The Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features introduce a new compression technique in DSP firmware and add enhancements to Cisco IOS that include cell switching on ATM segmentation and reassembly (SAR), and the use of an external BITS clocking source. These features enable Cisco multiservice routers to be used to transparently groom and compress traffic in a wireless service provider network and enable a service provider to optimize the bandwidth used to backhaul the traffic from a cell site to the mobile central office for more efficient use of existing T1 and E1 lines.
Feature Specifications for Cisco Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source
Feature History
Release
Modification
12.3(4)XD
These features were introduced.
12.3(7)T
These features were integrated into Cisco IOS Release 12.3(7)T.
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 Cisco Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
The Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features require a Cisco 3660 or Cisco 3745 with the following components installed:
Table 1
Supported Network Modules
Feature
Cisco 3660
Cisco 3745
Lossless compression R1
NM-HDV
NM-HDV
ATM cell switching
AIM-ATM or AIM-ATM-VOICE-30
NM-x
FE2W with VWIC-x
MFT-T1/E1
AIM-ATM or AIM-ATM-VOICE-30
NM-x
FE2W with VWIC-x
MFT-T1/E1
VWIC-x
MFT-T1/E1 (on-board WIC slot)
BITS clocking
NM-HDV
NM-x
FE2W with VWIC-x
MFT-T1/E1
NM-HDV
NM-x
FE2W with VWIC-x
MFT-T1/E1
VWIC-x
MFT-T1/E1 (on-board WIC slot)
Restrictions for Cisco Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
Operations, administration, and maintenance (OAM) cell insertion is not supported on cell-switched PVCs.
AIM-ATM and AIM-ATM-VOICE-30 modules support a maximum of four T1/E1s. This can consist of two incoming and two outgoing, or three incoming and one outgoing T1/E1s. An IMA group cannot be split between multiple AIMs.
Certain combinations of AIM modules can become inoperable when installed in a Cisco 3745. This problem only affects Cisco 3745 routers manufactured before June 11, 2003. See the following field notice for detailed information about this problem:
Voice activity detection (VAD) and echo cancellation are disabled when lossless compression is enabled.
Lossless compression R1 is supported for VoATM calls with AAL2 and subcell multiplexing. VoIP calls are not supported at this time.
ATM cell switching is limited to a maximum of 25 connections per AIM-ATM.
Do not configure more than 29 LLCC channels per NM-HDV module. Configuring more than 29 LLCC channels can cause unreliable operation.
J1 controller is not supported.
Traffic policing is not supported.
For Cisco 3660 routers with two NM-HDV modules installed, do not install the modules in the following slot combinations:
Slot 1 and Slot 3
Slot 2 and Slot 4
Slot 5 and Slot 6
Using these slot combinations can result in packet loss.
Information About Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
The Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features work together to groom and compress T1 and E1 traffic between cell sites and a mobile central office. These features require a Cisco 3660 or Cisco 3745 router to be installed at the base transceiver station (BTS). This cell site router performs ATM switching and compression of cell site traffic for transport to the base station controller (BSC). A Cisco MGX 8850 with AUSM and VISM-PR terminates the T1/E1 lines that carry lossless compression codec (LLCC) traffic, converting the traffic back to PCM before passing it to the BSC. The figure below shows a sample topology that makes use of the Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features.
Figure 1
Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source Features
The Lossless Compression R1 feature introduces a new compression technique in DSP firmware and the VISM card-- the lossless compression codec (LLCC). LLCC operates in a similar fashion to the existing clear channel codec: the decoded 64kbps PCM stream is a bit-exact replica of the PCM stream provided on the TDM side of the encoding DSP. However, rather than simply packetizing the PCM stream, the LLCC encoder applies a lossless data compression scheme. This results in a net reduction in the data transmission rate, yielding a reduction in the packet transmission rate.
ATM Cell Switching on AIM-ATM and AIM-ATM-VOICE-30
The Cisco ATM Cell Switching feature enables the router to perform cell switching between two ATM connections on AIM-ATM and AIM-ATM-VOICE-30 cards, giving the router the ability to receive ATM traffic from the BTS and backhaul it to the mobile central office.
BITS Clocking on the Cisco 3660 and Cisco 3745
BITS (Building Integrated Timing Supply) network clocking enables a Cisco 3660 or Cisco 3745 router to derive network timing from the central office. BITS must be configured on the cell site router to support this feature.
How to Configure Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
The procedures for configuring the Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features require the following tasks:
The instructions that follow refer to the sample configuration shown in the figure below. With this configuration, the cell site router supports three E1 connections to the BTS. Compressed cellular traffic is transported to the BSC (by way of the Cisco MGX 8850) over the E1 1/0 and E1 1/1 interfaces. Additionally, BITS clocking is derived from E1 1/1.
Configuring the Cell Site Router for BITS Clocking
BITS clocking enables the router at a cell site to derive timing from the mobile central office. BITS clocking ensures that data flows to a single network clock source, preventing mismatches and data slips in traffic between the BTS and the BSC. The procedure that follows configures the AIM to receive BITS clocking from E1 1/1 controller.
Summary Steps
enable
configureterminal
network-clock-participateslotnumber
network-clock-selectpriorityslotnumber
controllere1slot/port
clocksource{line[primary|bits]|internal}
Detailed Steps
SUMMARY STEPS
1.enable
2.configureterminal
3.network-clock-participateslotnumber
4.network-clock-selectpriorityslotnumber
5.controllert1|e1slot/port
6.clocksource{line [primary | bits] | internal}
DETAILED STEPS
Command or Action
Purpose
Step 1
enable
Example:
Router> enable
Enables privileged EXEC mode. Enter your password when prompted.
Step 2
configureterminal
Example:
Router# configure terminal
Enters global configuration mode.
