Table Of Contents
This chapter describes the SM-1-STM1 service modules (SM) and contains the following sections:
Service Module Overview
The SM-1-STM1-SM-C, shown in Figure 1-1, is a single-mode, high-speed, single-port multichannel STM-1 service module. SM-1-STM1-MM-C, shown in Figure 1-2, is a is a multi-mode, high-speed, single-port multichannel STM-1 service module. You can configure the SM-1-STM1 as a multichannel E1 STM-1 port, which can be configured into 63 individual E1 links. Each E1 link can carry a single channel at full or fractional rates, or it can be broken down into multiple DS0 rates.
The following restrictions exist:
•The maximum number of channels is limited to 226 per SM-1-STM1.
•This Cisco IOS software (Cisco IOS version 15.1(2)T) does not support more than two SM-1-STM1 SMs in the 3900 series ISRs.
•For OIR support, the STM-1 controller needs to be in a shutdown state before hot-swapping the module.
•Loopback support on the SONET controller is used for diagnostics only with no functional impact to the loopback feature. The following behavior is noted: Link is flapped on the peer interface when the SONET controller is set to loopback [local | network]. Using the shutdown/no shutdown command will overcome the link flap. Refer to "Shutting Down an Interface" section on page 4-2 for details on using the shutdown/no shutdown command.
•The maximum number of FIFO buffers is 2048. The FIFO buffers are shared among the interfaces; how they are shared is determined by speed. If all the FIFO buffers have been assigned to existing interfaces, a new interface cannot be created, and the "%Insufficient FIFOs to create channel group" error message is seen. FIFO allocation information is provided in Table 1-1, and examples of supported and unsupported configurations are provided in Table 1-2 and Table 1-3.
Table 1-1 FIFO Allocation
Number of Timeslots Number of FIFO Buffers
Following are three examples of supported and unsupported configurations.
Table 1-2 Supported Configurations
Supported Configurations Total FIFO Buffers
63 E1s -> x 32 FIFOs =
226 DSOs -> 226 x 3 FIFOs =
62 E1s + 21 DSOs -> (62 x 32) + (21 x 3) =
Table 1-3 Unsupported Configurations
Unsupported Configurations Result
228 DS0s ->
226 interface limit is exceeded
62 E1s with 31 DSOs -> (62 x 32) + (31 x 3) =
2077 FIFOs (exceeds 2048 FIFO limit)
The SM-1-STM1 supports up to three TUG-3/AU-3 transport slots numbered 1 to 3.
Figure 1-1 SM-1-STM1-SM-C—Faceplate View
Figure 1-2 SM-1-STM1-MM-C—Faceplate View
Figure 1-3 SM-1-STM1 Elements
Captive installation screw
Service module product name
Transmit out port
Laser warning label
Receive in port
Rx Carrier LED
Product ID card
Synchronous Digital Hierarchy (SDH) is the international standard for optical digital transmission at hierarchical rates from 155.520 Mbps (STM-1) to 2.5 Gbps (STM-16) and greater.
The International Telecommunications Union Telecommunication Sector (ITU-T) defines a series of SDH transmission rates beginning at 155.520 Mbps as follows:
Table 1-4 SDH Transmission Rates
SDH Transmission Rate
The SM-1-STM1 currently allows transmission over single-mode and multimode optical fiber only. Transmission rates are integral multiples of 51.840 Mbps, which can be used to carry E3 bit-synchronous signals.
Warning No user-serviceable parts inside. Do not open. Statement 1073
Warning Installation of the equipment must comply with local and national electrical codes. Statement 1074
Warning Use of controls, adjustments, or performing procedures other than those specified may result in hazardous radiation exposure. Statement 1057
SM-1-STM1 Multiplexing Hierarchy
Figure 1-4 illustrates the SDH multiplexing structure supported on the SM-1-STM1. The SM-1-STM1 multiplexing structure is a subset of that defined in ITU-T G.707. At the lowest level, containers (Cs) are input into virtual containers (VCs) with stuffing bits to create a uniform VC payload with a common bit-rate, ready for synchronous multiplexing. Then, the VCs are aligned into tributary units (TUs) where pointer processing operations are implemented, allowing the TUs to be multiplexed into TU groups (TUGs). Three TU-12s can be multiplexed into one TUG-2.
Figure 1-4 SM-1-STM1 Multiplexing Structure
The TUGs are then multiplexed into higher level VCs, which in turn are multiplexed into administration units (AUs). The AUs are then multiplexed into an AU group (AUG) and the final payload from the AUG is then multiplexed into the Synchronous Transport Module (STM).
The following is a list of features provided with the SM-1-STM1 service module:
•One channelized STM-1 port
•Channelized E1, fractional E1, and full-rate E1 supported
•Up to 226 usable channels allocated among the 63 E1 ports
•Internal or network clocking selectable on each E1
•64 kbps DS0 time slots
•Line and payload loopback capabilities—local and network at the E1 and STM-1 level
•Full bit-error-rate testing capabilities on any E1
•Programmable pseudo-random pattern up to 32 bits in length, including 2 11-1; 2 15-1; and 2 20-1, 0153, and QRSS
•32-bit error count and bit-count registers
•Detect test patterns conform to ITU-T 0.151 and 0.152 standards
•Online insertion and removal (OIR)
•Support for the following serial encapsulation protocols:
•IP protocol support
•16-bit or 32-bit CRC4 supported
•SDH / E1 functionality offered on the SM-1-STM1
Note SDH/E1 functionality may not be fully supported on the 3900 series ISRs.
