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2.0 Network Implementations

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2.2 Compare and contrast routing technologies and bandwidth management concepts

Makiel [Muh-Keel]
Last edited 524 days ago by Makiel [Muh-Keel]

What is Routing?

IP Routing is the process of moving packets from one network to another network using routers. The IP routing process is a super-important subject to understand because it pertains to all routers and configurations that use IP. Routers essentially complete the process of taking a packet from one device and sending it through the network to another device on a different network.
The logical network address of the destination device is used to get packets to the right network, and the hardware address of the device is used to deliver the packets to the correct device.
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You will need to understand the difference between a Routing Protocol and a Routed Protocol.
Routing Protocol
Basically, a Routing Protocol determines the path of a packet through an internetwork.
A tool used by routers to dynamically find all the networks in the internetwork as well as to ensure that all routers have the same routing table.
RIP, PSPF, BGPI.
Routed Protocol
Can be used to send user data (packets) through the established internetwork. Routed Protocols are assigned to an interface and determine the method of packet delivery.
Difference between Routing and Routed
Routing protocols are the means by which routers exchange next-hop reachability information with each other. A routing protocol enables one router to tell all the other routers to which it is connected about the networks that it can reach. OSPF, EIGRP, ISIS, and BGP are examples of routing protocols.
Routed protocols are the traffic that routers direct from source to destination. IP, HTTP, SSH, and SIP are examples of routed protocols.
Example:
For your router to be capable of doing it’s job, it must know at least the following information
Destination Network Address
Neighbor Routers from which it can learn about remote networks
Possible routers to all remote networks
The best route to each remote network
How to maintain and verify routing information.
The Router learns about remote networks from neighbor routers or from an administrator. The router then builds a Routing Table (a map of the internetwork)that describes how to find the remote networks. If a network is directly connected, then the router already knows how to get to it.
If a network isn’t directly connected to the router, the router has two options of getting to it
Static Routing
Manually typing all network locations into the routing table; Which can be exhausting depending on how big your network gets.
Use the command ip route [][][]
Ex. ip route 172.10.24.3 255.255.255.255 172.15.37.21
Dynamic Routing
Protocol on one router that communicates with the same protocol running on neighboring routers. The routers then update each other about all the networks they know and place this information into the routing table.
If a change occurs in the network, the dynamic routing protocols automatically inform all routers about the event.
Converged Routing Table
When the routing tables of all routers in the network are complete (because they include information about all the networks in the internetwork), they are considered converged, or in a steady state.
Administrative Distances
Used to rate the trustworthiness of routing information received on one router from its neighboring router. An AD is represented as an integer from 0 to 255, where 0 equals the most trusted route and 255 the least. A value of 255 essentially means, “No traffic is allowed to be passed via this route.”
If a router receives two updates listing the same remote network, the first thing the router checks is the AD. If one of the advertised routes has a lower AD than the other, the route with the lower AD is the one that will get placed in the routing table.
If both advertised routes to the same network have the same AD, then routing protocol metrics like hop count or the amount of bandwidth on the lines will be used to find the best path to the remote network. And as it was with the AD, the advertised route with the lowest metric will be placed in the routing table. But if both advertised routes have the same AD as well as the same metrics, then the routing protocol will load-balance to the remote network. To perform load balancing, a router will send packets down each link to test for the best one.
Default Route
A Default Route is the route that takes effect when no other route is available for an IP destination address.
A route when no other route matches; The “gateway of last resort”. Destination of 0.0.0.0/0
Time to Live
Refers to the amount of time or “hops” that a packet is set to exist inside a network before being discarded by a router.
Dynamic Routing (Detailed)
Dynamic routing protocols break up into many different categories or types of protocols, as shown in Figure 9.7. The first split in the dynamic protocol branch is the division of interior gateway protocols (IGPs) and exterior gateway protocols (EGPs). We are going to talk about each protocol and category, but for now the difference between IGP and EGP is interior or exterior routing of an autonomous system (AS)
Interior Gateway Protocol
IGP operates and routes within an AS
Exterior Gateway Protocol
EGP works outside or between more than one AS.
Autonomous System (AS)
A collection of networks or subnets that are in the same administrative domain. This is another way of saying an administrative domain is within your company's network, and you control or administer all the subnets that are within it. You control and set the policy for what happens in the network or autonomous system. I hope you can now see that an IGP operates and routes within an AS and an EGP works outside or between more than one AS.
There are a number of Routing Protocols that can be used: Routing Information Protocol (RIP), Open Shortest Path First (OSPF), Enhanced Interior Gateway Routing Protocol (EIGRP), Intermediate System to Intermediate System (IS-IS), and Border Gateway Protocol (BGP).
Each Routing Protocol is classified as Link State, Distance Vector, and Hybrid.
An Autonomous System is a collection of networks under a common administrative domain. IGPs operate within an autonomous system, and EGPs connect different autonomous systems together.
