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CoS Features and Limitations on M Series and T Series Routers

 

Juniper Networks M320 Multiservice Edge Routers and T Series Core Routers, as well as M Series Multiservice Edge Routers with enhanced Flexible PIC Concentrators (FPCs), have more CoS capabilities than M Series routers that use other FPC models. Table 1 lists some of these the differences.

To determine whether your M Series router is equipped with an enhanced FPC, issue the show chassis hardware command. The presence of an enhanced FPC is designated by the E-FPC description in the output.

user@host> show chassis hardware

Many operations involving the DSCP bits depend on the router and PIC type. For example, some DSCP classification configurations for MPLS and Internet can only be performed on M120 routers, M320 routers with Enhanced Type III FPCs, and MX Series routers only.

Table 1 summarizes CoS features and limitations on M Series and T Series routers.

Note

The T4000 router supports the lowest of the scaling numbers for classifiers, rewrite rules, and WRED associated with MX Series and T Series routers.

Table 1: CoS Features and Limitations on M Series and T Series Routers

CoS Feature

Interface Hardware

Details

FPCs in M120 Routers

Enhanced FPCs in M120 Routers

FPCs in M320 or T Series Routers

Type-4 or Enhanced Scaling FPCs in T Series Routers

Classifiers

Maximum number per FPC or PIC

1

8

64

64 or 58 total

On IQ2 and IQ2E PICs, the CoS classification and CoS rewrite processes are off-loaded from the FPC to the PIC, so the capabilities and limitations of these types of PICs must be taken into consideration.

For M Series router FPCs, the one-classifier limit includes the default IP precedence classifier. If you create a new classifier and apply it to an interface, the new classifier does not override the default classifier for other interfaces on the same FPC. In general, the first classifier associated with a logical interface is used. The default classifier can be replaced only when a single interface is associated with the default classifier.

Only 58 user-configurable BA classifiers can be attached to logical interfaces on Type-4 FPCs in T640, T1600, or T4000 routers, because six default classifiers are automatically attached to the interfaces. When interfaces on the FPC come up, three default classifiers are installed in the FPC ASIC table: IPv4 and IPv6, MPLS tagging, and multiservices. Next, three default BA classifiers are installed: DSCP IPv6 (9), and MPLS EXP (10), and IP precedence (13).

For user-defined BA classifier types (dscp, dscp-ipv6, ieee-802.1p, ieee-802.1ad, inet-precedence, and mpls-exp), you can attach a maximum of 32 classifiers of the same type (including one default classifier) to a logical interface hosted on a Type-4 FPC in a T640, T1600, or T4000 router.

You can attach a maximum of 8 user-configured BA classifiers of the same type to a logical interface hosted on an Enhanced Scaling FPC in a T640, T1600, or T4000 router.

dscp

No

Yes

Yes

Yes

On all routers, you cannot configure IP precedence and DiffServ code point (DSCP) classifiers on a single logical interface, because both apply to IPv4 packets.

dscp-ipv6

No

Yes

Yes

Yes

For T Series routers, you can apply separate classifiers for IPv4 and IPv6 packets per logical interface.

For M Series router enhanced FPCs, you cannot apply separate classifiers for IPv4 and IPv6 packets. Classifier assignment works as follows:

  • If you assign a DSCP classifier only, IPv4 and IPv6 packets are classified using the DSCP classifier.

  • If you assign an IP precedence classifier only, IPv4 and IPv6 packets are classified using the IP precedence classifier. The lower three bits of the DSCP field are ignored because IP precedence mapping requires the upper three bits only.

  • If you assign either the DSCP or the IP precedence classifier in conjunction with the DSCP IPv6 classifier, the commit fails.

  • If you assign a DSCP IPv6 classifier only, IPv4 and IPv6 packets are classified using the DSCP IPv6 classifier, but the commit displays a warning message.

ieee-802.1p

No

Yes

Yes

Yes

On M Series router enhanced FPCs and T Series routers, if you associate an IEEE 802.1p classifier with a logical interface, you cannot associate any other classifier with that logical interface.

For most PICs, if you apply an IEEE 802.1p classifier to a logical interface, you cannot apply non-IEEE classifiers on other logical interfaces on the same physical interface. This restriction does not apply to Gigabit Ethernet IQ2 PICs.

inet-precedence

Yes

Yes

Yes

Yes

On all routers, you cannot assign IP precedence and DSCP classifiers to a single logical interface, because both apply to IPv4 packets.

mpls-exp

Yes

Yes

Yes

Yes

For M Series router FPCs, only the default MPLS EXP classifier is supported; the default MPLS EXP classifier takes the EXP bits 1 and 2 as the output queue number.

