Basic Concepts of ASON

Basic Concepts of ASON The basic concepts related to the ASON are the three planes, label switched path (LSP) and rerouting. As shown in Figure 1, the ASON has three planes: the control plane, the transport plane, and the management plane. Figure 1 Three planes of the ASON

ASON ASON is a new generation optical network that has the following features:  Customers launch a service request dynamically.  Routes are selected automatically.  Signaling controls the creation and removal of connections.  Network connections are automatically and dynamically completed.  Switching and transmission are integrated into one system.

Control Plane The control plane consists of a group of communication entities. It is responsible for the calling control and connection control, including automatic setting up, releasing, monitoring, and maintaining connections. The control plane automatically restores the failed connections through signaling exchange.

Transport Plane The traditional WDM network is the transport plane. It transmits optical signals, configures crossconnection and protection switching for optical signals, and guarantees the reliability of all optical signals.

Management Plane The management plane is a complement to the control plane. It maintains the transport plane, the control plane and the whole system. It can configure end to end service. Its functions include performance management, fault management, configuration management and security management.

LSP Label switched path (LSP) is the path ASON services pass through. In an ASON, to create ASON services is to create LSPs. On U2000, LSP is also called ASON Trail.

WDM ASON Trail WDM ASON Trail is classified into WDM ASON OCh Trail and WDM ASON ODUk (k = 0, 1, 2, 3) Trail. See Figure 2. NOTE: OptiX OSN 8800 series support WDM ASON ODU0 Trail.  The WDM ASON OCh trail can be created when there are sufficient OCh TE link resources.  The WDM ASON ODUk trail can be created when there are sufficient TE link resources where the payload type is ODUk. Figure 2 WDM ASON Trail

Rerouting Rerouting is a means of resuming services. When an LSP is disconnected, the source node queries and finds the best route to resume services. Then, the initial node creates an LSP to transmit the service. After creating an LSP, the source node deletes the original LSP. CAUTION: After a revertive service reroutes, the original LSP is not deleted. NOTE: For more information on service restoration, refer to ASON Network Protection and Restoration.

Rerouting Lockout In some cases, rerouting is not required after failure in LSP. Then you need to set rerouting lockout.

Rerouting Policy Diamond, gold and silver services all support the following four rerouting polices:  Use existing trails whenever possible During rerouting, the route of the new LSP overlaps the original route whenever possible. This policy helps save network resources. When bandwidth resources are insufficient, the service is more likely to reroute successfully.

 Do not use existing trails whenever possible During rerouting, the route of the new LSP is separated from the original route whenever possible. This policy is applicable to a network with sufficient link resources.  No rerouting constraint During rerouting, the no rerouting constraint is computed for the new LSP. Whether the new or old route resources are utilized again is not considered. This policy chooses a route with the minimum cost as the new route after rerouting according to network conditions.  Use simulated section restoration During rerouting, the services must reuse the original routes without involving faulty spans. Endto-end rerouting is enabled only when rerouting on the faulty spans fails, and thus service route can be controlled and managed more easily.

Crankback Mechanism The crankback mechanism during rerouting, optimization, and creation of the wavelength/sub-wavelength LSP is supported. It takes a certain time to spread network routing information. When rerouting is performed, the source node may use the outdated network status information to calculate the trail. Therefore, the selected route may be unavailable, resulting in a rerouting failure. The ASON software supports the crankback rerouting mechanism. When setting up connections according to the calculated trail, the ASON software informs the source node of the information related to the faulty network nodes or links if the connection setup process is baffled due to insufficient network resources or network faults. In this case, the source node recalculates a trail that meets the constraint conditions but does not traverse the obstacle node and then establishes the connections for the calculated trail. This effectively restores a service by means of rerouting.

