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This chapter describes the OC3 POS line cards and contains the following sections:
The OC3 POS line card interface provides a direct connection between the Cisco 7304 router and external networks. You must use the appropriate optical fiber cables to connect the OC3 POS line card with an external OC-3 network. (See the "OC3 POS Line Card Optical Fiber Specifications" section and the "Cables and Connectors" section for more information on optical fiber cables.)
Six models of the OC3 POS line card are available:
The POS specification addresses the use of PPP encapsulation over SONET/Synchronous Digital Hierarchy (SDH) links. SONET is an American National Standards Institute (ANSI) standard (T1.1051988) for optical digital transmission at hierarchical rates from 51.840 Mbps (STS-1) to 2.488 Gbps (STS-48) and greater. SDH is the international standard for optical digital transmission at hierarchical rates from 155.520 Mbps (STM-1) to 2.488 Gbps (STM-16) and greater.
Because SONET/SDH is by definition a point-to-point circuit, PPP is well suited for use over these links. PPP was designed as a standard method of communicating over point-to-point links.
SONET is an octet-synchronous multiplex scheme that defines a family of standard rates and formats. The basic rate for POS is that of STS-3c/STM-1, which is 155.520 Mbps. The available information bandwidth is 149.760 Mbps, which is the STS-3c/STM-1 Synchronous Payload Envelope (SPE), the payload portion of the SONET frame into which the octet-oriented user data is mapped. (Octet boundaries are aligned with the SPE octet boundaries.) For the SPE with the OC3 POS line card, section, line, and path overhead are removed.
The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) defines a series of SDH transmission rates beginning at 155.520 Mbps as follows:
| SONET1 | SDH Equivalent |
|---|---|
| 1ANSI-defined SONET specifications.
2Currently supported by the OC3 POS line card. |
Despite the name, SONET is not limited to optical links. Electrical specifications have been defined for single-mode fiber, multimode fiber, and CATV 75-ohm coaxial cable. The OC3 POS line card 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 T3/E3 bit-synchronous signals.
The following transmission multiples are currently specified and commonly used:
The following references discuss concepts and specifications of POS and PPP:
The OC3 POS line card has the following features:
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Note For information on the single-mode and multimode cables to use with the OC3 POS line card, see the "OC3 POS Line Card Optical Fiber Specifications" section, and the "Cables and Connectors" section. |
The physical layer interface for the OC3 POS line card is Optical Carrier-3 (OC-3c, the specification for SONET STS-3c and SDH STM-1 transmission rates), and the OC3 POS line card is designed to comply with Packet-over-SONET specifications. The OC3 POS line card provides a single 155.520-Mbps Packet OC-3 network interface for all supported platforms.
Each OC3 POS line card has four MT-RJ small form factor type fiber receptacles to allow connection to single-mode or multimode optical fiber. (For more information on the optical fiber cables you should use with this line card, see the "OC3 POS Line Card Optical Fiber Specifications" section and the "Cables and Connectors" section.)
Packet data is transported using Point-to-Point Protocol (PPP) and is mapped into the STS-3c/STM-1 frame. The encapsulations used add approximately half the number of bytes of transport overhead as that involved with ATM using ATM Adaptation Layer 5 (AAL5) and line card control (LCC) Subnetwork Access Protocol (SNAP) encapsulations.
The OC3 POS line card interface is compliant with RFC 1619, PPP over SONET/SDH, and RFC 1662, PPP in HDLC-like Framing. The OC3 POS line card supports RFC 1619 PPP-over-SONET/SDH encapsulation, and provides support for SNMP agent v1 (RFC 1155-1157), and Management Information Base (MIB) II (RFC 1213).
The OC3 POS line card 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.
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, and multimode fiber allows multiple modes of light to propagate through the fiber.
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); therefore, single-mode fiber is capable of higher bandwidth and greater cable run distances than multimode fiber. Table 1-1 lists nominal OC-3 optical parameters for single-mode and multimode optical fiber transmission.
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Note If the distance between two connected stations is greater than the maximum distances listed, significant signal loss can result, making transmission unreliable. |
Table 1-1 lists the OC-3 optical parameters.
Table 1-1 OC-3 Optical Parameters
| Transceiver Type1 |
Transmit Power |
Maximum Power to Receiver2 |
Receiver Sensitivity | Loss Budgets |
Nominal Distance Between Stations |
|---|---|---|---|---|---|
-15 dBm min. |
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-20 dBm min. |
| 1This table gives nominal OC-3 optical parameters.
