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This chapter provides information about the Packet OC-3c Interface Processor (POSIP-OC3-20, POSIP-OC3-40, and POSIP-OC3-50), which for convenience is referred to in this chapter as POSIP, with specific differences clearly noted.
The following information is included:
The following are common Packet-over-SONET terms and acronyms for your reference:
The Packet-Over-SONET specification is primarily concerned with the use of the PPP encapsulation over SONET/SDH links. Since SONET/SDH is by definition a point-to-point circuit, PPP is well suited for use over these links. Point-to-Point Protocol (PPP) was designed as a standard method of communicating over point- to-point links.
The Synchronous Optical Network (SONET) is an octet-synchronous multiplex scheme that defines a family of standard rates and formats. The basic rate for Packet-Over-SONET 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 SPE with section, line, and path overhead removed.
The ITU-T defines a series of SDH transmission rates beginning at 155.520 Mbps, as follows:
| SONET1 | SDH equivalent |
|---|---|
| STS-3c1 | STM-12 |
| STS-12c | STM-4c |
| STS-48c | STM-16c |
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; however, the POSIP currently allows only transmission over single-mode and multimode optical fiber, and transmission rates are integral multiples of 51.840 megabits per second (Mbps), which can be used to carry T3/E3 bit-synchronous signals.
The following transmission multiples are currently specified and commonly used:
The Packet OC-3c Interface Processor (POSIP) (see Figure 11-1, Figure 11-2, and Figure 11-3) provides a single 155.520-Mbps, OC-3c network interface, which provides a direct connection between the high-speed Cisco Extended Bus (CxBus or CyBus) and your external networks. The physical layer interface on the POSIP is OC-3c.
 | Caution The POSIP is made up of two main parts: a dual-width port adapter and a motherboard. To prevent problems with the POSIP and with the system in which the POSIP is installed, do not attempt to separate the port adapter from its motherboard or to install other single- or dual-width port adapters on the POSIP motherboard. The entire POSIP assembly is a field replaceable unit (FRU). |
The POSIP-OC3-20 and POSIP-OC3-40 come configured with 16 MB and 32 MB of dynamic random-access memory (DRAM), respectively, and 1 or 2 MB of static random-access memory (SRAM), respectively, as factory default memory configurations. The DRAM and SRAM on the POSIP-OC3-20 models can be upgraded as your system configuration requires. (For DRAM and SRAM upgrade procedures, refer to the configuration note that ships with your upgrade kit.)
The POSIP-OC3-50 comes configured with 32 to 128 MB of synchronous dynamic random-access memory (SDRAM), and 4 to 8 MB of static random-access memory (SRAM). The SDRAM and SRAM on the POSIP-OC3-50 model can be upgraded as your system configuration requires. (For SDRAM and SRAM upgrade procedures, refer to the configuration note that ships with your upgrade kit.)
| Caution Traffic from multiple POSIP network interfaces could theoretically exceed the bandwidth of the CxBus or CyBus. This would cause packets to be dropped; therefore, a practical limit for the CxBus in Cisco 7000 series chassis is two POSIPs, and for the CyBus in Cisco 7500 series chassis, the practical limit is four POSIPs. |
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 of 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 OC-3c interface is compliant with RFC 1619, "PPP over SONET/SDH," and RFC 1662, "PPP in HDLC-like Framing." The POSIP supports RFC 1619 Point-to-Point Protocol over SONET/SDH encapsulation, and provides support for SNMP agent v1 (RFC 1155-1157), and MIB II (RFC 1213).
The following additional SDRAM and SRAM upgrade products are available only for the POSIP-OC3-50:
You can use any combination of available SDRAM and SRAM configurations on the POSIP-OC3-50.
The show version command displays the current hardware configuration of the router, including the system processor type. The show controller cbus command lists all interfaces and includes the currently loaded and running microcode version for each.
For specific software features and commands available for the POSIPs and the Cisco IOS release in which they are supported, refer to the Cisco IOS release note specific to your Cisco IOS release. Use the show version command to display the current system software version.
