Networks Technologies PDF

Networks technologies Routing principles for internal and external networks  What is the chapter about? – The role and importance of routing – Transmitting data to the Internet – Routing on local networks – Role of default gateway, locally connected networks – Routi...

Networks technologies Routing principles for internal and external networks  What is the chapter about? – The role and importance of routing – Transmitting data to the Internet – Routing on local networks – Role of default gateway, locally connected networks – Routing on remote networks – Routing traffic between LANs – How dynamic routing protocols work – Distance vector based and link state based protocols  From the previous episode... – We looked at the different addressing systems – Local use and structure of MAC addresses – The structure of IP addresses – Methodology for obtaining different addresses  The layers covered in this lesson Application layer Application layer Display layer Transport layer Session layer Transport layer Internet layer Network layer Data link layer Network Access Layer Physical layer  The network layer's role – For the network layer, the following function appeared: – Determine the path of packets from source to destination – The route can be: – Wired – it is created when the connection is established – it is defined for each packet separately – The aim is therefore to ensure that devices are aware of the route to the destination network  Network transit decision – The source device can implement three different addressing: – Send a message to itself (127.0.0.1, ::1) – It can send a message to a device on a local area network (LAN) – Send a message to a device on a remote network (WAN)  Network transit decision – The message sent to itself can be used to analyse the operation of the own device, i.e. the correct structure of the TCP/IP protocol set – The message sent to a device on the local network is forwarded directly to the destination device (in this case both IP and MAC address are available) – It cannot directly forward the message to the device on the remote network!  Remote network access mechanics – To access the remote network, you need the IP address of the device (Router) at the edge of the network – This device will be the so-called default gateway – If a local device wants to reach any remote device, the IP address will be the address of the specific target device, but the MAC address will be the address of the default gateway, since it must locally forward to it first Remote network access mechanics  Routing table – Computers and routers also have routing tables. – This table contains exactly which destination IP packet should be sent on which interface – On a computer, this table can be viewed with the netstat -r command Router routing table Marking of local routes  Marking of local routes – For local routes, there are three main components – The first letter indicates whether the network is directly connected or a local IP address. – For example. Next to 192.168.10.1 you would see an L if that is the IP address configured on the Router. – The second tag indicates what the specific network address or device IP address is – The third tag indicates the interface to which the network is connected or where the IP address is set Marking of remote routes  Marking of remote routes – For long-distance routes, there are many more components: – The route type will be discussed later – The destination network address – Administrative distance and metrics to indicate the actual distance to the destination network and the reliability of the route – Next-hop indicates the next IP address to which the packet should be forwarded directly – Also indicates the elapsed time since learning – Finally, it also indicates the interface through which the destination network can be reached  Remote network route types – Remote networks are divided into two broad categories – Network specified by static routes – Dynamically learned routing networks – In the case of static, the routes on the network device are set manually – In the dynamic case, different routing algorithms are based on the communication between routers  Static route types – Standard static route – Default static route – Summary static route – Floating static route  Static route types – Standard static route – To build a simple static route, you need to specify three parameters – The network address of the destination network – The subnet mask of the destination network – IP address of the next host to the destination network  Static route types – Default static route – The default static route is a special case, where you specify that if you don't have any route entries for a destination network, where to forward the packet  Static route types – Summary static route – This route type should be used when you do not want to set up routes to several similar networks one by one, but want to add them as one route  Static route types – Floating static route – The floating route can be seen as a kind of backup route, if the main route is disconnected, there should be one or more alternative routes that the package can use Dynamic routes types Dynamic routes types – Dynamic routes are divided into two broad groups – Exterior Gateway Protocols (EGP) – Interior Gateway Protocols (IGP) – The role of EGPs is to establish connections between IGP systems, so this is mostly the responsibility of the service providers Dynamic routes types – There are two broad categories of IGPs: – Distance vector based protocols – Link-state based protocols Dynamic routes types – For distance vector based protocols, the two most common directions are – The Router Information Protocol (RIP, RIPv2, RIPng) – The (Enhanced) Interior Gateway Routing Protocol (Cisco proprietary development) – Most used for link-state protocols – Open Shortest Path First (OSPF) Administrative distance of dynamic routes – The administrative distance was mentioned in the case of routes – This value represents the reliability of the protocol, it is used by the Router to decide which route to choose – This includes a metric value, which is calculated by the protocol itself, how reliable the route is based on its algorithm  How distance vector based protocols work – Using the Bellman Ford algorithm – All stations: – Receives information from its neighbours – Combines the information received with local information – Sends the processed results to all neighbours  Overall operation of the DV algorithm – The participant periodically sends route advertisements to all its neighbours – The advertisement contains the details of the available networks and their distance: – I can reach network X, distance from me: Y. – I can reach network Z, distance from me: W. –... – Neighbors receive ads and update their route tables – In the next round, each neighbour sends advertisements to its neighbours  Local operation of the DV algorithm – Runs when an ad arrives – Examines each entry in the ad: – If the neighbor reaches network X and I don't, I add a new entry to the route table for that network, the neighbor is next hop, with the distance it advertised – If I already know the network X and this neighbour is the next hop, I update the distance of my entry – If I already know the network X, but I receive an entry from another neighbour with a distance less than the current one, I replace the next hop entry with the new neighbour with the distance it advertises  Link-State Routing (LSR) algorithm – All nodes: – Advertise connection status information – Calculates the shortest route independently – Does not depend on the calculations of other nodes How the LSR algorithm works  SPF calculation method – The SPF algorithm that selects the shortest paths is based on a graph algorithm – This algorithm is called the Dijsktra algorithm and aims to determine the shortest path based on costs (weights) – For more information about the algorithm, see Algorithms, Data Structures Note II (Sándor Szénási) Comparison of dynamic protocols  Summary – Introduction to the role of Routing – Routing traffic on local networks, registering traffic control signs – Routing entries for remote networks – Introduction of static and dynamic routing Questions? Thank you for your attention!