Step 3
network-clock-participateslotnumber
Example:
Router(config)# network-clock-participate slot 1
Allows the network module in the specified slot to use the network clock for its timing.
Step 4
network-clock-selectpriorityslotnumber
Example:
Router(config)# network-clock-select 1 E1 1/1
Specifies a port to be used as a timing source for the network clock, and the priority level for the use of that port. The source that is given the highest priority is used first; if it becomes unavailable, the source with the second-highest priority is used, and so forth.
Step 5
controllert1|e1slot/port
Example:
Router(config)# controller e1 1/1
Enters controller configuration mode for the selected T1 or E1.
Step 6
clocksource{line [primary | bits] | internal}
Example:
Router(config-controller)# clock source line bits
Specifies that the clock is generated from the T1 or E1 BITS source.
Configuring ATM Cell Switching
The procedure that follows configures the cell site router to switch
ATM traffic with the Cisco MGX 8850 at the BSC. This procedure configures ATM
switching between E1 3/0 and E1 1/0, using the AIM installed in Slot 1.
Tunes the playout buffer to accommodate packet jitter caused by switches in the WAN. The nominal keyword specifies the initial (and minimum allowed) delay time that the DSP inserts before playing out voice packets, in milliseconds.
Associates this voice-port to destination-pattern 1001.
What to Do Next
Note
To ensure that the voice-port configuration takes affect, issue the shutdown command, followed by noshutdown to enable it again.
Disabling Connection Admission Control
Connection admission control (CAC) is a set of actions taken by each ATM switch during connection setup to determine whether the requested QoS will violate the QoS guarantees for established connections. CAC reserves bandwidth for voice calls, however, the bandwidth required when LLCC is used is dynamic and usually less than what is generally reserved by CAC. Disabling CAC may help in better utilization of bandwidth when LLCC is used. The procedure that follows disables CAC.
This section provides a set of
show commands you can use to verify the configuration of the Lossless Compression R1, ATM Cell Switching, and External BITS Clocking Source features. It includes the following commands:
show connection all
The following example shows output from the
showconnectionallcommand. In this example, Switched-Conn is a cell-switched connection established between PVC 10/110 and PVC 30/130, which are configured under ATM1/0 and ATM3/0 respectively.
Router# show connection all
ID Name Segment 1 Segment 2 State
========================================================================
3 V-100-700 E1 1/0(VOICE) 00 DSP 07/00/00 UP
4 V-120-700 E1 1/2(VOICE) 00 DSP 07/00/00 UP
5 Switched-Conn ATM1/0 10/110 ATM3/0 30/130 UP
Theshowconnectionall command displays the state of Switched-Conn. If it is in the UP state, then it means the ATM cell switching connection is operational.
show voice dsp
The following example shows output from the
showvoicedsp command:
Router# show voice dsp
DSP DSP DSPWARE CURR BOOT PAK TX/RX
TYPE NUM CH CODEC VERSION STATE STATE RST AI VOICEPORT TS ABORT PACK COUNT
==== === == ======== ======= ===== ======= === == ========= == ===== ==========
C549 000 04 llcc 4.3.392 busy idle 0 4/0:0 04 0 1752/1752
The
showvoicedsp command shows if the LLCC codec has been applied to the voice port. Additionally, the TX/RX COUNT indicates if packet exchange is occurring. If LLCC is operational, then TX/RX COUNT will display similar values.
show voice call
port-id
The
showvoicecallcommand gives detailed information about the lossless compression codec. The following example shows output from the
showvoicecall command:
Note
The
showvoicecall command has a limitation that causes it to display invalid values. To ensure that accurate values are reported, invoke this command twice and look at the second output.
Router# show voice call 4/0:0
4/0:0 1
vtsp level 0 state = S_CONNECTvpm level 1 state = S_TRUNKED
vpm level 0 state = S_UP
lossless compression summary:
average compression ratio since reset = 50
current compression ratio = 50
max buffer size (ms) = 41
nominal buffer size (ms) = 25
current buffer size (ms) = 26
total encoder input frame count = 5534
total encoder output frame count = 2767
encoded tx front-end compressed frame count = 2767
encoded tx back-end compressed frame count = 0
encoded tx frame count (no compression) = 0
underflow error count = 0
overflow error count = 0
decode error count = 0
tx signalling frame count = 11
rx signalling frame count = 10
rx bad checksum frame count = 0
rx good checksum frame count = 2777
show voice trunk supervisory summary
The following example shows output from the
showvoicetrunksupervisorysummary command:
Router# show voice trunk supervisory summary
SLOW SCAN
4/0:0(1) : state : TRUNK_SC_CCS_CONNECT, master
show interfaces
The following example shows output from the
showinterfaces command:
Router# show interfaces atm1/0
ATM1/0 is up, line protocol is up
Hardware is ATM AIM E1
MTU 4470 bytes, sub MTU 4470, BW 1920 Kbit, DLY 20000 usec,
reliability 0/255, txload 1/255, rxload 1/255
Encapsulation ATM, loopback not set
Encapsulation(s): AAL5
255 maximum active VCs, 256 VCs per VP, 0 current VCCs
VC Auto Creation Disabled.
VC idle disconnect time: 300 seconds
Last input never, output never, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: Per VC Queueing
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
0 packets input, 0 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
0 packets output, 0 bytes, 0 underruns
0 output errors, 0 collisions, 1 interface resets
0 output buffer failures, 0 output buffers swapped out
The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.
Feature Information for Lossless Compression R1 ATM Cell Switching and External BITS Clocking Source
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.
Table 2
Feature Information for Phrase Based on Module Title
These features were integrated into Cisco IOS Release 12.3(7)T.
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL:
www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1110R)
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.