Table Of Contents
Changes to this Document Since Release 5.1
MPSM-8T1E1 Card Common Features
Eight Port CESM and MPSM Card Features
CESM and MPSM Card Common Features
Asynchronous Clocking (Adaptive)
Introduction
This chapter introduces the CESM and MPSM cards that are supported in Cisco MGX Release 5.1 and Cisco MGX Release 1.3.
Also introduced is the Service Resource Module (SRM) which provides services to both the CESM and MPSM cards.
These topics introduce and describe the features of the CESM, MPSM, and SRM cards:
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Eight Port CESM and MPSM Card Features
CESM and MPSM cards are supported by the PXM1, PXM1E, and the PXM45 processor cards in Cisco MGX 8230, Cisco MGX 8250, Cisco MGX 8850 (PXM1), Cisco MGX 8850 (PXM1E/PXM45), and Cisco MGX 8830 (PXM1E/PXM45) switches.
Changes to this Document Since Release 5.1
Table 1-1 summarizes the changes made to this document since Release 5.1.
Table 1-1 Changes to This Guide Since Release 5.1
Book title
Update
Change MPSM in the title to MPSM-8-T1E1 to avoid confusion with the Cisco ATM and Frame Relay Services (MPSM-T3E3-155 and MPSM-16-T1E1) Configuration Guide and Command Reference for MGX Switches, Release 5.2 book.
All chapters
Update
Changed MGX 8830 to MGX 8830 (PXM1E/PXM45)
Update
Add PXM45/C to supported controllers in Table 1-3.
Correct SRME/B support by controller in Table 1-4.
Chapter 6, "CESM and MPSM Command Reference"
Update
Update display of dspcd command.
CESM and MPSM Card Types
The CESM and MPSM cards documented in this manual are the single-height CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES cell bus service modules.
Note
When operating under control of the PXM1, PXM1E, or PXM45 processor card, the Cisco MGX 8230, Cisco MGX 8250, Cisco MGX 8850 (PXM1), Cisco MGX 8850 (PXM1E/PXM45), or Cisco MGX 8830 (PXM1E/PXM45) switches support the CESM and MPSM cards listed in Table 1-2.
The R-RJ48-8T1, R-RJ48-8E1, and R-SMB-8E1 back cards support 1:N card redundancy through the optional MGX-SRM-3T3/C, SRME, and SRME/B cards.
Support for each type of the CESM and MPSM cards by the PXM1, PXM1E, and PXM45 processor cards is shown in Table 1-3
The main function of the Circuit Emulation Service Module (CESM) and the Multi Protocol Service Module (MPSM) is to provide a constant bit rate (CBR) circuit emulation service by converting data streams into CBR AAL1 cells for transport across an ATM network. The CESM and MPSM cards support the CES-IS specifications of the ATM Forum.
The most common application is legacy support for digitized voice from a PBX or video from a codec. Using circuit emulation, a company can expand its data communication network without specific voice or video cards to meet its voice or teleconferencing requirements.
The preferred tool for configuring, monitoring, and controlling service modules is the Cisco WAN Manager (CWM) application for equipment management and connection management. However, the command-line interface (CLI) also provides access to the service modules and is highly applicable during initial installation, troubleshooting, and any situation in which low-level control is useful.
MPSM Card Features
These topics describe the features of the MPSM card:
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MPSM-8T1E1 Card Common Features
Designed as a replacement for the existing cell bus service modules (AUSM-8T1/B, AUSM-8E1/B, CESM-8T1, CESM-8E1, FRSM-8T1, FRSM-8T1-C, FRSM-8E1, and FRSM-8E1-C), the MPSM-8T1E1 card is an Any Service Any Card (ASAC) service module. This supports multiple interface types (T1 and E1) and multiple service types (ATM, Frame Relay, and Circuit Emulation).
The MPSM-8T1E1 card can be used with or without services provisioned on the card. Without services provisioned on the card, the MPSM-8T1E1 is used in a redundancy group and retains its physical card type name of MPSM-8T1E1.
When provisioned for a specific interface and service type, the MPSM-8T1E1 card takes on a logical card type name depending upon what interface and service type has been configured. For example, if an MPSM-8T1E1 in standby state is provisioned (using the PXM cnfcdmode command) for Circuit Emulation services using a T1 interface, the card changes its name to the logical card type name of MPSM-8T1-CES.
Features common to the MPSM-8T1E1 regardless of the interface and service type configured include:
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MPSM-8T1-CES Card Features
When the MPSM-8T1E1 card is configured to support a T1 interface type and Circuit Emulation services, the card becomes an MPSM-8T1-CES card. It then supports the features common to all the CESM cards and the specific features of the CESM-8T1/B and CESM-8T1 cards.
The MPSM-8T1-CES provides eight T1 interfaces for full-duplex communications at up to 1.544 Mbps per interface. This supports a total card throughput of 12.352 Mbps. The physical connector for each line is an RJ48 connector.
