Cisco MWR 1941-DC Router Software Configuration Guide
Overview of the Cisco MWR 1941-DC Router
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Overview of the Cisco MWR 1941-DC Router

Table Of Contents

Overview of the Cisco MWR 1941-DC Router

Primary Uses of the MWR 1941-DC Router

IP-RAN Solution

Cell Site DCN Solution

Cisco IOS Software Features

Software Features for the IP-RAN Implementation

MIPs-Based Software Features

Network Processor (PXF) Software Features

Redundancy Support

IP-RAN Implementation Updates

Software Features for the Cell Site DCN Application

MIB Support

Limitations and Restrictions

IP-RAN Implementation Limitations and Restrictions

Cell Site DCN Implementation Limitations and Restrictions

New Features in Cisco IOS Release 12.2(15)MC2h

Support for 6 T1/E1 Interfaces per/MWR

Support for 1800 CIDs per/MWR

Support for Enhanced Link Noise Monitoring (LNM)


Overview of the Cisco MWR 1941-DC Router


The MWR 1941-DC Mobile Wireless Edge Router is a networking platform optimized for use in mobile wireless networks; specifically designed to be use at the cell site edge as a part of an IP Radio Access Network (IP-RAN) or Cell Site Data Communications Network (DCN).

The MWR 1941-DC router offers high performance at a low cost while meeting the critical requirements for deployment in cell sites, including small size, high availability, and DC input power flexibility.

This chapter includes the following sections:

Primary Uses of the MWR 1941-DC Router

Cisco IOS Software Features

Limitations and Restrictions

Primary Uses of the MWR 1941-DC Router

The MWR 1941-DC router is designed to be used at the cell site as part of an IP-RAN or Cell Site DCN solution.

IP-RAN Solution


Note Cisco IOS Release 12.3(11)T supports the Cisco IOS IP-RAN feature set (software image) for the MWR 1941-DC router.


In an IP RAN application, the MWR 1941-DC router extends IP connectivity to the cell site and Base Transceiver Station (BTS). Through a FastEthernet interface to the BTS, the MWR 1941-DC router provides bandwidth-efficient IP transport of voice and data bearer traffic, as well as maintenance, control, and signalling traffic, over the leased line backhaul network between the BTS and leased line termination and aggregation node via compression (cRTP/cUDP) and packet multiplexing (PPPmux and MLPPP).

Figure 1-1 shows the placement of and connections for the MWR 1941-DC router implemented in an IP-RAN solution.

Figure 1-1 MWR 1941-DC Router in an IP-RAN Solution

In the IP-RAN solution, the BTS site consists of a pair of MWR 1941-DC routers. The pair of MWR 1941-DC routers provides for an active and standby router for redundancy. A failure of the active MWR 1941-DC router causes the standby router to take over as the active router for the BTS site.

Each pair of MWR 1941-DC routers at the BTS site is identical in hardware configuration. They connect to each other through the BTS via the Fast Ethernet interfaces. The individual backhaul links to an MWR 1941-DC router are cabled from a single T1/E1 termination block in the BTS, connecting to both the active and standby routers utilizing a "Y" cable. The redundancy design to control the active/standby transitions of the router pair leverages HSRP to control the relays on the VWIC-2MFT-T1-DIR (or VWIC-2MFT-E1-DIR) in each router to ensure that the relays on the active router are closed and the relays on the standby router are open to avoid double termination of the T1 (or E1).

Cell Site DCN Solution


Note Cisco IOS Release 12.3(11)T does not support the Cisco IOS Cell Site DCN feature set (software image) for the MWR 1941-DC router.


In a Cell Site DCN, the MWR 1941-DC router can be used to extend a mobile operators DCN to the cell site, providing the ability to manage radio and cell site equipment remotely from the operations center.

A cell site DCN minimizes the need to dispatch technicians for every problem that might occur at the cell site by providing the ability to perform the following types of maintenance tasks remotely:

troubleshooting

diagnosis

repairs

control

upgrades

routine maintenance of the cell site devices

Additionally, the MWR 1941-DC router cell site DCN implementation also provides IP connectivity to the cell site, enabling the use of IP-related applications that provide operation support (for example, web camera for site surveillance, IP telephone for voice connectivity, and LAN extension to the cell site to provide remote access to network applications, data, and access to the Internet and/or intranet).