2This value represents the maximum power to which any receiver can be exposed. 3Complies with Bellcore GR-253-CORE Long Reach Specification (LR-1). 4Nominal wavelength is 1310 nm. 5Complies with Bellcore GR-253-CORE Intermediate Reach Specification (IR-1). 6Complies 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:
The OC3 POS line card faceplate has two LEDs that indicate line card status and two LEDs per port that indicate port status. (See Figure 1-7.)
After system initialization, the STATUS LED goes on to indicate that power is received and that the OC3 POS line card is enabled for operation.
The following conditions must all be met before the OC3 POS line card is enabled:
If any one of these conditions is not met, or if the initialization fails, the STATUS LED does not go on.
Table 1-2 lists LED colors and indications.
Table 1-2 OC3 POS Line Card LEDs
| LED Label | Color | State | Function |
|---|---|---|---|
Indicates that a valid SONET signal has been detected with no alarm conditions. |
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Indicates that a valid SONET signal has been detected but an alarm condition is present. See Table 1-3 for alarm definitions. |
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| 1This LED will be off if the port is in diagnostic loopback mode.
2When the Active/Loopback LED is in the Yellow state, the Carrier/Alarm LED is off. |
A yellow CARRIER/ALARM LED indicates the presence of an alarm condition. Table 1-3 lists the alarm conditions that might be present. Use the show controllers command to show the specific alarm condition.
| Alarm | Definition |
|---|---|
| Section | |
| Line | |
| Path | |
Use single-mode (for intermediate- or long-reach configurations) or multimode optical fiber cable to connect your router to a network or to connect two OC3 POS line card-equipped routers back to back.
The OC3 POS line card has one MT-RJ receptacle for each port (see Figure 1-9). For SONET/SDH single-mode and multimode optical fiber connections, use one MT-RJ-type cable (see Figure 1-8).
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Note For maximum cable lengths between stations, see Table 1-1. Single-mode and multimode optical fiber cables for the OC3 POS line card are not available from Cisco Systems; they are available from commercial cable vendors. |
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Note For important laser and LED safety information, see the "Laser and LED Safety" section 2-5. |
Attach one MT-RJ fiber cable between the line card and the device to which the line card is connected.
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Warning Invisible laser radiation can be emitted from the aperture of the port when no cable is connected. Avoid exposure to laser radiation and do not stare into open apertures. |
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Warning Class 1 laser product (single-mode). |
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Warning Class 1 LED product. |
The following encapsulation methods are supported by the OC3 POS line card:
We recommend that you refer to the Internet Draft Enabling Transparency for the PPP over SONET/SDH Mapping, which is recognized by the Internet Engineering Task Force (IETF) and Internet Engineering Steering Group (IESG) as an approved addendum to RFC 1619.
Statistical models more accurately determine the power budget than standard worst-case methods. Determining the link loss with statistical methods requires accurate knowledge of variations in the data link components. Statistical power budget analysis is beyond the scope of this document. For further information, refer to ITU-T standards and your equipment specifications.
The following publications contain information on determining attenuation and power budget:
The following section describes the slot locations on the Cisco 7304 router. This section includes the following subsection:
The OC3 POS line card can be installed in slots 2 through 5 in the Cisco 7304 router. Figure 1-10 shows a Cisco 7304 with OC3 POS line cards installed in slot 3, and slot 4.
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Note Slot 0 and slot 1 are for the network services engine (NSE) only. |
This section describes how to identify the interface address for the OC3 POS line card in a Cisco 7304 router. Interface addresses specify the actual physical location of each interface on a router.
The interfaces on the OC3 POS line card installed in a Cisco 7304 router maintain the same interface address regardless of whether other line cards are installed or removed. However, when you move a line card to a different slot, the first number in the interface address changes to reflect the new slot number.
Table 1-4 explains how to identify interface addresses.
Table 1-4 Identifying Interface Addresses
| Platform | Interface Address Format | Numbers | Syntax |
|---|---|---|---|
| 1Slot 0 and slot 1 are reserved for the network services engine (NSE). |
This section describes how to identify the interface addresses used for the OC3 POS line card in a Cisco 7304 router. The interface address is composed of a two-part number in the format slot-number/interface-port-number. See Table 1-4 for the interface address format.
In a Cisco 7304 router, slots are numbered, beginning with slot 0 (a dual-width slot reserved for the NSE-100) on the bottom, and continuing from the lower left to the upper right through slot 5.
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Note Slot 0 and slot 1 are for the network services engine (NSE) only. |
The interface address of the first interface on an OC3 POS line card in slot 2 is 2/0 (slot 2 and interface 0). If the OC3 POS line card was in slot 4, this same interface would be numbered 4/0 (slot 4 and interface 0).
Posted: Sun Feb 2 21:28:17 PST 2003
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