MPSM-8E1-CES Card Features
When the MPSM-8T1E1 card is configured to support an E1 interface type and Circuit Emulation services, the card becomes an MPSM-8E1-CES card. It then supports the features common to all the CESM cards and the specific features of the CESM-8E1 card.
The MPSM-8E1-CES provides eight E1 interfaces for full-duplex communications at up to 2.048 Mbps per interface. This provides a total card throughput of 16.384 Mbps. The physical connectors for each card can be either RJ48 connectors or SMB connectors.
MPSM-8T1E1 Card Differences
Differences between the MPSM-8T1E1 card and the CESM-8T1/B, CESM-8T1, and CESM-8E1 cards include:
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Eight Port CESM and MPSM Card Features
Table 1-4 summarizes the key features of the CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES cards:
These topics describe the features of the CESM and MPSM cards:
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CESM and MPSM Card Common Features
The CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES service modules:
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Peak Cell Rate Calculation
The following features are shared by the CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES service modules:
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T1/E1 Clocking Mechanism
The CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES provide the choice of a physical interface Tx clock from one of the following sources, as illustrated in Figure 1-1:
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Figure 1-1 T1/E1 Clocking Mechanisms
When deciding upon a network clocking architecture, it is important to develop a robust clocking plan for a network using CESM and MPSM cards, otherwise dribbling bit errors, frame slips, and other timing issues may be encountered in the network.
Synchronous Clocking
Synchronous clocking is available on structured and unstructured circuit emulation ports. The circuit data leaving the network uses the same clock as the Cisco MGX switch. This clock signal is available through the timing bus on the Cisco MGX backplane. Assuming the Cisco MGX network is synchronized, the ingress and egress data are also synchronized.
Asynchronous Clocking (SRTS)
Synchronous Residual Time Stamp (SRTS) clocking requires a Primary Reference Source (PRS) and network clock synchronization services. This clocking mode allows user equipment at the edges of an ATM network to use a clocking signal that is different (and completely independent) from the clocking signal being used in the ATM network. However, SRTS clocking is used only for unstructured (clear channel) CES services.
For example, as illustrated in Figure 1-2, user equipment at the edges of the network can be driven by clock B, while the devices within the ATM network are being driven by clock A. The user-end device introduces traffic into the ATM network according to clock B. The CESM or MPSM segments the CBR bit stream into ATM cells; it measures the difference between user clock B, which drives it, and network clock A. This delta value is incorporated into every eighth cell. As the destination CESM or MPSM receives the cells, the card not only reassembles the ATM cells into the original CBR bit stream, but also reconciles the user clock B timing signal from the delta value. Thus, during SRTS clocking, CBR traffic is synchronized between the ingress side of the CES circuit and the egress side of the circuit according to user clock signal B, while the ATM network continues to function according to clock A.
Figure 1-2 Asynchronous Clocking
Asynchronous Clocking (Adaptive)
Adaptive clocking requires neither the network clock synchronization services nor a global PRS for effective handling of CBR traffic. Rather than using a clocking signal to convey CBR traffic through an ATM network, adaptive clocking infers appropriate timing for data transport by calculating an average data rate for the CBR traffic. However, as in the case with SRTS clocking, adaptive clocking is used only for unstructured (clear channel) CES services. See Figure 1-3.
For example, if CBR data is arriving at a CES module at a rate of X bits per second, then that rate is used to govern the flow of the CBR data through the network. Actually the CES module automatically calculates the average data rate. This calculation occurs dynamically as user data traverses the network.
When the CES module senses that its segmentation and reassembly (SAR) buffer is filling up, it increases the rate of the (TX) clock for its output port, thereby draining the buffer at a rate that is consistent with the rate of data arrival.
Similarly, the CES module slows down the transmit clock of its output port if it senses that the buffer is being drained faster than the CBR data is being received. Adaptive clocking attempts to minimize wide excursions in SAR buffer loading, while at the same time providing an effective means of propagating CBR traffic through the network.
Relative to other clocking modes, implementing adaptive clocking is simple and straightforward. It does not require network clock synchronization services, a PRS, or the advance planning typically associated with developing a logical network timing map. However, adaptive clocking does not support structured CES services, and it exhibits relatively high wander characteristics.
Figure 1-3 Asynchronous Clocking (Adaptive)
Idle Suppression
Supported only on single timeslot connections and not on NxDS0 connections, the CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES cards in structured mode can interpret CAS robbed bit signalling for T1 (ABCD for ESF and AB for SF frames) and CAS for E1 (time slot 16). Called the OnHookCode, the ABCD code is user configurable per VC. By detecting on-hook states, AAL1 cell transmission is suppressed for the idle channel. This reduces the consumption of ATM backbone bandwidth. ON/OFF hook detection and Forced Idle Suppression can be enabled or disabled per VC by means of SNMP through the NMS or the Command Line Interface (CLI) using the -onhkcd option of the xcnfchan command (xcnfchan -onhkcd = 0-15; ABCD = 0000 = 0 ... ABCD = 1111 = 15).