Use Table 11-1 to determine CRC and SONET payload scrambling compatibility for the dual-width POS port adapter currently installed in your system. While the POSIP-OC3-50 supports CRC-32 and CRC-16, you can only use CRC-16 if you have a dual-width POS port adapter that is Hardware Version 1.5, 1.30, or 1.31.
| CRC-16 | CRC-32 | SONET Payload Scrambling | Hardware Version Required |
|---|---|---|---|
| Yes | Yes | No | Version 1.4, Version 1.14 (decimal) Version 1.4, Version 1.E (hexadecimal) |
| Yes | No | Yes | Version 1.5, Version 1.30, Version 1.31 (decimal) Version 1.5, Version 1.1E, Version 1.1F (hexadecimal) |
| - | - | - | Version 1.0 to Version 1.3 (beta hardware) |
The POSIP interface is full duplex. You must use the appropriate optical-fiber interface cable(s) to connect the POSIP with an external network. (Refer to the section "POSIP Interface Cables," on page 11-17, for descriptions of connectors and optical-fiber cables.) The POSIP provides an interface to switching fabrics for transmitting and receiving data at rates of up to 155.520 Mbps bidirectionally.
The POSIP connects to the following physical layers:
The Packet-Over-SONET specification for optical-fiber transmission defines two types of fiber: single-mode and multimode. 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, while multimode fiber allows multiple modes of light to propagate through the fiber.
Table 11-2 lists typical maximum distances for single-mode and multimode transmission.
| Transceiver Type | Power Budget | Transmit Power | Receive Power | Maximum Distance between Stations1 |
|---|---|---|---|---|
| Single-mode2 | 16 dB | -15 to -8 dBm, at 1270-1380 nm3 | -31 to -8 dBm | Up to 9 miles (15 kilometers) |
| Multimode2 | 11.5 dB | -18.5 to -14 dBm, at 1270-1380 nm | -30 to -14 dBm | Up to 1.5 miles (3 kilometers) |
The following variables reduce the power of the signal (light) transmitted to the receiver in multimode transmission:
Attenuation is significantly lower for optical fiber than for other media. For multimode transmission, chromatic and modal dispersion reduce the available power of the system by the combined dispersion penalty (dB). The power lost over the data link is the sum of the component, dispersion, and modal losses.
Table 11-3 lists the factors of attenuation and dispersion limits for typical optical-fiber cable.
| Limits | Single Mode | Multimode |
|---|---|---|
| Attenuation | 0.5 dB | 1.0 dB/km |
| Dispersion | No limit | 500 MHz(km)1 |
The LED used for a multimode transmission light source creates multiple propagation paths of light, each with a different path length and time requirement to cross the optical fiber, causing signal dispersion (smear). Higher order mode loss (HOL) results from light from the LED entering the fiber and being radiated into the fiber cladding. A worst case estimate of power margin (PM) for multimode transmissions assumes minimum transmitter power (PT), maximum link loss (LL), and minimum receiver sensitivity (PR). The worst case analysis provides a margin of error, although not all of the parts of an actual system will operate at the worst case levels.
The signal must meet the worst case optical power parameters listed in Table 11-4.
| Power Parameters | Single-Mode | Multimode |
|---|---|---|
| PT | -15 dBm | -18.5 dBm |
| PR | -31 dBm | -30 dBm |
| PM | 16 dB | 11.5 dB |
The power budget (PB) is the maximum possible amount of power transmitted. The following equation shows the calculation of the power budget for multimode, worst case:
The power margin (PM) calculation is derived from the power budget minus the link loss (LL), as follows:
If the power margin is positive, as a rule, the link will work.
Table 11-5 lists the factors that contribute to link loss and the estimate of the link loss value attributable to those factors.
| Link Loss Factor | Estimate of Link Loss Value |
|---|---|
| Higher order mode losses | 0.5 dB |
| Clock recovery module | 1 dB |
| Modal and chromatic dispersion | Dependent on fiber and wavelength used |
| Connector | 0.5 dB |
| Splice | 0.5 dB |
| Fiber attenuation | 1 dB/km |
After calculating the power budget minus the data link loss, the result should be greater than zero; this is the power margin. Results less than zero may have insufficient power to operate the receiver.
