Osi Layer 3. Network Layer (OSI Layer3) Explained Posted December 25 2016 December 25 2016 Networkel The Internet Protocol (IP) is the most popular implementation of a hierarchical network addressing scheme.
The third layer of the OSI Model the network layer is where most network engineers focus their time and expertise.
The Network Layer: Understanding layer 3 of the OSI Model
OSI Layer 3 Network Layer In the sevenlayer OSI model of computer networking the network layer is layer 3 The network layer is responsible for packet forwarding including routing through intermediate routers since it knows the address of neighboring network nodes and it also manages quality of service (QoS) and recognizes and forwards local host domain messages to the Transport layer (layer 4).
What is Layer 3 of the OSI Model: Network Layer? DDI
RoutingNetwork Layer Interaction with The Data Link LayerNetwork Layer (Layer 3) AddressingRouting ProtocolsRouting focuses on the endtoend logic of forwarding data Figure 51shows a simple example of how routing works The logic seen in the figure is relatively simple For PC1 to send data to PC2 it must send something to R1 when sends it to R2 then on to R3 and finally to PC2 However the logic used by each device along the path varies slightly In Figure 51 four different types of data links were used to deliver the data When the network layer protocol is processing the packet it decides to send the packet out the appropriate network interface Before the actual bits can be placed onto that physical interface the network layer must hand off the packet to the data link layer protocols which in turn ask the physical layer to actually send the data And as was described in Chapter 3 “Data Link Layer Fundamentals Ethernet LANs” the data link layer adds the appropriate header and trailer to the packet creating a frame before sending the frames over each physical network The routing process forwards the packet and only the packet from endtoend through the network discarding data link headers and trailers along the way The network layer processes deliver the packet endtoend using successive datalink headers and trailers just to get the packet to the next router or host in the path Each successive data lin One key feature of network layer addresses is that they were designed toallow logical grouping of addresses In other words something about the numericvalue of an address implies a group or set of addresses all of which areconsidered to be in the same grouping In TCP/IP this group is called anetwork or a subnet In IPX it is called a network InAppleTalk the grouping is called a cable range These groupings workjust like USPS ZIP codes allowing the routers (mail sorters) to speedilyroute (sort) lots of packets (letters) Just like postal street addresses network layer addresses are grouped basedon physical location in a network The rules differ for some network layerprotocols but the grouping concept is identical for IP IPX and AppleTalk Ineach of these network layer protocols all devices on opposite sides of a routermust be in a different Layer 3 group just like in the examples earlier in thischapter Routing relies on the fact that Layer 3 addresses are grouped Conveniently the routing tables in the example based on Figure 52had the correct routing information already in their routing tables In most cases these entries are built dynamically by use of a routing protocol Routing protocols learn about all the locations of the network layer “groups” in a network and advertise the locations of the groups As a result each router can build a good routing table dynamically Routing protocols define message formats and procedures just like any other protocol The end goal of each routing protocol is to fill the routing table with all known destination groups and with the best route to reach each group The terminology relating to routing protocols sometimes can get in the way A routing protocol learns routes and puts those routes in a routing table A routed protocol is the type of packet forwarded or routed through a network In Figures 51 and 52 the figures represent how IP packets are routed so IP would be the routed protocol If.
Osi Model The 7 Layers Of Network Architecture Bmc Software Blogs
Typical Features of OSI Layer 3 > Fundamentals of IP for the
Network Layer (OSI Layer3) Explained Networkel
Network Layer Layer 3 The OSIModel
Layer 3 of the OSI model (Network Layer) is the layer of the ISO Open Systems Interconnection (OSI) model that provides the functional and procedural means of transferring variable length data sequences from a source host on one network to a destination host on a different network while maintaining the quality of service requested by the transport layer (in contrast to the data link layer which connects hosts within the same network).