SLA The ASON network can provide services of different QoS to different clients. The service level agreement (SLA) is used to classify services according to the service protection, as listed in Table 1. The rerouting time is related to the device type, interrupted service, network resource and setting. The data are listed as follows only for reference. Table 1 Service level Service

Protection and Restoration Scheme

Implementation Means

Switching Time

Diamond service

Protection and restoration

Intra-board 1+1 protection, ODUk SNCP, SW SNCP and rerouting

Less than 50 ms

Gold service


ODUk SPRing protection and rerouting

Less than 50 ms

Silver service

Restoration

Rerouting

-

Rerouting Time

The rerouting time varies with the network size, capacity and service types. For the typical scenario of a four-NE mesh network transmitting no more than 40

Table 1 Service level Service

Protection and Restoration Scheme

Implementation Means

Switching Time

Rerouting Time

wavelengths, the rerouting time is counted in seconds. Copper service

No protection No restoration

-

-

-

Table 2 lists details of the TE links used by ASON services. Table 2 TE links used by WDM ASON trails Service Level

Working Resource of TE Link

Protection Resource of TE Link

Non-Protection Resource of TE Link

Diamond service

Not used

Not used

Used

Gold service

Used with the priority

Not used

Used when the resource is not enough

Silver service

Not used

Not used

Used

Copper service

Not used

Not used

Used

Parent topic: ASON Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Diamond WDM ASON Trail Diamond WDM ASON trails have the best protection ability. When there are enough resources in the network, diamond WDM ASON trails provide a permanent 1+1 protection. The diamond WDM ASON trails are classified into ODU0, ODU1 trail, ODU2 trail and ODU3 trail. Diamond services are applicable to voice and data services, VIP private line, such as banking, security and aviation. A diamond service is a service with 1+1 protection from the source node to the sink node. It is also called a 1+1 service. For a diamond service, there are two different LSPs available between the source node and the sink node. The two LSPs should be as separate as possible. One is the working LSP and the other is the protection LSP. The same service is transmitted to the working LSP and the protection LSP at the same time. If the working LSP is normal, the sink node receives the service from the working LSP; otherwise, from the protection LSP.

Figure 1 shows a diamond service. Figure 1 Diamond Services

There are three types of diamond services. 

Permanent 1+1 diamond service: rerouting is triggered once an LSP fails.



Rerouting 1+1 diamond service: rerouting is triggered only when both LSPs fail.



Non-rerouting diamond service: rerouting is never triggered.

Table 1 lists the attributes of the permanent 1+1 diamond service. Table 2 lists the attributes of the rerouting 1+1 diamond service. Table 3 lists the attributes of the non-rerouting 1+1 diamond service. Table 1 Attributes of the permanent 1+1 diamond services Attribute

Permanent 1+1 Diamond Service

Requirements for creation

Sufficient non-protection resources are available between the source node and the sink node.

Protection type

During creation, diamond services generate the services that have the traditional WDM 1+1 protection attribute at the same time. Different ASON trails support different protection schemes. For WDM ASON OCh trail: supports intra-board 1+1 protection. (The protection schemes are OTU intra-board dual-feed and OTU+OLP/DCP dual-feed.) For WDM ASON ODUk trail: supports ODUk SNCP






If the resources are sufficient, two LSPs are always available for a permanent 1+1 diamond service. One is the active LSP and the other is the standby LSP. If the resources are not sufficient, one LSP can still be reserved for

Table 1 Attributes of the permanent 1+1 diamond services Attribute

Permanent 1+1 Diamond Service a permanent 1+1 diamond service to ensure the service survivability.

Rerouting

        

 

Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout. Supports rerouting lockout. Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports three rerouting policies:  Use existing trails whenever possible  Do not use existing trails whenever possible  No rerouting constraint  Use simulated section restoration Supports rerouting triggered by SD. Supports setting the rerouting hold-off time.

