QoS – 642-642 Training: Introduction to Quality Of Service
1992 – Best Effort
1994 – Integrated Services
1996 – Differentiated Services
1998 – MPLS VPN + QoS
2002 – Auto QoS (Template)
2004 – QoS For Security (*NBAR = QoS at application level not just ports)
Understanding QoS Requirements
- Voice – Smooth traffic, constant stream, benign. Drop/delay sensitive
- Video – Bursty and greedy. Drop/delay sensitive. (Not as important as voice)
Citrix application is delay sensitive and similar to voice traffic/treatment on the network.
FTP is an example of data traffic that is not sensitive at all and uses TCP.
Four Evil Villians of Voice and Video
- Lack of bandwidth – QoS will not help you!!
- Packet Loss
- Delay – ITU best practice less than 150ms from point A to B. (ONE WAY only, not round trip time. PSTN quality voice…)
- Jitter – Variation of delay. 10ms and 50ms = 40ms jitter value (Dejitter buffer in place, which can have capacity issues causing jitter)
Methods of Deploying QoS
- CLI – Legacy
- Modular QoS CLI (MQC) – Groupings of QoS methods.
- AutoQoS – Great, but requires tuning.
- QoS Policy Manager – Works with Cisco Works – Legacy?
QoS Toolbelt: Classification + Marking
- Classification involves identifying and grouping different traffic types
- Marking tags or colors the packet, so it is can be quickly recognized elsewhere in the network.
QoS Toolbelt: Policing and Shaping
- Policing – Drops or marks packet when limit is reached
- Shaping – Queues packet when limit is reached. (Kinder than policing!)
QoS Toolbelt: Congestion Avoidance
- First In First Out – (FIFO) + Taildrop – Doors closing when buffer is full
- Random Early Detection – (RED) – Random packets dropped to stopped buffer overflow. Not supported by Cisco!
- Weighted Random Early Detection – (WRED) – Random packet with specific marking can be dropped. If all markings are the same, then WRED acts the same as RED.
QoS Toolbelt: Congestion Management
Queuing Methods.. more to follow.
QoS Toolbelt: Link Efficiency Tools
- Link Fragmentation + Interleaving (LFI) Chop up huge packets and make them smaller! (Fragmentation) – High level explanation more to follow..
This video was fairly vague as only really an introduction to QoS. More to follow..