chapter 1-BASICS

What's protocol?
A protocol is a set of rules for beahviour that people accept and obey. Then, what is TCP/IP?
TCP/IP is Transmission Control Protocol/Internet Protocol. It is a whole set of protocols for connecting computers into the Internet. So, what is Internet? Internet is millions of computers around the world connected by TCP/IP. TCP/IP is internationally accepted standard for networking.
TCP/IP is independent of all available alternatives such as:
-The network design.
-The transmission medium.
-Specific vendors.
-The operating system and computers hardware.
TCP/IP connects networks and the internet togehter, regardless of the hardware and software used to bulid those networks.

These are example of operating system that can be connected by TCP/IP:
-Microsoft-Windows 95/98/2000/XP
-LInux
-UNIX
-Mac 05
-z/OS and other IBM mainframe operating systems
-Compaq OpenVMS

Chapter 2-NETWORKS
networks are a combination of hardware and software. The TCP/IP protocols are the software that glue the hardware into a working network. Any devices that send or receives data can be part of a network, including:
-Computers
-Printers
-Communication devices

Connection media is used to connect all networks devices. The most important devie is a network interface card (NIC). It's an adaptor to allow the computer to be connected full time to a network without dialing in. Besides NIC, we also have modem, which connect us to the Internet by dialing telephone number.

What is network data?
Network data is data that we send or receive across a network, such as:
-An e-mail message
-A request t transfer file
-A request to see a Web-page

Packets is a small chunks of data which we send across the network. TCP/IP makes sure that our data doesn't get ruined in the process of getting split up and gather again. Each packet hold:
-One or more headers containing control information, which tells the network what to do with the packets, including IP address of destination, the number of packets that hold the data, the packet's sequence number.
-the data taht it has to trasmit.

The efficiencies of breaking data into packets are:
-Network efficiency, can balance traffic, faster delivery across the network.
-Network sharing, packets can slip into the network in between someone else's.
-Network availability, to arrive the data to the destination although ther is a problem in the network hardware.
-Data reliability, TCP error checks each packet, TCP resends an uncorrupted version of the packet to make all datas remain ungarbled and readable.

Ethernet is used area network architecture. Ethernet allows any devives to send packets to any other location, the packets can collide as a lot of devices send data silmutaneouslly. Ethernet will tell the devices to stop transmitting. The speed is around 10 Mbps.
Token Ring is more controlled and organized as tokn is passed among the devices on the ring. When a device want to send data, it should wait to get the token. Possesion of the token esures that the sending devie will not compete wth any other device. This allow no collision between the data. The speed is about 16Mbps.

Choosing between Ethernet and Token Ring:

-Availability of network interface cards for the paricular computers you're using, ethernet cards are more common adn cheaper.

-How fast you need to go, ethernet can provide you faster speed, about 1Gbps.

-Amount of traffic on your networl, collisions may slow down ethernet speed, compared to token ring which no collision occurs.

-Geographical area, the bigger the network area, token ring is better ss it has fewer dstance limitaions than ethernet.

-Likelihood of network failures, such as broken cables, when an ethernet cable is cut, we may still have other working networks in place, if token rinc cable is cut, we probably just have one disable token curve.

LAN and WAN:

LAN is connection over small geographical areas, WAN is the connaction between LANS, we can cosider WAN as internet.

5.Making Internal Calls:

When you call, you need to dial the phone number corresponding to the person's name. The signals are packetized and sent to the managing server, where the packet picks up the MAC address of the person you are calling. Then the package is forwarded to the switch, the port and finally to the IP telephone connevted to the port. The phone rings and when the coworker picks up the phone, a virtual connection is established between the coworker and yourself for the life of the call. IP telephony does all of this at lightning speed.

6.Making External Calls:

It use the same way but because the coworker is connected to a different LAN, the local server sneds the call not to a switch located on your LAN but through your WAN. Now IP telephony technically becomes VoIP. Your call begins as an Ip telephony call on your LAN. It then travels from your LAN through a gateway, switch or router that is programmed to re-packetize your call and encode the VoIP packet with additional information, such as the address for the destination LAN.

1.General Information:
VoiP is the technology that changes the meaning of "telephone call". It stands for voice over Internet protocol, means voice transmitted over a network or voice travels by way of the same protocols used on the Internet. VoiP referred to IPT (IP telephony) because it uses Internet protocols to make enhanced voice communications possible. VoiP unites many locations into a single converged communications network and provides a range support services and features unequalled in the world telephony. IPT uses in big buildings, a campus-like network, or even a LAN. When IPT crosses from the LAN to the WAN network (wide area network), it becomes VoiP.


