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Understanding Circuit Emulation Services and the Supported PIC Types

 

Circuit emulation service is a method through which data can be transmitted over ATM, Ethernet, or MPLS networks. This information is error-free and has a constant delay, thereby enabling you to use it for services that use time-division multiplexing (TDM). This technology can be implemented through Structure-Agnostic TDM over Packet (SAToP) and Circuit Emulation Service over Packet-Switched Network (CESoPSN) protocols.

SAToP enables you to encapsulate TDM bit-streams such as T1, E1, T3, and E3 as pseudowires over packet-switched networks (PSNs).

CESoPSN enables you to encapsulate structured (NxDS0) TDM signals as pseudowires over packet-switching networks.

A pseudowire is a Layer 2 circuit or service, that emulates the essential attributes of a telecommunications service— such as a T1 line, over an MPLS PSN. The pseudowire is intended to provide only the minimum necessary functionality to emulate the wire with the required degree of faithfulness for the given service definition.

The following Circuit Emulation PICs are specifically designed for mobile backhaul applications.

4-Port Channelized OC3/STM1 (Multi-Rate) Circuit Emulation MIC with SFP

The 4-port Channelized OC3/STM1 (Multi-Rate) Circuit Emulation MIC with SFP —MIC-3D-4COC3-1COC12-CE—is a channelized Circuit Emulation MIC with rate-selectability. You can specify its port speed as COC3-CSTM1 or COC12-CSTM4. The default port speed is COC3-CSTM1. To configure the 4-port Channelized OC3/STM1 Circuit Emulation MIC, see Configuring SAToP on 4-Port Channelized OC3/STM1 Circuit Emulation MICs.

All ATM interfaces are either T1 or E1 channels within the COC3/CSTM1 hierarchy. Each COC3 interface can be partitioned as 3 COC1 slices, each of which in turn can be partitioned further into 28 ATM interfaces and the size of each interface created is that of a T1 interface. Each CS1 interface can be portioned as 1 CAU4 interface, which can be further partitioned as E1-sized ATM interfaces.

The following features are supported on the MIC-3D-4COC3-1COC12-CE MIC:

  • Per-MIC SONET/SDH framing

  • Internal and loop clocking

  • T1/E1 and SONET clocking

  • Mixed SAToP and ATM interfaces on any port

  • SONET mode—Each OC3 port can be channelized down to 3 COC1 channels, and then each COC1 can channel down to 28 T1 channels.

  • SDH mode—Each STM1 port can be channelized down to 4 CAU4 channels, and then each CAU4 can channel down to 63 E1 channels.

  • SAToP

  • CESoPSN

  • Pseudowire Emulation Edge to Edge (PWE3) control word for use over an MPLS PSN

The MIC-3D-4COC3-1COC12-CE MIC supports T1 and E1 options with the following exceptions:

  • bert-algorithm, bert-error-rate, and bert-period options are supported for CT1 or CE1 configurations only.

  • framing is supported for CT1 or CE1 configurations only. It is not applicable in SAToP configurations.

  • buildout is supported in CT1 configurations only.

  • line-encoding is supported in CT1 configurations only.

  • loopback local and loopback remote are supported in CE1 and CT1 configurations only. By default, no loopback is configured.

  • loopback payload is not supported. It is not applicable in SAToP configurations.

  • idle-cycle-flag is not supported. It is not applicable in SAToP configurations.

  • start-end-flag is not supported. It is not applicable in SAToP configurations.

  • invert-data is not supported. It is not applicable in SAToP configurations.

  • fcs16 is not supported in E1 and T1 configurations only.

  • fcs32 is not supported in E1 and T1 configurations only. It is not applicable in SAToP configurations.

  • timeslots is not supported. It is not applicable in SAToP or ATM configurations.

  • byte-encoding is not supported in T1 configurations only. It is not applicable in SAToP configurations. nx56 byte encoding is not supported.

  • crc-major-alarm-threshold and crc-minor-alarm-threshold are T1 options supported in SAToP configurations only.

  • remote-loopback-respond is not supported. It is not applicable in SAToP configurations.

  • If you attempt to configure the local loopback capability on an at- interface—ATM1 or ATM2 intelligent queuing (IQ) interface or a virtual ATM interface on a Circuit Emulation (ce-) interface—by including the loopback local statement at the [edit interfaces at-fpc/pic/port e1-options], [edit interfaces at-fpc/pic/port e3-options], [edit interfaces at-fpc/pic/port t1-options], or the [edit interfaces at-fpc/pic/port t3-options] hierarchy level (to define the E1, E3, T1, or T3 physical interface properties) and commit the configuration, the commit is successful. However, local loopback on AT interfaces does not take effect and a system log message is generated stating that local loopback is not supported. You must not configure local loopback because it is not supported on at- interfaces.

  • Mixing T1 and E1 channels is not supported on individual ports.

For more information about MIC-3D-4COC3-1COC12-CE, see Channelized OC3/STM1 (Multi-Rate) Circuit Emulation MIC with SFP.

