Table of Contents

Product Description

E1-G.703/G.704 Overview

Balanced and Unbalanced Modes
Framed and Unframed Operation
CRC4
Clock Source

E1-G.703/G.704 Port Adapters and Cables

Port Adapter and Cable Model Numbers

FSIP LEDs

Installation Prerequisites

Distance Limitations
Software Prerequisites
Cable Connections

Configuring the Interfaces

Configuring Framed and Unframed Mode
Configuring Timing (Clock) Signals
Configuring CRC-4
Alarms
Loopback

Reference Information

Command Descriptions and Examples
E1-G.703/G.704 Port Adapter and Cable Pinouts
Cisco Information Online

FSIP and SSIP, E1-G.703/G.704 Port Adapter Interface Installation and Configuration

Product Numbers: PA-7KF-E1/120, PA-7KF-E1/120=, PA-7KF-E1/75, and PA-7KF-E1/75=

This document provides descriptions, installation instructions, and configuration guidelines for the Fast Serial Interface Processor (FSIP) and Standard Serial Interface processor (SSIP) E1-G.703/G.704 port adapter interface. The E1-G.703/G.704 interface supports both framed (G.704) and unframed (G.703) modes of operation; the default is unframed operation.

The E1-G.703/G.704 interface is a 2.048 megabit per second (Mbps), E1 telecommunications interface; all the other available FSIP interfaces are synchronous serial data communications interfaces.

Many of the FSIP and SSIP features and functions are common to both types of interfaces; this document describes the E1-G.703/G.704 features that differ from those for the data communications interfaces. Use this document as a supplement to the information in the configuration note Fast Serial Interface Processor (FSIP) Installation and Configuration (Document Number 78-1047-03, or later, or Standard Serial Interface Processor (SSIP) Installation and Configuration (Document Number 78-2245-01, or later). Refer to the FSIP or SSIP configuration notes as your primary source of information, and refer to this supplement for specific E1-G.703/G.704 information where the cross-references appear. Use of the E1-G.703/G.704 port adapter in the Standard Serial Interface Processor (SSIP) is identical to that in the FSIP.

The information in this supplement includes an overview of G.703, instructions for installing and connecting an FSIP with E1-G.703/G.704 interfaces, and descriptions of the E1-G.703/G.704 interface configuration subcommands. For complete descriptions of the interface subcommands and the configuration options available for serial interfaces, refer to the related software documentation.

The sections in this document that correspond to sections in the Fast Serial Interface Processor (FSIP) Installation and Configuration publication include the following:

Caution If you are installing a new E1-G.703/G.704 interface in an installed system, ensure that your system configuration meets the minimum requirements for the new interfaces. Refer to the section "Software Prerequisites" for a description of these prerequisites.

Product Description

The E1-G.703/G.704 interface mounts on the FSIP and connects Cisco 7000 series and Cisco 7500 series routers with 2.048-Mbps leased-line services. The E1-G.703/G.704 interface supports both framed and unframed modes of operation, a loopback test, and a four-bit cyclic redundancy check (CRC). The interface can operate with either a line-recovered or an internal clock signal.

The E1-G.703/G.704 interface eliminates the need for a separate, external data termination unit to convert a standard serial interface (such as V.35) to a G.703/G.704/G.732 interface.

Two versions of the E1-G.703/G.704 interface are available: one supports balanced mode, and the other supports unbalanced mode.

The FSIP uses special serial port adapters and port adapter cables. A port adapter is a daughter card that provides the physical interface for two serial interface ports. Both ports on each port adapter use the same connector type: either a high-density, 60-pin universal port that supports all data communications interfaces (Electronics Industries Association/Telecommunications Industry Association (EIA/TIA)-232, EIA/TIA-449, V.35, X.21, and EIA-530), or a 15-pin port that supports the E1-G.703/G.704 telecommunications interface. Figure 1 shows the layout of the FSIP with port adapters installed. Figure 2 shows both the universal and E1-G.703/G.704 interface port adapters.