SM-1-STM1 Optical Fiber Specifications
The SM-1-STM1 specification for optical fiber transmission defines two types of fiber: single-mode and multimode. Within the single-mode category, two types of transmission are defined: intermediate reach and long reach. Within the multimode category, only short reach is available. (See Table 1-5 for specifications.)
Modes can be thought of as bundles of light rays entering the fiber at a particular angle. Single-mode fiber allows only one mode of light to propagate through the fiber at one wavelength and polarization, and multimode fiber allows multiple modes of light to propagate through the fiber for each wavelength and polarization.
Multiple modes of light propagating through the fiber travel different distances depending on the entry angles, which causes them to arrive at the destination at different times (a phenomenon called modal dispersion). Model dispersion limits propagation distance in multimode fiber before attenuation does. Therefore, single-mode fiber is capable of higher bandwidth and greater cable run distances than multimode fiber is. Table 1-5 lists nominal OC-3 optical parameters for single-mode and multimode optical fiber transmission.
Note If the distance between two connected stations is greater than the maximum distances listed, significant signal loss can result, making transmission unreliable.
Table 1-5 OC-3 Optical Parameters
Receiver Sensitivity Loss
Single-mode3 intermediate reach
-15 dBm min.
to -8 dBm max.
at 1280-1335 nm
0 to 12 dB
Up to 9 mi (15 km)
-20 dBm min.
to -14 dBm max.
at 1280-1335 nm
0 to 7 dB
Up to 1.2 mi (2 km)
1 This table gives nominal OC-3 optical parameters.
2 This value represents the maximum power to which any receiver can be exposed.
3 Complies with ITU-T G.957 standard S.1-1 specification.
4 Complies with Short-Reach OC-3 Specification SR-OC-3.
To calculate link losses and dispersion losses for your application, refer to the following specifications and documents:
•EIA/TIA-IVa Dispersion Unshifted Single-Mode Fiber
•EIA-TIA-IVb Dispersion Shifted Single-Mode Fiber
•GR-20-CORE Generic Requirements for Optical Fiber and Fiber-Optic Cable
•ITU-T Recommendation G.957 Optical Interfaces for Equipment and Systems Relating to the Synchronous Digital Hierarchy
LEDs and Ports
Figure 1-5 shows the LEDs and Tx and Rx ports for the SM-1-STM1.
The green- or yellow-colored LEDs indicate service module status.
Figure 1-5 SM-1-STM1 LEDs
After system initialization, the ENABLED LED goes on to indicate that the SM has been enabled for operation.
The following conditions must be met before the SM-1-STM1 is enabled:
•The SM-1-STM1 is correctly connected and is receiving power.
•A valid system software image for the SM has been downloaded successfully.
•The system recognizes the SM-1-STM1.
If any of the above conditions are not met, or if the initialization fails for other reasons, the ENABLED LED does not go on.
Table 1-6 lists LED colors and indications.
Table 1-6 SM-1-STM1 LEDs
LED Label Color State Meaning
Service module is enabled for operation.
Indicates the SM-1-STM1 is receiving a good SDH signal.
1 LOS = loss of signal
2 LOF = loss of frame
Cables, Connectors, and Pinouts
Use a single-mode or multimode optical fiber interface cable to connect your router or switch to another router or switch. In general, multimode cables are gray or orange, and single-mode cables are yellow.
Note These cables are not available from Cisco Systems.
Figure 1-6 Duplex SC Cable Connector
Figure 1-7 Simplex SC Cable Connector
Attach either one duplex optical fiber cable or two simplex optical fiber cables between the service module and the device to which the service module is connected. Observe the receive (RX) and transmit (TX) cable relationship shown in Figure 1-8.
Figure 1-8 Attaching Simplex or Duplex Optical Fiber Cables
The following warnings apply when you work with optical fiber cable ports.
Warning Invisible laser radiation may be emitted from the end of the unterminated fiber cable or connector. Do not view directly with optical instruments. Viewing the laser output with certain optical instruments (for example, eye loupes, magnifiers, and microscopes) within a distance of 100 mm may pose an eye hazard. Statement 1056
Warning Class 1 Laser Product. Statement 1008
Warning Class 1 LED Product. Statement 1027
To locate MIBs and system messages associated with the SM-1-STM1 service module, see the following sites:
•The Error Message Decoder website allows you to determine the explanation and recommended action for an existing Cisco syslog message. You must be a registered Cisco.com user to access this document. To visit the Error Message Decoder website, go to this URL:
•You can find information about MIBs and OIDs at the Cisco IOS MIB Locator and SNMP Object Identifier website. The MIB Locator finds MIBs in Cisco IOS software releases. The SNMP Object Navigator translates OID's into SNMP names. To visit the Cisco IOS MIB Locator and SNMP Object Identifier website, go to this URL:
Service Module Slot Locations on the Cisco 3900 Series Integrated Services Routers
This section discusses service module slot locations on the supported platforms. The illustrations that follow summarize slot location conventions on each platform.
Cisco 3900 Series Routers Slot Numbering
See Overview of Cisco Network Modules and Service Modules for Cisco Access Routers general information and single- and double-wide slot numbering.
Figure 1-9 Cisco 3900 Series Router with Service Module Installed
Cisco 3945 series routers have four slots for service modules. You can place the service modules in any of the four slots.
Identifying Interface Addresses
This section describes how to identify interface addresses for the SM-1-STM1. Interface addresses specify the actual physical location of each interface on the router.
Interfaces on a SM-1-STM1 installed in a router maintain the same address regardless of whether other service modules are installed or removed. However, when you move a service module to a different slot, the first number in the interface address changes to reflect the new service module slot number.
Note Interface ports on the Cisco 3945 series routers are numbered from bottom right to top left starting with 1.
Table 1-7 summarizes the interface address formats for the supported platforms.