|
|
This chapter describes the 2-port OC-12ATM WAN Optical Services Modules (OSMs).
This chapter consists of these sections:
Asynchronous Transfer Mode (ATM) uses cell-switching and multiplexing technology that combines the benefits of circuit switching (constant transmission delay and guaranteed capacity) with those of packet switching (flexibility and efficiency for intermittent traffic).
ATM is a connection-oriented environment. All traffic to or from an ATM network is prefaced with a virtual path identifier (VPI) and virtual channel identifier (VCI). A VPI/VCI pair is considered a single virtual circuit. Each virtual circuit is a private connection to another node on the ATM network. Each virtual circuit is treated as a point-to-point mechanism to another router or host and is capable of supporting bidirectional traffic.
Each ATM node is required to establish a separate connection to every other node in the ATM network that it must communicate with. All such connections are established using a permanent virtual circuit (PVC), which a network operator configures, or a switched virtual circuit (SVC), which is set up and torn down with an ATM signaling mechanism. This signaling is based on the ATM Forum User-Network Interface (UNI) specification V3.x, 4.0.
The WAN ports on the 2-port OC-12 ATM OSMs support the following features:
 |
Note For the OC-12 ATM OSM, the Common Part Convergence Sub-layer User-to-User (CPCS-UU) field in the AAL5 CPCS PDU cannot be set, cleared, or transported correctly. This affects custom use of the field as well as FRF8.1, which uses the CPCS-UU byte to transport the frame relay command response (C/R) bit. |
For QoS configuration information and examples for the WAN OSM ports, see the "Configuring Traffic Shaping" section.
For MPLS QoS configuration information and examples for the WAN OSM ports, see the "Configuring MPLS QoS" section.
For general information on how to configure Cisco IOS QoS, refer to these Cisco IOS publications:
Cisco IOS Quality of Service Solutions Configuration Guide at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_c/index.htm
Cisco IOS Quality of Service Solutions Command Reference at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/qos_r/index.htm
This section provides procedures for initial configuration of an OC-12 ATM OSM interface:
On power up, the interfaces on a new OC-12 ATM OSM are shut down. To enable an interface, you must enter the no shutdown command in configuration mode. When the OC-12 ATM interface is enabled with no additional configuration, the default interface configuration file parameters are used. These default parameters are listed in Table 8-1.
Table 8-1 OC-12c/STM-4c ATM Module Configuration Default Values
|
After you verify that the new OC-12 ATM module is installed correctly (the active LED goes on and all cables are correctly connected), you can use the configure command to configure the ATM interfaces.
A Catalyst 6000 family switch and Cisco 7600 series Internet Router identifies an interface address by its slot number and port number in the format slot/port. For example, the slot/port address of an interface on a 2-port OC-12 ATM OSM installed in slot 4 is 4/1.
Before using the configure command, you must enter the privileged level mode of the EXEC command interpreter by using the enable command. The system will prompt you for a password if one is set.
Use the following procedure to configure the 2-port OC-12 ATM OSMs. Press the Return key after each configuration step unless otherwise noted.
To configure the ATM interfaces, perform this task:
This example shows how to configure an OC-12 ATM OSM interface:
The default number of VPIs per ATM interface is 15. The maximum number of VCIs per VPI is 1023.
Table 8-2 shows the valid VCs per VP and maximum VPI configurations.
The ATM interfaces are configured by default to allow a maximum of 1023 VCs per VP. To change this value, perform this task beginning in global configuration mode:
|
This section provides basic information for configuring PVCs, bridged PVCs (RFC 1483), PVC traffic parameters, and SVCs. In addition, this section documents commands and configurations that are unique to the 2-port OC-12 ATM OSMs.
For all other Cisco IOS features and commands supported on the OC-12 ATM OSMs, refer to the "Configuring ATM" chapter in the Cisco IOS Wide-Area Networking Configuration Guide, Release 12.1 at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/wan_c/wcdatm.htm
For complete command syntax information, refer to the ATM chapter in the Cisco IOS Wide-Area Networking Command Reference, Release 12.1 at this URL:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121cgcr/wan_r/wratm/index.htm
To create a PVC on the ATM interface and enter interface-ATM-VC configuration mode, perform this task in interface configuration mode:
|
This example shows how to create a PVC:
RFC 1483 bridging as implemented on the OC-12 ATM OSMs supports point-to-point bridging of Layer 2 PDUs between the ATM interfaces on the OC-12 ATM OSMs and Ethernet ports.
