System management

You can configure a name for the system device. The name is used in the prompt string. Only one system name can be configured. If multiple system names are configured the last one encountered overwrites the previous entry. Use the following command to configure the system name.

configure system name

Use the contact command to specify the name of a system administrator, IT staff member, or other administrative entity. Use the following command to configure the system contact.

configure system contact

Use the location command to specify the system location of the device. For example, enter the city, building address, floor, room number, and so on, where the router is located. Use the following command to configure the system location.

configure system location

You can optionally configure the GPS location of the device. If the string contains special characters (#, $, spaces, and so on), the entire string must be enclosed within double quotes. Use the following command to configure the system coordinates.

configure system coordinates

Do not configure named objects with a name that starts with ‟_tmnx_”, or with ‟_” in general.

A CLLI code string for the device is an 11-character standardized geographic identifier that uniquely identifies the geographic location of places and specific functional categories of equipment unique to the telecommunications industry. The CLLI code is stored in the Nokia Chassis MIB tmnxChassisCLLICode object.

The CLLI code can be any ASCII-printable text string of up to 11 characters.

DNS Security (DNSSEC) Extensions are now implemented in the SR OS, allowing operators to configure DNS behavior of the router to evaluate whether the Authenticated Data bit was set in the response received from the recursive name server and to trust the response, or ignore it.

Setting a time zone in SR OS allows for times to be displayed in the local time rather instead of UTC. SR OS has both user-defined and system-defined time zones.

A user-defined time zone has a user-assigned name of up to four printable ASCII characters in length and is unique from the system-defined time zones. For user-defined time zones, the offset from UTC is configured as well as any summer time adjustment for the time zone.

configure system time prefer-local-time

• log filenames and log header information

• times in rollback information

• times in rollback and configuration files header information

• times related to CRON scripts

• times in the event handler system

• times in NETCONF and gRPC date-and-time leafs

configure log log-id time-format

The SR OS system-defined time zones are listed in System-defined time zones, which includes both time zones with and without summer time correction.

NTP is the Network Time Protocol defined in RFC 1305, Network Time Protocol (Version 3) Specification, Implementation and Analysis and RFC 5905, Network Time Protocol Version 4: Protocol and Algorithms Specification. It allows for the participating network nodes to keep time more accurately and more importantly they can maintain time in a more synchronized fashion between all participating network nodes.

SR OS uses an NTP process based on a reference build provided by the Network Time Foundation. Nokia strongly recommends that the users review RFC 8633, Network Time Protocol Best Current Practices, when they plan to use NTP with the router. The RFC section ‟Using Enough Time Sources” indicates that using only two time sources (NTP servers) can introduce instability if they provide conflicting information. To maintain accurate time, Nokia recommends configuring three or more NTP servers.

NTP uses stratum levels to define the number of hops from a reference clock. The reference clock is considered to be a stratum-0 device that is assumed to be accurate with little or no delay. Stratum-0 servers cannot be used in a network. However, they can be directly connected to devices that operate as stratum-1 servers. A stratum-1 server is an NTP server with a directly-connected device that provides Coordinated Universal Time (UTC), such as a GPS or atomic clock.

The higher stratum levels are separated from the stratum-1 server over a network path, therefore, a stratum-2 server receives its time over a network link from a stratum-1 server. A stratum-3 server receives its time over a network link from a stratum-2 server.

SR OS routers normally operate as a stratum-2 or higher device. The router relies on an external stratum-1 server to source accurate time into the network. However, SR OS also allows for the use of the local PTP recovered time to be sourced into NTP. In this latter case, the local PTP source appears as a stratum-0 server and SR OS advertises itself as a stratum-1 server. Activation of the PTP source into NTP may impact the network NTP topology because the SR OS router is promoted to stratum-1.

SR OS router runs a single NTP clock which then operates NTP message exchanges with external NTP clocks. Exchanges can be made with external NTP clients, servers, and peers. These exchanges can be through the base, management, or VPRN routing instances.

NTP operates associations between clocks as either client or server, symmetric active and symmetric passive, or broadcast modes. These modes of operation are applied according to which elements are configured on the router. To run server mode, the operator must enable NTP server mode for the base and each needed VPRN routing instance. To run client mode, the operator must configure external servers. If both the local router and remote router are configured with each other as peers, then the router operates in symmetric active mode. If only one side of the association has peering configured, then the modes are symmetric passive. To operate using broadcast mode, interfaces must be configured to transmit as broadcast servers or receive as broadcast clients.

NTP server operation for both unicast and broadcast communication within a VPRN is configured within the VPRN (see the NTP Within a VPRN Service section in 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN).

The following NTP elements are supported:

• server mode

  In this mode, the node advertises the ability to act as a clock source for other network elements. The node, by default, transmits NTP packets in NTP version 4 mode.

• authentication keys

  Authentication keys implement increased security support in carrier and other networks. Both DES and MD5 authentication are supported, as well as multiple keys.

• operation in symmetric active mode

  This capability requires that NTP be synchronized with a specific node that is considered more trustworthy or accurate than other nodes carrying NTP in the system. This mode requires that a specific peer is set.

• server and peer addressing using IPv6

  Both external servers and external peers may be defined using IPv6 or IPv4 addresses. Other features (such as multicast, broadcast) use IPv4 addressing only.

• broadcast or multicast modes

  When operating in these modes, the node receives or sends using either a multicast (default 224.0.1.1) or a broadcast address. Multicast is supported only on the CPM MGMT port.

• alert when NTP server is not available

  When none of the configured servers are reachable on the node, the system reverts to manual timekeeping and issues a critical alarm. When a server becomes available, a trap is issued indicating that standard operation has resumed.

• NTP and SNTP

  If both NTP and SNTP are enabled on the node, then SNTP transitions to an operationally down state. If NTP is removed from the configuration or shut down, then SNTP resumes an operationally up state.

• gradual clock adjustment

  As several applications (such as Service Assurance Agent (SAA)) can use the clock, and if determined that a major (128 ms or more) adjustment needs to be performed, the adjustment is performed by programmatically stepping the clock. If a minor (less than 128 ms) adjustment must be performed, then the adjustment is performed by either speeding up or slowing down the clock.

• To avoid the generation of too many events/trap the NTP module rates limit the generation of events/traps to three per second. At that point a single trap is generated that indicates that event/trap squashing is taking place.

