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Table Of Contents
HPR Capable SNA Routing Services
Dynamic CP Name Generation Support
Responsive Mode Adaptive Rate-Based Flow Control
Trap MIB Support for Advanced Network Management Awareness
LAN and IP-Focused Connection Types
Token Ring, Ethernet, and FDDI
Connection to Frame Relay Transport Technologies
Connection to Channel Interface Processor and Channel Port Adapter
Transport over DLSw+ Supported Media
DLC Switching Support for Access to SDLC and QLLC
Native IP Data-Link Control (HPR/IP)
Reduced Configuration Requirements
Increased Management Capabilities
Supported MIBs, RFCs, and Standards
Defining a SNASw Control Point Name
Defining a SNASw Partner LU Location
Starting SNASw and SNASw Ports and Links
Stopping SNASw and SNASw Ports and Links
Monitoring and Maintaining SNASw
SNASw over Token Ring without HPR Configuration Example
SNASw over Token Ring with HPR Configuration Example
SNASw Connecting to a CIP over VirtualToken Ring with SRB Configuration Example
SNASw over HPR/IP Configuration Example
SNASw using Local Switching with QLLC Configuration Example
SNASw using Local Switching with SDLC Configuration Example
SNASw with Ethernet LAN Emulation over ATM Configuration Example
SNASw with SRB Frame Relay (Frame Relay BAN Support) Configuration Example
SNASw with FRAS Host (Downstream Frame Relay BNN Support) Configuration Example
SNA Switching Services
This feature module describes the SNA Switching Services (SNASw) feature and includes the following major sections:
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Supported MIBs, RFCs, and Standards
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Feature Overview
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SNASw provides an easier way to design and implement networks with Systems Network Architecture (SNA) routing requirements. Previously, this network design was accomplished using Advanced Peer-to-Peer Networking (APPN) with full network node (NN) support in the Cisco router. This type of support provided the SNA routing functionality needed, but was inconsistent with the trends in Enterprise networks today. The corporate intranet is replacing the SNA WAN. Enterprises are replacing their traditional SNA network with an IP infrastructure that supports traffic from a variety of clients, using a variety of protocols, requiring access to applications on a variety of platforms, including SNA applications on Enterprise servers.
While SNA routing is still required when multiple servers must be accessed, the number of nodes required to perform this function is decreasing as the IP infrastructure grows and as the amount of native SNA traffic in the network decreases.
SNASw enables an enterprise to develop their IP infrastructure, while meeting SNA routing requirements.
The number of NNs in the network and the amount of broadcast traffic are reduced. Configuration is simplified, and SNA data traffic can be transported within the IP infrastructure. The following features provide this functionality:
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HPR Capable SNA Routing Services
SNASw provides the following SNA routing functions:
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Branch Extender
SNASw features use branch network nodes (BrNNs). The Branch Extender (BEX) function enhances scalability and reliability of SNA routing nodes by eliminating topology updates and broadcast directory storms that can cause network instability. BEX appears as an NN to downstream end node (EN), low-entry networking (LEN) node, and PU 2.0 devices, while also appearing as an EN to upstream devices. The BEX function eliminates APPN topology and APPN broadcast search flows between SNASw nodes and the SNA data hosts in the network. This feature is key to providing a reliable turn-key installation because the network administrator no longer needs to develop in-depth knowledge of the level and characteristics of broadcast directory search and topology update traffic in the network. Such knowledge and analysis was commonly required to build successful networks utilizing NN technology without BEX.
illustrates the BEX functionality.
Figure 1 BEX Functionality
Enterprise Extender (HPR/IP)
SNASw also supports the Enterprise Extender (EE) function. EE offers SNA HPR support directly over IP networks. EE also uses connectionless User Datagram Protocol (UDP) transport. SNA COS and transmission priority are maintained by mapping the transmission priority to the IP precedence and by mapping transmission priority to separate UDP port numbers, allowing the IP network to be configured based on these elements. Cisco's IP prioritization technologies, such as weighted fair queuing (WFQ), prioritize the traffic through the IP network. EE support on the IBM Communications Server for S/390 allows users to build highly reliable SNA routed networks that run natively over an IP infrastructure directly to the Enterprise servers. These network designs reduce points of failure in the network and provide reliable SNA networks.
illustrates the EE functionality.
