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QoS Concepts - Coggle Diagram

- - - - Sessions, or flows, are analyzed to determine what traffic class they belong to.
        
        When the traffic class is determined, the packets are marked.
    - - Traffic classes are allotted portions of network resources, as defined by the QoS policy.
        
        The QoS policy also identifies how some traffic may be selectively dropped, delayed, or re-marked to avoid congestion.
        
        The primary congestion avoidance tool is WRED and is used to regualte TCP data traffic in a bandwidth-efficient manner before tail drops caused by queue overflows occur.
    - - When traffic exceeds available network resources, traffic is queued to await availability of sources
        
        Common Cisco IOS-based congestion managment tools include BWFQ and LLQ algorithms
- - - - The variable amount of time a frame or packet waits to be transmitted on the link
    - - The fixed amount of time it takes to transmit a frame onto the wire
    - - The variable amount of time it takes for the frame to travel between the source and destination
    - - The fixed amount of time it takes to buffer a flow of packets and then send them out in evenly spaced intervals
- - - - Voice traffic is predictable and smooth, however, voice is very sensitive to delays and dropped packets.
    - - Video traffic tends to be unpredictable, inconsistent, and bursty compared to voice traffic. Compared to voice, video is less resilient to loss and has a higher volume of data per packet.
    - - Data applications that have no tolerance for data loss, such as email and web pages, use TCP to ensure that, if packets are lost in transit, they will be resent.
- - - - FIFO has no concept of priority or classes of traffic and consequently, makes no decision about packet priority. There is only one queue, and all packets are treated equally. Packets are sent out an interface in the order in which they arrive
    - - WFQ applies priority, or weights, to identified traffic and classifies it into conversations or flows, as shown in the figure.
    - - Class-Based Weighted Fair Queuing (CBWFQ) extends the standard WFQ functionality to provide support for user-defined traffic classes. With CBWFQ, you define traffic classes based on match criteria including protocols, access control lists (ACLs), and input interfaces.
    - - Strict PQ allows delay-sensitive packets such as voice to be sent before packets in other queues. LLQ provides strict priority queuing for CBWFQ, reducing jitter in voice conversations, as shown in the figure.