Transmission is a physical movement of information and concern issues like bit polarity, synchronisation, clock etc.
Communication means the meaning full exchange of information between two communication media.
Transmission is a one way scheme while communication is two-way scheme
Signals are usually transmitted over some transmission media that are broadly classified in to two categories:-
These are those that provide a conduit from one device to another that include twisted-pair, coaxial cable and fiber-optic cable. A signal traveling along any of these media is directed and is contained by the physical limits of the medium. Twisted-pair and coaxial cable use metallic that accept and transport signals in the form of electrical current. Optical fiber is a glass or plastic cable that accepts and transports signals in the form of light.
This is the wireless media that transport electromagnetic waves without using a physical conductor. Signals are broadcast either through air. This is done through radio communication, satellite communication and cellular telephony.
HUb: limited port compare to switch.less speed compare to switch because more collision.
Switch: To Avoid collision we use switch. In switch Each Port having own collision Domain.
HUB:Hub is a layer-1 device,in this data transmission in the form of bits.
SWITCH:Switch is a layer-2 device,in this data transmission in the form of frames.
Bi directional information.
It exchanges the data
to connect the computers
It gives the acknowledgment for received data
SIP is meant for Session Initiation Protocol. It works in application layer. It specially used for initiating, modifying and terminating a session. you can find all details in rfc3261.
When hierarchical routing is used, the routers are divided into what we call regions, with each router knowing all the details about how to route packets to destinations within its own region, but knowing nothing about the internal structure of other regions.