The FSIP can be configured to support up to eight E1-G.703/G.704 ports (four ports per module, two modules per FSIP). FSIP bandwidth can be allocated by the user, and the maximum aggregate bandwidth per four-port module is 16 Mbps, full duplex. We recommend that you leave one port on each module shut down to avoid exceeding this 16-Mbps maximum per module. Each of the four interfaces can operate up to 2.048 Mbps, which potentially presents a load greater than 16 Mbps, full duplex, if all four interfaces are configured. Eight E1-G.703/G.704 ports can be supported up to the 16-Mbps aggregate bandwidth capability; however, it is not possible to simultaneously support eight E1-G703/G.704 ports at 100-percent peak bandwidth utilization without exceeding the 16-Mbps maximum per module.

If you need to install or replace an E1-G.703/G.704 port adapter on your FSIP, refer to the section "Replacing Port Adapters"of the Fast Serial Interface Processor (FSIP) Installation and Configuration publication (Document Number 78-1047-03, or later) for instructions.

The following sections provide an overview of G.703 operation and describe the configuration options on the E1-G.703/G.704 interface.

E1-G.703/G.704 Overview

G.703 is an International Telecommunication Union Telecommunication Standardization Sector (ITU-T) electrical and mechanical specification for connections between telecommunications interfaces and data communications equipment (DTE).

Typically, G.703 provides a means of connecting standard serial interfaces such as V.35 to telephone lines or Postal Telephone and Telegraph (PTT) networks.

The E1-G.703/G.704 port adapter supports point-to-point connections to Cisco 7000 series and Cisco 7500 series routers from 2.048-Mbps, E1 leased-line services, and eliminates the need for a separate, external data termination unit that is typically used to convert standard serial interfaces, such as V.35, to E1-G.703/G.704.

Balanced and Unbalanced Modes

The E1-G.703/G.704 interface is available in either balanced or unbalanced mode. A unique port adapter supports each type. Neither the modes nor the cables are interchangeable; you cannot configure a balanced port to support an unbalanced line, nor can you attach an interface cable intended for a balanced port to an unbalanced port.

Balanced interfaces typically use three conductors and three signal states: high, low, and ground. The high and low signals mirror each other. Unbalanced interfaces use only two signals: signal and ground.

In addition to the agency approval label on each FSIP port, the show controller cbus command shows the mode of each interface. Following is an example:

Framed and Unframed Operation

The E-G.703 interface is divided into 32 time slots or frames. (See Figure 3.) Each of the 32 time slots is an 8-bit frame that transmits data at 64 kbps. Each of these time slots can be configured to carry data or to remain empty. (The E1-G.703/G.704 port adapter inserts an idle pattern into empty time slots.)

Time slot 0, or the first 8 bits, is reserved as overhead. The remaining 248 bits (31 frames with 8 bits each) are designated time slots 1 through 31. Time slot 16 is also designated as a framing slot when using framed mode. When you use unframed mode (G.703), the default, you can configure time slot 16 to carry data and operate as any of the other slots; therefore, in framed mode time slot 0 must be designated as a framing signal; time slot 16 can be configured for either data or framing.

Unframed mode uses all 32 time slots for data (data is also called payload). None of the 32 time slots are used for framing signals. This allows each of the 32 time slots to transmit at 64 kilobits per second (kbps). (For example, 32 time slots x 64 kbps = 2.048 Mbps.)

CRC4

Framed mode supports a four-bit CRC, which you enable with a software command. The default is for no CRC. Refer to the section "Configuring CRC-4".

Clock Source

The E1-G.703/G.704 interface does not operate in the DTE and data communications equipment (DCE) modes that are typical of data communications interfaces. The E1-G.703/G.704 interface operates with either a line-recovered or an internal clock signal. The default is for a line clock signal that the interface recovers from the received data stream. The interface can also operate with an internal clock signal. The E1-G.703/G.704 port adapter generates the internal clock signal; the interface does not use the FSIP clock. Because the E1-G.703/G.704 interfaces operate at a default clock rate of 2.048 Mbps (E1 speed), we recommend that you leave one port on each module shut down to avoid exceeding the 8 Mbps maximum for each module.

