Synchronous Ethernet (SyncE) ESMC and SSM

Customers using a packet network find it difficult to provide timing to multiple remote network elements (NEs) through an external time division multiplexed (TDM) circuit. The SyncE feature helps to overcome this problem by providing effective timing to the remote NEs through a packet network. SyncE leverages the physical layer of the Ethernet to transmit frequency to the remote sites. SyncE's functionality and accuracy resemble the SONET/SDH network because of its physical layer characteristic. SyncE uses ESMC to allow the best clock source traceability to correctly define the timing source and help prevent a timing loop.

SONET/SDH use 4 bits from the two S bytes in the SONET/SDH overhead frame for message transmission. Ethernet relies on ESMC that is based on an IEEE 802.3 organization-specific slow protocol for message transmission. Each NE along the synchronization path supports SyncE, and SyncE effectively delivers frequency in the path. SyncE does not support relative time (for example, phase alignment) or absolute time (Time of Day).

SyncE provides the Ethernet physical layer network (ETY) level frequency distribution of known common precision frequency references. Clocks for use in SyncE are compatible with the clocks used in the SONET/SDH synchronization network. To achieve network synchronization, synchronization information is transmitted through the network via synchronous network connections with performance of egress clock. In SONET/SDH the communication channel for conveying clock information is Synchronization Status Message (SSM), and in SyncE it the Ethernet Synchronization Message Channel (ESMC).

ESMC carries a Quality Level (QL) identifier that identifies the timing quality of the synchronization trail. QL values in QL-TLV are the same as QL values defined for SONET and SDH SSM. Information provided by SSM QLs during the network transmission helps a node derive timing from the most reliable source and prevents timing loops. ESMC is used with the synchronization selection algorithms. Because Ethernet networks are not required to be synchronous on all links or in all locations, the ESMC channel provides this service. ESMC is composed of the standard Ethernet header for an organization-specific slow protocol; the ITU-T OUI, a specific ITU-T subtype; an ESMC-specific header; a flag field; and a type, length, value (TLV) structure. The use of flags and TLVs improves the management of SyncE links and the associated timing change. For details on Synchronous Ethernet support on Cisco 7600 series routers see Cisco 7600 Series Ethernet Services Plus (ES+) and Ethernet Services Plus T (ES+T) Line Card Configuration Guide .

SUMMARY STEPS

1.    enable

2.    network-clock set l ockout {external slot / card / port[10m| 2m| t1{sf | esf | d4}] | interface type slot / port}

3.    network-clock clear lockout {external slot / card / port [10m| 2m| t1 {sf | esf | d4}] | interface type slot / port}

4.    network-clock switch force { external slot / card / port [ 10m | 2m] | t0 | t1 {sf | esf | d4} t0 | internal { external slot / card / port[10m | 2m] | t0} | interface type slot / port external slot / card / port [ 10m | 2m] | t0 }

5.    network-clock switch manual { interface type slot /port { external slot / card / port [10m | 2m ] | t0 } | external slot / card / port{10m | 2m | t0 | t1 {sf | esf | d4} | internal { external slot / card / port[10m | 2m] | t0} }

6.    network-clock clear switch {t0 | external slot / card / port [10m | 2m]}

7.    configure terminal

8.    network-clock synchronization automatic

9.    network-clock synchronization ssm option {1| 2{GEN1| GEN2}}

10.    network-clock input-source priority {external slot / card / port [ 10m | 2m | t1 {sf | esf | d4}] | interface type slot / port}

11.    network-clock synchronization mode ql-enabled

12.    network-clock hold-off {0| milliseconds}

13.    network-clock wait-to-restore seconds

14.    esmc process

15.    network-clock external slot / card / port hold-off {0 | milliseconds}

16.    network-clock quality-level {tx| rx} value {interface type slot / port | external slot / card / port [10m | 2m | t1 {sf | esf | d4}]

17.    network-clock output-source {line | system} priority interface type slot / port external slot / card / port[10m | 2m | t1{sf | esf | d4} ]

