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This chapter describes how to connect Asynchronous Transfer Mode (ATM) network modules for Cisco modular routers. It contains the following sections:
The ATM-25 network module (see Figure 12-1) provides ATM traffic shaping, for use with asymmetric digital subscriber line (ADSL) uplink speeds, and protocol support for permanent virtual circuit (PVC) environments. The network module provides full support for multiprotocol encapsulation over ATM Adaptive Layer 5 (RFC 1483), classic IP over ATM encapsulation (RFC 1577), and Point-to-Point Protocol (PPP) over ATM.
The ATM-25 port is a standard RJ-45 jack, color-coded light green. Use a straight-through modular RJ-45 UTP Category 3, 4, or 5 cable or STP Category 1, 1A, 9, or 9A cable to connect the port to an external ADSL modem. (See Figure 12-2.)
Figure 12-3 shows ATM-25 network module LEDs.
All network modules have an enable (EN) LED. The enable LED indicates that the module has passed its self-tests and is available to the router. The ATM-25 network module has the additional LEDs shown in Table 12-1.
| LED | Meaning |
|---|---|
RX | Module is receiving ATM traffic |
TX | Module is transmitting ATM traffic |
ATM T3 and E3 network modules provide T3 and E3 ATM connectivity for high-bandwidth data applications. (See Figure 12-4 and Figure 12-5.) They offer full support for multiprotocol encapsulation over ATM Adaptive Layer 5 (RFC 1483), classic IP over ATM encapsulation (RFC 1577), Point-to-Point Protocol (PPP) over ATM, and LAN Emulation (LANE). Up to 1,024 virtual circuits (VCs) are supported.
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Note The ATM T3 network module has a sensitive receiver. If you use a short T3 cable, it is possible to saturate the receiver, leading to bit errors. If this occurs, Cisco recommends one of the following: |
Use a coaxial cable to connect the module's BNC port to a T3 or E3 network.
ATM T3 and E3 network modules have the LEDs shown in Table 12-2.
| LED | Color | Meaning |
|---|---|---|
EN | Green | Module has passed its self-tests and is available to the router. |
RCLK | Green | Receive clock has been detected. |
FERF | Yellow | Far End Receive Failure. |
OOF | Yellow | Out Of Frame. |
AIS | Yellow | Alarm Indication Signal. |
This section describes the following 1-port ATM OC-3 (Optical Carrier level 3) network modules for Cisco 3600 series routers:
These modules provide full 155-Mbps ATM connectivity, including STS-3c and STM-1 framing, for high-bandwidth data applications and voice-data integration applications. Circuit emulation service allow the network module to carry voice traffic, such as telephone calls and faxes, over an ATM network simultaneously with data traffic.
If you are using the ATM OC-3/STM-1 Circuit Emulation Service network module, you need both the network module and a 1- or 2-port T1 or E1 multiflex trunk interface card (VWIC-1MFT-T1, VWIC-1MFT-E1, VWIC-2MFT-T1, VWIC-2MFT-E1, VWIC-2MFT-T1-DI, VWIC-2MFT-E1-DI) for a voice connection. You can install one multiflex trunk interface card (providing up to two voice ports) in the ATM OC-3/STM-1 Circuit Emulation Service network module. If a multiflex trunk interface card is not installed, the ATM OC-3/STM-1 Circuit Emulation Service network module will continue to perform data-routing functions.
To install a multiflex trunk interface card in a network module, see the Cisco WAN Interface Cards Hardware Installation Guide. To obtain this publication, see the "Obtaining Documentation" section.
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Note Online insertion and removal (OIR) is not supported on ATM OC-3/STM-1 Circuit Emulation Service network modules. |
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Note 1- or 2-port T1 or E1 multiflex trunk interface cards that support G.703 (VWIC-1MFT-G703, VWIC-2MFT-G703) are not supported in ATM OC-3/STM-1 Circuit Emulation Service network modules. |
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Note ATM OC-3 network modules are supported in Cisco 3600 series routers only. |
Cisco 3620 routers require a minimum PCMCIA controller revision level to recognize ATM OC-3 network modules; otherwise an error message appears. Cisco 3620 routers installed in the field before April 1999 contain a Revision C PCMCIA controller, which is not compatible with these modules. Starting in April 1999, all Cisco 3620 routers shipped from the factory include Revision E PCMCIA controllers, which are fully compatible with all three ATM OC-3 network modules.
You can identify the version of PCMCIA controller in your Cisco 3620 by entering the show pci hardware command in enable mode, or by examining the part number on the motherboard. Supported versions are shown in Table 12-3.
| Does Not Support ATM OC-3 | Supports ATM OC-3 | |
|---|---|---|
PCMCIA Controller | 0x22, 0xE2 | 0x20, 0xE0 |
Motherboard | 73-1850-10 and older | 73-1850-11 or newer |
The output of the show pci hardware command looks similar to this:
Router# show pci hardware
CLPD6729 registers:
(0x00) Chip Revision = 0x82
(0x1E) Misc Control 2 = 0x08
(0x1F) Chip Information = 0xE2
If you have incompatible hardware, contact the Cisco Systems Technical Assistance Center (TAC) at 800 553-24HR or 408 526-7209, or send e-mail to tac@cisco.com to request a free replacement Cisco 3620 router.
ATM OC-3 network modules use a small laser to generate the fiber-optic signal. Keep the transmit port covered whenever a cable is not connected to it.
