CoS Features and Limitations on PTX Series Routers

Table 1 summarizes CoS features and limitations on PTX Series Packet Transport Routers.

The following table lists the CoS features supported on the PTX Series router, as well as the limitations relevant to the PTX Series router. Note that this list is a subset of the overall CoS feature set.

Table 1: CoS Features and Limitations on PTX Series Routers
CoS Feature	Capacity	Comments
Classifiers
Maximum number per PFE	64	L2 classifiers (sum of IEEE-802.1p and IEEE-802.1ad cannot exceed 32) DSCP and IP precedence classifiers (sum of DSCP and IP precedence classifiers cannot exceed 32) DSCP IPv6 classifiers MPLS EXP classifiers
`dscp`	Yes	DSCP and IP precedence classifiers cannot be configured on the same logical interface.
`dscp-ipv6`	Yes	Separate classifiers can be applied for IPv4 and IPv6 packets per logical interface.
`ieee-802.1p` and `ieee-802.1ad`	Yes	You can associate IEEE-802.1p and IEEE-802.1ad classifiers with any other type of classifier on the same logical interface. For L3 packets, an L3 classifier takes precedence over an IEEE classifier.
`inet-precedence`	Yes
`mpls-exp`	Yes	Note: MPLS EXP classifiers are not supported on PTX10001-20C routers.
Loss priorities based on the Frame Relay discard eligible (DE) bit	No
Drop Profiles
Maximum number	32	You can configure up to 32 drop-profiles in the PTX chassis.
Per queue	Yes
Per loss priority	Yes
Per Transmission Control Protocol (TCP) bit	No
`protocol` option	`protocol any` only	PTX Series PFEs not support drop-profile assignments for a queue based on the protocol. As a consequence, the `protocol` option for the `drop-profile-map` configuration statement is treated as `protocol any`.
Note: PTX10K-LC1201 and PTX10K-LC1202 line cards on PTX10001-36MR, PTX10004, PTX10008, and PTX10016 routers support one or two drop profile points (fill level/drop probability pairs) per drop profile: Discrete and interpolated drop profiles are equivalent on these platforms; the hardware ignores the interpolated option. You cannot configure both discrete and interpolated pairs on a single drop profile. Point one drop probability must be less than or equal to 25%. You must configure fill level and drop probabilities in pairs and in ascending order. Figure 1 shows how two point RED curves generate a single line. Figure 1: Two Drop Profile Points Although the first point is (35,10), we see the drop profile points starting earlier where the line intersects the X axis. At the second point (60,50), the drop probability is maximum and remains at point 50 from TAQL 60% through 100%, after which the tail drop happens.
Policing
Traffic policing	Yes
Two-rate tricolor marking (TCM)	Yes
Queuing
Priority	Yes (4)	On PTX Series routers, strict-high-priority queues and high-priority queues are assigned different hardware priorities. Strict-high-priority can starve other queues if a rate limiter is not applied on PTX Series routers.
Per-queue output statistics	Yes	Red-dropped counters are not maintained per drop precedence. Also tail drop counters always show zero because packets are always dropped by the RED algorithm. On PTX Series routers, transmitted byte counters are computed using the full Layer 2 overhead (including all L2 encapsulation and CRC) plus 12 for the inter-packet gap plus 8 for the preamble. On Junos OS Evolved PTX Series routers , the tail-dropped counters and the RED-dropped counters are displayed separately in the output of the `show interfaces queue` command. On Junos OS PTX Series routers, tail-dropped counters are always zero. All the packet drops are shown as RED-dropped in the `show interfaces voq` output.
`transmit-rate percent`	Yes	Percentage transmit rate for a scheduler has the range 1 through 100 percent. Unconfigured interfaces are equivalent to `percent 0`.
Excess bandwidth sharing	Yes	On PTX Series routers, excess bandwidth is shared based on the ratio of the configured transfer rate. Therefore, all priority queues get a share of excess bandwidth.
Virtual Output Queueing	Yes	PTX Series routers support a virtual output queuing (VOQ) architecture and the fabric schedulers utilize the CoS scheduling parameters to configure the fabric schedulers. There is not a separate configuration for the fabric schedulers on PTX Series routers. With the VOQ architecture, packets are queued and dropped on ingress during congestion.
Buffer latency	Yes	On PTX Series routers, `buffer-size percent 100` requests the platform's full buffer latency at the port or shaping rate, that is, a nominal queue limit of (`productFullLatency × portRate`) bytes. For all PTX routers, the `productFullLatency` is 100 ms except for the PTX10001, and line cards LC1201 and LC1202, which have a 25 ms buffer.
Rewrite Markers
Maximum number per PFE	64	The sum of L2 and L3 rewrite rules cannot exceed 64.
`dscp`	Yes
`dscp-ipv6`	Yes
`ieee-802.1p` and `ieee-802.1ad`	Yes	PTX Series routers support Layer 2 rewrite of 802.1p and 802.1ad, to either the outer VLAN tag, or both outer and inner VLAN tags. L2 and L3 rewrites can be applied to the same packet simultaneously.
`inet-precedence`	No
`mpls-exp`	Yes	PTX Series routers support rewrite of both DSCP and DSCP IPv6 for protocol MPLS.

For PTX Series routers running Junos OS Evolved:

PTX Series routers running Junos OS Evolved support Layer 3 VPNs.
Junos OS Evolved does not support applying classifier and rewrite rules to IRB interfaces on PTX Series routers.