Cisco network modules and WAN interface cards used with the MWR 1941-DC router provide a variety of connectivity options at the cell site.

Figure 1-2 shows an example placement and connections for the MWR 1941-DC router implemented in a Cell Site DCN solution.

Figure 1-2 MWR 1941-DC Router in an Cell Site DCN Solution

In the Cell Site DCN solution, the MWR 1941-DC router provides a channelized T1/E1 interface to the BTS and routes management and control traffic via one DS0 from a T1. Additionally, the MWR 1941-DC router supports a variety of interfaces to monitored and controlled devices using Cisco network modules installed in the MWR 1941-DC router.

Cisco IOS Software Features

There are two versions of software available for the Cisco MWR 1941-DC router. One version of software is required for implementing the Cisco MWR 1941-DC router in an IP RAN; the other for implementing the router in a Cell Site DCN.

The software features vary depending on the version of software running on the MWR 1941-DC router.

Software Features for the IP-RAN Implementation

Software Features for the Cell Site DCN Application

Software Features for the IP-RAN Implementation

The software required for implementing the MWR 1941-DC router in an IP-RAN consists of two components: Cisco IOS software running on the MIPs-based route processor portion of the MWR 1941-DC router hardware, and microcode running on the Cisco network processor, also known as "Parallel eXpress Forwarding (PXF)." When deployed in an IP-RAN, the MWR 1941-DC router is customized for performance, high availability, quality of service, and link efficiency.

Cisco IOS software functions added to the MWR 1941-DC router for the IP-RAN implementation include:

Redundancy logic—For monitoring Hot Standby Routing Protocol (HSRP) information to determine the active and standby router and control T1 termination.

Failover logic—To force a switchover for hardware failures or an over-temperature condition.

Relay control—To open and close the T1/E1 interfaces on the active and standby routers.

Diagnostic functions—To monitor the "health" of the standby MWR 1941-DC router.

This section contains the following information:

MIPs-Based Software Features

Network Processor (PXF) Software Features

Redundancy Support

IP-RAN Implementation Updates

MIPs-Based Software Features

Standard Cisco IOS software features supported in the MWR 1914-DC router for the IP-RAN implementation include:

IP Fragmentation

IP Multicast

IGMP

MLP, PPP Control Path (IPCP, NCP, LCP, CLNS)

ACFC and PFC Handling During PPP Negotiation

HSRP

OSPF

DHCP

CDP

NTP

SNMP

Network Processor (PXF) Software Features

To achieve the required efficiency, when implemented in an IP-RAN, the MWR 1941-DC router additionally has microcode running on the network processor to offload the fast-path processing of packets. This allows the MWR 1941-DC router to support the traffic of up to 4 T1s or E1s (up to 60,000 packets per second) at a targeted 80% processor utilization while performing UDP/RTP header compression/decompression (cUDP/cRTP) and PPPmux.

The following features are supported in the network processor:

MAC Classify

ICMP

FIB (CEF)

Load-balancing

MAC Rewrite

QoS Matching, including IP Access Lists (Input/Output Security ACLs are not supported), QoS Group, IP Precedence, IP DSCP, and Input Interface

QoS Actions, including Set IP Precedence, Set IP DSCP, Set QoS Group, Traffic Shaping, Class Based WFQ (CB-WFQ), and Low Latency Queuing (LLQ)

Maintenance of statistics, such as Forwarding, Drop, and Interface

IPv4

MLPPP, MLP, PPP Data Path (MLP LFI is not supported)

PPPmux

cRTP/cUDP

Link Noise Monitoring (LNM) provides configuration monitoring of individual T1/E1 circuit quality

PPP Multiplexing/Demultiplexing

Encapsulated PPP frames contain several bytes of header information, which adds overhead to a network that is used to transport PPP frames.

RFC 3153 describes a way to overcome this overhead. On the sending end, a multiplexor concatenates multiple PPP frames (subframes) into a single, multiplexed frame (superframe). One header is included in the superframe and the individual PPP subframes are separated by delimiters. On the receiving end, a demultiplexor uses the delimiters to separate the individual PPP subframes.

The MWR 1914-DC router network processor software conforms to this specification and acts as both a multiplexor and a demultiplexor.

RTP/UDP Header Compression

RTP is a protocol used for carrying packetized audio and video traffic over an IP network. RTP, described in RFC 1889, is not intended for data traffic, which uses TCP or UDP. Instead, RTP provides end-to-end network transport functions intended for applications with real-time requirements (such as audio, video, or simulation data) over multicast or unicast network services.