Figure 2 EX Functionality
Usability Features
SNASw contains the following usability features designed to make SNA networks easier to design and maintain:
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Dynamic CP Name Generation Support
When scaling the SNASw function to hundreds or thousands of nodes, many network administrators find that defining a unique control point (CP) name on each node provides unnecessary configuration overhead. Dynamic CP name generation offers the ability to use the Cisco IOS hostname as the SNA CP name or to generate a CP name from an IP address. These facilities reuse one SNASw configuration across many routers and eliminate the specific configuration coordination previously required to configure a unique CP name for each SNA node in the network. However, the ability to explicitly configure each CP name still exists.
Dynamic SNA BTU Size
Most SNA node implementations require specific tuning of the SNA basic transmit unit (BTU) in the configuration. SNASw analyzes the interface maximum transfer units (MTUs) of the interfaces it uses and dynamically assigns the best MTU values for that specific port. For served dependent PU 2.0 devices, SNASw uses the downstream MAXDATA value from the host and dynamically sets the SNA BTU for that device to the MAXDATA value.
DLUR Connect-Out
SNASw can receive connect-out instructions from the IBM Communications Server for S/390. This function allows the system to dynamically connect-out to devices that are configured on the host with the appropriate connect-out definitions. This feature allows connectivity to SNA devices in the network that were traditionally configured for connect-out from the host.
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Responsive Mode Adaptive Rate-Based Flow Control
Early HPR implementations failed to perform well in environments subject to packet loss (for example, Frame Relay, IP transport) and performed poorly when combined with other protocols in multiprotocol networks. SNASw implements the second-generation HPR flow control architecture, called Responsive Mode Adaptive Rate-Based (ARB) architecture. Responsive Mode ARB addresses all the drawbacks of the earlier ARB implementation, providing faster ramp-up, better tolerance of lost frames, and better tolerance of multiprotocol traffic.
User-Settable Port Limits
SNASw offers full control over the number of devices supported by a specific node. The max-links configuration on the SNASw port controls the number of devices that are served by this node. When the max-links limit is reached, SNASw no longer responds to explorers attempting to establish new connections. SNASw allows load sharing among different SNASw nodes that offer service to the same SNA MAC addresses.
Management Enhancements
SNASw contains the following enhanced tools for managing SNA networks:
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Console Message Archiving
Messages issued by SNASw are archived in a buffer log that is queried and searched on the console or transferred to a file server for analysis. Each message has a single line that identifies the nature of the event that occurred. The buffer log also maintains more detailed information about the message issued.
Data-Link Tracing
SNA frames entering or leaving SNASw are traced to the console or to a cyclic buffer. These frames are analyzed at the router or transferred to a file server for analysis. The trace is sent to a file server in a SNA-formatted text file or in binary format readable by existing traffic analysis applications. SNASw also captures record frames natively, eliminating the need for network analyzers to capture network events for analysis.
Interprocess Signal Tracing
The SNASw internal information is traced in binary form, offering valuable detailed internal information to Cisco support personnel. This information helps diagnose suspected defects in SNASw.
Trap MIB Support for Advanced Network Management Awareness
SNASw supports the APPN Trap MIB, which proactively sends traps with information about changes in SNA resource status. This implementation reduces the frequency of SNMP polling necessary to manage SNA devices in the network.
LAN and IP-Focused Connection Types
SNASw supports several connection types to serve all SNA connectivity options, including the following types:
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Token Ring, Ethernet, and FDDI
SNASw natively supports connectivity to Token Ring, Ethernet, and FDDI networks. In this configuration mode, the MAC address used by SNASw is the local configured or default MAC address of the interface.
Virtual Token Ring
Using virtual Token Ring allows SNASw access to source-route bridging (SRB), which allows the following configuration:
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Attachment to Local LANs
Virtual Token Ring allows you to connect to local LAN media through SRB technology. Because there is no limit to the number of virtual Token Ring interfaces that can connect to a specific LAN, this technology allows configuration of multiple MAC addresses, which respond to SNA requests over the same LAN. When using native LAN support, SNASw responds only to requests that target the MAC address configured on the local interface. Virtual Token Ring and SRB allow SNASw to respond to multiple MAC addresses over the same physical interface.
Connection to Frame Relay Transport Technologies
Virtual Token Ring and SRB connect SNASw to a SNA Frame Relay infrastructure. FRAS host and SRB Frame Relay are configured to connect virtual Token Ring interfaces that offer SNASw support for Frame Relay boundary access node (BAN) or boundary network node (BNN) technology.