Synchronization between the CPMs includes the following:

• Configuration and boot-env synchronization

• State database synchronization

The 7750 SR supports frequency synchronization using a Layer 1 interface such as synchronous Ethernet, and ToD synchronization using a protocol such as NTP or PTP. In cases where these methods are not possible, or where accuracy cannot be ensured for the service, you can deploy a GNSS receiver as a synchronous timing source. GNSS data is used to provide network-independent frequency and ToD synchronization.

GNSS receivers on the following platforms support GPS and Galileo reference using an integrated GNSS RF port:

• 7750 FP5 SR-1x-48D
• 7750 FP5 SR-1-24D
• 7750 FP5 SR-1-48D
• 7750 FP5 SR-1x-92S
• 7750 FP5 SR-1-46S
• 7750 FP5 SR-1-92S
• 7750 FP5 SR-1se
• 7750 FP5 SR-2se

A 7750 SR chassis equipped with a GNSS receiver and an attached GNSS antenna can be configured to receive frequency traceable to Stratum-1 (PRC/PRS). The GNSS receiver provides a synchronization clock to the SSU in the router with the corresponding QL for SSM. This frequency is distributed to the rest of the router from the SSU as configured with the following commands:

If GNSS signal loss or jamming result in the unavailability of timing information, the GNSS receiver automatically prevents output of clock or synchronization data to the system, and the system can revert to alternate timing sources. With Assisted Partial Timing Support (APTS), the system can perform a seamless switch when reverting to a backup PTP session; see GNSS failure with APTS.

The CRON feature supports periodic and date and time-based scheduling in SR OS. CRON can be used, for example, to schedule Service Assurance Agent (SAA) functions. CRON functionality includes the ability to specify scripts that need to be run, when they are scheduled, including one-time only functionality (one-shot), interval and calendar functions. Scheduled reboots, peer turn ups, service assurance agent tests and more can all be scheduled with CRON, as well as OAM events, such as connectivity checks, or troubleshooting runs.

CRON supports the schedule element. The schedule function configures the type of schedule to run, including one-time only (one-shot), periodic, or calendar-based runs. All runs are determined by month, day of month or weekday, hour, minute, and interval (seconds).

The redundancy features enable the duplication of data elements and software functionality to maintain service continuation in case of outages or component failure.

See the 7450 ESS, 7750 SR, and VSR Multiservice ISA and ESA Guide for information about redundancy for the Integrated Service Adapter (ISA).

In a control plane failure or a forced switchover event, the router continues to forward packets using the existing stale forwarding information. Nonstop forwarding requires clean control plane and data plane separation. Usually, the forwarding information is distributed to the IOMs, XCMs and XMAs.

Nonstop forwarding is used to notify peer routers to continue forwarding and receiving packets, even if the route processor (control plane) is not working or is in a switch-over state. Nonstop forwarding requires clean control plane and data plane separation and usually the forwarding information is distributed to the line cards. This method of availability has both advantages and disadvantages. Nonstop forwarding continues to forward packets using the existing stale forwarding information during a failure. This may cause routing loops and black holes, and also requires that surrounding routers adhere to separate extension standards for each protocol. Every router vendor must support protocol extensions for interoperability.

With nonstop routing (NSR) on the SR-series router devices, routing neighbors are unaware of a routing process fault. If a fault occurs, a reliable and deterministic activity switch to the inactive control complex occurs such that routing topology and reachability are not affected, even in the presence of routing updates. NSR achieves high availability through parallelization by maintaining up to date routing state information, at all times, on the standby route processor. This capability is achieved independently of protocols or protocol extensions, providing a more robust solution than graceful restart protocols between network routers.

The NSR implementation on the SR-series routers supports all routing protocols. NSR makes it possible to keep the existing sessions (BGP, LDP, OSPF, and so on) during a CPM switchover, including support for MPLS signaling protocols. Peers do not see any change.

Protocol extensions are not required. There are no interoperability issues and there is no need to define protocol extensions for every protocol. Unlike nonstop forwarding and graceful restart, the forwarding information in NSR is always up to date, which eliminates possible blackholes or forwarding loops.

Traditionally, addressing high availability issues have been patched through non-stop forwarding solutions. With the implementation of NSR, these limitations are overcome by delivering an intelligent hitless failover solution. This enables a carrier-class foundation for transparent networks, required to support business IP services backed by stringent SLAs. This level of high availability poses a major issue for conventional routers whose architectural design limits or prevents them from implementing NSR.

During a switchover, system control and routing protocol execution are transferred from the active to the standby CPM.

An automatic switchover may occur under the following conditions:

• A fault condition that causes the active CPM to crash or reboot.

• The active CPM is declared down (not responding).

• Online removal of the active CPM.

A manual switchover can occur if a switchover is forced from an active CPM to a standby, using the admin redundancy force-switchover command. Use the following command to configure a batch file that executes automatically after a CPM failover:

• MD-CLI

  configure redundancy switchover-exec

• classic CLI

  configure system switchover-exec

Synchronization between the CPMs includes the following:

• Configuration and boot-env synchronization

• State database synchronization

A high rate of DHCP renewals can create a load on the compact flash file system when subscriber management and DHCP server persistence is enabled. To optimize the access to the Dynamic Data Persistency (DDP) files on the compact flash, a lease-time threshold can be specified that controls the eligibility of a DHCP lease for persistency updates when no other data other than the lease expiry time is to be updated.

The following example shows the configuration of a DHCP lease-time threshold.

[ex:/configure system persistence]
A:admin@node-2# info
    dhcp-server {
        location cf2
    }
    subscriber-mgmt {
        location cf2
    }
    options {
        dhcp-leasetime-threshold 90061
    }

A:node-2>config>system>persistence# info
----------------------------------------------
            subscriber-mgmt
                location cf2:
            exit
            dhcp-server
                location cf2:
            exit
            options
                dhcp-leasetime-threshold days 1 hrs 1 min 1 sec 1
            exit
----------------------------------------------

DS1 signals can carry an indication of the quality level of the source generating the timing information using the SSM transported within the 1544 kb/s Extended Super Frame (ESF) Data Link (DL) of the signal as specified in Recommendation G.704. No such provision is extended to SF formatted DS1 signals.

The format of the data link messages in ESF frame format is "0xxx xxx0 1111 1111", transmitted rightmost bit first. The six bits denoted "xxx xxx" contain the actual message; some of these messages are reserved for synchronization messaging. It takes 32 frames (such as 4 ms) to transmit all 16 bits of a complete DL.

