EPIC Networks

Port Check and data transfer verification The netcat utility or nc basically given in any linux and its working TCP/IP networks.nc tool is well known to System Administrators and Network Administrators as it has a wide range of capabilities. The Netcat utility is used for  Netcat can open TCP connections,  send UDP packets of data, listen on arbitrary TCP and UDP ports, carry out port scanning, transfer data from one server to another.  Server :- nc - l -p {port number}  [data]  Client :- nc {server Ip} {Portnumber opened}  [data]

Active and Passive FTP The FTP server may support Active or Passive connections, or both.  In an Active FTP connection, the client opens a port and listens and the server actively connects to it.  In a Passive FTP connection, the server opens a port and listens (passively) and the client connects to it.  You must grant Auto FTP Manager Access to the Internet and to choose the right type of FTP Connection Mode. Most FTP client programs select passive connection mode by default because server administrators prefer it as a safety measure.  Firewalls generally block connections that are "initiated" from the outside.  Using passive mode, the FTP client is "reaching out" to the server to make the connection.  The firewall will allow these outgoing connections, meaning that no special adjustments to firewall settings are required. If you are connecting to the FTP server using Active mode of connection you must set your firewa...

To establish a connection, TCP uses a three-way handshake. Before a client attempts to connect with a server, the server must first bind to and listen at a port to open it up for connections: this is called a passive open. Once the passive open is established, a client may initiate an active open. To establish a connection, the three-way (or 3-step) handshake occurs: 1.            SYN: The active open is performed by the client sending a SYN to the server. The client                         sets the segment's sequence number to a random value A. 2.            SYN-ACK: In response, the server replies with a SYN-ACK. The acknowledgment number                    is set to one more than the received sequence number i.e. A+1, and the sequence          ...

What is the Difference Between TCP and UDP? TCP and UDP are both protocols used to send data over the internet but they do this in a slightly different way. Transmission Control Protocol (TCP) is the most commonly use protocol on the internet. When information is sent as data packets through TCP, your browser will stitch these packets back together to present you, for example, with a web page that you requested. TCP will make sure that the packets are all received and in the right order before it servers you the page so it guarantees delivery. User Datagram Protocol (UDP) on the other hand, will not perform any of the error checking that TCP does making it significantly faster. This is why UDP is better for video streaming or gaming, for example, while TCP is the go-to protocol for your normal browsing. UDP TCP Reliability: UDP is less reliable as it is a connectionless protocol. When you send a message using UDP internet protocol, it is not guaranteed if it will reach the des...

LLC The primary responsibilities of LLC are: Network Layer protocol Multiplexing/De-Multiplexing Interfacing with the Network (Layer3) above by doing L3 protocol multiplexing/de-multiplexing. On receiving a frame from the physical layer below, the LLC is responsible for looking at the L3 Protocol type and handing over the datagram to the correct L3 protocol (de-multiplexing) at the network layer above. On the sending side, LLC takes packets from different L3 protocols like IP, IPX, ARP etc., and hands it over to the MAC layer after filling the L3 protocol type in the LLC header portion of the frame (multiplexing). Logical Link Services LLC can optionally provide reliable frame transmission by the sending node numbering each transmitted frame (sequence number), the receiving node acknowledging each received frame ( acknowledgment number) and the sending node retransmitting lost frames.  It can also optionally provide flow control by allowing the receivers to control the sender...