On the ingress side (ATM port to ATM network), the CESM or MPSM card monitors the signalling bits of the TDM data frames. Whenever a particular connection goes to on-hook or off-hook states, the CESM or MPSM card senses this condition by comparing the ABCD bits in the TDM frames with the configured OnHookCode for that channel.
When an on-hook state is detected on the near-end CESM or MPSM card, keep-alive ATM cells are sent once every second to the far-end CESM or MPSM. When the far-end CESM or MPSM card detects the on-hook state as well, and also receives the keep-alive ATM cells sent from the near-end CESM or MPSM card, it will start sending keep-alive ATM cells to the near-end CESM or MPSM card and suppress the channel (stop sending ATM cells to the ATM network except the keep-alive ATM cells) in the far-end to near-end direction.
When the near-end CESM or MPSM card receives the keep-alive ATM cells and the on-hook state is still detected, it will also start suppressing the channel in the near-end to far-end direction. After both ends suppress the channel there will be only keep-alive ATM cells transmitted on the channel, but no user data. This conserves ATM network bandwidth.
When either the near-end or far-end CESM or MPSM cards stop detecting the on-hook code or the keep-alive ATM cells, channel suppression will cease and user data will start being sent to the ATM network.
Structured Data Transfer
If you configure an individual port for structured data transfer, the CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES support:
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Unstructured Data Transfer
If you configure an individual port for unstructured data transfer, the CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES support:
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Cell Delay Treatment
For each connection on CESM-8T1/B, CESM-8T1, CESM-8E1, MPSM-8T1-CES, and MPSM-8E1-CES cards, you can configure a tolerable variation in the cell arrival time (CDVT) according to the expected reliability of the route. The CDVT applies to the AAL1 receive buffer. After an underrun, the receiver places the contents of the first cell to arrive in a receive buffer, then plays it out at least one CDVT value later. For each VC, the maximum cell delay and CDVT (or jitter) are
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SRM Card Services
These topics describe the services that the SRM card provides to the CESM and MPSM cards:
Overview of the SRM Card
The Cisco MGX switch supports both 1:1 and 1:N card redundancy for service modules. The 1:N card redundancy feature requires that a Service Resource Module (SRM) card be installed in the MGX switch. If there are redundant PXMs installed in the MGX switch, then the SRMs must likewise be installed in redundant pairs. In Cisco MGX Releases 5.1 and 1.3, three models of the SRM are supported on Cisco MGX switches: the SRM-3T3/C, the SRME, and the SRME/B.
The SRM manages Bulk Mode Distribution with 1:N Redundancy, Non-Bulk Mode 1:N Redundancy, and BERT functions on T1 or E1 service module lines and ports. Cards that have the T1 or E1 access lines physically connected to their back cards are in non-bulk mode. Cards that receive T1 or E1 access lines from the SRM across the backplane of the switch are in bulk mode.
Line redundancy is available to service modules if they are configured for bulk distribution using the SRME or SRME/B card. By using the optical back card option, intercard APS line redundancy is available only if the SRM and PXM have been installed in redundant pairs.
For non-bulk mode cards 1:N redundancy uses the redundancy bus on the backplane to pass the user traffic from the back card of the failed primary card to the active secondary front card. In non-bulk mode, multiple 1:N redundancy groups can be defined but an active backup operation is permitted only in one of the groups in a given bay at any given time. In this mode, a back card is not required for the SRM.
For cards in bulk mode, the distribution bus is used to pass the user traffic to the secondary card. In bulk distribution mode, multiple 1:N redundancy groups can be defined. Because the distribution bus can handle multiple traffic flows, multiple secondary cards can be active at the same time.
SRM Card Features
Support for each type of the SRM cards by the PXM1, PXM1E, and PXM45 processor cards is shown in Table 1-5.
The SRM-3T3/C provides redundancy services, BERT services, and T3 to T1 line distribution. The SRM-3T3/C T1 line distribution feature has the following capabilities and limitations:
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The SRME provides redundancy services, BERT services, and OC-3/STM-1 to T1/E1 line distribution. The SRME T1 and E1 line distribution feature has the following capabilities and limitations:
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The SRME/B provides redundancy services, BERT services, OC-3/STM-1 to T1/E1 line distribution, and T3 to T1 line distribution. The SRME/B T1 and E1 line distribution feature has the combined capabilities and limitations of the SRM-3T3/C and SRME cards.
Table 1-6 summarizes card redundancy, bulk distribution, and BERT services that the SRM card provides to the CESM and MPSM cards. When consulting this table, remember that the SRME and SRME/B supports bulk distribution of both T1 and E1 lines and the SRM-3T3/C supports only bulk distribution of T1 lines.
For more information on BERT, see Chapter 5, "Managing CESM and MPSM Cards."
Note