12-Port Channelized T1/E1 Circuit Emulation PIC

The 12-port Channelized T1/E1 Circuit Emulation PIC supports TDM interfaces by using the SAToP protocol [RFC 4553] encapsulation, and supports T1/E1 and SONET clocking features. The 12-port Channelized T1/E1 Circuit Emulation PIC can be configured to work as either 12 T1 interfaces or 12 E1 interfaces. Mixing T1 interfaces and E1 interfaces is not supported. To configure the 12-Port Channelized T1/E1 Circuit Emulation PIC, see Configuring the 12-Port Channelized T1/E1 Circuit Emulation PIC.

The 12-port Channelized T1/E1 Circuit Emulation PICs support T1 and E1 options, with the following exceptions:

  • bert-algorithm, bert-error-rate, and bert-period options are supported for CT1 or CE1 configurations only.

  • framing is supported for CT1 or CE1 configurations only. It is not applicable in SAToP configurations.

  • buildout is supported in CT1 configurations only.

  • line-encoding is supported in CT1 configurations only.

  • loopback local and loopback remote are supported in CE1 and CT1 configurations only.

  • loopback payload is not supported. It is not applicable in SAToP configurations.

  • idle-cycle-flag is not supported. It is not applicable in SAToP or ATM configurations.

  • start-end-flag is not supported. It is not applicable in SAToP or ATM configurations.

  • invert-data is not supported. It is not applicable in SAToP configurations.

  • fcs32 is not supported. fcs is not applicable in SAToP or ATM configurations.

  • timeslots is not supported. It is not applicable in SAToP configurations.

  • byte-encoding nx56 is not supported. It is not applicable in SAToP or ATM configurations.

  • crc-major-alarm-threshold and crc-minor-alarm-threshold are not supported.

  • remote-loopback-respond is not supported. It is not applicable in SAToP configurations.

8-Port OC3/STM1 or 12-port OC12/STM4 ATM MIC

The 8-port OC3/STM1 or 2-port OC12/STM4 Circuit Emulation ATM MIC supports both SONET and SDH framing mode. The mode can be set at the MIC level or at the port level. ATM MICs are rate-selectable at the following rates: 2-port OC12 or 8-port OC3. The ATM MIC supports ATM pseudowire encapsulation and swapping of VPI and VCI values in both directions.

Note

Cell-relay VPI/VCI swapping and cell-relay VPI swapping on both egress and ingress are not compatible with the ATM policing feature.

16-Port Channelized E1/T1 Circuit Emulation MIC

The 16-port Channelized E1/T1 Circuit Emulation MIC (MIC-3D-16CHE1-T1-CE) is a channelized MIC with 16 E1 or T1 ports.

The following features are supported on the MIC-3D-16CHE1-T1-CE MIC:

  • Each MIC can be separately configured in either T1 or E1 framing mode.

  • Each T1 port supports superframe (D4) and extended superframe (ESF) framing modes.

  • Each E1 port supports G704 with CRC4, G704 without CRC4, and unframed framing modes.

  • Clear channel and NxDS0 channelization. For T1 the value of N ranges from 1 through 24 and for E1 the value of N ranges from 1 through 31.

  • Diagnostic features:

    • T1/E1

    • T1 facilities data link (FDL)

    • Channel service unit (CSU)

    • Bit error rate test (BERT)

    • Juniper Integrity Test (JIT)

  • T1/E1 alarm and performance monitoring (a Layer 1 OAM function)

  • External (loop) timing and internal (system) timing

  • TDM circuit emulation services CESoPSN and SAToP

  • CoS parity with IQE PICs. The CoS features supported on MPCs are supported on this MIC.

  • Encapsulations:

    • ATM CCC cell relay

    • ATM CCC VC multiplex

    • ATM VC multiplex

    • Multilink Point-to-Point Protocol (MLPPP)

    • Multilink Frame Relay (MLFR) FRF.15

    • Multilink Frame Relay (MLFR) FRF.16

    • Point-to-Point Protocol (PPP)

    • Cisco High-Level Data Link Control

  • ATM class-of-service (CoS) features—traffic shaping, scheduling, and policing

  • ATM Operation, Administration, and Maintenance

  • Graceful Routing Engine switchover (GRES)

    Note
    • When GRES is enabled you must execute the clear interface statistics (interface-name | all) operational mode command to reset the cumulative values for local statistics. For more information, see Resetting Local Statistics.

    • Unified ISSU is not supported on the 16-port Channelized E1/T1 Circuit Emulation MIC (MIC-3D-16CHE1-T1-CE).

For more information about MIC-3D-16CHE1-T1-CE, see Channelized E1/T1 Circuit Emulation MIC.

Layer 2 Circuit Standards

Junos OS substantially supports the following Layer 2 circuit standards:

  • RFC 4447, Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP) (except section 5.3)

  • RFC 4448, Encapsulation Methods for Transport of Ethernet over MPLS Networks

  • Internet draft draft-martini-l2circuit-encap-mpls-11.txt, Encapsulation Methods for Transport of Layer 2 Frames Over IP and MPLS Networks (expires August 2006)

Junos OS has the following exceptions:

  • A packet with a sequence number of 0 is treated as out of sequence.

    • Any packet that does not have the next incremental sequence number is considered out of sequence.

    • When out-of-sequence packets arrive, the expected sequence number for the neighbor is set to the sequence number in the Layer 2 circuit control word.

  • Internet draft draft-martini-l2circuit-trans-mpls-19.txt, Transport of Layer 2 Frames Over MPLS (expires September 2006).

These drafts are available on the IETF website at http://www.ietf.org/.