The following is an example of a multimode power margin (PM) calculation based on the following variables:
Estimate the power margin as follows:
The positive value 3.5 dB indicates that this link would have sufficient power for transmission.
The single-mode signal source is an injection laser diode. The multimode signal source is a light-emitting diode (LED). Single-mode transmission is useful for longer distances because there is a single transmission path within the fiber, and dispersion does not occur. In addition, chromatic dispersion is also reduced because laser light is essentially monochromatic.
Power specifications for single-mode transmission follow:
Power specifications for multimode transmission follow:
You can calculate the single-mode power budget using the equation PB = PM - LL. The following example of a single-mode power budget is based on two buildings, 11 kilometers apart (with a loss of .05 dB/km), connected through a patch panel in an intervening building with a total of 12 connectors (each with a loss of 0.5 dB). Use the single-mode power margin (PM) value of 16db from Table 11-4.
Estimate the single-mode power budget as follows:
The value of 5.5 dB indicates that this link would have sufficient power for transmission and is not in excess of the maximum receiver input power.
Statistical models more accurately determine the power budget than the worst case method. 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 references discuss concepts and specifications of Packet-Over-SONET and PPP:
For SONET/SDH single-mode and multimode optical-fiber connections, use one duplex SC-type cable (see Figure 11-4) or two simplex SC-type cables (see Figure 11-5).
Attach either two simplex fiber cables or one duplex fiber cable between the POSIP interface port and your network. (See Figure 11-6 for the POSIP orientation applicable to your chassis type.)
Ensure that you observe the receive (RX) and transmit (TX) cable relationship shown in Figure 11-6.
 | Warning Invisible laser radiation may be emitted from the aperture ports of the single-mode products when no fiber cable is connected. Avoid exposure and do not stare into open apertures. |
| Warning Class 1 laser product. |
The POSIP has three LEDs on it faceplate that indicate status. (See Figure 11-7.)
The enabled LED on the POSIP and on all interface processors should go on. The console screen will also display a message as the system discovers each interface during its reinitialization. After system initialization, the enabled LED goes on to indicate that the POSIP is enabled for operation.
The following conditions must all be met before the POSIP is enabled:
If any one of these conditions is not met, or if the initialization fails, the enabled LED does not go on.
The two status LEDs indicate the following:
Verify that the POSIP is connected correctly as follows:
Step 1 While the system reinitializes each interface, observe the console display messages and verify that the system discovers the POSIP. The system should recognize the POSIP interface but leave it configured as down.
Step 2 When the reinitialization is complete, verify that the enabled LED on the POSIP is on and remains on. If the LED does stay on, proceed to Step 5. If the enabled LED does not stay on, proceed to the next step.
Step 3 If the enabled LED on the POSIP fails to go on, suspect that the POSIP board connector is not fully seated in the backplane. Loosen the captive installation screws, then firmly push the top ejector down while pushing the bottom ejector up until both are parallel to the POSIP faceplate. Tighten the captive installation screws. After the system reinitializes the interfaces, the enabled LED on the POSIP should go on. If the enabled LED goes on, proceed to Step 5. If the enabled LED does not go on, proceed to the next step.
Step 4 If the enabled LED still fails to go on, remove the POSIP and try installing it in another available interface processor slot.
Step 5 Use the show interfaces or show controllers cbus command to verify the status of the POSIP interface. (If the POSIP interface is not configured, you must configure it using the procedures in the section "Configuring the POSIP.")
This section describes the procedures required to configure the OC-3c interface on a POSIP. If you want to change the configuration of an interface, you must enter configuration mode to configure it. After you boot the system (and all cables are correctly connected and the enabled LED goes on), you can use the configure command to configure the new OC-3c interface.
Be prepared with the information you will need, such as the interface IP address, MTU size, framing mode, loopback modes (if testing is required), and clocking. On power up, the interface on a new POSIP is shut down. To enable the interface, you must enter the no shutdown command in configuration mode.