E1 signals can carry an indication of the quality level of the source generating the timing information using the SSM as specified in Recommendation G.704.

One of the Sa4 to Sa8 bits, (the actual Sa bit is for operator selection), is allocated for Synchronization Status Messages. To prevent ambiguities in pattern recognition, it is necessary to align the first bit (San1) with frame 1 of a G.704 E1 multiframe.

The numbering of the San (n = 4, 5, 6, 7, 8) bits. A San bit is organized as a 4-bit nibble San1 to San4. San1 is the most significant bit; San4 is the least significant bit.

The message set in San1 to San4 is a copy of the set defined in SDH bits 5 to 8 of byte S1.

The SSM of SDH and SONET interfaces is carried in the S1 byte of the frame overhead. Each frame contains the four bit value of the QL.

DS3/E3 signals are not required to be synchronous. However, it is acceptable for their clocking to be generated from a synchronization source. The 7750 SR and the 7450 ESS allow E3/DS3 physical ports to be specified as a central clock input reference.

DS3/E3 signals do not support an SSM channel. QL-override should be used for these ports if ql-selection is enabled

For a BITS physical port, or for a synchronous Ethernet interface that supports Ethernet Synchronization Message Channel (ESMC), a timing input or PTP clock class provides a quality level value to indicate the source of timing of the far-end transmitter. These values provide input to the selection process on the nodal timing subsystem. This selection process determines which input to use to generate the signal on the SSM egress ports and the reference to use to synchronize the nodal clock, as follows.

• For the two reference inputs (ref1 and ref2) and for the BITS input ports, if the interface configuration supports the reception of a QL over SSM or ESMC, the quality level value is associated with the timing derived from that input.

• For the two reference inputs and for the BITS input ports, if the interface configuration is T1 with SF framing, the quality level associated with the input is QL-UNKNOWN.

• For the two reference inputs, if they are synchronous Ethernet ports and the ESMC is disabled, the quality level value associated with that input is QL-UNKNOWN.

• For the two reference inputs and for the BITS input ports, if the interface configuration supports the reception of a QL over SSM (and not ESMC), and no SSM value has been received, the quality level value associated with the input is QL-STU.

• For the two reference inputs and for the BITS input ports, if the interface configuration supports the reception of a QL over SSM or ESMC, but the quality level value received over the interface is not valid for the type of interface, the quality level value associated with that input is QL-INVALID.

• For the two reference inputs, if they are external synchronization ports, the quality level value associated with the input is QL-UNKNOWN.

• For the two reference inputs, if they are synchronous Ethernet ports and the ESMC is enabled, but no valid ESMC Information PDU has been received within the previous 5 s, the quality level value associated with that input is QL-FAILED.

• For GNSS reference input, the quality level is PRS if a frequency is successfully recovered; otherwise, the quality level is QL-FAILED.

• If the user has configured an override for the quality level associated with an input, the node displays both the received and override quality level value for the input. If no value has been received, the associated value is displayed instead.

After the quality level values have been associated with the system timing inputs, the two reference inputs and the external input timing ports are processed by the system timing module to select a source for the SSU. This selection process is as follows.

• Before an input can be used as a potential timing source, it must be enabled using the following command:

  • MD-CLI

    configure system central-frequency-clock ql-selection

  • classic CLI

    configure system sync-if-timing ql-selection

  If the ql-selection command option is disabled, the priority order of the inputs for the Synchronous Equipment Timing Generator (SETG) is the priority order configured under the following command:

  • MD-CLI

    configure system central-frequency-clock ref-order

  • classic CLI

    configure system sync-if-timing ref-order

• If the ql-selection command is enabled, the priority of the inputs is calculated using the associated quality level value of the input and the priority order configured under the ref-order command. The inputs are ordered by the internal relative quality level based on their associated quality level values. If two or more inputs have the same quality level value, they are placed in order based on where they appear in the ref-order priority. The priority order for the SETG is based on both the reference inputs and the external synchronization input ports.

• After a prioritized list of inputs is calculated, the SETG and the external synchronization output ports are configured to use the inputs in their respective orders.

• After the SETG and external synchronization output ports priority lists are programmed, the highest-qualified priority input is used. To be qualified, the signal is monitored to ensure that it has the expected format and a frequency that is within the pull-in range of the SETG.

The IEEE 1588v2 standard allows for synchronization of the frequency and time from a timeTransmitter clock to one or more timeReceiver clocks over a packet stream. This packet-based synchronization can be over unicast UDP/IPv4, UDP/IPv6, or multicast Ethernet.

As part of the basic synchronization timing computation, a number of event messages are defined for synchronization messaging between the PTP timeReceiver port and PTP timeTransmitter port. A one-step or two-step synchronization operation can be used, with the two-step operation requiring a follow-up message after each synchronization message. Ordinary clock timeTransmitter and boundary clock timeTransmitter ports use one-step operation; ordinary clock timeReceiver and boundary clock timeReceiver ports can accept messages from either one-step or two-step operation timeTransmitter ports.

The IEEE 1588v2 standard includes a mechanism to control the topology for synchronization distribution. The Best TimeTransmitter Clock Algorithm (BTCA) defines the states for the PTP ports on a clock. One port is set into timeReceiver state and the other ports are set to timeTransmitter (or passive) states. Ports in timeReceiver state recovered synchronization delivered by from an external PTP clock and ports in timeTransmitter state transmit synchronization to toward external PTP clocks.

The basic synchronization timing computation between the PTP timeReceiver and PTP timeTransmitter is shown in PTP timeReceiver and timeTransmitter time synchronization computation. This figure illustrates the offset of the timeReceiver clock referenced to the best timeTransmitter signal during startup.

When using IEEE 1588v2 for distribution of a frequency reference, the timeReceiver calculates a message delay from the timeTransmitter to the timeReceiver based on the timestamps exchanged. A sequence of these calculated delays contain information of the relative frequencies of the timeTransmitter clock and timeReceiver clock but has a noise component related to the packet delay variation (PDV) experienced across the network. The timeReceiver must filter the PDV effects so as to extract the relative frequency data and then adjust the timeReceiver frequency to align with the timeTransmitter frequency.

