Session Initiation Protocol (SIP) is the IETF protocol for IP telephony. It only supports IP-based phones. It has a smaller footprint than H.323 so it's faster and more scalable. The problem lies in the fact that it's a newer protocol, and therefore fewer products exist that use it. However, SIP addresses some of
the shortcomings of H.323 by making users easier to identify, making it easier to connect two circuit-switched networks across an IP network, and decreasing the delay in call setup time.SIP identifies users with a Hierarchical URL. This URL is based on a user's phone number or host name and looks similar to an e-mail address (Example, SIP: demouser@abc.com).
The SIP server may or may not be a proxy server. A SIP proxy server receives the request and figures out the user's location using its internal algorithms.
A non-proxy SIP server functions as a redirect server in that it sends back to the user the SIP URL that the user uses to query. In both the redirect and proxy server cases, the server's address is obtained by querying the Domain Name Service (DNS).
Once the SIP URL is found, the request finally makes it to the person you're trying to call. If the person picks up the call, the receiver's client responds to the invite request with the capabilities of its software
(videoconferencing,whiteboarding,and so forth), and the connection is established.
SIP has two features that really make it unique:
It can split an incoming call so that multiple extensions can be rung at once. When the invite request comes in, the SIP server can return to the initiator of the call a Web Interactive Voice Response (IVR) page,
which contains extensions of different departments or users in a list.All you have to do is click on the link to call the appropriate person or department.
It can return different media types.SIP is simple and easy to deploy because its only job is to identify the user call. It utilizes existing DNS instead of having to create a separate database for telephony. It also interfaces with circuit-switched networks (the PSTN) more easily than H.323.
Computer/PC/Desktop - Keyboard Types:
Computer/PC/Desktop - keyboards are of different types. Some of the popular keyboard types are as follows :
1) XT Keyboard
2) AT Keyboard
3) Enhanced Keyboard
4) Windows Keyboard
5) Natural or ergonomic keyboard
Some Popular Laptop Issues/Problems are as follows :
1) Power-related issues with external power supplies, batteries or capacitors
2) External monitors or cutoff switches
3) Function keys - Fn keys
4) Pointer recalibration
5) Tablet PC stylus and word recognition issues
Computer/PC/Desktop - keyboards are of different types. Some of the popular keyboard types are as follows :
1) XT Keyboard
2) AT Keyboard
3) Enhanced Keyboard
4) Windows Keyboard
5) Natural or ergonomic keyboard
Some Popular Laptop Issues/Problems are as follows :
1) Power-related issues with external power supplies, batteries or capacitors
2) External monitors or cutoff switches
3) Function keys - Fn keys
4) Pointer recalibration
5) Tablet PC stylus and word recognition issues