E1-G.703/G.704 Port Adapters and Cables

The FSIP is configured at the factory with from one to four E1-G.703/G.704 interface port adapters. Each port adapter provides two 15-pin, D-shell (DB-15) receptacles, which support only E1-G.703/G.704 interfaces. (See Figure 4.)

• Unbalanced (75 ohm) coaxial cables with BNC connectors at the network end (used primarily for connection in the United Kingdom); see Figure 5
  
  
• Balanced (120 ohm) with a DB-15 connector at the network end; see Figure 6
  
  
• Balanced (120 ohm) twinaxial split cable at the network end, with separate transmit and receive cables, each with a twinax connector; see Figure 7
  
  

In addition to these cables, some connections require bare-wire connections (directly to terminal posts).

Port Adapter and Cable Model Numbers

Table 1 lists the model numbers and descriptions of the E1-G.703/G.704 port adapters and cables.

FSIP LEDs

The E1-G.703/G.704 interfaces use the same FSIP LEDs as all the other FSIP serial interfaces. Table 2 shows the LED states (for both balanced and unbalanced ports).

Installation Prerequisites

In addition to the prerequisites described in the FSIP Installation and Configuration publication, ensure that your existing system components meet the compatibility requirements described in this section. Also, read the list of parts and tools you will need to perform the installation, and the safety and ESD-preventive guidelines for avoiding bodily injury or equipment damage.

Distance Limitations

Unbalanced G.703 interfaces allow for a longer maximum cable length than those specified for balanced circuits. Table 3 lists the maximum cable lengths for each FSIP E1-G.703/G.704 cable type by the connector used at the network (non-FSIP) end.

Software Prerequisites

Before installing an FSIP with E1-G.703/G.704 interfaces in your Cisco 7000 series or Cisco 7500 series router, ensure that your current system software is one of the following:

• Maintenance Release 9.17(10) or a later
  
  
• Cisco Internetwork Operating System (Cisco IOS) Release 10.2 or later (or a later maintenance release of Cisco IOS Release 10.2)
  
  

• The FSIP with E1-G.703/G.704 interfaces operates with any of the Cisco IOS releases running in the currently shipping Cisco 7500 series routers: Cisco 7505, Cisco 7507, and Cisco 7513.
  
  

Cable Connections

Figure 5, Figure 6, and Figure 7 show the unbalanced and balanced cables used for connection between the E1-G.703/G.704 port adapter and your network. The port-adapter end of each cable has a DB-15 connector.

Caution It is a requirement of the statutory approval of the E1-G.703/G.704 interface that the jackscrews of the connector backshell are securely screwed down while the FSIP is operating.

Configuring the Interfaces

This section describes the commands for configuring individual interfaces for framed or unframed mode, four-bit CRC, and loopback, and for specifying a clock source.

After you verify that the new FSIP is installed correctly (the enabled LED goes on), use the privileged-level configure command to configure the new interfaces.

Be prepared with the information you will need, such as the following:

• Timing source for each new interface (a line-derived or internal clock signal)
  
  
• Whether you will use framed or unframed mode on E1-G.703/G.704 interfaces
  
  

The following are the default settings for all E1-G.703/G.704 interfaces; each can be enabled or disabled with software commands:

• Unframed mode
  
  
• No CRC enabled
  
  
• Time slot 16 is not used for payload
  
  
• No loopback
  
  
• Clock source operation (line or internal)
  
  

Caution Always issue a clear interface command after altering the configuration of an interface, particularly after changing a time slot or CRC4 setting.

Configuring Framed and Unframed Mode

The E1-G.703/G.704 interfaces support both framed (G.704) and unframed (G.703) modes of operation; the default is unframed operation. To enable framed operation, you must specify the start and stop slots, separated by a hyphen, as follows:

Following is a sample display of the timeslot command with a start slot of 1 and a stop slot of 13:

Nonsensical combinations of start and stop slots will be ignored, and the interface will be left unchanged.