Loss priorities based on the Frame Relay discard eligible (DE) bit

No

No

No

No

Drop Profiles

Maximum number per FPC or PIC

2

16

32

32

Per queue

No

Yes

Yes

Yes

Per loss priority

Yes

Yes

Yes

Yes

Per Transmission Control Protocol (TCP) bit

No

Yes

Yes

Yes

Policing

Adaptive shaping for Frame Relay traffic

No

No

No

No

Traffic policing

Yes

Yes

Yes

Yes

Two-rate tricolor marking (TCM)

No

No

Yes

Yes

Allows you to configure up to four loss priorities. Two-rate TCM is supported on T Series routers with Enhanced III FPCs and the T640 Core Router with Enhanced Scaling FPC4.

Virtual channels

No

No

No

No

Queuing

Priority

No

Yes

Yes

Yes

Gigabit Ethernet IQ2 PICs support only one queue in the scheduler map with medium-high, high, or strict-high priority. If more than one queue is configured with high or strict-high priority, the one that appears first in the configuration is implemented as strict-high priority. This queue receives unlimited transmission bandwidth. The remaining queues are implemented as low priority, which means they might be starved.

On the IQE PIC, you can rate-limit the strict-high and high queues. Without this limiting, traffic that requires low latency (delay) such as voice can block the transmission of medium-priority and low-priority packets. Unless limited, high and strict-high traffic is always sent before lower priority traffic.

Support for the medium-low and medium-high queuing priority mappings varies by FPC type.

Per-queue output statistics

No

Yes

Yes

Yes

Per-queue output statistics are shown in the output of the show interfaces queue command.

Rewrite Markers

Maximum number per FPC or PIC

No maximum

No maximum

64

64

On IQ2 and IQ2E PICs, the CoS classification and CoS rewrite processes are off-loaded from the FPC to the PIC, so the capabilities and limitations of these types of PICs must be taken into consideration.

dscp

No

Yes

Yes

Yes

For M Series router Enhanced FPCs, bits 0 through 5 are rewritten, and bits 6 through 7 are preserved.

For M320 and T Series router non-IQ FPCs, bits 0 through 5 are rewritten, and bits 6 through 7 are preserved.

For M320 and T Series router FPCs, you must decode the loss priority using the firewall filter before you can use loss priority to select the rewrite CoS value.

For M320 and T Series router FPCs, Multiservices and Services PIC link services IQ interfaces (lsq-) do not support DSCP rewrite markers.

dscp-ipv6

No

Yes

Yes

Yes

For M Series router Enhanced FPCs and M320 and T Series router FPCs, bits 0 through 5 are rewritten, and bits 6 through 7 are preserved.

For M320 and T Series routers FPCs, you must decode the loss priority using the firewall filter before you can use loss priority to select the rewrite CoS value.

For M320 and T Series router FPCs, Multiservices and Services PIC link services IQ interfaces (lsq-) do not support DSCP rewrite markers.

frame-relay-de

No

No

No

No

ieee-802.1

No

Yes

Yes

Yes

For M Series router enhanced FPCs and T Series router FPCs, fixed rewrite loss priority determines the value for bit 0; queue number (forwarding class) determines bits 1 and 2. For IQ PICs, you can only configure one IEEE 802.1 rewrite rule on a physical port. All logical ports (units) on that physical port should apply the same IEEE 802.1 rewrite rule.

On T Series routers only, when you configure IEEE 802.1p rewrite marking on Gigabit Ethernet IQ, Gigabit Ethernet IQ2, Gigabit Ethernet Enhanced IQ (IQE), and Gigabit Ethernet Enhanced IQ2 (IQ2E) PICs, you cannot configure more than eight forwarding classes. This limitation does not apply to M Series routers. On M Series routers, you can configure up to 16 forwarding classes when you configure IEEE 802.1p rewrite marking on any of these PICs.

inet-precedence

Yes

Yes

Yes

Yes

For M Series router FPCs, bits 0 through 2 are rewritten, and bits 3 through 7 are preserved.

For M Series router Enhanced FPCs, bits 0 through 2 are rewritten, bits 3 through 5 are cleared, and bits 6 through 7 are preserved.

For M320 and T Series routers FPCs, bits 0 through 2 are rewritten and bits 3 through 7 are preserved.

For M320 and T Series router FPCs, you must decode the loss priority using the firewall filter before you can use loss priority to select the rewrite CoS value.

mpls-exp

Yes

Yes

Yes

Yes

For M320 and T Series router FPCs, you must decode the loss priority using the firewall filter before you can use loss priority to select the rewrite CoS value.

For M Series routers FPCs, fixed rewrite loss priority determines the value for bit 0; queue number (forwarding class) determines bits 1 and 2.