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Cable Service Class in Cisco uBR

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Cable Service Class in Cisco uBR

I am migrating my network to DOCSIS 1.1 and have been a little lost about what the "Cable Service Class" commands in the Cisco uBR. I have looked through Cisco's site but have not had much luck. I have a DOCSIS 1.1 CM file I have created and have been able to successfully provision it to a modem and the modem operate but all my research shows the "Cable Service Class" set on the CMTS its self.


Some reading:

I don't run any Ciscos, but this might point you in the right direction.

It's $60USD but should cover anything you ever want to configure. Example regarding Cable Service Class.

Also: Shows many examples.

Cable Service Class vs Flows

Well what I guess I am needing to find out is what are the cable service class used for and how do you tie them to a CM that has registered with an already set up downstream and upstream flow and classifier. Also what is the difference between a flow and a cable service class?

Service classes is the

Service classes is the docsis 1.0 way of bandwidth management with classes you can set things like max up/down bandwidth burst speed etc.. but it is for all traffic.

Cable service classes can be set by the modems when they register or by hand via cli, the only reasons you would want to do it by hand I can think of is to do 1) policing, i.e. if user A uses too much bandwidth in a given time switch him to a different class of service for a penalty period. 2) you are trying to prevent hackers from being able to create their own class of service, by manually creating all the needed QOS and setting 'no cable qos permission modems' which tells cmts to ignore modem created QOS.

Service flows are the docsis 1.1+ way of bandwidth management, they allow you to classify the traffic and apply different policies to different types of traffic. i.e. one service flow for VOIP traffic and one for other types of traffic.

Service flows are a lot more flexible than service classes, but they require docsis 1.1 or higher to use.

Not "Class of Service" but "Cable Service Class"

I think your describing a "Class of Service" policy while I am asking about a "Cable Service Class". Some how they are used to preallocate resources on the CMTS for a service flow but I am needing a more technical description of there purposes and how they are tied to the DOCSIS 1.1 CM file. "Cable Service Class" replaced cable qos profile.


Sorry I misunderstood your

Sorry I misunderstood your question

Cable Service class is mostly used to set schedule-type specific settings at the CMTS

it is usually used to set the sched-type specific Settings for UGS (Unsolicited Grant Scheduling Service)

Here is an example of setting up UGS on an upstream service flow.

so if in your config file you had (taken from Arris packetAce)
in your config file you would set SfClassName to the name you gave your service-class on the CMTS, so when it registers it will configure some additional settings for that service flow.

SfReference = 1
SfClassName = "UP_UGS"
SfQosSetType = 7
SfTrafficPriority = 7
SfMaxTrafficRate = 256000
SfSchedulingType= 6
SfRqTxPolicy = 256

On your CMTS you would need to have the following
Router(config)# cable service class 1 name UP_UGS
Router(config)# cable service class 1 sched-type 6
Router(config)# cable service class 1 grant-size 100
Router(config)# cable service class 1 grant-interval 20000
Router(config)# cable service class 1 grant-jitter 4000
Router(config)# cable service class 1 grants-per-interval 1
Router(config)# cable service class 1 min-packet-size 100
Router(config)# cable service class 1 req-trans-policy 0x1FF
Router(config)# cable service class 1 tos-overwrite 0x1F 0xE0
Router(config)# cable service class 1 activity-timeout 30
Router(config)# cable service class 1 admission-timeout 30

Thus the Cable Service Class configures the CMTS specific settings for whatever Scheduling Type your using.

The cmts command Reference for cable service class has some other examples

What about on the Downstream with only Max-Rate

I have been doing some contract work for an ISP and they have on there uBR the "Cable Service Class" settings set up for there downstream, they appear to be their different levels of service. For example it would be

cable service class 1 name 1meg
cable service class 1 downstream
cable service class 1 max-rate 1000000


For downstream service flows

For downstream service flows the only scheduling type I am aware of is Best Effort, which is the default and only has one setting max-rate, which can also be set in the modem config,

unless they are not specifying the max-rate in the modem config (which I am not sure would even work, but I have never tried it that way) this just seems superfluous. The only thing it would enable I am aware of is more completeness when running the command 'show cable service-class' which just lists configured cable service classes, which would be a good way to get a look at service offerings per CMTS but otherwise not really helpful.

Edit: found this in Cisco's docs (emphasis added) so yes you could use sevice classes to control bandwidth for docsis 1.1 networks instead of putting it in the config file.

Service Classes

The use of the service class provides the following benefits for a DOCSIS 1.1 network:

* It allows operators to move the burden of configuring service flows from the provisioning server to the CMTS. Operators provision the modems with the service class name; the implementation of the name is configured at the CMTS. This allows operators to modify the implementation of a given service to local circumstances without changing modem provisioning. For example, some scheduling parameters might need to be set differently for two different CMTSs to provide the same service. As another example, service profiles could be changed by time of day.
* It allows CMTS vendors to provide class-based-queuing if they choose, where service flows compete within their class and classes compete with each other for bandwidth.
* It allows higher-layer protocols to create a service flow by its service class name. For example, telephony signaling might direct the cable modem to instantiate any available provisioned service flow of class G.711.
Note The service class is optional. The flow scheduling specification may always be provided in full; a service flow may belong to no service class whatsoever. CMTS implementations may treat such unclassed flows differently from classed flows with equivalent parameters.

Did anyone manage to get

Did anyone manage to get second point to work?
I mean : "It allows CMTS vendors to provide class-based-queuing if they choose, where service flows compete within their class and classes compete with each other for bandwidth."

i did create two downstream service flows in CM config file, one 4M service class on CMTS(cisco) and the result is disapointing: two 4M service flows instead of two balanced SFs with combined bandwidth of 4M