DOCSIS 11 Configuration File
The DOCSIS 1.1 configuration file format is somewhat more complex than that for a DOCSIS 1.0 cable modem. This is because a DOCSIS 1.1 configuration file must include a set of operational parameters for multiple service flows. Information required for the classification, marking, and rate management of each service flow must be included in the file. The following list includes only those parameters that differ materially from DOCSIS 1.0. A DOCSIS 1.1 configuration file is not complete unless it contains a configuration for both an upstream and a downstream service flow. It is generally incompatible with DOCSIS 1.1 modems if it simultaneously contains DOCSIS 1.0 rate limit parameters.
The list of available parameters configured in a DOCSIS 1.1 configuration file includes the following:
• CPE—The 1.1 configuration file can include a list of CPE MAC addresses to filter if necessary.
• Upstream packet classification—As traffic is transmitted upstream in DOCSIS 1.1 it is classified into service flows. The upstream packet classification portion of the 1.1 configuration file contains the traffic characteristics by which service flows are differentiated. Traffic can be sorted into service flows based upon the following packet characteristics: IP type of service (ToS) values, ToS mask, IP protocol, IP source address, IP source mask, IP destination address, IP destination mask, IP source port start and port end (allowing for a range of ports), destination port start and port end (allowing for a range of ports), destination MAC address, source MAC address, Ethernet/DSA/MAC type, user priority (IEEE 802.1P), virtual LAN identification (VLAN ID) (IEEE 802.1Q), and any one of many vendor-specific parameters. Each classifier (set of characteristics) is assigned a unique classifier reference number, an associated service flow reference number, a rule priority (when packets are classified, they are compared against classifiers with higher priority first), activation state (on or off), and dynamic service change ability.
• Downstream packet classification—DOCSIS 1.1 allows for the same parameters used in the upstream to be set for downstream transmission. Packets transmitted downstream are likewise classified based on the following: IP ToS value, ToS mask, IP protocol, IP source address, IP source mask, IP destination address, IP destination mask, IP source port start and port end, destination port start and port end, destination MAC address, source MAC address, Ethernet/DSA/MAC type, user priority (IEEE 802.1P), VLAN ID (IEEE 802.1Q), and any one of many vendor-specific parameters. Each classifier is assigned a classifier reference number, a service flow reference, a rule priority, activation state, and dynamic service change ability. In general, the CMTS becomes responsible for enforcing and controlling the settings in the downstream packet classification when data traffic is forwarded to the cable modem.
• Upstream service flow—After it is classified, traffic upstream is assigned a set of QoS and other parameters for transmission. These parameters include the following: traffic priority (roughly equivalent to ToS bit but used only on the DOCSIS network), maximum sustained traffic rate, maximum traffic burst, minimum reserved traffic rate, assumed minimum reserved rate packet size, timeout for active QoS parameters, timeout for admitted QoS parameters, maximum concatenated burst, service flow scheduling type, request per transmission policy, nominal polling interval, tolerated poll jitter, unsolicited grant size, nominal grant interval, tolerated grant jitter, grants per interval, and vendor-specific settings. Associated with each service flow is a unique flow reference number, a service class name, a QoS parameter set type, and a ToS bit overwrite value. Service class names reference QoS parameters that can be saved as named profiles on the CMTS instead of being specified in the configuration file. The ToS bit overwrite value is important when a service flow requires QoS
parameters to be set end-to-end across the MSO's network. By using the ToS bit overwrite value the system administrator causes packets to be given a set ToS bit value when they exit the DOCSIS network.
• Downstream service flow—After it is classified, downstream service flows are assigned the same set of values as upstream service flows. However, grant-specific and upstream specific parameters such as tolerated grant jitter, grants per interval, and so on are not specified. Downstream maximum and minimum rates and downstream latency are configurable in DOCSIS 1.1, and only limited downstream parameters are available through DOCSIS 1.0.
• Payload header suppression—In certain circumstances, the transmitted headers on a service flow are identical between packets. Payload header suppression (PHS) allows traffic to be transmitted without headers, thus increasing throughput efficiency. PHS parameters can be specified per service flow and can include multiple parameters including vendor-specific PHS parameters.
Example 13-3 shows DOCSIS 1.1 configuration file parameters in simple text. The network access control field is shown with access enabled and is identical to what would be configured with DOCSIS 1.0. Both upstream and downstream flows are defined with upstream classifiers based on port number, IP source address, and IP destination address specified. When encoded in an actual DOCSIS 1.1 file the configuration parameters are formatted as binary TLV groupings.
Example 13-3 Sample DOCSIS 1.1 Configuration File
22 (US Classifier Encoding)
S01 (Classifier Reference)= 1 S03 (Flow Reference) = 5
S09 (IP Packet Classification) T07 (Source Port Start) = 1000 T08 (Source Port End) = 1000 T09 (Dest port Start) = 1400 T10 (Dest port Start) = 1400
23 (US Classifier Encoding)
S01 (Classifier Reference)= 2 S03 (Flow Reference) = 6
S09 (IP Packet Classification) T02 (IP Protocol) = 17 T03 (IP src) = 9.0.0.0 T04 (IP src mask) = 255.0.0.0 T05 (IP dest) = 10.20.112.0 T06 (IP dest mask) = 255.255.255.
24 (Upstream Service Flow Encodings) S01 (Service Flow Reference) = 1
Example 13-3 Sample DOCSIS 1.1 Configuration File (Continued)
506 (QoS Parameter Set Type) = 7
507 (Traffic Priority) = 4
25 (Downstream Service Flow Encodings) S01 (Service Flow Reference) = 2
506 (QoS Parameter Set Type) = 7
507 (Traffic Priority) = 1
24 (Upstream Service Flow Encodings) S01 (Service Flow Reference) = 5
506 (QoS Parameter Set Type) = 7
507 (Traffic Priority) = 4
508 (Max Traffic Rate) = 300000
509 (Max Traffic Burst)= 2500
25 (Upstream Service Flow Encodings) S01 (Service Flow Reference) = 6
506 (QoS Parameter Set Type) = 7
507 (Traffic Priority) = 4
508 (Max Sustained Traffic Rate) = 2500000
509 (Max Traffic Burst) = 2500
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