Figure 8-1 shows a topology where two OC-12 ATM OSMs are used to forward Layer 2 PDUs through an ATM cloud. In this example, VLANs are forwarded over trunk links between the switches and ATM ports on modules installed in the routers. The traffic is then forwarded out through the ATM ports, configured for RFC 1483 on the OC-12 ATM OSMs, and through the ATM cloud.
RFC 1483 bridging for the OC-12 ATM OSM is supported on AAL5-MUX and AAL5-LLC Subnetwork Access Protocol (SNAP) encapsulated PVCs. RFC 1483 bridged PVCs must terminate on the ATM OSM, and the traffic forwarded over this bridged connection to the edge must be forwarded through an Ethernet port, as shown in Figure 8-1. Bridging between RFC 1483 bridged PVCs is not supported.
|
Note RFC 1483 bridging in a switched virtual circuit (SVC) environment is not supported. |
|
Note For Virtual Trunking Protocol (VTP) to work properly, ensure that each main interface has a subinterface configured for a VC bound to VLANs 1 and 1002-1005. |
To configure RFC 1483 bridging for PVCs, use the following commands beginning in global configuration mode:
|
|
1 When the dot1q keyword is specified, the 802.1Q header is transported across the ATM PVC. This allows CoS information to be preserved across the PVC. Without the dot1q keyword, the ingress side uses 0 as the CoS values when performing QoS. 2 When the dot1q-tunnel keyword is specified, 802.1Q tunneling is enabled, and service providers can use a single VLAN to support customers who have multiple VLANs, while preserving customer VLAN IDs and keeping traffic in different customer VLANs segregated. For more information on 802.1Q tunneling, see Configuring 802.1Q Tunneling 3 The lan-fcs keyword option applies only to the FlexWAN. |
In the following example, bridging is enabled on the main ATM interface on an OC-12 ATM OSM, one PVC with aal5snap encapsulation is bound to VLAN 666, and another PVC is bound to VLAN 777:
The following commands verify the interface configuration and status:
You can enable RFC 1483 Bridging on the main interface using the bridge-vlan command. In the following example, bridging is enabled on the main ATM interface—a PVC is configured on the main interface on an OC-12 ATM OSM with PVC 10/10 bound to VLAN 99 and PVC 10/11 bound to VLAN 100. The show interface atm command displays the interface configurations and status:
802.1Q tunneling enables service providers to use a single VLAN to support customers who have multiple VLANs, while preserving customer VLAN IDs and keeping traffic in different customer VLANs segregated. Dot1q tunneling and L2 protocol tunneling are configured only on the service provider router. The customer side is not aware of such configuration.
Figure 8-2 shows two customer premise equipment (CPE) devices (CPE 1 and CPE 2). Each CPE device has a PVC bound to VLAN 15, which is enabled using the following commands:
At the service provider (SP) side, the PVC is bound to VLAN 99 and the dot1q-tunnel keyword is specified. The main ATM interface also has the atm bridge-enable dot1q-tunnel command. With the dot1q-tunnel keyword, the spanning tree BPDU filter and L2 protocol tunneling are both enabled automatically. The following example shows this configuration:
In this example, the customer's vlan is tunneled by the service provider. Frames enter the SP domain with an explicit 802.1Q tag of 15. The frames are then forwarded with an SP VLAN tag of 99. In the service provider network, the network only sees the service provider VLAN. The original customer VLAN is recovered when it leaves the service provider network—VLAN 99 is stripped and the original frame is recovered as it leaves the dot1q-tunnel interface.
For complete information on 802.1Q tunneling on the Cisco 7600 Internet Router, see the
Cisco 7600 Series Cisco IOS Software Configuration Guide, 12.1E at the following URL:
http://www.cisco.com/univercd/cc/td/doc/product/core/cis7600/ios121_8/swcg/dot1qtnl.htm
You can enable 802.1Q tunneling using the bridge-vlan <vlan> dot1q-tunnel command:
The following example shows how to configure 802.1Q tunneling on the customer side:
|
Note To enable 802.1Q tunneling on the customer side, you must enter the dot1q keyword with the bridge-vlan command. |
The following example shows how to configure 802.1Q tunneling on the service provider side:
