CST311.5 Module Five

 

CST311.5 Module Five

What I learned this week:

This week we covered the Network Layer, and how it's essentially the glue of the network. The book breaks it down into two interacting parts, one being the data plane and the other being the control plane. for the data plane its primary focus is set toward forwarding packets, as a per router function in the network layer this means as a datagram arrives at the routers input link it is then forwarded to the appropriate output link. Where as the control plane handles the network-wide logic which is dictated by routing algorithms and in some cases Software-Defined Networking in which a remote controller broadcasts forwarding tables across the network to intended routers for their forwarding function. As can be seen the two most essential functions of the network layer are forwarding and routing of datagrams. Where the data plane is focused on forwarding and the control plane handles the routing of datagrams. Overall the Network Layer offers the end-to-end delivery of packets, the network layer service they offer is a best-effort service in which packets are neither guaranteed to be received in order in which sent, and no guarantee of eventual delivery, no guarantee of minimal bandwidth, which seems far from reliable, however it seems to somehow manage quite-well even with real-time applications running on it.

The components of a router consist of input ports, output ports, switching fabric and the routing processor. the input port is in charge of receiving incoming packets, calling a lookup function for intended destination, and queueing. The switching fabric connects the input ports to output ports and is completed contained within the router. Where as the output port stores the packet from the switching fabric and finally transmits these packets on outgoing link. The routing processor is the brain and returns from an input ports request for lookup by indexing the forward lookup table. Queeing can occur within routers, and quite often this is where packets get dropped or lost. they can occur in two places the input port at entry of switching fabric or output port upon entry from the fabric, So that is why scheduling is often needed. Similar to our course in OS, they operate under similar algorithms such as FIFO, Priority, and Round Robin, oh and also Weighted Fiar Queuing which is similar to Round Robin however, each class has an assigned weight of time in which it takes share for the transmission line.

We also covered the difference between IPv4 and IPv6, their headers, the math behind fragmentation. We learned primarily about addressing, how subnets are defined, and what an interface really is,.We also covered DHCP and its "plug-and-play" capabilities. How to request for an IP address from DHCP. Another interesting coverage was on Network Address Translation (NAT) ad how it is a middlebox on the network, capable of multiple things.

    graph LR
    A --- B
    B-->C[fa:fa-ban forbidden]
    B-->D(fa:fa-spinner);
    
    click B "http://www.google.com"