When the POSIP is enabled (taken out of shutdown) with no additional arguments, the default interface configuration file parameters are as listed in Table 11-6.
| Parameter | Configuration Commands | Default Value |
|---|---|---|
| MTU | mtu bytes (no mtu bytes) | 4470 bytes |
| Framing | pos framing-sdh (no posip framing-sdh) | SONET framing |
| Loopback internal | loop internal (no loop internal) | No internal loopback |
| Loopback line | loop line (no loop line) | No line loopback |
| Transmit clocking | pos internal-clock | Loop timing |
| SONET payload scrambling | pos scramble-atm | No scrambling |
With the loop internal command, packets from the router are looped back in the framer. Outgoing data gets looped back to the receiver without actually being transmitted. With the loop line command, the receive (RX) fiber is logically connected to the transmit (TX) fiber so that packets from the remote router are looped back to it. Incoming data gets looped around and retransmitted without actually being received.
For additional descriptions of configuration subcommands and the configuration options available for Packet-Over-SONET, refer to the appropriate router system software configuration publications listed in the section "If You Need More Information," in the chapter "Using the Interface Processors."
Configuring the POSIP first requires privileged-level access to the EXEC command interpreter. (Refer to the section "Using the EXEC Command Interpreter" in the chapter "Using Interface Processors.") Also, privileged-level access usually requires a password. (Contact your system administrator, if necessary, to obtain privileged-level access.)
The Cisco 7000 series and 7500 series routers identify an interface address by its interface processor slot number, port adapter number, and interface port number, in the format slot/port-adapter/port. Each POSIP contains a single (dual-width) port adapter and a single OC-3c interface; therefore, the port adapter number and interface port number are always 0/0. For example, the slot/port-adapter/port address of an OC-3c interface on a POSIP installed in interface processor slot 0 would be 0/0/0; if installed in interface processor slot 1, the address changes to 1/0/0.
The system will prompt you for a password if one is set. Press the Return key after each configuration step unless otherwise noted.
Step 1 At the privileged-mode prompt, enter configuration mode and specify that the console terminal will be the source of the configuration subcommands as follows:
configure terminal
Step 2 At the prompt, specify the new interface to configure by entering the interface pos slot/port-adapter/port command:
interface pos 0/0/0
Step 3 Determine the configure commands available for the POSIP's interface by entering pos ? at the Interface mode prompt, as follows:
pos ?
Use the preceding configuration commands according to your specific requirements and based on their functions as described in the section "Customizing the POSIP Configuration," on page 11-25, and in the appropriate software configuration publications.
Step 4 Determine the loopback commands available by entering loop ? at the Interface mode prompt, as follows:
loop ?
Use the preceding configuration commands according to your specific requirements and based on their functions as described in the section "Customizing the POSIP Configuration," on page 11-25, and in the appropriate software configuration publications.
Step 5 If IP routing is enabled on the system, you can assign an IP address and subnet mask to the interface with the ip address configuration subcommand, as in the following example:
ip address 1.1.1.3 255.255.255.0
Step 6 Change the shutdown state to up and enable the interface as follows:
no shutdown
The no shutdown command passes an enable command to the POSIP. It also causes the POSIP to configure itself based on the previous configuration commands sent.
Step 7 Add any additional configuration subcommands required to enable routing protocols and adjust the interface characteristics.
Step 8 When you have included all of the configuration subcommands to complete the configuration, enter Ctrl-Z (hold down the Control key while you press Z) to exit configuration mode.
Step 9 Write the new configuration to memory as follows:
copy running-config startup-config
The system will display an OK message when the configuration has been stored.
For an explanation of show commands that allow you to check the interface configuration, refer to the section "Using show Commands to Check the Configuration" on page 11-29. For additional configuration options, proceed to the following section.
Router(config)#interface posx/y/z
where x is the slot number and differs by the Cisco router in which the POSIP is installed, y is the port adapter slot (always 0), and z is the interface (always 0).
