Signalling :- Some Important questions?

1. What is the diffetrence between circuit signaling and non circuit related signalling??
Ans.:--
Signalling was initially introduced to initiate the call process i.e. setting up and clearing down connection between trunks.Traditionally, once a circuit was set up, no other signaling was performed apart from releasing the call; therefore, all calls were simple, basic telephone service calls. However, modern telephone networks can perform signaling while a call is in progress, especially for supplementary services—for example, to introduce another called party into the call, or to signal the arrival of another incoming call (call waiting) to one of the parties.

When there is signalling when there is no call to be establish then this signalling is known as  non circuit related signalling. It is primarily used for query and response with telecommunications databases to support cellular networks, intelligent networks, and supplementary services. For example, in Public Land Mobile Networks (PLMNs), the visitor location register (VLR) that is in charge of the area into which the subscriber has roamed updates the home location register (HLR) of the subscriber's location.

Purging Time

As we know to allow roaming in a GSM  network VLR uses the temporary data of subscriber form HLR. this data remains as long as the subscriber is connected to the BSS that is  apart of that MSC/VLR area. But interesting thing is that the subscriber data remins even after the mobiel system is switched.
But the question arises, upto what time??
yes that is what Purging comes out of the box.
After an extended period of the MS being switched off, the subscription data willbe purged from the MSC.
Purging is that time , which defines the data retainment within MSC.

Multihoming

Multi homing is a method to connect a single devide with more than one IP addresses to ensure reliability in the network.

Multihoming is a mechanism used to configure one computer with more than one network interface and multiple IP addresses. It provides enhanced and reliable Internet connectivity without compromising efficient performance. The multihoming computer is known as the host and is directly or indirectly connected to more than one network.


Point to remember:-

1.) Multihoming is intended to increase the reliability of network applications but it does not necessarily improve their performance. 
2.)

Stream Control Transmission Protocol

SCTP protocols is  transport layer protocol that is same as TCP or UDp, but supports the service features of both:
1.)message-oriented like UDP and
2.)in-sequence transport of messages with congestion control like TCP.


Features

Features of SCTP include:

    Multihoming support in which one or both endpoints of a connection can consist of more than one IP address, enabling transparent fail-over between redundant network paths.
    Delivery of chunks within independent streams eliminate unnecessary head-of-line blocking, as opposed to TCP byte-stream delivery.
    Path selection and monitoring select a primary data transmission path and test the connectivity of the transmission path.
    Validation and acknowledgment mechanisms protect against flooding attacks and provide notification of duplicated or missing data chunks.
    Improved error detection suitable for Ethernet jumbo frames.

The designers of SCTP originally intended it for the transport of telephony (Signaling System 7) over Internet Protocol, with the goal of duplicating some of the reliability attributes of the SS7 signaling network in IP. This IETF effort is known as SIGTRAN. In the meantime, other uses have been proposed, for example, the Diameter protocol and Reliable server pooling (RSerPool).

Intelligent Network Application Part (INAP)

Intelligent Network Application Part (INAP) is the signaling protocol used in Intelligent Networking.INAP is a signaling protocol between a service switching point (SSP), network media resources (intelligent peripherals), and a centralized network database called a service control point (SCP). The SCP consists of operator or 3rd party derived service logic programs and data.

Address Resolution Protocol (ARP)

Address Resolution Protocol (ARP) is a protocol for mapping an Internet Protocol address (IP address) to a physical machine address that is recognized in the local network. For example, in IP Version 4, the most common level of IP in use today, an address is 32 bits long. In an Ethernet local area network, however, addresses for attached devices are 48 bits long. (The physical machine address is also known as a Media Access Control or MAC address.) A table, usually called the ARP cache, is used to maintain a correlation between each MAC address and its corresponding IP address. ARP provides the protocol rules for making this correlation and providing address conversion in both directions.
How ARP Works
When an incoming packet destined for a host machine on a particular local area network arrives at a gateway, the gateway asks the ARP program to find a physical host or MAC address that matches the IP address. The ARP program looks in the ARP cache and, if it finds the address, provides it so that the packet can be converted to the right packet length and format and sent to the machine. If no entry is found for the IP address, ARP broadcasts a request packet in a special format to all the machines on the LAN to see if one machine knows that it has that IP address associated with it. A machine that recognizes the IP address as its own returns a reply so indicating. ARP updates the ARP cache for future reference and then sends the packet to the MAC address that replied.

Since protocol details differ for each type of local area network, there are separate ARP Requests for Comments (RFC) for Ethernet, ATM, Fiber Distributed-Data Interface, HIPPI, and other protocols.

There is a Reverse ARP (RARP) for host machines that don't know their IP address. RARP enables them to request their IP address from the gateway's ARP cache.

Rehoming and resources sharing in network

A method, system, and apparatus enables automatic radio base station (RBS) rehoming from a first radio network controller (RNC) to a second RNC when the first RNC becomes overloaded and/or automatic resource sharing between/among RNCs when one RNC becomes overloaded. A managing/controlling entity receives load measuring reports from RNCs and analyzes them. If a first RNC is frequently and/or constantly experiencing an overcapacity condition, then an RBS of the RNC may be rehomed to a second RNC without operator intervention. If a first RNC temporarily experiences an overcapacity condition, then the workload of the first RNC may be shared by a second RNC also without operator intervention. When rehoming an RBS or sharing a load of a first RNC, ongoing connections are completed by the first RNC where the connection was initiated, but new connections are (for the rehoming case) or new connections may be (for load sharing cases) initiated using a second RNC.