When using IEEE 1588v2 for distribution of time, the 7750 SR and 7450 ESS use the four timestamps exchanged using the IEEE 1588v2 messages to determine the offset between the router time base and the external timeTransmitter clock time base. The router determines the offset adjustment and then in between these adjustments, the router maintains the progression of time using the frequency from the central clock of the router. This allows time to be maintained using a BITS input source or a Synchronous Ethernet input source even if the IEEE 1588v2 communications fail. When using IEEE 1588v2 for time distribution, the central clock should at a minimum have a system timing input reference enabled. Using IEEE 1588v2 for time distribution displays how IEEE 1588v2 is used for time distribution.

Although IEEE 1588v2 can be used on a network that is not PTP-aware, the use of PTP-aware network elements (boundary clocks) within the packet-switched network improves synchronization performance by reducing the impact of PDV between the grandmaster clock and the timeReceiver clock. In particular, when IEEE 1588v2 is used to distribute high-accuracy time, such as for mobile base station phase requirements, then the network architecture requires the deployment of PTP awareness in every device between the grandmaster and the mobile base station timeReceiver.

In addition, performance is also improved by the removal of any PDV caused by internal queuing within the boundary clock or timeReceiver clock. This is accomplished with hardware that is capable of detecting and time stamping the IEEE 1588v2 packets at the Ethernet interface. This capability is referred to as port-based time stamping.

For each PTP message type to be exchanged between the router and an external 1588 clock, a unicast session must be established using the unicast negotiation procedures. The router allows the configuration of the message rate to be requested from external 1588 clocks. The router also supports a range of message rates that it grants to requests received from the external 1588 clocks. The IEEE 1588 standard allows the grantor port to respond with a shorter duration than what was in the request. The router can accept such a grant and uses that duration. The router issues a renegotiation before the duration expires.

Message rates ranges and defaults describes the ranges for both the rates that the router can request and grant.

State and statistics data for each PTP peer are available to assist in the detection of failures or unusual situations.

Traditionally, only clock frequency is required to ensure smooth transmission in a synchronous network. The PTP ordinary clock with timeReceiver capability on the router provides another option to reference a Stratum-1 traceable clock across a packet-switched network. The recovered clock can be referenced by the internal SSU and distributed to all slots and ports. timeReceiver clock shows a PTP ordinary timeReceiver clock network configuration.

The PTP timeReceiver capability is implemented on the CPM, version 3 or later. The IEEE 1588v2 messages can ingress and egress the router on any line interface. Ordinary timeReceiver clock operation shows the operation of an ordinary PTP clock in timeReceiver mode.

The router supports the PTP ordinary clock in timeTransmitter mode. Normally, an IEEE 1588v2 grandmaster is used to support many timeReceivers and boundary clocks in the network. In cases where only a small number of timeReceivers and boundary clocks exist and only frequency is required, a PTP integrated timeTransmitter clock can greatly reduce hardware and management costs to implement PTP across the network. It also provides an opportunity to achieve better performance by placing a timeTransmitter clock closer to the edge of the network, as close to the timeReceiver clocks as possible. PTP timeTransmitter clock shows a PTP timeTransmitter clock network configuration.

All packets are routed to their destination via the best route as determined in the route table; see Ordinary timeTransmitter clock operation. It does not matter which ports are used to ingress and egress these packets (unless port based time stamping is enabled for higher performance).

The router supports boundary clock PTP devices in both timeTransmitter and timeReceiver states. IEEE 1588v2 can function across a packet network that is not PTP-aware; however, the performance may be unsatisfactory and unpredictable. PDV across the packet network varies with the number of hops, link speeds, utilization rates, and the inherent behavior of the routers. By using routers with boundary clock functionality in the path between the grandmaster clock and the timeReceiver clock, one long path over many hops is split into multiple shorter segments, allowing better PDV control and improved timeReceiver performance. This allows PTP to function as a valid timing option in more network deployments and allows for better scalability and increased robustness in various topologies, such as rings. Boundary clocks can simultaneously function as a PTP timeReceiver of an upstream grandmaster (ordinary clock) or boundary clock, and as a PTP timeTransmitter of downstream timeReceivers (ordinary clock) and boundary clocks, as shown in the following figure.

In addition, the use of port-based timestamping in every network element between the grandmaster and the end timeReceiver application is highly recommended for delivering time to meet one microsecond accuracies required of mobile applications.

The router always uses the frequency output of the central frequency clock to maintain the timebase within the router. When using the G.8275.1 profile, it is mandatory to have the central frequency clock configured to use a Layer 1 frequency source, such as a BITS input or a SyncE port. For other profiles, Nokia recommends using a Layer 1 frequency source. If a Layer 1 frequency source is unavailable, enable PTP as a source for the central frequency clock to have frequency for timestamping traceable to a high accuracy source.

When a router with an enabled GNSS port is configured with boundary clock functionality, the boundary clock acts as a grandmaster clock. The timeReceiver function stops and the timeTransmitter ports use frequency and time recovered from the GNSS port.

PTP timeTransmitter clock capability for frequency and time distribution is implemented on the following 7750 SR equipment:

• 7750 FP5 SR-1x-48D

• 7750 FP5 SR-1-24D

• 7750 FP5 SR-1-48D

• 7750 FP5 SR-1x-92S

• 7750 FP5 SR-1-46S

• 7750 FP5 SR-1-92S

• 7750 FP5 SR-1se

• 7750 FP5 SR-2se

GNSS must be the active system timing and frequency reference for routers that are used as a grandmaster clock. The PTP timeTransmitter clock can be used for frequency and time distribution. See Configuring system timing to use a GNSS RF port for information about configuring the router to use GNSS as a system timing reference.

Use the following commands to configure the router as a grandmaster clock:

• MD-CLI

  configure system ptp profile ieee1588-2008
  configure system ptp clock-type master-only
  configure system ptp admin-state enable

• classic CLI

  configure system ptp profile ieee1588-2008
  configure system ptp clock-type ordinary master
  configure system ptp no shutdown

The 7750 SR supports Recommendation ITU-T G.8275.2, which, similar to Recommendation ITU-T G.8275.1, specifies the architecture that allows the distribution of time and phasing. Recommendation ITU-T G.8275.1 supports full-timing from the network and Recommendation ITU-T G.8275.2 supports partial-timing (PTS) and APTS.

