancel not yet fully

established session. REGISTER Purpose of REGISTER request is to let

registrar know of current user's location.

SIP Messages (Cont.) SIP Responses;

The reply code is an integer number from 100 to 699 and indicates type of the response.

1xx are provisional responses. A provisional response is response that tells to its recipient is received but result of the processing is not known yet.

2xx responses are positive final responses. 3xx responses are used to redirect a caller. 4xx are negative final responses. 5xx means that the problem is on server's side. 6xx reply code means that the request cannot be

fulfilled at any server.

Transactions

SIP is transactional protocol. A transaction is a sequence of SIP messages

exchanged between SIP network elements. SIP messages:

SIP user#1 SIP user#2 INVITE ----------> <---------- 200 OK ACK ---------->

SIP Messages

Dialogs

A dialog represents a peer-to-peer SIP relationship between two user agents.

For instance, INVITE message establishes a dialog, because it will be later followed by BYE request which will tear down the session established by the INVITE. This BYE is sent within the dialog established by the INVITE.

SIP Dialogs

Typical SIP Scenarios

Registration Session Invitation Session Termination Record Routing Event Subscription and Notification Instant Messages

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

VoIP Network

Solution for Enterprise from AudioCodes Ltd.: IP-PBX IP Telephony Survivable Network PBX VoIP Networking Contact Center for Enterprises Unified Messaging for Enterprises Conferencing for Enterprises

IP-PBX

IP Telephony Survivable Network

PBX VoIP Networking

Contact Center for Enterprises

Unified Messaging for Enterprises

Conferencing for Enterprises

VOIP

VOIP Definition VOIP Service Providers VOIP Benefits VOIP Protocols VOIP Networks VOIP Open Source Software

IPTEL SIP Server: SER – SIP Express Router (Registrar/Proxy/Redirect

server) Support database backends: MySQL, Oracle,

Postgres. RTP Proxy, NAT traversal Interoperability with Cisco, Microsoft. PingTel,

Siemens, Xten and many others. http://www.iptel.org/ser

VOIP Open Source Software

VOIP Open Source Software (Cont.)

Asterisk: Most popular open source VOIP software. IP PBX which connect users over IP to PSTN, T1/E1. Media gateway, bridge the legacy PSTN to IP

telephony. Media server with IVR, voice mail, automated

attendant, unified messaging. Call Center, ACD, advance skills-based routing. http://www/asterisk.org

References

SIP: http://www.sip.org/ IPTEL: http://www.iptel.org IPTel: http://www.iptel.org/sip/intro AudiCodes:

http://www.audiocodes.com/Content.aspx?voip=2421

Asterisk: http://www.asterisk.org

The End of PART I

Questions

PART II

WIRELESS NETWORKING

WIRELESS NETWORKING

Presenter: Nhan Nguyên Phương

Section One - Wireless Networking

Section Two - Wireless Networking and the Internet

Section One - Wireless Networking

What is wireless networking? Wireless network components? What is IEEE 802.11? Wireless equipment from different vendors? Communications between computers from WLAN and LAN Wireless network range? How many wireless networked computers can use a single access point? Can I have more than one access point? What is Roaming? How can I use a wireless network to interconnect two LANs? Is it true that wireless networking is only good for laptop computers? 1. Wireless Network Security?

1. What is wireless networking?

Wireless networking: two or more computers to communicate using standard network protocols without network cabling.

IEEE 802.11 (WiFi) IEEE 802.16 (WiMax - Worldwide Interoperability for Microwave Access,

operates < 66 GHz) IEEE 802.20 (MBWA - Mobile Broadband Wireless Access) IEEE 802.22 (WRAN – Wireless Regional Area Network) HomeLAN Bluetooth ….

2. Wireless network components

Two kinds of wireless networks:

a. Ad-hoc / peer-to-peer wireless network consists of A number of computers each equipped with a wireless networking interface

card. Each computer can communicate directly with all of the other wireless

enabled computers. They can share files and printers, but may not be able to access wired LAN

resources, unless one of the computers acts as a bridge to the wired LAN using special software. (This is called "bridging")

• Figure 1: Ad-Hoc or Peer-to Peer Networking.

Each computer with a wireless interface can communicate directly with all of the others.

b. Infrastructure Wireless Network: A wireless network can also use an access point, or base station.

It can connect (or "bridge") the wireless LAN to a wired LAN, allowing wireless computer access to LAN resources.

There are two types of access points: Hardware access points offer comprehensive support of most wireless

features

Figure 2: Hardware Access Point.Wireless connected computers using a Hardware Access Point.

Software Access Points which run on a computer equipped with a wireless network interface card as used in an ad-hoc or peer-to-peer wireless network. (See Figure 3)

Figure 3: Software Access Point.Wireless connected computers using a Software Access Point.

3. What is IEEE 802.11?

The most widely used standard is IEEE802.11 produced by the Institute of Electrical and Electronic Engineers (IEEE). This is a standard defining all aspects of Radio Frequency Wireless networking.

802.11b 802.11g 802.11a 802.11n

802.11b: slowest and least expensive. IEEE802.11b transmits in the 2.4 GHz frequency band of the radio spectrum. It can handle up to 11 megabits of data per second, and it uses complimentary code keying (CCK) coding.

802.11g transmits at 2.4 GHz like 802.11b, but much faster it can handle up to 54 megabits of data per second. (Mbps) It also uses orthogonal frequency-division multiplexing (OFDM),

a more efficient coding technique that splits that radio signal into several sub-signals before they reach a receiver

802.11a transmits at 5GHz and can move up to 54 megabits of data per second. It is also much faster because it uses the same OFDM coding as 802.11g..

