Circuit Emulation over IP (CEoIP) provides a virtual circuit through an IP network--similar to a leased line--to integrate solutions that require a time-sensitive, bit-transparent transport into IP networks. Data, with proprietary framing or without, arrives at its destination unchanged; the transport is transparent to the destination.
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
Prerequisites for Circuit Emulation over IP
The CEoIP feature requires a CEoIP network module (NM) on each end of the connection, either the NM-CEM-4TE1 NM or the NM-CEM-4SER NM. You do not need to use the same type of CEoIP NM on both ends of the connection.
The CEoIP feature requires 300 KB of flash memory and 1 MB of DRAM in addition to your Cisco IOS software requirements.
Restrictions for Circuit Emulation over IP
NM-CEM-4TE1 supports only B8ZS (T1) and HDB3 (E1) line codes.
E1 lines do not support 56 kbps connections.
CEoIP software cannot run payload compression for more than 3.088 Mbps) per network module.
If you configure four T1, E1, or serial cables (over 1.544 M) at the same time in Cisco 2600XM series routers, you cannot turn on the data-protection and payload compression features. Also, in framed mode (channelized), you can use up to 60 channels without the data protection and payload compression features on Cisco 2600XM series routers. However, you can turn on the data protection and payload compression feature in one T1/E1.
There is a limitation on the data protection and payload compression features on Cisco 3660 routers. If you configure four T1, E1, or serial cables on Cisco 3660 routers, you can turn on data protection for up to two T1/E1s. In framed mode, you can use 88 channels.
Circuit emulation is an end-to-end service that allows Layer 1 data to be transported transparently through an IP network. Applications that require circuit emulation need the network to provide a constant rate bit stream.
Configuration Circuit Emulation (CEM) can be configured in unidirectional mode using the emulation-mode option. Once configured, traffic will flow only in that direction through the CEM channel. When one direction of CEM traffic is detected on that channel, the CEM channel is considered to be active and a new status of the CEM channel is created to reflect the uni-directional channel.
CEoIP may use adaptive clocking as a means of synchronizing the clock frequencies at the two endpoints. Channel associated signaling (CAS) transport is provided as an optional feature to allow channelized voice applications. Payload compression is provided as an optional feature to improve bandwidth efficiency and data protection is provided to reduce the probability of data loss.
CEoIP software supports the following network modules:
The NM-CEM-4SER, a network module with four serial ports. To configure CEoIP software for the NM-CEM-4SER, you must configure the options of the ports. Options include dejitter buffer, payload compression, and payload size.
The NM-CEM-4TE1, a network module with four ports that you can configure as T1 or E1 (where all four ports support the same interface type). To configure CEoIP software for the NM-CEM-TE1, you must define the card type and then configure the options of the port.
Benefits of CEM over IP
CEoIP provides a simple migration path to IP-only networks. Examples of solutions that CEoIP integrates with IP include the following:
Legacy data services
Legacy video applications
Satellite data streams
Radar data streams
Telemetry for automated industrial environments (for example, power distribution)
Crypto tunneling for multilevel security
Adaptive Clocking for CEoIP
The adaptive clocking option of CEoIP allows the egress clock to vary by expanding or contracting the clock period from the nominal clock. After you have implemented the clocking feature, the adaptive clocking circuits continuously adjust the selected clock based on the data buffer level. You can implement adaptive clocking on each port independently.
Clock Switchover
The clock switchover option allows you to switch the clock source over to the internal clock. The switchover ensures continuity of the CEM channel when disruption in receiving the clock from the customer premises equipment (CPE) occurs. To specify the input lead state change that triggers the clock switching over from line to internal or from internal to line, use this option in Data Circuit Terminating Equipment (DCE) split mode.
Payload Compression for CEoIP
The payload compression option minimizes the amount of bandwidth that traffic consumes. It compresses the transmission of any repetitive data pattern (for example, idle code, HDLC flags, and so on) to increase the efficiency of the solution across the network.
With CEoIP software, you can adjust the size (in bytes) of the payload for the IP packet to configure efficiency as opposed to packetization. Larger payloads provide more efficiency but increase the delay. With smaller packets the overhead of the header increases. Payload compression is disabled by default.
Data Protection (Sample Repetition)
The data protection option, also known as sample repetition, reduces the probability of errors due to packet loss by sending each sample twice, in two different IP packets. Data protection consumes more bandwidth than standard transmission, but you can minimize the amount of traffic with payload compression. This feature is disabled by default.
Dejitter
The dejitter buffer size determines the ability of the emulated circuit to tolerate network jitter. The dejitter buffer in CEoIP software is configurable up to 500 milliseconds; the maximum amount of network jitter that CEoIP can tolerate is ±250 milliseconds.