The system default is not to use time slot 16 for data. To use slot 16 for data, use the timeslot 16 command. To restore the system default, use the no timeslot 16 command.

Configuring Timing (Clock) Signals

The E1-G.703/G.704 port operates either with an external clock signal that it recovers from the received data stream (the default clocking) or its own internal clock signal. To specify the clock source, use the clock source {line | internal} command.

To change the default and use the internal clock, use the clock source internal command.

To return the interface to the default state, use the clock source line command. (You can also negate either of these commands to change a setting; for example, the no clock source internal command also returns the interface to the default state.) All E1-G.703/G.704 interfaces operate at a default clock rate of 2.048 Mbps; the clock rate cannot be configured.

Configuring CRC-4

CRC-4 is a 4-bit error checking technique that uses a calculated numeric value to perform an ongoing data integrity check and detect errors in transmitted data. (Refer to Fast Serial Interface Processor (FSIP) Installation and Configuration for a description of CRCs.) The E1-G.703/G.704 interface supports CRC in framed mode only. By default, CRC-4 is not enabled.

To enable CRC4 on the E1 interface, specify the slot and port address of the interface followed by the command crc4. press Ctrl-Z after altering the configuration and before exiting the configuration mode. In the example that follows, the top port on an FSIP in interface processor slot 3 is configured for CRC:

To disable CRC and return to the default of no CRC error checking, specify the slot and port address and use the no crc4 command. For complete command descriptions and instructions, refer to the Router Products Configuration Guide and Router Products Command Reference publications.

Alarms

Following are definitions and descriptions of the five alarms used with the E1-G.703/G.704 interface:

• AIS—The alarm indication signal occurs and a failure is declared (for E1 links) when 64 consecutive ones occur on the Receive Data (RD) line between the applique and the FSIP.
  
  
• RAI—The remote alarm indication (also called the far end alarm and distant alarm for E1 links) is sent by the remote end of the link to indicate failure at the remote end. This failure is declared (for E1 links) when 32 contiguous pulse positions have no pulses of either positive or negative polarity.
  
  
• LOS—The loss of signal alarm occurs and a failure is declared (for E1 links) when more than ten consecutive zeroes are detected.
  
  
• LOF—The loss of frame alarm occurs and a failure is declared (for E1 links) when an out-of-frame (OOF) defect has persisted for T seconds, where 2 ð T ð 10. This failure is cleared when there have been no OOF defects during a period T seconds, where 0 ð T ð 20.
  
  
• SQ—The signal quality alarm occurs and a failure is declared (for E1 links) when the bit error rate (BER) is greater than 10^-3 on the RD line between the applique and the FSIP.
  
  

Loopback

The E1-G.703/G.704 interface supports the same local loopback test as the other (data communications) FSIP interfaces. Loopback functions enable you to check the integrity of the physical data path between the FSIP and the E1 port adapter with the loopback command. The no loopback command disables all loopback tests on the interface.

Because the E1-G.703/G.704 interfaces uses a default clock rate of 2.048 Mbps, you do not have to configure a clock signal on the interface before performing a loopback test.

The loopback command tests the path between the FSIP and the interface port (without leaving the FSIP and port adapter). On the E1 port adapter, the loopback signal follows this path regardless of whether or not a cable is attached to the port. Figure 8 shows the path of the loopback function.

Reference Information

This reference section describes the show command that you can use to verify the current system status and configuration. It also lists cable pinouts for the port adapter cables.

Command Descriptions and Examples

The show controllers cxbus command displays the interface type on each FSIP port. The display for E1-G.703/G.704 interfaces indicates whether the interface is balanced or unbalanced.

In the following example of the show controllers cxbus command display, the interfaces on the first two ports (0 and 1) are balanced interfaces.

E1-G.703/G.704 Port Adapter and Cable Pinouts

Table 4 shows the signal pinouts for each type of E1-G.703/G.704 interface cable. All cables use a DB-15 connector at the FSIP end.

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Posted: Mon Oct 14 13:36:43 PDT 2002
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