When the 7750 SR is configured to use the G.8275.1 or G.8275.2 profile, it uses an alternate BTCA for best timeTransmitter clock selection. This BTCA includes a PTP dataset comparison that is defined in IEEE 1588-2008, but with the following differences:

• the priority1 value is removed from the dataset comparison
• the master-only value must be considered
• multiple active grandmaster clocks are allowed; therefore, the BTCA selects the nearest clock of equal quality
• a port-level local-priority attribute value is used to select a timeReceiver port if two ports receive an Announce message. This attribute is used as a tiebreaker in the dataset comparison algorithm if all other previous attributes of the datasets being compared are equal.
• the local-priority value is considered for the default dataset

When the clock is configured as a boundary clock, the GNSS is treated as a virtual PTP port into the BTCA. On systems with redundant GNSS, the preference in the BTCA shall be the local GNSS followed by the standby GNSS. The GNSS receiver shall only be considered into the BTCA if it is in locked state. Also in these systems, when one of the GNSS is selected as the parent clock, there may still be a PTP port running frequency and time recovery from a remote PTP timeTransmitter port as a backup. The ptp statistics reflect this backup session.

When the PTP clock is configured to use the G.8275.2 profile without GNSS configured, the clock operates using PTS. When the PTP clock is configured to use the G.8275.2 profile and the internal GNSS is configured and operationally up, GNSS is the preferred reference by default and is selected as the source of time for PTP. For extra resilience, APTS can be deployed by configuring a PTP backup over a network with PTP support to a remote grandmaster clock.

When the clock is configured as a boundary clock, the GNSS is treated as a virtual PTP port into the BTCA. On systems with redundant GNSS, the preference in the BTCA is the local GNSS followed by the standby GNSS. The GNSS receiver is considered into the BTCA once it is in locked state. Also in these systems, when one of the GNSS is selected as the parent clock, there may still be a PTP port running frequency and time recovery from a remote PTP timeTransmitter port as a backup. The PTP statistics reflect this backup session.

During normal operation, the local GNSS source is the reference for time and frequency. If the GNSS source fails, the PTP backup is automatically used to keep the clocks synchronized and stable. The delay offset value, which is calculated while the GNSS source was up, is applied to the PTP backup to keep time and phase as accurate as possible. See GNSS failure with APTS for more information about APTS functionality during a GNSS failure.

The following table describes the mapping between ITU-T G.8275.2 and PTP clock types. T-BC-A and T-TSC-A clocks are applicable to APTS only for 7750 SR FP5 systems with GNSS.

The PTP module in the router exists on the CPM. The PTP module on the standby CPM is kept synchronized to the PTP module on the active CPM. All sessions with external PTP peers are maintained over a CPM switchover.

For physical ports located on an MDA/IMM/XMA/MDA-s of a 7750 SR or a 7950 XRS platform, PTP messages are supported in the following encapsulations:

• PTP within raw Ethernet (no VLAN header)
• PTP within UDP/IPv4 or UDP/IPv6 within raw Ethernet (no VLAN header)
• PTP within UDP/IPv4 or UDP/IPv6 within dot1q Ethernet (one VLAN header)

For the SyncE/1588 ports located on the CPM or CCM of a 7750 SR or a 7950 XRS platform, PTP supports PTP messages within raw Ethernet (no VLAN header).

For physical ports located on a 7210 SAS satellite, PTP supports PTP messages within raw Ethernet (no VLAN header).

No other encapsulations are supported.

PTP has the potential to provide much more accurate time into the router than can be obtained with NTP. This PTP recovered time can be made available for system time and OAM packet time stamping to improve the accuracies of logged events and OAM delay measurements. The mechanism to activate PTP as the source for these internal time bases is to allocate PTP as a local server into NTP. This allows the NTP time recovery to use PTP as a source for time and then distribute it within the router to system time and the OAM process. This activation also affects the operation of the NTP server within the SR OS. The PTP server appears as NTP stratum 0 server and therefore the SR OS advertises itself as an NTP Stratum 1 server to external peers and clients. This activation may impact the NTP topology.

PTP is supported over direct Ethernet encapsulation (that is, PTP ports) and UDP/IP encapsulation (that is, PTP peers). PTP ports operate below the routing plane. They can be used on appropriate ports irrespective of any type of router interface also on the port. PTP peers operate at the routing plane and have restrictions based on and across the following router instances.

Transmission and reception of PTP messages using PTP peers is supported in the following contexts:

• Network interface in the Base routing instance (configure router interface)

• IES interface (configure service ies interface)

• VPRN interface (configure service vprn interface)

Transmission and reception of PTP messages using PTP peers is not supported in the following contexts:

• IES spoke SDP interface (configure service ies spoke-sdp interface)

• VPRN spoke SDP interface (configure service vprn spoke-sdp interface)

• VPRN transport tunnel (configure service vprn auto-bind-tunnel or configure service vprn spoke-sdp)

• Any interface of the management router instance

• Any interface of the vpls-management router instance

• Any interface of a user created CPM router instance

It is important to note that there is only one PTP clock within the router. All PTP ports and PTP peers communicate into one clock instance. Only one router instance may have PTP peers configured, which means that only that router instance (or PTP port) can run the timeReceiver functionality and recover time from an external PTP clock. All other router instances only support the dynamic PTP peers. The PTP process in the router only includes outward server time toward the dynamic PTP peers. The dynamic PTP peers are shared across all router instances. If it is needed to control the number of dynamic peers that can be consumed by a routing instance, then it must be configured for that routing instance.

The PTP clock in the router monitors the Sync, Follow_Up (if present), and Delay_Resp messages received from external neighbor ports. If a high variation is detected in the network path between the external neighbor port and the local port, that neighbor port is considered unusable (PTSF-unusable as defined in the ITU-T G.8275.1 recommendation). When a neighbor is unusable, all Announce messages from that neighbor are discarded on reception and excluded from the BMCA. If the neighbor is the parent clock to the local clock, the local clock must either select a new parent clock or go into holdover. In addition, any neighbor clock marked as unusable cannot act as the parent to the local PTP clock until underlying condition is investigated and resolved, and the unusable state is cleared. The unusable state is cleared when PTP, PTSF-unusable monitoring, or the local PTP port is administratively disabled, the PTP port is deleted, or the external neighbor port stops sending messages to the node. It can also be cleared by using the appropriate clear command.