To set the maximum transmission unit (MTU) size, use the mtu byte command as follows:
Router(config-if)#mtubytes
where bytes is in the range of 64 through 4,470 bytes; the default is 4,470 bytes. (4,470 bytes exactly matches the MTU of FDDI and HSSI interfaces for autonomous switching.)
Use the no mtu command to restore the default of 4,470 bytes:
Router(config-if)# no mtu
The default framing setting is SONET STS-3c. To configure for SDH STM-1, use the pos framing-sdh command as follows:
Router(config-if)# pos framing-sdh
To change back to SONET STS-3c, use the no pos framing-sdh command.
To configure an interface for internal loopback, use the loop internal command as follows:
Router(config-if)# loop internal
Local loopback is useful for checking that the POSIP is working. Packets from the router are looped back in the framer.
Use the no loop internal command to disable internal loopback:
Router(config-if)# no loop internal
To configure an interface for line loopback, use the loop line command as follows:
Router(config-if)# loop line
The receive fiber (RX) is logically connected to the transmit fiber (TX) so that packets from the remote router are looped back to it.
Use the no loop line command to disable line loopback:
Router(config-if)# no loop line
Router(config-if)# pos internal-clock
Use the no pos internal-clock command to restore loop timing:
Router(config-if)# no pos internal-clock
SONET payload scrambling applies a self-synchronous scrambler (x^43+1) to the Synchronous Payload Envelope (SPE) of the POS interface to ensure sufficient bit transition density.
To enable SONET payload scrambling on a POSIP, use the pos scramble-atm interface command. To disable SONET payload scrambling, use the no form of this command: no pos scramble-atm. This command has no keywords or arguments; the default is SONET payload scrambling disabled.
To determine whether SONET payload scrambling is enabled on a POS interface, use show startup-config command; if enabled, the following line is displayed: pos scramble-atm.
(Also refer to the section "POSIP-OC3-50 Installation Prerequisites," on page 11, for specific hardware and software requirements for using the SONET payload scrambling feature.)
The following example enables SONET payload scrambling on a POS interface:
Router(config)#interface pos 3/0/0Router(config-if)#pos scramble-atmRouter(config-if)#no shutdownRouter(config-if)#end
The following example disables SONET payload scrambling on a POS interface:
Router(config)#interface pos 3/0/0Router(config-if)#nopos scramble-atmRouter(config-if)#end
After configuring the new interface, use the show commands to display the status of the new interface or all interfaces. Following are descriptions and examples of show commands that display POSIP information.
Router# sh cont cbus
MEMD at 40000000, 2097152 bytes (unused 1888, recarves 3, lost 0)
RawQ 48000100, ReturnQ 48000108, EventQ 48000110
BufhdrQ 48000130 (2955 items), LovltrQ 48000148 (10 items, 1632 bytes)
IpcbufQ 48000150 (24 items, 4096 bytes)
3570 buffer headers (48002000 - 4800FF10)
pool0: 16 buffers, 256 bytes, queue 48000138
pool1: 229 buffers, 1536 bytes, queue 48000140
pool2: 332 buffers, 4480 bytes, queue 48000158
pool3: 4 buffers, 4512 bytes, queue 48000160
(additional displayed text omitted from this example)
slot0: VIP2, hw 2.3, sw 21.44, ccb 5800FF40, cmdq 48000090, vps 8192
software loaded from flash slot1:muck/biff/vip2_21-44
FLASH ROM version 255.255
POS0/0/0, applique is SONET
gfreeq 48000158, lfreeq 48000168 (4480 bytes), throttled 0
rxlo 4, rxhi 332, rxcurr 0, maxrxcurr 0
txq 48001A00, txacc 48001A02 (value 221), txlimit 221
Router# sh int pos 0/0/0
POS0/0/0 is up, line protocol is up
Hardware is cyBus Packet over Sonet