Revertive

Supports Automatically Revertive, Non-Revertive, and Scheduled revertive.  After the automatically revertive diamond service is rerouted, the service is automatically reverted to the original path if the fault in the original path is rectified.  After the scheduled revertive diamond service is rerouted, the user can set the service to be reverted to the original path at a specific future time (ranging from 10 minutes to 30 days) on the NMS if the fault in the original path is rectified.  After the non-revertive diamond service is rerouted, the service is not reverted to the original route after the fault is rectified.

Preset restoration trail

Supports setting two preset restoring trails. Preset restoration trails are preferred in rerouting.

Service Upgrade and Downgrade

 

Service migration

  

Supports traditional 1+1 WDM trails upgrade to diamond WDM ASON trails. Supports diamond WDM ASON trails downgrade to traditional 1+1 WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Migration between electrical-layer diamond WDM ASON trails and gold WDM ASON trails is not supported Supports migration between electrical-layer diamond WDM ASON


Permanent 1+1 Diamond Service 

trails and silver WDM ASON trails. Supports migration between electrical-layer diamond WDM ASON trails and copper WDM ASON trails.

Service switching

Supports manual switching.

Service optimization

Supports manual service optimization.

Table 2 Attributes of the rerouting 1+1 diamond service Attribute

Rerouting 1+1 Diamond Service



Protection type



  

Rerouting

        



When the standby LSP fails, services are not switched. Rerouting is not triggered. When the active LSP fails, services are switched to the standby LSP for transmission. Rerouting is not triggered. When both the active and the standby LSPs fail, rerouting is triggered to create an LSP to restore services. Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout. Supports rerouting lockout. Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports three rerouting policies:  Use existing trails whenever possible  Do not use existing trails whenever possible  No rerouting constraint  Use simulated section restoration Supports rerouting triggered by SD.


Permanent 1+1 Diamond Service 

Supports setting the rerouting hold-off time.

Revertive





 

Service migration

   

Supports traditional 1+1 WDM trails upgrade to diamond WDM ASON trails. Supports diamond WDM ASON trails downgrade to traditional 1+1 WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Migration between electrical-layer diamond WDM ASON trails and gold WDM ASON trails is not supported Supports migration between electrical-layer diamond WDM ASON trails and silver WDM ASON trails. Supports migration between electrical-layer diamond WDM ASON trails and copper WDM ASON trails.

Service switching




Table 3 Attributes of the non-rerouting 1+1 diamond service Attribute

Non-rerouting 1+1 diamond service



Protection type

During creation, diamond services generate the services that have the traditional WDM 1+1 protection attribute at the same time. Different ASON trails support different protection schemes.


Non-rerouting 1+1 diamond service For WDM ASON OCh trail: supports intra-board 1+1 protection. (The protection schemes are OTU intra-board dual-feed and OTU+OLP/DCP dual-feed.) For WDM ASON ODUk trail: supports ODUk SNCP


  


 

Service migration

   

When the active LSP fails, services are switched to the standby LSP for transmission. Rerouting is not triggered. When the standby LSP fails, services are not switched. Rerouting is not triggered. When both the active and the standby LSPs fail, rerouting is not triggered. Supports traditional 1+1 WDM trails upgrade to diamond WDM ASON trails. Supports diamond WDM ASON trails downgrade to traditional 1+1 WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Migration between electrical-layer diamond WDM ASON trails and gold WDM ASON trails is not supported Supports migration between electrical-layer diamond WDM ASON trails and silver WDM ASON trails. Supports migration between electrical-layer diamond WDM ASON trails and copper WDM ASON trails.

