The basic concept behind MPLS is that of labeling packets. In a traditional routed IP network, each router makes an independent forwarding decision for each packet based solely on the packet’s network-layer header. Thus, every time a packet arrives at a router, the router has to “think through” where to send the packet next The key thing to remember about MPLS is that it’s a technique, not a service – so it can be used to deliver anything from IP VPNs to Metro Ethernet services, or even to provision optical services. So although carriers build MPLS backbones, the services that users buy may not be called MPLS. They could be called anything from IP VPN to Metro Ethernet – or whatever the carriers’ marketing departments dream up next. With MPLS, the first time the packet enters a network, it’s assigned to a specific forwarding equivalence class (FEC), indicated by appending a short bit sequence (the label) to the packet.
Each router in the network has a table indicating how to handle packets of a specific FEC type, so once the packet has entered the network, routers don’t need to perform header analysis. Instead, subsequent routers use the label as an index into a table that provides them with a new FEC for that packet. This gives the MPLS network the ability to handle packets with particular characteristics (such as coming from particular ports or carrying traffic of particular application types) in a consistent fashion. Packets carrying real-time traffic, such as voice or video, can easily be mapped to low-latency routes across the network – something that’s challenging with conventional routing. The key architectural point with all this is that the labels provide a way to “attach” additional information to each packet – information above and beyond what the routers previously had. UC allows an individual to send a message on one medium and receive the same communication on another medium. For example, one can receive a voicemail message and choose to access it through e-mail or a cell phone. If the sender is online according to the presence information and currently accepts calls, the response can be sent immediately through text chat or video call. Otherwise, it may be sent as a non real-time message that can be accessed through a variety of media Unified communication (UC) is the integration of real-time communication services such IM (chat), presence information, telephony (including IP telephony),video conferencing, data sharing ,call control and speech recognition with non-real-time communication services such as unified messaging (integrated voicemail, e-mail, SMS and fax).
UC is not a single product, but a set of products that provides a consistent unified user interface and user experience across multiple devices and media types. In its broadest sense UC can encompass all forms of communications that are exchanged via the medium of the TCP/IP network to include other forms of communications such as Internet Protocol Television (IPTV) and Digital Signage Communications as they become an integrated part of the network communications deployment and may be directed as one to one communications or broadcast communications from one to many.