Link-State
Link state protocols are also called shortest-path-first protocols. Link state routing protocols have a complete picture of the network topology. Hence they know more about the whole network than any distance vector protocol. They use their knowledge about the entire topology to make routing decisions.
Each router independently calculates the best next hop from it for every possible destination in the network using local information about the topology. The collection of best-next-hops forms the routing table. The routing table is used to make routing decisions.
OSPF
OSPF (Open Shortest Path First) is an open-source interior gateway protocol that operates at the IP layer of the OSI model while converging quickly (although not as fast as EIGRP), and it supports multiple, equal-cost routes to the same destination. It supports both IP and IPv6 routed protocols, but OSPF must maintain a separate database and routing table for each, meaning you're basically running two routing protocols if you are using IP and IPv6 with OSPF.
OSPFv3 is used to support IPv6.
OSPF has an AD of 110.
It's an interior gateway protocol (IGP) meaning its been designed to be used within a single autonomous system.
OSPF learns about every router and subnet in the entire Network; The result is every router has the same information about the network as each other by sending LSA (Link State Advertisement) using IP Connectivity. Once it gains info from the LSAs, it uses this information to create the Routing Tables.
Link State Advertisement
LSA - Link state advertisement - Contains information about the subnet, router and some other network information
It’s a fast, scalable, and robust protocol that can be actively deployed in thousands of production networks. One of OSPF's most noteworthy features is that after a network change, such as when a link changes to up or down, OSPF converges with serious speed!
OSPF has the 2nd fastest convergence time out of all the network protocols; Convergence refers to when all routers have been successfully updated with the change.
OSPF works by using the Dijkstra algorithm; It also builds an hierarchical network using areas.
OSPF is supposed to be designed in a hierarchical fashion, which basically means that you can separate the larger internetwork into smaller internetworks called areas. This is definitely the best design for OSPF.
The following are reasons you really want to create OSPF in a hierarchical design:
To decrease routing overhead To speed up convergence To confine network instability to single areas of the network
Benefits of OSFP
With OSPF, there is no limitation on the hop count.
OSPF uses LSA’s to spread information about how the entire network operates and runs by sending out LSA’s to each router in the internetwork.
OSPF uses IP multicast to send link-state updates and LSAs. This ensures less process resource consumption on routers that do not listen to OSPF packets. Updates are only sent in case routing changes occur instead of periodically. This ensures efficient bandwidth.
OSPF allows for better load balancing.
OSPF allows for a logical definition of networks where routers can be divided into areas. This limits the explosion of link state updates over the whole network. This also provides a mechanism to aggregate routes and decrease the unnecessary propagation of subnet information.
OSPF allows for routing authentication through different methods of password authentication.
IS-IS
IS-IS (Intermediate System to Intermediate System)is a Link-State routing protocol and Interior Gateway Protocol (IGP) that operates at Data Link layer 2 and distributes routing information between routers belonging to a single Autonomous System (AS).
IS-IS is a link-state routing protocol, providing fast convergence and excellent scalability. Like all link-state protocols, IS-IS is very efficient in its use of network bandwidth.
Intermediate System is just another word for Router. Essentially, IS-IS (Intermediate System to Intermediate System) is just fancy talk for Router-to-Router.
IS-IS is a link-state routing protocol, meaning it operates by reliably flooding topology information to a network of routers. Each router then independently builds a picture of the network's topology, just as they do with OSPF. Packets or datagrams are forwarded based on the best topological path through the network to the destination.
IS-IS also uses the Dijkstra Algorithm to to discover the shortest path through the network to a destination network.
IS-IS, although comparable to OSPF, is actually preferred by ISPs because of its ability to run IP and IPv6 without creating a separate database for each IP protocol as OSPF does. That single feature makes it more efficient in very large networks.
IS-IS sends LSP’s (Link State Packets) to exchange and gain information about the network topology
In an LSP you’ll find some type of metric & information about any adjacent neighboring routers.
Image of IS-IS
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Differences Between OSFP & IS-IS
Differences Between OSFP and IS-IS
OSFP
IS-IS
1
OSPF Requires the IP Connectivity between the routers to share the routing information.
IS-IS doesn’t require IP connectivity between the routers as updates are sent via CLNS on Layer-2 instead of IP.
2
OSPF router can belong to multiple areas.
IS-IS router can belong to only one area.
3
OSPF uses Router id to identify a router on network.
IS-IS uses System ID to identify a router on the network.
4
Area, Non Backbone Area, Backbone Area, ABR, ASBR, Host.
IS, Level 1, Level 2, L1/L2, Subdomain, ES.
There are no rows in this table
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Distance Vector
The distance-vector protocols find the best path to a remote network by judging—you guessed it—distance. Each time a packet goes through a router, it equals something we call a hop, and the route with the fewest hops to the destination network will be chosen as the best path to it.
The distance-vector routing algorithm passes its complete routing table contents to neighboring routers, which then combine the received routing table entries with their own routing tables to complete and update their individual routing tables. This is called routing by rumor because a router receiving an update from a neighbor router believes the information about remote networks without verifying for itself if the news is actually correct.
