CST311.6 Module Six

 

CST311.6 Module Six

What I learned this week:

Continuing on our progress from last week's module of the Network Layer, this week we dove deeper and incorporated the control plane into the overall diagram we have of the network. Distinguishing the difference of how we previously perceived the control plane where individual routing algorithms were ran in per router control fashion. and elaborated more about the what's and how's if the control plane were logically centralized where a remote controller distributes the forwarding tables to be used by each and every router.

We then went over two basic algorithms that formatted the way routing tables are calculated, with one being Dijkstra's Algorithm as it can determine the shortest path between a source and all destinations within a network. We also covered the Distance Vector Routing Algorithm which attributes the Bellman-Ford equation, and it also has a means to determine the shortest path. However, while they both can assist in determining routes for shortest path, they also have some distinguishable differences.

In order to understand the differences, we have to understand the the internet is comprised of a network of networks. Where each network has some form of centralized authority, and would like to operate as they wish and employ policies how they see best fit. We also unveiled in our study of the basic routing algorithms that they do not scale with the vastness of how big the internet and amount of routers needed to operate. it is for these reasons of scale and administrative autonomy, that shape the solution of organizing routers into autonomous systems(AS) where one algorithm will be used for intra-AS routing protocol(Dijkstra's) and the DV algorithm will be used for inter-AS routing protocol(DV). Distributing them in this fashion allows the internet to benefit on the side of scalability and also administrative autonomy, as each network within the network can enforce policies at one end, without interfering with the operations of another network.

Dijkstra's algorithm is used in OSPF, which is a link-state protocol, and uses flooding of link-state information in order to construct a complete topological map of the designated Autonomous system. Where individual link costs are configured by network administrators. Some benefits of OSPF include: security measures, load balancing in the case of multiple low-cost routes to destination, Integration of unicast and multicast, and overall support for hierarchy with a single AS.

Distance Vector algorithm is decentralized, thus it is used as a inter-AS protocol, known as the Border Gateway Protocol(BGP). BGP provides each router a means to obtain prefix reachability information from neighboring AS's who then can determine the "best" routes within their respected AS, to the first gateway router within their network. BGP also has a format of messaging in which is accessible to gateway routers and to other gateway routers as well as the routers  within their AS