Connection to Channel Interface Processor and Channel Port Adapter
Virtual Token Ring and SRB can be used to connect SNASw to the Channel Interface Processor (CIP) or Channel Port Adapter (CPA) in routers that support those interfaces.
Virtual Data-Link Control
SNASw uses Virtual Data-Link Control (VDLC) to connect to DLSw+ transport and local switching technologies. VDLC is used for a number of connectivity options, including the following two:
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Transport over DLSw+ Supported Media
Using VDLC, SNASw gains full access to the DLSw+ transport facilities, including DLSw+ transport over IP networks, DLSw+ transport over direct interfaces, and DLSw+ support of direct Frame Relay encapsulation (without using IP).
DLC Switching Support for Access to SDLC and QLLC
Through VDLC, SNASw gains access to devices connecting through SDLC and QLLC. This access allows devices connecting through SDLC and QLLC access to SNASw.
Native IP Data-Link Control (HPR/IP)
SNASw support for the EE function provides direct HPR over UDP connectivity. This support is configured for any interface that has a configured IP address. HPR/IP uses the interface IP address as the source address for IP traffic originating from this node.
Benefits
Scalable APPN Networks
With the BEX function, the number of network nodes and the amount of broadcast traffic are reduced.
IP Infrastructure Support
Limiting SNASw routers to the data center and using the BEX function eliminates SNA broadcasts from the IP network. With EE, SNA traffic is routed using the IP routing infrastructure while maintaining end-to-end SNA services.
Reduced Configuration Requirements
By eliminating NNs and using the BEX function, configuration tasks are minimized. Additionally, Cisco has enhanced its auto-configuration capability to eliminate previously required commands.
Network Design Simplicity
By placing all SNA routers in the data center, few SNA routers are required, and they can be easily configured using virtually identical configurations.
Improved Availability
By adding Cisco-unique capabilities to connect-out and distribute traffic across multiple ports, access to resources is improved and traffic can be distributed across multiple ports. Additionally, by supporting the newest HPR ARB flow control algorithm, bandwidth management for SNA traffic is improved.
Increased Management Capabilities
Two new traces, interprocess and data-link, provide an easier way to view SNASw activity. The APPN Trap MIB allows the user to notify the operator in event of a debilitating problem. Console message archiving provides better tracking of network activity. The ability to format traces in a format so that they are readable by other management products simplify network management because results are more readily available.
Architectural Compliance
Even though SNASw is easier to use and SNASw networks are easier to design, SNASw interfaces with APPN implementations on the market: ENs, NNs, and LEN nodes. It also provides full DLUR support to allow older resources to take advantage of the APPN architecture.
Restrictions
Memory Requirements
SNASw requires sufficient memory to perform properly. describes the SNASw memory requirements.
Supported Platforms
SNASw features are supported on the following platforms:
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Supported MIBs, RFCs, and Standards
MIBs
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For descriptions of supported MIBs and how to use MIBs, see the Cisco MIB web site on CCO at http://www.cisco.com/public/sw-center/netmgmt/cmtk/mibs.shtml.
RFCs
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Configuration Tasks
To configure SNASw in your network, perform the tasks discussed in the following sections. Because of the hierarchical nature of SNASw definitions, configure SNASw in the order specified. Definition of an SNASw cpname and at least one SNASw port are required. The other tasks are optional. Depending on your network, they may need to be configured.
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Defining a SNASw Control Point Name
A SNASw CP definition is required to use SNASw. This definition adds the fully qualified CP name for the node. The fully qualified CP name for the node is a combination of a network identifier and a CP name. The network identifier is typically configured to match the identifier configured in the SNA hosts in the network. The CP name identifies this node uniquely within the particular subnetwork.
To define a SNASw CP name, use the following command in global configuration mode:
[ip-address interface-name]Defines an SNASw CP name.
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Configuring a DLUS
If you plan to use DLUR to provide services for dependent LUs connected to this SNASw node, you must configure at least one primary DLUS. In addition, you can configure node-wide defaults for the DLUS and backup DLUS that this node contacts.
To specify DLUR or DLUS services for this CP name, use the following command in SNASw control point configuration mode:
Specifies the parameters related to DLUR/DLUS functionality.
