Chapter 4: Routing Packets Across a Network Flashcards
What is the Network Layer (Layer 3) of the protocol stack responsible for doing?
Responsible for finding a route over the network that will allow the packet to teach its ultimate destination
Each ___ has a ___ that contains the ___ of the ___ ___
Packet, header, address, final, destination
At the highest level, the internet can be _____
considered a connection of large sub-networks called autonomous systems (AS)
Each AS is identified by what?
Autonomous System Number (ASN), which are autonomous
The Internet Assigned Number Authority (IANA) assigns what?
Autonomous System Numbers (ASNs) and IP addresses
Interior Gateway Protocols (IGPs) are what?
They are routing protocols that direct packets between nodes within an Autonomous System
Exterior Gateway Protocols (EGPs) are what?
They are routing protocols that direct packets between AS networks. The Border Gateway Protocol is the most reelvant
What is a switch?
Switches are connection oriented and are aware of the source and final destination of the packet
What is a router?
Routers are connectionless and forwards the packet along a next hop without any knowledge of what the rest of the path is going to look like
Why must every AS peer with at least one other AS?
The internet is based on global/end-to-end reachability
Define a Circuit Switched scenario
The switches simply serve to connect a direct wire between the source and destination
Define a Whole File Transfer scenario
The entire file is sent in one-piece with N_o overhead bits
Define a Packet Transfer scenario
The file is divided into K packets before transmission. Each packet is transmitted using N_o overhead bits
What is the purpose of maintaining a routing table?
Allows routers to not have to know the entire route a packet will take. It only needs to forward it to the next hop along the journey. We utilize hierarchical routing
What is the purpose for hierarchical routing?
Makes it so that routers do not need to keep every possible destination stored on a routing table
What is the NetID in an IP address?
Describes the network that the user is on
What is the HostID in an IP address?
Describes the host that is on a specific network (described by the NetID)
In the simplest case, what is a NetID? And why is it “simple”/convenient?
Each NetID is a single router that is connected via a LAN to all the hosts within that network. Routers outside of each network now only need to store the NetIDs in their routing table, similar to a postal office organizing based on country
What is the purpose of subnetting?
Allows us to overcome the inflexibility of having a limited number of NetIDs and HostIDs for a number of networks.
How does subnetting work?
Done by defining a subnet mask that is then ANDed with an IP address to determine its subnet address
Define Classless Interdomain Routing (CIDR)
The removal of class distinctions within addresses and was replaced with a variable length subnet mask that indicates the NetID portion of the address
What is the purpose of Classless Interdomain Routing (CIDR)
Allows multiple levels of hierarchical addressing to be used in the internet than just one. The length of the netmask increases as the packet gets closer to its destination
Why are MAC addresses used by ethernet connections?
Once a packet reaches its final subnet, it is necessary to map its IP address to a MAC address so it may reach its destination
What is the Address Resolution Protocol (ARP)? And how does it work?
ARP is used to map an IP address to a MAC address via Ethernet. Asks the computer with a specific IP address to reply
