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layer 4 switchA network device that integrates routing and switching by forwarding traffic at layer 2 speed using layer 4 and layer 3 information. When packets are inspected at layer 4, the sockets can be analyzed and decisions can be made based on the type of application being serviced. See layer 4-7, layer 3 switch and Web switch.
layer 4-7The two layers in a network packet that identify its content (for details about layers, see TCP/IP and OSI model). The bottom layers 1, 2 and 3 are the protocols that move a network packet from source to destination. Layers 4 and 7 identify the application that created the packets as well as the specifics of the request. For example, inspecting layer 4 can identify HTTP traffic (Web traffic), but inspecting layer 7 can determine what the HTTP request is for (see Web switch). See layer 4 switch and well-known port.
TCP/IP SWITCHING/ROUTING DECISIONSLayer and ForwardingProtocol DecisionInspected Based on 2 - Ethernet MAC address 3 - IP Network address 3 - IP Service quality 4 - TCP/UDP Traffic type socket (HTTP, FTP, etc.) 7 - HTTP HTTP request type
transport layerThe processing in a network protocol that provides end-to-end management. The transport layer is layer 4 of 7 in the OSI model, and it may or may not guarantee error-free delivery depending on the specific protocol used. See transport protocol, TCP/IP and OSI model.
transport protocolA communications protocol responsible for establishing a connection and ensuring that all data has arrived safely. It is defined in layer 4 of the OSI model. Often, the term transport protocol also implies transport services, which includes the lower-level data link protocol that moves packets from one node to another. See TCP/IP, OSI model and transport services.
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