There is one PTP clock within an SR OS system. The clock runs a BTCA and can set a port into timeReceiver state to recover frequency, time, or both. The recovery process is controlled by the rules of a primary profile. The SR OS also allows frequency, time, or both to be distributed outward from the clock using PTP messages that conform to the rules of an alternate profile. The primary profile and alternate profiles include a parameter to configure the standard profile that defines these rules. The following guidelines apply to profile interworking:

• Alternate profiles can only be configured if the primary profile is using standard profile g8275dot1-2014 or g8275dot2-2016.
• Alternate profiles can use standard profiles ieee1588-2008, g8265dot1-2010, g8275dot1-2014, or g8275dot2-2016.
• The primary profile and an alternate profile can use the same standard profile.
• Multiple alternate profiles can also use the same standard profile.

Alternate profiles are associated with PTP ports and peers. Alternate profile associations are configured for PTP ports and learned by PTP peers. PTP peer alternate profiles are learned by matching the domain number of received unicast messaging with the domain of the configured alternate profile. Configured peers always use the primary profile.

The following table lists the profile interworking between the primary and alternate profiles depending on the standard profile used in the primary.

Support is provided for the collection of performance monitoring statistics for the time recovery algorithm based on Annex J/IEEE1588-2019. The following table describes the record index values.

Each record includes the average, minimum, maximum, and standard deviation for the following statistics:

• offset-from-master
• mean-path-delay
• timeTransmiter-to-timeReceiverDelay (master-to-slave-delay)
• timeRecevier-to-timeTransmitter delay (slave-to-master-delay)

When a platform includes a GNSS receiver that is being used as a PTP time source with G.8275.1 or G.8275.2 as the PTP profile, the PTP clock runs a PTP timeReceiver port with an external timeTransmitter port, if one is available. If the PTP clock runs a PTP timeReceiver port, the Annex J statistics are computed as a comparison between the timeReceiver computed time and the GNSS time. Computing the Annex J statistics this way can provide a good indication for PTP performance should the GNSS lose lock and the node switches use PTP input as its source of time.

When referencing satellite ports, always use 1 for the slot number.

Use the following format to reference Ethernet satellite client ports:

port esat-sat-id/1/portNum

port esat-4/1/2

port esat-sat-id/1/uportNum

port esat-5/1/u2

port tsat-sat-id/1/portNum.channel

port tsat-3/1/4.1

port tsat-sat-id/1/uport.channel

port tsat-4/1/u1.1

The local forwarding capability allows traffic to be forwarded between two client satellite ports without going through the SR host, which allows for optimal forwarding by preserving uplink bandwidth.

• Locally forwarded traffic is identified based on the ingress VLAN tag.

• The outer VLAN tag used to identify the traffic to be locally forwarded can be different at the two bypass endpoints. In that case, as traffic is forwarded from the ingress to the egress, the outer VLAN tag is modified.

• The bypass paths are bidirectional, so only a single local-forwarding path needs to be defined to allow for traffic flow in both directions.

Local forwarding shows an example of local forwarding.

A local-forward bypass is created by using the following commands to create a local-forward bypass, then associating a set of two satellite access points as endpoints for the local-forward bypass.

• The two endpoints must be ports on the same Ethernet satellite chassis.

• If a LAG is used as an endpoint, all member links must be ports on the same Ethernet satellite.

• All satellite ports must be client ports by default, or must be configured as a client port using the port-template command.

The following example shows the commands to configure a local-forward bypass between client ports esat-2/1/1:66 and esat-2/1/50:101.

[ex:/configure satellite]
A:admin@node-2# info
    ethernet-satellite 10 {
        admin-state enable
        description "local-forward to offload router"
        port-map esat-2/1/1 {
        }
        port-map esat-2/1/50 {
        }
    }

A:node-2>config>system>satellite# info
----------------------------------------------
          local-forward 10 create
               description "local-forward to offload router"
               sap esat-2/1/1:66 create
               exit
               sap esat-2/1/50:101 create
               exit
               no shutdown
          exit
----------------------------------------------

The port-template command hierarchy allows the creation of a satellite template that reconfigures the port role and uplink association for one or more satellite ports. This template can then be applied to one or more Ethernet satellite instances, in which case those satellites inherit the specified port role and uplink associations.

The port template is necessary when reconfiguring a satellite uplink as a client port for use as part of a local-forward bypass path. Use the following command to create satellite templates:

• MD-CLI

  configure satellite port-template

• classic CLI

  configure system satellite port-template

Ports 51 and 52 on the 48xGE + 4x10GE satellite chassis can be reassigned as client ports instead of uplink ports. This provides the flexibility to offer 10GE services from these satellite chassis. These two 10GE ports can be reconfigured as client ports using the port-template configuration commands described above. The port template configuration must be done before SAPs, interfaces, or services can be applied to the associated satellite ports.

Ports 67 and 68 on the 64x10GE + 4x100GE satellites (sat-type es64-10gb-sfpp+4-100gb-cfp4) and connectors 3 and 4 on the 64x10GE+4xQSFP28 (sat-type es64-10gb-sfpp+4-100gb-qsfp28) can be reassigned as client ports instead of uplinks. This provides the flexibility to offer 100GE services from these satellite chassis. These two 100GE ports can be reconfigured as client ports using the port-template configuration commands. The port template must be configured before port topology bindings are configured as well as before SAPs, interfaces, or services can be applied to the associated satellite ports.

On the 7210 SAS-Sx 64x10GE+4x100GE (es64-10gb-sfpp+4-100gb-cfp4) and 64x10GE+4xQSFP28 (sat-type es64-10gb-sfpp+4-100gb-qsfp28) satellite, selected 10GE ports can be reconfigured and used as satellite uplinks to the host router running SR OS.

Up to 16 10GE interfaces can be used as uplinks for the associated satellite. You must create a new satellite template that configures the needed 10GE interfaces as uplinks. In addition, use a port template to specify the uplink association between the remaining client ports and configured uplinks.

Apply the new template to the satellite using the template-name command, where the template-name is the name configured in the port-template context.

This feature requires the 7210 SAS-Sx to be running Release 9.0.R10 or later for the 7210 SAS-Sx 64x10GE+4x100GE and 7210 SAS Release 10.0 or later for the 64x10GE+4xqSFP28 satellite.

The following restrictions apply:

• The 10GE ports used as satellite uplinks must start at port 1 and be sequential, up to the maximum of 16 10GE uplinks.

• When 10GE ports are used as uplinks, the 4x100GE port are not available for use and should be configured as role none.

The following example shows the 10GE port satellite uplink configuration.