The vector indicates the direction to the remote network. RIP, RIPv2, and Enhanced Interior Gateway Routing Protocol (EIGRP) are distance-vector routing protocols. These protocols send the entire routing table to all directly connected neighbors.
RIP
Routing Information Protocol (RIP) is an outdated vendor-neutral distance vector routing protocol that uses only one thing to determine the best way to reach a remote network—the hop count. And because it has a maximum allowable hop count of 15 by default, a hop count of 16 would be deemed unreachable.
RIP works fairly well in small networks, it's pretty inefficient on large networks with slow WAN links or on networks populated with a large number of routers.
RIP is also notorious for being very slow at converging, which causes latency in your network.
RIPv1 uses only classful routing, which means that all devices in the network must use the same subnet mask for each specific address class; RIPv1 doesn’t send updates with subnet mask information.
RIP uses little router processing power, but also uses a lot of bandwidth to do its job.
RIPv2
Routing Information Protocol Version 2 is the next evolutionary step after RIPv1; It has a number of notable differences from version 1.
One of the key differences is that RIPv2 performs classless subnetting; Meaning RIPv2 subnet information is sent with each route update
RIPv2 supports VLSM
Variable-Length Subnet Mask (VLSM) is the ability to use a different subnet mask when subnetting. Basically instead of using the same subnet mask across an entire sub network, you can allocate almost the exact amount that you need.
This saves address space.
Ex. We don’t need to use a /23 subnet mask in all of our subnets. We can instead of use /23 for the subnets that really use that amount of subnets, and /15 for other subnets that only need /15 subnet masks.
Differences between RIPv1 & RIPv2
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RIPng
RIPng (RIP Next Generation) exchanges routing information used to compute routes and is intended for IP version 6 (IPv6)-based networks.
Uses UDP port 521
Hybrid
A hybrid protocol uses aspects of both distance vector and link state.
EIGRP & BGP are placed in this category.
EIGRP
EIGRP (Enhanced Interior Gateway Protocol) is a classless, enhanced hybrid distance-vector protocol. It’s a hybrid routing protocol because it has characteristics of both distance-vector and link-state protocols.
Holds #1 fast convergence time out of all Protocols.
Has a default Administrative Distance of 90.
EIGRP has link-state characteristics as well as Distance vector characteristics—it synchronizes routing tables between neighbors at startup and then sends specific updates only when topology changes occur. This makes EIGRP suitable for very large networks.
To determine the best path to each network, EIGRP uses bandwidth and delay of the line as well as sending reliability, load, and the MTU information between routers, but it only uses bandwidth and delay by default
EIGRP uses successor routes to forward traffic to a destination and is stored in the routing table. It is backed up by a feasible successor route that is stored in the topology table—if one is available. Remember that all routes are in the topology table.
There are a number of powerful features that make EIGRP a real standout from RIP, RIPv2, and other protocols. The main ones are listed here:
Support for IP and IPv6 (and some other useless routed protocols) via protocol-dependent modules
Considered classless (same as RIPv2 and OSPF)
Support for VLSM/Classless Inter-Domain Routing (CIDR)
Support for summaries and discontiguous networks
Efficient neighbor discovery
Communication via Reliable Transport Protocol (RTP)
Best path selection via Diffusing Update Algorithm (DUAL)
BGP
BGP (Border Gateway Protocol) is a hybrid external routing protocol (used between autonomous systems, unlike RIP or OSPF, which are internal routing protocols) that uses a sophisticated algorithm to determine the best route.
Classified under EGP, and to be honest, it’s the only External Gateway Protocol known.
BGP is used with IGPs to connect ASs together in larger networks
BGP uses Autonomous Systems to build out the routing table.
Because the Internet's growth rate shows no signs of slowing, ISPs use BGP for its ability to make classless routing and summarization possible. These capabilities help to keep routing tables smaller and more efficient at the ISP core.
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Bandwidth Management is the process of regulating the amount of data on a network by setting specific allocations to every data-consuming application and device on the network. It helps alleviate network congestion or bottlenecks and ensures enough bandwidth for critical applications within an organization.
The concept behind bandwidth management is similar to rationing. At the height of the coronavirus pandemic, some countries had to set a fixed number of commodities like paper towels, rubbing alcohol, and canned goods, for every consumer.
Traffic Shaping
A form of rate limiting; It’s an Internetworking traffic management technique that delays some or all packets to bring them into compliance with your or your company's traffic profile.
This process is used to optimize or guarantee performance, improve latency, and/or increase usable bandwidth for some kinds of packets by delaying other kinds, decided on by you; Using a contract.
Quality of Service (QoS)
Refers to the way the resources are controlled so that the quality of services is maintained. It's basically the ability to provide a different priority for one or more types of traffic over other levels; priority is applied to different applications, data flows, or users so that they can be guaranteed a certain performance level.
QoS can ensure that applications with a required bit rate receive the necessary bandwidth to work properly. Clearly, on networks with excess bandwidth, this is not a factor, but the more limited your bandwidth is, the more important a concept like this becomes.
Quality of service (QoS) allows administrators to predict, monitor, and control bandwidth use to ensure it is available to programs and apps that need it.
QoS methods focus on one of five problems that can affect data as it traverses network cable:
Delay
Dropped packets
Error
Jitter
Out-of-order delivery
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Testing Your Understanding Of How IP Routing Works

