IOS-based QoS architecture and configuration
- Guidelines for QoS deployment
- QoS framework in IOS devices
- Specific configuration
- What’s the purpose of deploying QoS. What is the most original requirement?
- Find out which applications should be classified. What is the protocol from the network perspective, what is the port number?
- Analyze what QoS tools should be used according to your needs.
- Consider how to configure according to the specific equipment to be used.
- Experimental environment test
- Find a pilot to do the test
- Production network is gradually deployed
QoS specific framework
1.classification: in which class the packet is placed
2.markings: According to the classification, modify the header in the data packet (such as COS in Layer 2, DSCP in Layer 3)
- Policing (dropping and markdown): Discard or remark the packet according to the classification of the packet.
4.Shaping: Reduce the speed of traffic to a speed.
- Queuing: Interface queuing strategy
6.bandwidth allocation: Ensure that the resources of the outbound interface do not exceed the configured bandwidth resources.
- Admission control: Depending on the usage of the resource, reject or pass some kind of packet.
QoS execution order
In general, QoS is divided into four categories in terms of execution order:
1.Classification: classified according to traffic type
2.Pre-queuing: Do packet loss, marking, policing in this place.
- Queuing: Outbound queuing
4.post-queuing: This is the example mentioned in the book: When performing some operations on the traffic according to the order of transmission order (such as encryption and compression), QoS will be done after the queue at this time.The SPOTO club instructor will also explain this very clearly.
Let’s come back and look at this picture. In fact, the 1, 2, 6, 7, 12 in the picture have nothing to do with QoS. The classification of 3/8 is actually the sooner the better. The significance of the existence of 8 is that Two points. One of them is a locally generated data packet. It is not going to go to step 3. The other thing is that it is classified according to the next hop or the outbound interface. This can’t be classified before 7. 4 /9 is the same.
This is mainly related to the configuration. Everyone has configured the QoS of the Cisco device and probably knows what it is. In fact, it is three maps, class-map classification, policy-map, what to do for the class (this place can be done) There are so many, all the various decelerations mentioned above, queuing, etc. are all done in this place.) Finally, the service policy is called on an interface.
Class-map is the classification of traffic. There are three tools that can be used to classify:
The marking field of the package itself, the second layer of COS, the third layer of DSCP, the MPLS EXP and the like
Data packet Layer 2 to Layer 3 information. In fact, it can be said that 1 is a subset of 2. This place mainly refers to the address, port, one of the fields, which is matched by ACL. COS and DSCP are actually information about Baotou.
The specific application. This place is the specific implementation of cisco, he is to match the application through the contents of the package payload. For example, if you want to match the Skype traffic, you can directly match the protocol skype. Looking very cool, but actually, there are a lot of problems, such as when the implementation of skype changes, there may be cases where the matching method of cisco may not match.
This place is about the classification of traffic processing. The specific processing methods are various, the previously mentioned processing of the data packet is in the policy-map. The processing method is as follows:
- Bandwidth allocation
- Outbound queuing
- Traffic shaping
- Traffic policing
- Re-marking the package
- Package count (I don’t know what this bird is specifically for)
- Baotou compression (not heard of)
- Packet drop and packet pass
This is the outbound or inbound application policy-map specific to the logical Layer 3 interface.
This thing I actually saw, will automatically generate a lot of configuration. What we need to do is to configure a command on the interface, declare what the interface is doing, and then the system automatically help you get it. The most common application scenario is the VOIP of the IOS platform.
On a Catalyst switch, auto QoS VOIP does the following:
Ensure that this port is a trusted Cisco IP phone
Guarantee port is an access interface
For the voice will use a strict-priority queue, the rest of the traffic is weighted round-robin way
The Layer 2 COS will automatically map to the Layer 3 IP DSCP.
Will be discharged according to the COS field to the queue
May change the size and weight of the queue
For low-speed interfaces, FR, ATM, HDLC, and PPP will also have some Auto QoS policies. Generally, the link will not be fully used. However, these links are now less likely to be used. So, I will be a little here.
Simply put, you can configure this port to become Cisco’s voice or video device with a command. Then the system automatically generates the configuration and then adjusts the weight of the queue to the queue.
The bandwidth is not detailed here. What kind of impact. Because Auto QoS is designed to simplify the configuration, if you study it carefully, there is no need to use this auto QoS. Careful research will be more complicated than your own. And this is a Cisco implementation technology, he is always ready. Can be updated.