Idle Pattern
The idle pattern option specifies the idle pattern to transmit when the circuit goes down. You can specify a maximum of 64 bits with two 32-bit patterns for the NM-CEM-4SER and 8-bit patterns for the NM-CEM-4TE1.
Payload Size
Payload size is the number of bytes put into each IP packet. This parameter impacts packetization delay and efficiency. Configure a high payload size to increase packetization delay and efficiency. A smaller payload size reduces packetization delay and efficiency.
Signaling for CEoIP
CEoIP software supports the transport of channel associated signaling (CAS) bits in channelized T1/E1 mode. This option extracts incremental signaling information and sends that information in separate packets.
Control Lead Configurations
CEoIP software supports the monitoring and transport of serial interface control leads.
Use the slotand port arguments to specify the slot number and port number to be configured.
Step 2
Do one of the following:
framing {esf | sf | unframed}
framing {crc4 | no-crc4 | unframed}
Example:
Router(config-controller)# framingesf
Example:
Router(config-controller)# framingcrc4
(Optional) Configures the framing format for a T1 or E1 port to synchronize the port and the attached device.
T1 port framing options:
Use the esf keyword to specify Extended Superframe as the T1 framing type.
Use the sf keyword to specify the Superframe (also commonly called D4 framing) as the T1 framing type. This is the default.
E1 port framing options:
Use the crc4 keyword to specify the G.704 standard with optional CRC4 mechanism defined in timeslot zero (0) enabled as the E1 framing type. This is the default.
Use the no-crc4 keyword to specify the G.704 standard with optional CRC4 mechanism defined in timeslot zero (0) disabled as the E1 framing type.
T1 or E1 port framing options:
Use the unframed keyword to specify the unchannelized mode of framing.
Note
If you do not configure framing, the framing on the customer premises equipment (CPE) devices on each end of the connection must match.
Use the internal keyword to specify that the port transmit clock is derived from the time-division multiplexing (TDM) bus backplane clock, if one exists in the router, or the on-board oscillator on the network module.
Use the line keyword to specify that the port transmit clock is derived from the the receive clock on the same port.
Use the adaptive keyword to specify that the port transmit clock is locally synthesized based on the average data content of the dejitter buffer of one of the channels on this port.
If the adaptive keyword is selected, use the channel-number argument to specify the channel whose dejitter buffer is to be used to synthesize the transmit clock of the port.
Step 4
cablelength {long | short} {attenuation| length}
Example:
Router(config-controller)# cablelengthlong-15db
(Optional) Specifies the line build-out characteristics of the internal CSU on a T1 port.
Use the long keyword to specify that the signal characteristics are set for a long cable length.
Use the short keyword to specify that the signal characteristics are set for a short cable length.
If the long keyword is selected, use the attenuation argument to specify the T1 signal attenuation.
If the short keyword is selected, use the length argument to specify the T1 cable length.
Note
This command does not apply to an E1 port.
Step 5
crc-thresholdvalue
Example:
Router(config-controller)# crc-threshold512
(Optional) Configures the number of cyclical redundancy check (CRC) errors in one second that results in the second being declared as a Severely Errored Second (SES).
Use the value argument to specify the number of CRC errors. Default is 320.
(Optional) Specifies a text description of the port.
Step 7
loopback{local {line | payload}| network}
Example:
Router(config-controller)# loopbacknetwork
(Optional) Creates a loopback from a T1 or E1 port.
Use the local keyword to create a loopback where the information from a locally-attached CPE is transmitted back to the locally-attached CPE.
Use the network keyword to create a loopback where the data received over the network from a remotely-attached CPE is transmitted back to the remotely-attached CPE.
If the local keyword is selected, use the line keyword to create a full physical layer loopback of all bits, including data and framing.
If the local keyword is selected, use the payload keyword to create a loopback of the data in the individual timeslots only. In this mode, framing bits are terminated on entry and regenerated on exit instead of being looped back. This mode is not available if the port is configured for framingunframed.
Creates a circuit emulation channel from one or more timeslots of a T1 or E1 line of an NM-CEM-4TE1.
The group-number
keyword identifies the channel number to be used for this channel. For T1 ports, the range is 0-23. For E1 ports, the range is 0-30.
Use the unframed keyword to specify that a single CEM channel is being created including all timeslots and the framing structure of the line.
Use the timeslots keyword and the timeslot-rangeargument to specify the timeslots to be included in the CEM channel. The list of timeslots may include commas and hyphens with no spaces between the numbers, commas, and hyphens.
Use the speed keyword to specify the speed of the channels by specifying the number of bits of each timeslot to be used. This keyword applies only to T1 channels.
Step 2
exit
Example:
Router(config-controller)# exit
Example:
Router(config)#
Exits controller configuration mode and returns to global configuration mode.