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In this example, we have two LANs (Router A LAN + Router B LAN w/ HTTP Server)and two routers connecting these two LANs via a wireless network connection. Host A is trying to connect to the resources on Router B’s LAN. To do this, a few things will occur. Host A’s Destination for its Frame Address will be Fa0/0 of Router A. The destination of any data packets for Host A will be the IP address of the NIC card in the HTTP server on Router B’s LAN. The destination port number of Host A will be Port-80 due to the HTTP Server being on Port 80.
To summarize again, in order for a host or device to acquire a network resource that’s on another LAN a(Network), 3 Different Destinations for the Host to Communicate To (The device that wants to access the resource) has to be known:
You need to know where the frame address is going to go; Destination Frame Address.
You need to know where the data packets are going to go; Destination IP address.
You need to know the port number of the resource you’re accessing; Destination Port Number.

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In order for Host A on Router A to communicate with the HTTPS Server on a switch, you’ll need to know the following three destinations:
Destination Frame Address: In this case, its the Fa0/0 interface of Router A
Destination Data Packet Address: In this case, it’s the IP address of the NIC card in the HTTPS Server
Destination Resource Port Number: In this case, HTTPS has a port number of 443.
Remember switches have nothing to do with routing, so it’s important to never include them in any kind of routing decisions; Completely ignore them when it comes to Routing decisions unless they are Layer-3 Switches.

What is Routing?
Testing Your Understanding Of How IP Routing Works
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