In an RTP frame, there is a minimum 12 bytes of the RTP header, combined with 20 bytes of IP header, and 8 bytes of UDP header. This creates a 40-byte IP/UDP/RTP header. By comparison, the RTP packet has a payload of approximately 20 to 160 bytes for audio applications that use compressed payloads. Given this ratio, it is very inefficient to transmit the IP/UDP/RTP header without compressing it.

Figure 1-3 RTP Header Compression

RFCs 2508 and 2509 describe a method for compressing not only the RTP header, but also the associated UDP and IP headers. Using this method, the 40 bytes of header information is compressed into approximately 2 to 4 bytes, as shown in Figure 1-3. Because the frames are compressed on a link-by-link basis, the delay and loss rate are lower, resulting in improved performance.

The MWR 1914-DC router network processor offloads both the compression and decompression of RTP frames from the Cisco IOS software.


Note The MWR 1941-DC router can be configured to perform only IP/UDP compression, in which case the header is reduced from 28 bytes to 2 to 4 bytes.


Redundancy Support

In an IP-RAN application, to ensure availability, the backhaul links to an MWR 1941-DC router are redundantly cabled to the VWIC-2MFT-T1-DIR/ VWIC-2MFT-E1-DIR cards. This card, designed specifically for the MWR 1941-DC router, is a modified 2-port T1/E1 Multiflex VWIC with Drop and Insert.The modifications include the addition of relays to activate the T1/E1 ports. The relays allow "Y" cabling for router redundancy where the T1/E1 link is not redundant and default to open. The relays are controlled by HSRP/redundancy protocol between the two routers connected to the same T1/E1.


Note If you choose to use the MWR 1941-DC router in a non-redundant configuration, you must close the relays on the card using the standalone subcommand. Also, redundancy parameters are processed when the router is booted up. These parameters cannot be changed "on the fly."


HSRP

Cisco's Hot Standby Router Protocol (HSRP) is used to control which router is active and which is standby. HSRP uses a priority scheme to determine which HSRP-configured router is to be the default active router. Priority is determined first by the configured priority value, and then by the IP address. In each case a higher value is of greater priority.

IP-RAN Implementation Updates

This section lists MWR 1941-DC router product updates:

Traffic Recovery Over MLP After T1 Failure

With Cisco IOS Release 12.2(8)MC2b and later, you can use the keepalive interface configuration command to configure traffic over an MLP link to recover within 6 second if a T1 failure should occur.

ACFC and PFC Support on PPP Multilink Interfaces

With Cisco IOS Release 12.2(8)MC2c and later, by default, Address and Control Field Compression (ACFC) and Protocol Field Compression (PFC) are enabled on PPP interfaces. Both features are always enabled and will be negotiated on all serial interfaces.


Note If upgrading for this support, ensure that you upgrade the MGX-RPM-1FE-CP back card images first. After doing so, immediately upgrade all MWR 1941-DC routers connected to the MGX-RPM-1FE-CP back card.


Ignore IP ID Field Delta in cUDP Packet Flows

With Cisco IOS Release 12.2(8)MC2c and later, by default, the ability to ignore IP ID field delta in cUDP traffic flows is enabled. This ability eliminates the need to send information about the IP header ID field in compressed packets. The decompressor saves the original ID field from the full header packet and generates an ID field by incrementing it by one for each decompressed packet. This feature improves processing efficiency; helping to minimize dropped packets and link saturation.

Link Noise Monitor

Noise on T1 and E1 links that span between the BTS and central office can affect voice quality for mobile users to the point where it becomes unacceptable. Therefore, with Cisco IOS release 12.2(8)MC2d and later, you can configure the Link Noise Monitor (LNM) on the MWR 1941-DC router to monitor the quality of individual links in a multilink bundle. The LNM provides the ability to detect, alert, and remove noisy links from a bundle based on user-defined thresholds and durations. For more information on the LNM feature, see "Configuring the Link Noise Monitor" section.

First Two Packets Sent with Full cUDP Headers

With Cisco IOS Release 12.2(8)MC2d and later, at the start of a call flow, the MWR 1941-DC router and the MGX 8850 RPM-PR back card send the first two packets of the flow with full headers. This feature helps to minimize the loss of cUDP headers (and therefore misrouted packets) in noisy and/or congested networks.

