Chapter 1 Flashcards
What is network edge? and whats its purpose?
refers to the part of a network that connect end-users devices such as smartphones, computers, and IOT devices, acting as an entry and exit point for data and connecting these devices to the larger network or internet.
hosts: clients and servers
servers are in data centers
What is network core?
It is the central part of a network that is designed to be reliable and capable of handling large amounts of data traffic. It connects different parts of a network to each other and ensures that data can be efficiently transmitted across the network.
- mesh of interconnected routers
- What is hosts?
- What is Packet switches?
- Examples of communication links?
- Network
- end systems (smartphones, computers, etc)
- Forwards packets (chunks of data), routers, switches
- Fiber, copper, radio, satellite
transmission_rate: bandwidth - collection of devices, routers,
links: managed by an organization
What are network protocols?
Sets of rules and conventions that dictate how data is transmitted and received over a network. It enables different network devices and software applications to communicated with each other.
Common examples of network protocols include:
- HTTP for web browsing
- SMTP for email
- TCP/IP for internet communication
Protocols ensure that data is transferred efficiently, securely, and reliably across the network
What is packets of data?
When host sends information, it breaks it into smaller chunks, known as “packets”, of length L bits
transmits packet into network at transmission rate, R
packet time needed L (bits)
transmission = to transmit L-bit = ___
delay packet into link R(bits/sec)
What is packet-switching?
it is where the data is broken down into packets before being sent over a network.
Break down data: divided into smaller, manageable pieces known as packets
network forwards packets from one router to the next, across links on path from source to destination
Packet transmission delay: L / R
L: stands for the length of the packet. Measured in bits and indicates the size of the packet being transmitted
R: stands for the TRANSMISSION RATE of the link. Rate at which bits can be transmitted through the network and is usually measured in bits per second (bps)
What is circuit-switching?
Circuit switching is a method of networking in which a dedicated communication path is established between two nodes for the duration of the transmission. This path is a sequence of physical links, with each link being set to a dedicated channel (like a specific frequency in the case of traditional telephony).
Here’s a simplified explanation:
Establishment: Before any data can be transmitted, a dedicated circuit must be established. This involves setting up all the intermediate switches and nodes to create a continuous physical connection between the sender and receiver. Transmission: Once the circuit is established, data can flow along this dedicated path for the entirety of the session. The channel remains reserved exclusively for this connection, whether data is being sent or not. Teardown: After the session is complete, the circuit is terminated, and the previously reserved resources are released so that they can be used for other connections.
Packet-switching vs circuit switching:
Packet-switching:
1. Scalable: it’s more scalable to large amounts of data and a high number of users because it does not have required dedicated path per communication
2. Suitable for bursty data: more efficient for data that is bursty in nature because network resources are used only when data is being transmitted
3. Dynamic routing: each data packet can take a different path to the destination
Circuit-switching:
1. Limited scalability: it’s less calable because each communication requires a dedicated path, limiting number of simultaneous communications
2. Suitable for continuous data: it is efficient for communications that need a constant amount of bandwidth
Packet delay formula:
d (nodal) = d(proc) + d (queue) + d (trans) + d (prop)
Packet delay: four sources
1. Queuing
- occurs when work arrives faster than it can be serviced:
- queue length grows when arrival rate to link exceeds output link capacity
- packet loss occurs when memory to hold queued packets fills up
From the formula:
d (nodal) = d(proc) + d (queue) + d (trans) + d (prop)
d (proc): nodal processing
d(proc): Processing Delay
This is the time a router takes to process the packet header, check for bit-level errors, determine the outgoing link, and other necessary processing before forwarding
From the formula:
d (nodal) = d(proc) + d (queue) + d (trans) + d (prop)
d (queue) : Queuing delay
d(queue): Queuing Delay
- This delay occurs as packets wait in the queue until they can be processed. Its length can vary greatly depending on the congestion in the network (how many packets are waiting to be sent)
- time waiting at output link for transmission
From the formula:
d (nodal) = d(proc) + d (queue) + d (trans) + d (prop)
d (trans) =transmission delay
d (trans): Transmission Delay
-time it takes to push all the packet’s bits onto the wire
where:
L: packets length (bits)
R: link transmission rate (bps)
d (trans) = L/R
From the formula:
d (nodal) = d(proc) + d (queue) + d (trans) + d (prop)
d (prop) = propagation delay
d (prop) = Propagation delay
- This is the time it takes for a bit to travel from the beginning of the link to the end of the link. It’s determined by the distance the packet must travel and the propagation speed of the medium
where:
d: length of physical link
s: propagation speed (2x10^8 m/sec)
d (prop) = d/s