Description: PRI-T1 net to zippy (4K) to Pac-Bell
Internet address is 1.1.1.1/27
MTU 4470 bytes, BW 1000 Kbit, DLY 40000 usec, rely 255/255, load 1/255
Encapsulation HDLC, loopback not set, keepalive set (3 sec)
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 00:23:09
Queueing strategy: fifo
Output queue 0/40, 0 drops; input queue 0/75, 0 drops
5 minute input rate 0 bits/sec, 1 packets/sec
5 minute output rate 1000 bits/sec, 1 packets/sec
1046 packets input, 54437 bytes, 0 no buffer
Received 485 broadcasts, 0 runts, 0 giants, 0 parity
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
4013 packets output, 1357412 bytes, 0 underruns
0 output errors, 0 applique, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
Router# sh diag 2
Slot 2:
Physical slot 2, ~physical slot 0xD, logical slot 2, CBus 0
Microcode Status 0x4
Master Enable, LED, WCS Loaded
Board is analyzed
Pending I/O Status: None
EEPROM format version 1
VIP2 controller, HW rev 2.4, board revision B0
Serial number: 03514213 Part number: 73-1684-03
Test history: 0x00 RMA number: 00-00-00
Flags: cisco 7000 board; 7500 compatible
EEPROM contents (hex):
0x20: 01 15 02 03 00 35 9F 65 49 06 94 03 00 00 00 00
0x30: 06 3C 00 2A 1A 00 00 00 00 00 00 00 00 00 00 00
Slot database information:
Flags: 0x4 Insertion time: 0x1294 (00:13:39 ago)
Controller Memory Size: 32 MBytes DRAM, 1024 KBytes SRAM
PA Bay 0 Information:
POS PA, 1 port
EEPROM format version 1
HW rev 1.3, Board revision UNKNOWN
Serial number: 00000032 Part number: 73-1803-03
Router# sh version
Cisco Internetwork Operating System Software
IOS (tm) GS Software (RSP-JV-M), Released Version 11.1(8)CA [biff 100]
Copyright (c) 1986-1996 by cisco Systems, Inc.
Compiled Fri 10-May-96 06:48 by biff
Image text-base: 0x600108A0, data-base: 0x60936000
ROM: System Bootstrap, Version 5.3(16645) [biff 571], INTERIM SOFTWARE
ROM: GS Bootstrap Software (RSP-BOOT-M), Version 11.1(8)CA, RELEASE SOFTWARE (fc2)
Router uptime is 2 minutes
System restarted by power-on
System image file is "biff/rsp-jv-mz", booted via tftp from 1.1.1.253
cisco RSP2 (R4600) processor with 16384K bytes of memory.
R4600 processor, Implementation 32, Revision 2.0
Last reset from power-on
G.703/E1 software, Version 1.0.
SuperLAT software copyright 1990 by Meridian Technology Corp).
Bridging software.
X.25 software, Version 2.0, NET2, BFE and GOSIP compliant.
TN3270 Emulation software (copyright 1994 by TGV Inc).
1 POSIP controller (1 POSI).
1 Packet over Sonet network interface.
125K bytes of non-volatile configuration memory.
8192K bytes of Flash PCMCIA card at slot 0 (Sector size 128K).
8192K bytes of Flash internal SIMM (Sector size 256K).
No slave installed in slot 7.
Configuration register is 0x0
(display text omitted)
Router# sh running-config
interface pos0/0/0
ip address 1.1.1.3 255.255.255.0
appletalk address 10.1
appletalk zone posip
The only error message you should see would be of the following type and format:
%POSIP-0-MSG: %DEBUGGER-0-STACK_DATA8: 00E0 FFFFFFFF 80057F50 00000000 00000000 FFFFFFFF 80032CD4 00000000 00000000
Following is an example of two sample configuration files from two routers connected back to back through their POSIP interfaces.
First router:
interface POS0/0/0 ip address 1.1.2.3 255.0.0.0 no keepalive posip internal-clock
Second router
interface POS0/0/0 ip address 1.1.2.4 255.0.0.0 no keepalive
To connect two POSIP-equipped routers back to back, attach the appropriate cable between the OC-3c interface port on each POSIP. By default, the POSIP uses loop timing mode. To specify that the POSIP generates the transmit clock internally, add the posip internal-clock command to your configuration.
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