Service switching




NOTE: When diamond ODUk ASON WDM trails are created, setting the SNC/N(PM) and SNC/S(TCM) modes is supported. When k is 0, only the non-intrusive monitoring (SNC/N) is supported. When k is 1 or 2, the sub-layer monitoring (SNC/S) and non-intrusive monitoring (SNC/N) are supported. When the SNCP type is set as sub-layer monitoring, the U2000 supports setting TCM layers (TCM = 1-5). Traditional services in the SNC/I, SNC/N, and SNC/S modes can be upgraded into diamond ASON services. After rerouting, the SNC mode of services in the SNC/I and SNC/N(TCM) modes is changed into SNC/N(PM). Parent topic: ASON Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Diamond WDM ASON Trail

Diamond WDM ASON trails have the best protection ability. When there are enough resources in the network, diamond WDM ASON trails provide a permanent 1+1 protection. The diamond WDM ASON trails are classified into ODU0, ODU1 trail, ODU2 trail and ODU3 trail. Diamond services are applicable to voice and data services, VIP private line, such as banking, security and aviation. A diamond service is a service with 1+1 protection from the source node to the sink node. It is also called a 1+1 service. For a diamond service, there are two different LSPs available between the source node and the sink node. The two LSPs should be as separate as possible. One is the working LSP and the other is the protection LSP. The same service is transmitted to the working LSP and the protection LSP at the same time. If the working LSP is normal, the sink node receives the service from the working LSP; otherwise, from the protection LSP. Figure 1 shows a diamond service. Figure 1 Diamond Services

There are three types of diamond services. 

Permanent 1+1 diamond service: rerouting is triggered once an LSP fails.



Rerouting 1+1 diamond service: rerouting is triggered only when both LSPs fail.



Non-rerouting diamond service: rerouting is never triggered.

Table 1 lists the attributes of the permanent 1+1 diamond service. Table 2 lists the attributes of the rerouting 1+1 diamond service. Table 3 lists the attributes of the non-rerouting 1+1 diamond service. Table 1 Attributes of the permanent 1+1 diamond services Attribute

Permanent 1+1 Diamond Service



Protection type

During creation, diamond services generate the services that have the traditional WDM 1+1 protection attribute at the same time. Different


Permanent 1+1 Diamond Service ASON trails support different protection schemes. For WDM ASON OCh trail: supports intra-board 1+1 protection. (The protection schemes are OTU intra-board dual-feed and OTU+OLP/DCP dual-feed.) For WDM ASON ODUk trail: supports ODUk SNCP






Rerouting

        

 

If the resources are sufficient, two LSPs are always available for a permanent 1+1 diamond service. One is the active LSP and the other is the standby LSP. If the resources are not sufficient, one LSP can still be reserved for a permanent 1+1 diamond service to ensure the service survivability. Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout. Supports rerouting lockout. Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports three rerouting policies:  Use existing trails whenever possible  Do not use existing trails whenever possible  No rerouting constraint  Use simulated section restoration Supports rerouting triggered by SD. Supports setting the rerouting hold-off time.

Revertive




Table 1 Attributes of the permanent 1+1 diamond services Attribute Service Upgrade and Downgrade

Permanent 1+1 Diamond Service  

Service migration

   


Service switching




Table 2 Attributes of the rerouting 1+1 diamond service Attribute

Rerouting 1+1 Diamond Service



Protection type



  

Rerouting

    

When the standby LSP fails, services are not switched. Rerouting is not triggered. When the active LSP fails, services are switched to the standby LSP for transmission. Rerouting is not triggered. When both the active and the standby LSPs fail, rerouting is triggered to create an LSP to restore services. Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout. Supports rerouting lockout.


Permanent 1+1 Diamond Service    

 

Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports three rerouting policies:  Use existing trails whenever possible  Do not use existing trails whenever possible  No rerouting constraint  Use simulated section restoration Supports rerouting triggered by SD. Supports setting the rerouting hold-off time.

Revertive





 

Service migration

   


Service switching





Non-rerouting 1+1 diamond service



Protection type



  


 

Service migration

   

When the active LSP fails, services are switched to the standby LSP for transmission. Rerouting is not triggered. When the standby LSP fails, services are not switched. Rerouting is not triggered. When both the active and the standby LSPs fail, rerouting is not triggered. Supports traditional 1+1 WDM trails upgrade to diamond WDM ASON trails. Supports diamond WDM ASON trails downgrade to traditional 1+1 WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Migration between electrical-layer diamond WDM ASON trails and gold WDM ASON trails is not supported Supports migration between electrical-layer diamond WDM ASON trails and silver WDM ASON trails. Supports migration between electrical-layer diamond WDM ASON trails and copper WDM ASON trails.