Software Features for the Cell Site DCN Application

The software required for implementing the MWR 1941-DC router in a Cell Site DCN runs on the MIPs-based router processor portion of the MWR 1914-DC router hardware.

Standard Cisco IOS software features supported in the MWR 1914-DC router for the Cell Site DCN implementation include:

Standard and extended Access Control Lists

IP Fragmentation

IP Multicast

IGMP

MLPPP

PPPo HDLC

HSRP

OSPF

DHCP

IP Precedence

cRTP/cUDP

CB-WFQ

Traffic shaping

TDM Drop & Insert

DS0-level grooming

NTP

SNMP

MIB Support

The MWR 1914-DC router supports the following MIBs:

CISCO-ACCESS-ENVMON-MIB

CISCO-CDP-MIB

CISCO-CLASS-BASED-QOS-MIB

CISCO-CONFIG-COPY-MIB

CISCO-CONFIG-MAN-MIB

CISCO-ENVMON-MIB

CISCO-FLASH-MIB

CISCO-HSRP-EXT-MIB

CISCO-HSRP-MIB

CISCO-ICSUDSU-MIB

CISCO-IMAGE-MIB

CISCO-IP-STAT-MIB

CISCO-IPMROUTE-MIB

CISCO-MEMORY-POOL-MIB

CISCO-MOBILE-IP-MIB

CISCO-PROCESS-MIB

CISCO-QUEUE-MIB

CISCO-SYSLOG-MIB

CISCO-TCP-MIB

ENTITY-MIB

IF-MIB

IGMP-MIB

IPMROUTE-MIB

OLD-CISCO-CHASSIS-MIB

OLD-CISCO-FLASH-MIB

OLD-CISCO-INTERFACES-MIB

OLD-CISCO-IP-MIB

OLD-CISCO-SYSTEM-MIB

OLD-CISCO-TS-MIB

RFC1213-MIB

RFC1253-MIB

RFC1406-MIB

TCP-MIB

UDP-MIB


The MWR 1914-DC router uses the same software base as the Cisco 10000. As such, it shares the same QoS MIB limitations of the Cisco 10000. For information about the Cisco10000 MIB support, see the Cisco 10000 Series ESR MIB Specifications Guide on CCO at http://www.cisco.com/univercd/cc/td/doc/product/aggr/10000/10kmibs/specgdll/index.htm.

Limitations and Restrictions


Caution The Cisco MWR 1941-DC router does not support online insertion and removal (OIR) of WAN interface cards. Any attempt to perform OIR on a card in a powered up router might cause damage to the card.


Caution Removing the compact flash from the Cisco MWR 1941-DC router during a read/write operation might corrupt the contents of the compact flash, rendering it useless. To recover from an accidental removal of or corruption to the compact flash, a maintenance spare with the appropriate bootable Cisco IOS software image might be needed.

IP-RAN Implementation Limitations and Restrictions

The following list of restrictions applies when implementing the MWR 1941-DC router in an IP-RAN.

Cisco IOS Software Features not Supported on the MWR 1941-DC Router

The Cisco MWR 1941-DC router requires a special version of Cisco IOS software. Not all Cisco IOS software features can be used with the Cisco MWR 1941-DC router as the core routing is handled by the network processor. A list of supported features is included in the "Cisco IOS Software Features" section. The following standard Cisco IOS software features are not supported on the Cisco MWR 1941-DC router:

Security Access Control Lists

MPLS

802.1Q VLANs

Frame Relay (FR)

MLP LFI

ATM

Use of additional WICs. The only supported WIC is the VWIC-2MFT-T1DIR/VWIC-2MFT-E1DIR. (IP-RAN implementation only.)

Upgrading the VWIC-2MFT-T1-DIR Microcode

When upgrading the image on your Cisco MWR 1941-DC router, power cycle the router or perform a microcode reload on the VWIC-2MFT-T1-DIR to ensure that the firmware for the VWIC-2MFT-T1-DIR is updated during the upgrade.

Disabling PPP Multiplexing

To fully disable PPP multiplexing (PPPMux), issue the no ppp mux command on the T1 interfaces of the routers at both ends of the T1 link. If PPP multiplexing remains configured on one side of the link, that side will offer to receive PPP multiplexed packets.