Configuring the Connection Using the xconnect Command
Perform this task to create a connection using the xconnect command, starting in global configuration mode. This task applies to configuring CEoIP on both the NM-CEM-4TE1 and the NM-CEM-4SER.
Note
To properly configure the CEoIP feature, two CEoIP network modules must use the same UDP port number to communicate.
Enters CEM configuration mode to configure CEM channels.
Use the slot argument to specify the slot number in which the network module is installed.
Use the port argument to specify the port number of the CEM channel to be configured.
Use the channel argument to specify the CEM channel number to be configured. For a serial channel enter zero. For a T1 or E1 channel enter the channel number defined in the cem-group command (see the Creating CEM Channels on the T1 E1 Line).
This task must be repeated on the other CEM network module and each end of the CEM connection must be configured identically to allow traffic to pass between the network modules. When both network modules have been configured, continue to the Configuring the CEM Channel.
Configuring the CEM Channel
Perform this task to configure the CEM T1/E1 or serial channel, starting in CEM configuration mode.
(Optional) For serial channels only. Specifies the nominal bit rate of a serial CEM channel.
Use the rate argument to specify the data rate of the channel in bps. Default is 64000.
Step 2
clockmode{normal | split}
Example:
Router(config-cem)# clockmodesplit
(Optional) For serial channels only. Specifies the clock mode of a serial CEM channel.
Use the normal keyword to specify that the Data Circuit-terminating Equipment (DCE) provides both the Receive Clock (RxC) and the Transmit clock (TxC) to the attached Data Terminal Equipment (DTE).
Use the split keyword to specify that the DCE provides the Receive Clock (RxC) to the attached DTE, and the DTE provides the external Transmit Clock (XTC or TT) to the DCE.
Note
Depending on the serial cable attached to the port, the port is automatically configured as either a DCE or DTE.
Step 3
clocksource {internal | loop| adaptive}
Example:
Router(config-cem)# clocksourceloop
(Optional) Configures the clock source for a serial CEM channel.
This step applies only to configuring serial channels. For information about configuring the clock source for T1 or E1 ports, see the Configuring the T1 E1 Line.
Use the internal keyword to specify that the clock(s) provided by the network module to the CPE is derived from the TDM bus backplane clock, if one exists in the router, or the on-board oscillator on the network module.
Use the loop keyword to specify that the clock provided by the network module to the CPE is derived from the the clock receive from the CPE on the same port.
Use the adaptive keyword to specify that the clock(s) provided by the network module to the CPE is locally synthesized based on the average data content of the local dejitter buffer.
Note
The loop keyword is valid only when the clockmodesplit command is configured.
Step 4
payload-sizesize
Example:
Router(config-cem)#payload-size512
(Optional) Specifies the number of bytes encapsulated into a single IP packet.
Use the size argument to specify the number of bytes included in the payload of each packet. Default is 32 bytes for a serial CEM channel.
For more information about T1 and E1 default values, see the payload-size command in the "Command Reference" section.
Step 5
dejitter-buffersize
Example:
Router(config-cem)# dejitter-buffer80
(Optional) Specifies the size of the dejitter buffer used to compensate for the network filter.
Use the size argument to specify the size of the buffer in milliseconds. Default is 60.
Step 6
control-leadsampling-raterate
Example:
Router(config-cem)# control-leadsampling-rate10
(Optional) Specifies the sampling rate of input control leads on a serial CEM channel.
This command is used only on serial channels.
Use the rate argument to specify the frequency with which the control leads are sampled, in samples per second. Default is 0.
Note
Control lead update packets are independent of the data packets from the same channel.
(Optional) Specifies the state of each output control lead on a serial CEM channel.
This command is used only on serial channels.
Use the active keyword to specify the state of the control lead when the connection is active.
Use the fail keyword to specify the state of the control lead when the connection has failed.
Use the output-leadargument to specify the name of the control lead.
Use the on keyword to specify that the control lead is permanently asserted.
Use the off keyword to specify that the control lead is permanently not asserted.
Use the follow keyword to specify that the control lead is to follow any changes in the state of an input control lead specified by the local or remote keywords and the input-lead argument.
Use the input-lead argument to specify the name of the local or remote control lead to follow.
Note
Control lead update packets are independent of the data packets for the same channel.
Note
The control-leadsampling-rate parameter must be set to non-zero for this feature to operate.
Step 8
data-strobeinput-lead{on| off}
Example:
Router(config-cem)# data-strobedtron
(Optional) Specifies that an input control lead is to be monitored and data is packetized and sent only when the specified control lead is in the specified state.
This command is used only on serial channels.