Service switching




NOTE: When diamond ODUk ASON WDM trails are created, setting the SNC/N(PM) and SNC/S(TCM) modes is supported. When k is 0, only the non-intrusive monitoring (SNC/N) is supported. When k is 1 or 2, the sub-layer monitoring (SNC/S) and non-intrusive monitoring (SNC/N) are supported. When the SNCP type is set as sub-layer monitoring, the U2000 supports setting TCM layers (TCM = 1-5). Traditional services in the SNC/I, SNC/N, and SNC/S modes can be upgraded into diamond ASON services. After rerouting, the SNC mode of services in the SNC/I and SNC/N(TCM) modes is changed into SNC/N(PM).


Silver WDM ASON Trail Silver WDM ASON trail, including WDM ASON OCh trails, ODU0 trails, ODU1 trails, ODU2 trails and ODU3 trails, the revertive time is several seconds. The silver level service is suitable for those data or internet services that have low real-time requirement. Silver services are also called rerouting services. When an LSP failure, the ASON triggers rerouting to restore the service. If there are not enough resources, service may be interrupted. As shown in Figure 1, A-B-G-H-I is a silver service trail. If the fiber between B and G is cut, the ASON triggers rerouting from A to create an LSP that does not pass the cut fiber. Hence, services are protected. Figure 1 A silver service

Table 1 lists the attributes of silver services. Table 1 Attributes of silver services Attribute

Silver Services



Service restoration

When the original LSP fails, rerouting is triggered to create an LSP to restore services.

Rerouting

   

Supports setting the revertive mode. Supports setting the WTR time. Supports setting the scheduled reversion time. Supports setting revertive lockout.

Table 1 Attributes of silver services Attribute

Silver Services     

 

Supports rerouting lockout. Supports setting the rerouting priority. Supports setting the crankback times. Supports setting the trigger condition. Supports three rerouting policies:  Use existing trails whenever possible  Do not use existing trails whenever possible  No rerouting constraint  Use simulated section restoration Supports rerouting triggered by SD. Supports setting the rerouting hold-off time.

Revertive




Service upgrade and downgrade

 

Service migration

   

Supports traditional unprotected WDM trails upgrade to silver WDM ASON trails. Supports silver WDM ASON trails downgrade to traditional unprotected WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Supports migration between electrical-layer silver WDM ASON trails and diamond WDM ASON trails. Supports migration between electrical-layer silver WDM ASON trails and gold WDM ASON trails. Supports migration between electrical-layer silver WDM ASON trails and copper WDM ASON trails.



Service association

Supports service association.

Parent topic: ASON

Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Copper WDM ASON Trail The copper services are seldom used. Generally, temporary services, such as the abrupt services in holidays, are configured as copper services.The copper WDM ASON trails are classified into OCh trail, ODU0 trail, ODU1 trail, ODU2 trail and ODU3 trails . Copper services are also called non-protection services. If an LSP fails, services do not reroute and are interrupted. Table 1 lists the attributes of copper services. Table 1 Attributes of copper services Attribute

Silver Service



Service restoration

Does not support rerouting.

Rerouting

 Supports rerouting priority.  Supports setting the crankback times. NOTE: USP V100R005 support the priority and cranback times. Copper electrical-layer WDM ASON trail does not support the priority.

Service upgrade and downgrade

 

Service migration

   

Supports traditional unprotected WDM trails upgrade to copper WDM ASON trails. Supports copper WDM ASON trails downgrade to traditional unprotected WDM trails. Migration between optical-layer WDM ASON OCh trails is not supported. Supports migration between electrical-layer copper WDM ASON trails and diamond WDM ASON trails. Supports migration between electrical-layer copper WDM ASON trails and gold WDM ASON trails. Supports migration between electrical-layer copper WDM ASON trails and silver WDM ASON trails.



