Module 13: Quality of Service Flashcards
Packet Classification and Scheduling
partitions incoming traffic into flows, each with their own FIFO queue
decide when and what packets to send on output link
How to classify packets?
FIFO link scheduling
Link Scheduling Strict Priority
danger here is starvation
linked scheduling: weighted fairness
linke schedulers: trade offs
Packet Scheduling
make sure that at any time the flow receives at least the allocated rate ra
The canonical example of such a scheduler: weighted fair queueing (WFQ)
QoS in practice: integrated services
RSVP Multicast Tree
Which of the following is incorrect about IntServ.
After the per-flow state is set up on every router along the path, if the sender sends another packet, this packet will be scheduled based on the ToS bits.
correct stuff:
After the per-flow state is set up on every router along the path, if the sender sends another packet, this packet will be routed to the high priority queue and each router tries to do per-flow scheduling. Scheduling based on ToS bits is the behavior for DiffServ
It provides guarantees at a per-flow granularity
The path needed to be established between the sender and the receiver
After sender sends TSpec and receiver replies, a per-flow state is set up on every router along the path
specifying tspec (bursty traffic)
token bucket and arrival curve
TSpec: the token bucket
how is the token bucket used?
delay and buffer bounds
QoS guarantees: per hop reservation
Differentiated Services (DiffServ)
DiffServ in IP
Classification and Conditioning
Per Hop Behaviors
Assured Forwarding (AF) PHB
uses Random Early Detection