2.POTS:

POTS stands for "plain old telephone service". POTS runs over a network called PSTN, public switched telephone network. These system use the tried-and-true method of telephone service known as circuit-switched telephony. People have to rely on their "bottom line-POTS" which means that if the line is cut they can not communicate any more. Besides that POTS also costs a lot of money compared with VoiP. Moreover VoiP also has better quality.
3.Packets:
VoiP technology enables traditional telephony services to operate over computer networks using packet- switched protocols. Packed-switched VoiP puts voice signals into packets, similar to an electronic envelope. VoiP packet includes both caller's and receiver's network addresses. Because it uses packets, you can carry more information compared to traditional telephony system. In POTS world, if one line is down then the call can not go through. On the contrary, in a packet-switched network, the packet can switch to another working route to keep the call continue.VoiP are also portable, they will work with any IP-enabled device such as an IP telephone or PDA. All IP telephone has network interface card and is it the same as a physical address to communicate over the network. The address is called MAC address.
4.Server:
They are just like personal computers except that they have more memory speed and capacity. Depending on the numbers of users or the size of the LAN, we need switches. They are boxes for and have several ports for many LAN to connect.

VoIP uses internet to connect computer to computer, or computer to phone,without using the telephone company service. The prize is cheaper as VoIP provides us a flexible and economic system. We pay as how much we use, not how long we talk. VoIP will charge us depend on the kilobyte. When we are not talking, they will not charge us. Therefore, VoIP is more efficient when we want to call someone overseas. VoIP has 2 systems:
-Cicuit Switching: depends on how long you talk
-Packet Switching:depends on how many packets you send

Future Telephony

VoIP, or Voice over Internet Protocol, is a method for taking analog audio signals and turning them into digital data that can be transmitted over the Internet. By VoIP, you can call someone overseas with cheaper prize as it costs you on how much you talk, not how long you talk. Basically, VoIP uses internet as the media to call and bypassing the telephone company.

There are three different kinds of VoIP:
-ATA
The ATA allows you to connect a standard phone to your computer or your Internet connection for use with VoIP. The ATA is an analog-to-digital converter. It takes the analog signal from your traditional phone and converts it into digital data for transmission over the Internet.

-IP Phones
These specialized phones look just like normal phones with a handset, cradle and buttons. But instead of having the standard RJ-11 phone connectors, IP phones have an RJ-45 Ethernet connector. IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call.

-Computer-to-computer
There are several companies offering free or very low-cost software that you can use for this type of VoIP. All you need is the software, a microphone, speakers, a sound card and an Internet connection, preferably a fast one like you would get through a cable or DSL modem. Except for your normal monthly ISP fee, there is usually no charge for computer-to-computer calls, no matter the distance.

Express talk protocol

what is SIP server?

The Session Initiation Protocol (SIP)

-a signalling protocol, widely used for setting up and breaking down/stopping multimedia communication sessions. Other feasible application examples include video conferencing, streaming multimedia distribution, instant messaging, presence information and online games.

- TCP/IP-based Application Layer protocol.

- designed to be independent of the underlying transport layer;

- can run on TCP, UDP, or SCTP.

- a text-based protocol, incorporating many elements of the Hypertext Transfer Protocol (HTTP) and the Simple Mail Transfer Protocol (SMTP)

--> allowing for easy inspection by administrators.

Uses of protocol:

1. create

2. modify

3. terminate

two-party/ multiparty sessions consisting of one or several media streams.

-The modification --------> 1. changes addresses or ports

2. invites more participants

3. adds or deletes media streams, etc.



multimedia communication sessions-->e.g voice and video calls over the Internet.

The Internet Protocol Suite (commonly known as TCP/IP)

-the set of communications protocols used for the Internet and other similar networks.

- named from two of the most important protocols in it:

the Transmission Control Protocol (TCP)

the Internet Protocol (IP)

which were the first two networking protocols defined in this standard.

How to call each other using Express talk?
1.download + install express talk
2. Install brekeke (get your SIP user name and pw)
3.using IP address of one particular computer, try to call each other by just typing their name into the space,instead of something like ziyi@(IP ADDRESS).

ziyi@(IP ADDRESS) is only needed when you try to call each other without brekeke.

Failure to call each other through brekeke and or directly using the express talk-->maybe due to firewall blockage of such functions.

The interesting thing about VoIP is that there is not just one way to place a call. There are three different "flavors" of VoIP service in common use today:
-ATA: analog telephone adaptor- The ATA allows you to connect a standard phone to your computer or your Internet connection for use with VoIP.
-IP phonaes :IP phones connect directly to your router and have all the hardware and software necessary right onboard to handle the IP call
-Computer-to-computer: There are several companies offering free or very low-cost software that you can use for this type of VoIP