[ex:/configure satellite]
A:admin@node-2# info
    port-template "10gUp" {
        admin-state enable
        sat-type es64-10gb-sfpp+4-100gb-cfp4
        port "1/1/1" {
            role uplink
        }
        port "1/1/2" {
            role uplink
        }
        port "1/1/3" {
            role uplink
        }
        ...
        port "1/1/9" {
            uplink 1/1/1
        }
        port "1/1/10" {
            uplink 1/1/1
        }
        ...
        port "1/1/16" {
            uplink 1/1/2
        }
        port "1/1/17" {
            uplink 1/1/2
        }
        port "1/1/65" {
            role none
        }
        port "1/1/66" {
            role none
        }
        ...
    }
    ethernet-satellite 20 {
        admin-state enable
        mac-address d0:99:d5:96:ee:41
        sat-type es64-10gb-sfpp+4-100gb-cfp4
        software-repository rep1
        port-template "10gUp"
    }

A:node-2>config>system>satellite# info
----------------------------------------------
          port-template "10gUp" sat-type "es64-10gb-sfpp+4-100gb-cfp4" create
               port 1/1/1
                    role uplink
                    uplink none
               exit
               port 1/1/2
                    role uplink
                    uplink none
               exit
               port 1/1/3
                    role uplink
                    uplink none
               exit
               ...
               port 1/1/9
                    uplink 1/1/1
               exit
               port 1/1/10
                    uplink 1/1/1
               exit
               ...
               port 1/1/16
                    uplink 1/1/2
               exit
               port 1/1/17
                    uplink 1/1/2
               exit
               ...
               port 1/1/65
                    role none
               exit
               port 1/1/66
                    role none
               exit
               ...
               no shutdown
          exit
          eth-sat 20 create
               mac-address d0:99:d5:96:ee:41
               sat-type "es64-10gb-sfpp+4-100gb-cfp4"
               port-template "10gUp"
               software-repository "rep1"
               no shutdown
          exit
----------------------------------------------

An option in the port-map configuration allows a secondary uplink to be assigned to enable uplink resiliency. A secondary uplink is used to carry the traffic associated with the client port if the primary uplink becomes unavailable. If traffic is switched to the secondary uplink, when the primary uplink becomes available, traffic is reverted to the primary as soon as possible.

Use the following command to configure a secondary uplink per client port:

• MD-CLI

  configure satellite ethernet-satellite port-map secondary

• classic CLI

  configure system satellite eth-sat port-map secondary

To configure a secondary uplink, after the primary uplink is specified, the secondary keyword should be included, followed by the intended uplink to be used as the secondary uplink.

[ex:/configure satellite]
A:admin@node-2# info
     ethernet-satellite 1 {
          port-map esat-1/1/2 {
               primary esat-1/1/u1
               secondary esat-1/1/u3
          }
     }

A:node-2>config>system>satellite# info
----------------------------------------------
          eth-sat 1 create
               port-map esat-1/1/2
               primary esat-1/1/u1
               secondary esat-1/1/u3
          exit
----------------------------------------------

The host system can use the dynamic uplink resiliency mechanism to automatically manage uplink resiliency assignments. Through this mechanism, the host dynamically assigns a primary and secondary uplink for each satellite access port. Depending on the configuration options specified, the uplinks (primary and secondary) can be distributed over one or two FP forwarding engines.

[ex:/configure satellite]
A:admin@node-2# info
    ethernet-satellite 1 {
        admin-state enable
        sat-type es48-1gb-sfp
        dynamic-uplink true
        uplink-distribution dual-complex
    }

A:node-2>config>system>satellite# info
----------------------------------------------
          eth-sat 1 create
               sat-type es48-1gb-sfp
               dynamic-uplink true
               uplink-distribution dual-complex
               no shutdown
          exit
----------------------------------------------

Ethernet LAGs can use a mixture of physical Ethernet ports (including connector-based ports) and satellite access ports. However, satellite access ports are not supported within mixed speed LAGs.

Satellite client ports can also be used in MC-LAGs as both primary and standby link members, either using LACP or power-off signaling modes. MC-LAGs can also use a combination of physical and satellite client ports as link members.

All SR OS service access capabilities are supported. Where satellite access ports are used, the service entry point begins at the satellite access port.

This topic describes CRC monitoring for Ethernet satellite ports.

configure port ethernet crc-monitor

For CRC monitoring on Ethernet satellite ports, limit the setting of signal-failure thresholds to only a subset of the uplinks. Setting the signal-failure threshold on all the links could result in satellite isolation if CRC errors are seen simultaneously on all the uplinks. If a port enters a signal-failed state, it must be administratively reset to be re-enabled. If this occurs on the satellite uplink side, console access to the satellite must be available or the satellite must be rebooted.

[ex:/configure port 1/1/1 ethernet crc-monitor]
A:admin@node-2# info
    port esat 2/1/r/u {
        admin-state enable
        ethernet {
            crc-monitor {
                signal-degrade {
                    threshold 9
                }
                signal-failure {
                    threshold 9
                }
            }
        }
    port 1/1/c35/1 {
        admin-state enable
        ethernet {
            crc-monitor {
                signal-degrade {
                    threshold 9
                }
                signal-failure {
                    threshold 9
                }
            }
        }

A:node-2>config#  info
----------------------------------------------
        port esat2/1/r/u
            ethernet 
                crc-monitor
                    sd-threshold 9
                    sf-threshold 9
                exit
            exit
            no shutdown
        exit
        port 1/1/c35/1
            ethernet
                crc-monitor
                    sd-threshold 9
                    sf-threshold 9
                exit
            exit
            no shutdown
        exit

The boot-env option enables a synchronization of all the files used in system initialization.

When configuring the system to perform this synchronization, the following occurs:

1. The BOF used during system initialization is copied to the same compact flash on the standby CPM (in redundant systems). The synchronization options on the standby CPM are preserved.

2. The primary, secondary, and tertiary images, (provided they are locally stored on the active CPM) are copied to the same compact flash on the standby CPM.

3. The primary, secondary, and tertiary configuration files, (provided they are locally stored on the active CPM) are copied to the same compact flash on the standby CPM.

The config option synchronizes configuration files by copying the files specified in the active CPM BOF file to the same compact flash on the standby CPM.

Both image files (CPM and IOM) on the 7450 ESS must be located in the same directory. Failure to locate and synchronize both images causes an error to be generated.

The force-switchover now command forces an immediate switchover to the standby CPM card.