18.    interface type number

19.    synchronous mode

20.    esmc mode [ql-disabled| tx| rx] value

21.    network-clock source quality-level value {tx | rx}

22.    network-clock hold-off {0 | milliseconds}

23.    network-clock wait-to-restore seconds

24.    end

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	network-clock set l ockout {external slot / card / port[10m| 2m| t1{sf | esf | d4}] | interface type slot / port} Example: Router# network-clock set lockout GigabitEthernet7/1	Sets the lockout state of input to "on." The input then is no longer considered available by the selection process.
Step 3	network-clock clear lockout {external slot / card / port [10m| 2m| t1 {sf | esf | d4}] | interface type slot / port} Example: Router# network-clock clear lockout GigabitEthernet7/1	Sets the lockout state of input to "off." The input then is considered available by the selection process.
Step 4	network-clock switch force { external slot / card / port [ 10m | 2m] | t0 | t1 {sf | esf | d4} t0 | internal { external slot / card / port[10m | 2m] | t0} | interface type slot / port external slot / card / port [ 10m | 2m] | t0 } Example: Router# network-clock switch force interface GigabitEthernet 7/1 t0	Overrides the currently selected synchronization source when the synchronization source is enabled and not locked out. If the source selected by the forced switch command is disabled or locked out, the forced switch command is automatically rejected.
Step 5	network-clock switch manual { interface type slot /port { external slot / card / port [10m | 2m ] | t0 } | external slot / card / port{10m | 2m | t0 | t1 {sf | esf | d4} | internal { external slot / card / port[10m | 2m] | t0} } Example: Router# network-clock switch manual interface GigabitEthernet 7/1 t0	Selects the synchronization source interface when it is enabled and not locked out. Manual switching is used to override the previously assigned synchronization source priorities.
Step 6	network-clock clear switch {t0 | external slot / card / port [10m | 2m]} Example: Router# network-clock clear switch t0	Clears the forced switch and manual switch commands. If the interface is not specified, the force/manual selected interface gets automatically cleared.
Step 7	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 8	network-clock synchronization automatic Example: Router(config)# network-clock synchronization automatic	Enables the network clock selection algorithm. This command disables the Cisco-specific network clock process and turns on the G.781-based automatic clock selection process.
Step 9	network-clock synchronization ssm option {1| 2{GEN1| GEN2}} Example: Router(config)# network-clock synchronization ssm option 2 GEN2	Configures the router to work in a synchronization network. Option 1 refers to synchronization networks designed for Europe. This is the default value. Option 2 refers to synchronization networks designed for United States.
Step 10	network-clock input-source priority {external slot / card / port [ 10m | 2m | t1 {sf | esf | d4}] | interface type slot / port} Example: Router(config)# network-clock input-source 1 interface GigabitEthernet 7/1	Enables selecting an interface that is configured as clock source line, an external timing input interface, a GPS interface, or a packet-based timing recovered clock as the input clock for the system. Interface can be SyncE or channelized SONET.
Step 11	network-clock synchronization mode ql-enabled Example: Router(config)# network-clock synchronization mode ql-enabled	Configures the automatic selection process ql-enabled mode. QL is disabled by default. ql-enabled mode can be used only when the synchronization interface is capable to send SSM.
Step 12	network-clock hold-off {0| milliseconds} Example: Router(config)# network-clock hold-off 0	(Optional) Configures hold-off timer for the interface.
Step 13	network-clock wait-to-restore seconds Example: Router(config)# network-clock wait-to-restore 70	(Optional) Configures wait-to-restore timer for the SyncE interface.
Step 14	esmc process Example: Router(config)# esmc process	Enables the ESMC process.
Step 15	network-clock external slot / card / port hold-off {0 | milliseconds} Example: Router(config)# network-clock external 0/1/0 hold-off 0	Overrides the hold-off timer value for the external interface.
Step 16	network-clock quality-level {tx| rx} value {interface type slot / port | external slot / card / port [10m | 2m | t1 {sf | esf | d4}] Example: Router(config)# network-clock quality-level rx QL-STU GigabitEthernet 0/0/0	Forces the QL value for line or external timing input and output.
Step 17	network-clock output-source {line | system} priority interface type slot / port external slot / card / port[10m | 2m | t1{sf | esf | d4} ] Example: Router(config)# network-clock output-source line 1 GigabitEthernet1/2 external 0/0/1 10m	Transmits the signal from the external timing input interface to the external timing output interface.
Step 18	interface type number Example: Router(config)# interface GigabitEthernet 0/0	Enters interface configuration mode.
Step 19	synchronous mode Example: Router(config-if)# synchronous mode	Configures the Ethernet interface to synchronous mode and automatically enables the ESMC and QL process on the interface.
Step 20	esmc mode [ql-disabled| tx| rx] value Example: Router(config-if)# esmc mode rx QL-STU	(Optional) Enables the ESMC process on the interface.
Step 21	network-clock source quality-level value {tx | rx} Example: Router(config-if)# network-clock source quality-level QL-ST4 tx	(Optional) Provides the forced QL value to the local clock selection process.
Step 22	network-clock hold-off {0 | milliseconds} Example: Router(config-if)# network-clock hold-off 0	(Optional) Configures the hold-off timer for the interface.
Step 23	network-clock wait-to-restore seconds Example: Example: Router(config-if)# network-clock wait-to-restore 70	(Optional) Configures the wait-to-restore timer for the SyncE interface.
Step 24	end Example: Router(config-if)# end	Exits interface configuration mode and returns to privileged EXEC mode.

SUMMARY STEPS

1.    enable

2.    configure terminal

3.    snmp-server enable traps netsync

4.    no snmp-server enable traps netsync

5.    end

6.    show running-config all | include traps

DETAILED STEPS

	Command or Action	Purpose
Step 1	enable Example: Router> enable	Enables privileged EXEC mode. Enter your password if prompted.
Step 2	configure terminal Example: Router# configure terminal	Enters global configuration mode.
Step 3	snmp-server enable traps netsync Example: Router(config)# snmp-server enable traps netsync	Enables the SyncE traps.
Step 4	no snmp-server enable traps netsync Example: Router(config)# no snmp-server enable traps netsync	(Optional) Disables the SyncE traps.
Step 5	end Example: Router(config)# end	Exits global configuration mode.
Step 6	show running-config all | include traps Example: Router# show running-config all | include trap	(Optional) Displays the SyncE traps that are enabled on the router.