Use the input-lead argument to specify the input control lead to be monitored to determine whether input data is to be packetized.
Use the on keyword to specify that data packets are to be sent from this CEM channel only when the specified input lead is asserted.
Use the off keyword to specify that data packets are to be sent from this CEM channel only when the specified input lead is not asserted.
Use this command to save bandwidth when the attached CPE is inactive.
Note
Control lead update packets are still sent even if data packets are withheld.
(Optional) Defines the idle data pattern to send to the attached CPE when packets are lost or the de-jitter buffer experiences an under-run condition.
For serial CEM channels:
A bit pattern up to 64 bits long may be specified.
Use the pattern1 argument to specify up to 32 bits of the least significant bits of the idle data pattern, in hex notation. Default is 0xFF.
Use the pattern2 argument to specify the most significant bits of the idle data pattern, in hex notation. If the length argument is 32 bits or less, this argument is not permitted.
Use the length argument to specify the total length of the repeating bit pattern. Default is 8 bits.
For T1 or E1 CEM channels:
An eight-bit pattern is specified.
Step 10
signaling
Example:
Router(config-cem)# signaling
(Optional) Enables the transport of Channel Associated Signaling (CAS) bits.
Note
This command applies only to framed T1 or E1 data channels.
Step 11
payload-compression
Example:
Router(config-cem)# payload-compression
(Optional) Enables payload compression on a CEM channel.
Note
Enabling payload compression adds a delay equal to one packet time.
Step 12
data-protection
Example:
Router(config-cem)# data-protection
(Optional) Enables data protection by transmitting each data bit twice, once in each of two consecutive data packets.
Use the data-protection command to protect transmissions from the effects of lost IP packets.
Caution
Use this command carefully because it increases the network bandwidth used by the CEM connection.
Step 13
ipdscpdscp
Example:
Router(config-cem)#ipdscp36
(Optional) Configures the IP Differentiated Service Code Point (DSCP) for packets originating from this CEM channel.
Use the dscp argument to specify the value placed in the DSCP field of IP packets originating from this channel. Default is 46.
Note
If DSCP is configured, the iptos and ipprecedence commands are not available because they are mutually exclusive.
Step 14
iptostos
Example:
Router(config-cem)# iptos11
(Optional) Configures the IP type of service (ToS) bits for the CEM channel.
Use the tos argument to specify the value placed in the ToS field of IP packets originating from this channel. Default is 5.
Note
If DSCP is configured, the iptos command is not available because they are mutually exclusive.
Step 15
ipprecedenceprecedence
Example:
Router(config-cem)# ipprecedence7
(Optional) Configures the IP precedence bits for the CEM channel.
Use the precedence argument to specify the value placed in the precedence field of IP packets originating from this channel. Default is 0.
Note
If DSCP is configured, the ipprecedence command is not available because they are mutually exclusive.
Step 16
loopback{local | network}
Example:
Router(config-cem)# loopbacknetwork
(Optional) Creates a loopback from a CEM serial channel.
Use the local keyword to create a loopback where the information from a locally-attached CPE is transmitted back to the locally-attached CPE.
Use the network keyword to create a loopback where the data received over the network from a remotely-attached CPE is transmitted back to the remotely-attached CPE.
Definitions of Managed Objects for the DS1 and E1 Interface Types
RFC 2495
Definitions of Managed Objects for the DS1, E1, DS2 and E2 Interface Types
Note
CEoIP supports RFC2495 to the same extent as IOS supports this RFC.
Technical Assistance
Description
Link
Technical Assistance Center (TAC) home page, containing 30,000 pages of searchable technical content, including links to products, technologies, solutions, technical tips, and tools. Registered Cisco.com users can log in from this page to access even more content.
The following commands are introduced or modified in the feature or features documented in this module. For information about these commands, see the Cisco IOS Interface and Hardware Component Command Reference
at
http://www.cisco.com/en/US/docs/ios/interface/command/reference/ir_book.html.
For information about all Cisco IOS commands, go to the Command Lookup Tool at
http://tools.cisco.com/Support/CLILookup
or to the Cisco IOS Master Commands List
.
cem
cem-group
clearcem
clockmode
clocksource(CEM)
clock-switchover
control-leadsampling-rate
control-leadstate
crc-threshold
data-protection
data-strobe
default(CEM)
dejitter-buffer
emulation-mode
framing(CEM)
idle-pattern
ipdscp
localipaddress
localudpport
loopback(CEM)
payload-compression
payload-size
remoteudpport
showcem
signaling
xconnect(CEM)
Feature Information for Circuit Emulation over IP
The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on Cisco.com is not required.
Release
Modification
12.3(7)T
This feature was introduced.
12.2(33)SRD
Included information on clock switchover and unidirectional emulation mode.
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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.