Service association

Supports service association.


Value Range

Description

SNC/I

Indicates the SNC protection for inherent monitoring, and the protection triggering condition is the overhead alarm on the SM section.

SNC/S

Indicates the SNC protection for sub-layer monitoring, and the protection triggering condition is the overhead alarm on the SM or TCM layer.

SNC/N

Indicates the SNC protection for non-intrusive monitoring, and the protection triggering condition is the overhead alarm on the SM, TCM, or PM section.

ASON Protocol Huawei OptiX GCP applies the link management protocol (LMP) as the link management protocol, OSPFTE as the routing protocol, and RSVP-TE as the signaling protocol. The following sections describe the functions of these protocols in an ASON network.

LMP The LMP performs the following functions in an ASON network. 

Creating and maintaining the control channels between adjacent nodes. The following is the procedure of creating control channels. 

See Figure 1. When two adjacent ASON NEs start up, the LMP uses the OTN overheads or the DCC channels of the OSC to transmit messages. Node 1 transmits messages to Node 2, which performs the check to the received messages. If the messages pass the check, Node 2 returns messages to Node 1. If the messages do not pass the check, Node 2 returns a message to Node 1, indicating that the messages fail to pass the check. In this way, Node 2 waits for another check. Hence, a control channel between the two adjacent nodes is created.



After the control channel is created, the two nodes store the information about the control channel and identify the control channel according to the ID.

Figure 1 Creating control channels



Verifying component links and TE links. The following is the procedure of verifying TE Links. 

After the control channels are configured, an attribute consistency check is performed to the TE links to see if the information is identical at both ends of dynamically discovered or manually configured TE links. If the check succeeds, the OSPF protocol is used to flood the information of the TE links to the entire network.



As shown in Figure 2, Node 1 transmits messages and the content to be checked to Node 2, which checks if it has the same information and returns the check result to Node 1.

Figure 2 Verifying TE links

OSPF-TE The control plane of Huawei OptiX GCP applies the OSPF-TE, which is an extended protocol for OSPF, and performs the following functions. 

Creates neighbor relations.



Creates and maintains control links.



Floods and collects the information about the control links on the control plane. According to the information, the protocol then generates the information about the routes that are required for forwarding messages on the control plane.



Floods and collects the information about the TE links on the transport plane. The protocol then generates the information about the network service topologies for service trail computation.

RSVP-TE The RSVP-TE is a protocol for resource reservation. It is a type of signaling. In terms of traffic engineering, the RSVP is extended to RSVP-TE. The RSVP-TE mainly supports the following functions: 

LSP creation



LSP deletion



LSP attribute modification



LSP rerouting



LSP trail optimization

Protocol Encryption An external entity may modify the OSPF-TE protocol packets of the network, counterfeit a node of this network and transmit packets, or receive the packets transmitted by nodes in the network and repeat the attack. To prevent these network insecurities, the ASON provides the function to encrypt protocols. In an ASON domain, the RSVP and OSPF-TE protocols are encrypted for authentication. The RSVP authentication is configured for nodes and the OSPF-TE authentication for interconnected interfaces (slots and optical interfaces). The authentication can be non-authentication, plain text authentication or MD5 authentication. 

Non-authentication: No authentication is required in this mode.



Plain text authentication: To verify the preset password. The authentication code must be a character string with no more than eight characters.



MD5 authentication: To verify the information that is encrypted by the MD5 algorithm. The authentication code must be a character string with no more than 64 characters.

The check succeeds only when the authentication modes and passwords of adjacent nodes are the same. Parent topic: ASON Huawei Proprietary and Confidential Copyright © Huawei Technologies Co., Ltd.

Basic Concepts of ASON

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