If the active and standby are not synchronized for some reason, users can manually synchronize the standby CPM by rebooting the standby by issuing the admin reboot command on the active or the standby CPM.

You can optionally configure the GPS location of the device. If the string contains special characters (#, $, spaces, and so on), the entire string must be enclosed within double quotes. Use the following command to configure the system coordinates.

configure system coordinates

The zone command sets the time zone and time zone offset for the router. The router supports system-defined and user-defined time zones. The system-defined time zones are listed in System-defined time zones. Use the following command to configure the system time zone.

configure system time zone

Configure the start and end dates and offset for summer time or daylight savings time to override system defaults or for user defined time zones. When configured, the time is adjusted by adding the configured offset when summer time starts and subtracting the configured offset when summer time ends. Use commands in the following context to configure summer time coordinates.

configure system time dst-zone

If the time zone configured is listed in System-defined time zones, the starting, ending, and offset do not need to be configured with this command unless there is a need to override the system defaults. The command returns an error if the start and ending dates and times are not available either in System-defined time zones or entered as configuration options in this command.

NTP is the Network Time Protocol defined in RFC 1305, Network Time Protocol (Version 3) Specification, Implementation and Analysis and RFC 5905, Network Time Protocol Version 4: Protocol and Algorithms Specification. It allows for the participating network nodes to keep time more accurately and more importantly they can maintain time in a more synchronized fashion between all participating network nodes.

SR OS uses an NTP process based on a reference build provided by the Network Time Foundation. Nokia strongly recommends that the users review RFC 8633, Network Time Protocol Best Current Practices, when they plan to use NTP with the router. The RFC section ‟Using Enough Time Sources” indicates that using only two time sources (NTP servers) can introduce instability if they provide conflicting information. To maintain accurate time, Nokia recommends configuring three or more NTP servers.

NTP uses stratum levels to define the number of hops from a reference clock. The reference clock is considered to be a stratum-0 device that is assumed to be accurate with little or no delay. Stratum-0 servers cannot be used in a network. However, they can be directly connected to devices that operate as stratum-1 servers. A stratum-1 server is an NTP server with a directly-connected device that provides Coordinated Universal Time (UTC), such as a GPS or atomic clock.

The higher stratum levels are separated from the stratum-1 server over a network path, therefore, a stratum-2 server receives its time over a network link from a stratum-1 server. A stratum-3 server receives its time over a network link from a stratum-2 server.

SR OS routers normally operate as a stratum-2 or higher device. The router relies on an external stratum-1 server to source accurate time into the network. However, SR OS also allows for the use of the local PTP recovered time to be sourced into NTP. In this latter case, the local PTP source appears as a stratum-0 server and SR OS advertises itself as a stratum-1 server. Activation of the PTP source into NTP may impact the network NTP topology because the SR OS router is promoted to stratum-1.

SR OS router runs a single NTP clock which then operates NTP message exchanges with external NTP clocks. Exchanges can be made with external NTP clients, servers, and peers. These exchanges can be through the base, management, or VPRN routing instances.

NTP operates associations between clocks as either client or server, symmetric active and symmetric passive, or broadcast modes. These modes of operation are applied according to which elements are configured on the router. To run server mode, the operator must enable NTP server mode for the base and each needed VPRN routing instance. To run client mode, the operator must configure external servers. If both the local router and remote router are configured with each other as peers, then the router operates in symmetric active mode. If only one side of the association has peering configured, then the modes are symmetric passive. To operate using broadcast mode, interfaces must be configured to transmit as broadcast servers or receive as broadcast clients.

NTP server operation for both unicast and broadcast communication within a VPRN is configured within the VPRN (see the NTP Within a VPRN Service section in 7450 ESS, 7750 SR, 7950 XRS, and VSR Layer 3 Services Guide: IES and VPRN).

The following NTP elements are supported:

• server mode

  In this mode, the node advertises the ability to act as a clock source for other network elements. The node, by default, transmits NTP packets in NTP version 4 mode.

• authentication keys

  Authentication keys implement increased security support in carrier and other networks. Both DES and MD5 authentication are supported, as well as multiple keys.

• operation in symmetric active mode

  This capability requires that NTP be synchronized with a specific node that is considered more trustworthy or accurate than other nodes carrying NTP in the system. This mode requires that a specific peer is set.

• server and peer addressing using IPv6

  Both external servers and external peers may be defined using IPv6 or IPv4 addresses. Other features (such as multicast, broadcast) use IPv4 addressing only.

• broadcast or multicast modes

  When operating in these modes, the node receives or sends using either a multicast (default 224.0.1.1) or a broadcast address. Multicast is supported only on the CPM MGMT port.

• alert when NTP server is not available

  When none of the configured servers are reachable on the node, the system reverts to manual timekeeping and issues a critical alarm. When a server becomes available, a trap is issued indicating that standard operation has resumed.

• NTP and SNTP

  If both NTP and SNTP are enabled on the node, then SNTP transitions to an operationally down state. If NTP is removed from the configuration or shut down, then SNTP resumes an operationally up state.

• gradual clock adjustment

  As several applications (such as Service Assurance Agent (SAA)) can use the clock, and if determined that a major (128 ms or more) adjustment needs to be performed, the adjustment is performed by programmatically stepping the clock. If a minor (less than 128 ms) adjustment must be performed, then the adjustment is performed by either speeding up or slowing down the clock.

• To avoid the generation of too many events/trap the NTP module rates limit the generation of events/traps to three per second. At that point a single trap is generated that indicates that event/trap squashing is taking place.

SNTP is a compact, client-only version of the NTP. SNTP can only receive the time from SNTP/NTP servers; it cannot be used to provide time services to other systems. SNTP can be configured in either broadcast or unicast client mode.

The CRON feature supports periodic and date and time-based scheduling in SR OS. CRON can be used, for example, to schedule Service Assurance Agent (SAA) functions. CRON functionality includes the ability to specify scripts that need to be run, when they are scheduled, including one-time only functionality (one-shot), interval and calendar functions. Scheduled reboots, peer turn ups, service assurance agent tests and more can all be scheduled with CRON, as well as OAM events, such as connectivity checks, or troubleshooting runs.

CRON supports the schedule element. The schedule function configures the type of schedule to run, including one-time only (one-shot), periodic, or calendar-based runs. All runs are determined by month, day of month or weekday, hour, minute, and interval (seconds).