What is the difference between CSMA/CD and CSMA/CA?
The flaw in the IEEE 802.11 MAC is CSMA/CA, (Carrier Sense Multiple Access with Collision Avoidance). CSMA/CA operates on the principles of the ALOHA system developed by Abramsom (1973,1977) and others at the University of Hawaii. The ALOHA system has been studied and proven to have a maximum throughput of only about 33% of the available bandwidth. Further, the ALOHA system and CSMA/CA protocols are inherently unstable. That is, as the amount of network traffic increases, the actual throughput may be far below the theoretical 33% maximum.
CSMA/CD is a highly efficient, stable improvement over CSMA/CA. The main difference between CSMA/CD and CSMA/CA is collision detection. Devices on a wired network can detect when their transmissions collide with other devices. Unfortunately, devices on a wireless network, due to radio frequency transmission power issues, can not detect when their transmissions collide with other devices. Therefore, as attractive as CSMA/CD is, it simply can't be used in wireless networks.
What is IP address?
An identifier for a computer or device on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 1.160.10.240 could be an IP address.
Within an isolated network, you can assign IP addresses at random as long as each one is unique. However, connecting a private network to the Internet requires using registered IP addresses (called Internet addresses) to avoid duplicates.
The four numbers in an IP address are used in different ways to identify a particular network and a host on that network. Four regional Internet registries -- ARIN, RIPE NCC, LACNIC and APNIC -- assign Internet addresses from the following three classes.
Class A - supports 16 million hosts on each of 126 networks
Class B - supports 65,000 hosts on each of 16,000 networks
Class C - supports 254 hosts on each of 2 million networks
The number of unassigned Internet addresses is running out, so a new classless scheme called CIDR is gradually replacing the system based on classes A, B, and C and is tied to adoption of IPv6.
What is Media Address Control?
In computer networking a Media Access Control address (MAC address) or Ethernet Hardware Address (EHA) or hardware address or adapter address is a quasi-unique identifier attached to most network adapters (NICs). It is a number that acts like a name for a particular network adapter, so, for example, the network cards (or built-in network adapters) in two different computers will have different names, or MAC addresses, as would an Ethernet adapter and a wireless adapter in the same computer, and as would multiple network cards in a router. However, it is possible to change the MAC address on most of today's hardware, often referred to as MAC spoofing.
Most layer 2 network protocols use one of three numbering spaces managed by the IEEE: MAC-48, EUI-48, and EUI-64, which are designed to be globally unique. Not all communications protocols use MAC addresses, and not all protocols require globally unique identifiers. The IEEE claims trademarks on the names "EUI-48" and "EUI-64". (The "EUI" stands for Extended Unique Identifier .)
MAC addresses, unlike IP addresses and IPX addresses, are not divided into "host" and "network" portions. Therefore, a host cannot determine from the MAC address of another host whether that host is on the same layer 2 network segment as the sending host or a network segment bridged to that network segment.
ARP is commonly used to convert from addresses in a layer 3 protocol such as Internet Protocol (IP) to the layer 2 MAC address. On broadcast networks, such as Ethernet, the MAC address allows each host to be uniquely identified and allows frames to be marked for specific hosts. It thus forms the basis of most of the layer 2 networking upon which higher OSI Layer protocols are built to produce complex, functioning networks.
Difference between client and server?
The client drops all references to an object, after which the ORB local to the client then can clean up all of its data structures related to that object, and
The server can decide that the object needs to be destroyed, and it then does the job of deactivating the object (so that the POA can know not to answer any more queries to that object) and freeing associated resources, etc.
