1.1) Primer on Latency and Bandwidth Flashcards
Latency
The time from the source sending a packet to the destination receiving it.
Bandwidth
Maximum throughput of a logical or physical communication path.
Propagation delay
Amount of time required for a message to travel from the sender to receiver, which is a function of distance over speed with which the signal propagates.
Transmission delay
Amount of time required to push all the packet’s bits into the link, which is a function of the packet’s length and data rate of the link.
Processing delay
Amount of time required to process the packet header, check for bit-level errors, and determine the packet’s destination.
Queuing delay
Amount of time the incoming packet is waiting in the queue until it can be processed.
“on the wire”
A term used to describe transmission of a packet. Example: It will take 10 seconds to put a 10 Mb file on the wire over a 1 Mbps link.
“bufferbloat”
Bufferbloat describes the problem of local router’s with large incoming buffers, intended to avoid dropping packets, breaking TCP’s congestion avoidance mechanisms and introducing high and variable latency delays into the network.
Content Delivery Network (CDN)
CDNs distribute content around the globe and serve that content from a nearby location to the client significantly reducing the propagation time of data packets.
Last-Mile Latency
The phenomenon that it is often the last few miles where significant latency is introduced. This is also referred to as the “last-mile problem”. Last-mile latency varies wildly based on your ISP, the deployed technology, topology of the network, and even the time of day.
ISP
Internet Service Provider
CLI command:
- traceroute (Unix)
- tracert (Windows)
Traceroute is a simple network diagnostic tool for identifying the routing path of the packet and the latency of each network hop in an IP network.