802.11n : newest. This standard significantly improves speed and range. IEEE802.11n can achieve speeds as high as 140 megabits per second.

4. Wireless equipment from different vendors

Yes and No: Frequency Hopping (FH) and Direct Sequence Spread Spectrum (DSSS or DS) are not interoperable.

Be sure to obtain guarantees from the vendors that the hardware will

interoperate and follows the standards.

5. Communications between computers from WLAN and LAN

Bridge between the wireless and wired network is needed either with a hardware access point or a software access point.

If more features required on wired network, a software access point may be the best solution.

6. Wireless Network Range?

The actual distance varies depending upon the environment; indoor and outdoor ranges

Typical indoor ranges are 150-300 feet, but can be shorter if the building construction interferes with radio transmissions. Longer ranges are possible, but performance will degrade with distance.

Outdoor ranges are quoted up to 1000 feet, but again this depends upon the environment.

To extend the range, by using more than a single access point or using a wireless relay /extension point

7. How many wireless networked computers can use a single access point?

This depends upon the manufacturer. Some limit of 10, more expensive units support up to 100 wireless connections.

Using more computers than recommended will cause performance and reliability to suffer.

Software access points has user limitations, but this depends upon the specific software, and the host computer's ability

8. Can I have more than one access point?

Yes, multiple access points can be connected to a wired LAN, or sometimes even to a second wireless LAN if the access point supports this.

In most cases, separate access points are interconnected via a wired LAN, providing wireless connectivity in specific areas such as offices or classrooms, but connected to a main wired LAN for access to network resources, such as file servers. (See Figure 4)

Figure 4: Multiple Access Points.Wireless connected computers using Multiple Access Points.

If a single area is too large to be covered by a single access point, then multiple access points or extension points can be used. – (Note that an "extension point" is not defined in the wireless standard, but have been developed by some manufacturers).

Some manufacturers produce extension points, which act as wireless relays, extending the range of a single access point. Multiple extension points can be strung together to provide wireless access to far away locations from the central access point. (See Figure 5)

Figure 5: Extension Point.Wireless connected computers using an Access Point with an Extension Point.

9. What is Roaming?

A wireless computer can "roam" from one access point to another,

Usually this is completely transparent to the user. Some access point configurations require security authentication when swapping access points, usually in the form of a password dialog box.

Access points are required to have overlapping wireless areas to achieve this as can be seen in the following diagram: Figure 6: Roaming.A user can move from Area 1 to Area 2 transparently. The Wireless networking hardware automatically swaps to the Access Point with the best signal.

Not all access points are capable of being configured to support roaming. Any access points for a single vendor should be used when implementing roaming, as there is no official standard for this feature.

10. Connecting 2 LANS using Wireless Network

Wireless networking offers a cost-effective solution to users with difficult physical installations such as campuses, hospitals or businesses with more than one location in immediate proximity but separated by public thoroughfare.

This type of installation requires two access points. Each access point acts as a bridge or router connecting its own LAN to the wireless connection.

The wireless connection allows the two access points to communicate with each other, and therefore interconnect the two LAN's.

Figure 7: LAN to LAN Wireless CommunicationsA Hardware Access Point providing wireless connectivity to local computers and a software access point. The software access point provides Wired Ethernet network 2 computers access to Wired Network 1.

Note that not all hardware access points have the ability to directly interconnect to another hardware access point, and that the subject of interconnecting LAN's over wireless connections is a large and complex one, and is beyond the scope of this introduction

11. Is it true that wireless networking is only good for laptop computers?

Wireless networking has benefits for mobile laptop. There are benefits for users of fixed position computers as well.

It is also beneficial to many schools and businesses with unsuitable building layouts or walls that cannot be wired making it difficult or impossible to build a wired network.

computers are separated from a main network a wireless link may be more cost effective than network cabling although the latter is perfectly feasible.

Temporary wireless LANs can easily be created for exhibitions, school or business projects, all without any trailing cabling.

12. Wireless Network Security

Wireless communications is easy to get intruded.

IEEE 802.11 wireless communications have a function called WEP (Wired Equivalent Privacy), a form of encryption which provides privacy comparable to that of a traditional wired network

Traditional Virtual Private Networking (VPN) techniques will work over wireless networks in the same way as traditional wired networks.

Section Two - Wireless Networking and the Internet

How can I use a wireless network to share an Internet connection?

1. If I have more than one hardware access point, how can I share a single Internet connection?

13. Internet Share Connection over Wireless Network?

To share an Internet connection across a LAN you need two things: an Internet sharing hardware device or software program a LAN

Requires: Hardware or software access point and a wireless LAN.

Figure 8: Software Access Point.Wireless connected computers using a Software Access Point for shared Internet access.

A hardware access point may provide Internet Sharing capabilities to Wired LAN computers, but does not usually provide much flexibility beyond very simple configurations. (See Figure 9)

Figure 9: Hardware Access Point.Wireless connected computers using a Hardware Access Point for shared Internet access

14. If I have more than one hardware access point, how can I share a single

Internet connection?

If an existing wired LAN already has an Internet connection, then the hardware access points simply connect to your LAN and allow wireless computers to access the existing Internet connection in the same way as wired LAN computers.

Figure 10: Multiple Access Points.

Wireless connected computers using Multiple Access Points.

The End of Part II

Thank you for your attention