MLP LFI Support

MLP LFI is not supported by the Cisco MWR 1941-DC router. Therefore, MLP LFI must be disabled on peer devices connecting to the Cisco MWR 1941-DC router T1 MLP connections.

ACFC and PFC Support on PPP Interfaces

If upgrading to Cisco IOS Release 12.2(8)MC2c or later for the ACFC and PFC support on PPP interfaces, ensure that you upgrade the MGX-RPM-1FE-CP back card image first. After doing so, immediately upgrade all MWR 1941-DC routers connected to the MGX-RPM-1FE-CP back card.

Cell Site DCN Implementation Limitations and Restrictions

The following list of restrictions applies when implementing the MWR 1941-DC router in a Cell Site DCN.


Caution The Cisco MWR 1941-DC router does not support online insertion and removal (OIR) of network modules. Any attempt to perform OIR on a card in a powered up router might cause damage to the card.

Using the 1-port T3/E3: NM-1T3/E3(=)

When using the 1-port T3/E3 network module in your MWR 1941-DC router configuration, note that E3 mode is not supported with Cisco IOS Release 12.2(15)MC1a. E3 mode is supported with Cisco IOS Release 12.2(15)MC1b and later.

Also, when used with the MWR 1941-DC router, the NM-1T3/E3 supports line rate throughput for traffic with packet sizes of 1500 bytes. For traffic with smaller packet sizes, degradation in throughput will be seen.

Upgrading the VWIC-2MFT-T1-DIR Microcode

When upgrading the image on your Cisco MWR 1941-DC router, power cycle the router or perform a microcode reload on the VWIC-2MFT-T1-DIR to ensure that the firmware for the VWIC-2MFT-T1-DIR is updated during the upgrade.

New Features in Cisco IOS Release 12.2(15)MC2h

The following new features are implemented in Cisco IOS Release 12.2(15)MC2h and later releases:

Support for 6 T1/E1 interfaces per/MWR

Support for 1800 Context IDs (CIDs) per/MWR

Support for enhanced Link Noise Monitoring (LNM)

Support for 6 T1/E1 Interfaces per/MWR

The new MWRs support up to 6 T1/E1 interfaces on the platform. These interfaces are configured by IOS software as controller t1 0/4 and controller t1 0/5 for the T1 interface, and as controller e1 0/4 and controller e1 e1 0/5 for the E1 interface. In effect, the multilink interface can now be configured with 6 T1 or 6 E1 interfaces under it. Also, the number of serial interfaces can increase depending upon how the T1/E1 interfaces are split up by the configuration. All controller specific commands are applicable to the new T1/E1 interfaces.

Support for 1800 CIDs per/MWR

With Cisco IOS Release 12.2(15)MC2h, the maximum number of connections is increased to 1800 for the interface configuration command ip rtp compression-connections. This command is also used to specify the total number of Real-Time Transport Protocol (RTP) header compression connections that can exist on an interface. The default is 16 CID connections.

Command
Purpose

Router(config-if)# ip rtp compression-connections number

Number of RTP header compression connections the cache supports in the range of 3 to 1800.


To restore the default value, use the no form of this command.

Support for Enhanced Link Noise Monitoring (LNM)

With Cisco IOS Release 12.2(15)MC2h, LNM algorithm support has been changed or updated. There is no longer support for the existing or previous LNM algorithm. The enhanced LNM algorithm is now supported by default. However, the existing or previous LNM CLI is still used to set the threshold and duration values.

The averaging algorithm is responsible for maintaining the simple moving average of link quality Bit Error Rate (BER), Line Code Violation/Path Code Violation (LCV/PCV) values as and when noise samples arrive. The noise is calculated as a simple moving average for the duration configured. The average noise at any time represents the noise average for the last configured duration in seconds. It is recalculated each second as the noise samples arrive each second. Basically, it's a sliding window of noise averages for the last duration in seconds.

The Benefits of this new algorithm are the following:

Improves CDMA backhaul link robustness by detecting noisy spans and removing them out of service 100 percent of the time and restoring them back 100 percent of the time when the link quality reaches an acceptable value.

Improves CDMA Link Noise Monitoring Capability through intelligent threshold setting by using the averaging algorithm and providing better detection at a wide range of Bit Error Rate levels.

100 percent detection at the Threshold which the customer sets to.

Alerts the customer 100 per cent of the time about the quality of the spans.

Removes the degraded span effectively and having only acceptable spans in service.