The module faceplate carries a Class 1 laser warning label. (See Figure 12-12.)
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Warning Because invisible laser radiation may be emitted from the aperture of the port when no fiber cable is connected, avoid exposure to laser radiation and do not stare into open apertures. |
This section describes Synchronous Optical Network (SONET) specifications for fiber-optic transmissions, defines the power budget, and helps you estimate your power margin for multimode and single-mode transmissions. This section contains the following information:
The SONET specification for fiber-optic transmission defines two types of fiber, single-mode and multimode. Single-mode fiber allows only one bundle of light rays to propagate through the fiber, while multimode fiber allows multiple bundles entering at different angles. Because different bundles (referred to as modes) travel different distances, depending on the entry angle, they arrive at the destination at different times (modal dispersion). Single-mode fiber is therefore capable of higher bandwidth and greater cable run distances than multimode fiber.
Table 12-4 lists typical maximum distances for single-mode and multimode transmissions, as defined by SONET. Use the calculations described in this section to determine the actual maximum for your network. If the distance between two connected stations exceeds this limit, transmission can become unreliable.
| Transceiver Type | Maximum Distance between Stations |
|---|---|
MM | 1.5 mi (3 km) |
SMI | 9 mi (15 km) |
SML | 28 mi (45 km) |
Proper operation of an optical data link depends on modulated light reaching the receiver with enough power to be demodulated. The power budget (PB) is the difference between transmitter power (PT) and receiver sensitivity (PR). For instance, if transmitter power is -20 dB and receiver sensitivity is -30 dB, the power budget is 10 dB:
The SONET specification requires the signal to meet the worst-case requirements listed in Table 12-5.
| MM | SMI | SML | |
|---|---|---|---|
Transmitter power | -20 dBm | -15 dBm | -5 dBm |
Receiver sensitivity | -30 dBm | -31 dBm | -34 dBm |
Power budget | 10 dBm | 16 dBm | 29 dBm |
The difference between the power budget and the link loss (LL) is called the power margin (PM). If the power margin is zero or positive, the link should work. If it is negative, the signal may not arrive with enough power to operate the receiver.
Power loss over a fiber-optic link arises from the following causes:
The power lost over the data link is the sum of all these losses. Table 12-6 gives an estimate of the amount of loss attributable to each cause.
| Cause | Amount of Loss |
|---|---|
Fiber attenuation | 0.5 dB/km (SM, 1 dB/km (MM) |
Splice | 0.5 dB |
Connector | 0.5 dB |
Modal and chromatic dispersion | Depends on fiber and wavelength1 |
Higher-order mode losses | 0.5 dB |
Clock recovery | 1 dB |
| 1Dispersion is usually negligible for single-mode fiber. For multimode fiber, the product of bandwidth and distance should be less than 500 MHz-km. |
The following example calculates a multimode power margin based on these values:
The power margin is:
The positive result means this link should have enough power for transmission. The product of bandwidth and distance is 155 MHz x 3 km = 465 MHz-km; this is within the dispersion limit of 500 MHz-km.
Single-mode transmission is useful for longer distances, because there is a single transmission path within the fiber and modal dispersion does not occur.
The maximum receive power for SML is -10 dBm, and the maximum transmit power is 0 dBm. The SML receiver can therefore be overloaded when using short lengths of fiber. Overloading the receiver does not damage it, but can cause unreliable operation. To prevent overloading an SML receiver, insert a minimum 10-dB attenuator on the link between any SML transmitter and the receiver.
The SMI receiver cannot be overloaded by the SMI transmitter and does not require a minimum fiber cable length or loss.
The following example of a single-mode power margin assumes these values:
The positive value means this link should have enough power for transmission.
To connect an ATM OC-3 network module to the network, insert a fiber-optic cable with one duplex SC connector (see Figure 12-13) or two simplex SC connectors (see Figure 12-14) into the ATM interface, color-coded light green.
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Note The network modules are shipped with a dust plug to protect this interface. Pull to remove it. |
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Note Cisco Systems does not sell these fiber-optic cables, but they are available from many cable vendors. Cables should perform to the specifications listed in Table 12-7. |
| Standard | Maximum Path Length | Cabling |
|---|---|---|
ISO/IEC 9314-3 | 1.24 mi (2 km) all cables in a connection, end to end | 62.5-micron core with an optical loss of 0 to 9 dB, or 50-micron core with an optical loss of 7 dB |
IEC 793-2 | 27.9 mi (45 km) for SML and 9.3 mi (15 km) for SMI | 9-micron core |
ANSI/TIA/EIA-492 | 27.9 mi (45 km) for SML and 9.3 mi (15 km) for SMI | 9-micron core |
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Note A single fiber link should not mix 62.5- and 50-micron cable. |
Figure 12-15 and Figure 12-16 show ATM OC-3 network module LEDs. Table 12-8 describes their functions.
| LED | Color | Meaning |
|---|---|---|
EN | Green | Module has passed its self-tests and is available to the router. |
RCLK | Green | Receive clock has been detected. |
FERF | Yellow | Far End Receive Failure. |
OOF | Yellow | Out Of Frame. |
AIS | Yellow | Alarm Indication Signal. |
CES | Green | An active CES connection is established (ATM OC-3/STM-1 Circuit Emulation Service network module only). |
Posted: Mon Jul 3 17:32:20 PDT 2000
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