Configuring DLC Support
There are several ways that SNASw enables connectivity over different interface types. In the simplest cases, using automatically configured real LAN interfaces enables default interface definitions. SNASw is also capable of connecting to virtual interfaces that are not preconfigured on the router.
Virtual Token Ring interfaces are useful for connections to a CIP/CPA in the same router and for connectivity to Frame Relay transport solutions via SRB. Multiple virtual Token Ring interfaces allow SNASw to respond to multiple MAC addresses through the same real router LAN interface. Use the following commands to configure a virtual interface:
Defining a SNASw Port
A SNASw port definition associates SNA capabilities with a specific interface that SNASw will use. Each interface that is used for SNASw communications requires an SNASw port definition statement.
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A port may also be associated with the VDLC or HPR/IP features. The VDLC feature enables SNASw to send and receive traffic to other Cisco IOS software features such as DLSw+. If a port is associated with a VDLC interface, that port does not take an interface name as generally required by the snasw port command.
The HPR/IP feature establishes SNASw links over IP networks. If a port is associated with an HPR/IP interface, then you must configure HPR/IP first, followed by the interface name.
To associate a port with a specific interface, use the following command in global configuration mode:
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Warning
Changing active SNASw interfaces might interrupt SNASw connections.
Defining a SNASw Link
In many cases, if the partner node is initiating the connection, a link definition is not necessary. A link definition is built dynamically when the partner node initiates the connection. Links typically need to be defined for upstream connectivity. Downstream devices initiate connectivity into SNASw; therefore, a link definition is not necessary to downstream devices.
In SNASw link configuration, you must associate the link with the SNASw port that it will use. For all traditional links, the snasw link command must be associated with a remote MAC address. The MAC address identifies the partner address to which SNASw attempts to establish a link. For all HPR/IP links, the command is associated with a remote IP address. The IP address identifies the partner address to which SNASw attempts to establish a link.
To define a SNASw logical link, use the following command in global configuration mode:
Defines a SNASw logical link.
Defining a SNASw Partner LU Location
The SNASw directory stores names of resources and their owners. Usually this information is learned dynamically using Locate searches. You might wish to manually define the location of specific resources. SNASw is known for its dynamic capabilities, not its need for system definition. For this reason, and for easier management, define location names only when necessary.
When a LEN node is attached to a SNASw node, all destination resources that reside on the LEN node must be defined to SNASw if the resource is to be the target of a session request. This definition enables the LEN node resources to be reached through SNASw.
To define a resource location, use the following command in global configuration mode:
Configures the location of a resource.
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Starting SNASw and SNASw Ports and Links
SNASw starts automatically when a CP name is configured. SNASw ports and links are also automatically started once they are configured. If stopped, they can be restarted using one of the following privileged EXEC commands:
Router# snasw startStarts SNASw.
Activates the specified SNASw link.
Activates the specified SNASw port.
Stopping SNASw and SNASw Ports and Links
Unless otherwise defined with the nostart operand, SNASw and SNASw port and link definitions are started automatically when SNASw starts. To stop SNASw or to stop SNASw ports and links when making configuration changes or when resetting the ports or links, use one of the following commands in privileged EXEC mode:
Router# snasw stopDeactivates SNASw.
Deactivates the specified SNASw link.
Deactivates the specified SNASw port.
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Verifying SNASw
To verify that you have SNA connectivity between the router and each host system, enter the
ping sna command, specifying the mode and the link name:ping sna -m IBMRDB STARW.BUDDHAMonitoring and Maintaining SNASw
You can monitor the status and configuration of SNASw by issuing any of the following commands in privileged EXEC mode:
Troubleshooting Tips
You can troubleshoot SNASw by issuing any of the following commands in privileged EXEC mode:
You can also troubleshoot SNASw by issuing any of the following commands in global configuration mode:
Configuration Examples
This section provides the following configuration examples:
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SNASw over Token Ring without HPR Configuration Example
illustrates a basic SNASw link over Token Ring without HPR. In this figure, Port TOK0 is used for upstream links toward the host, and Port TOK1 is used for downstream devices connecting to SNASw. These devices are configured to connect to 4000.1234.abcd.
Figure 3 SNASw over Token Ring without HPR
The configuration for SNASw over Token Ring without HPR is as follows:
interface TokenRing0/0no ip addressno ip directed-broadcastno ip route-cacheno ip mroute-cachering-speed 16interface TokenRing0/1mac-address 4000.1234.abcdno ip addressno ip directed-broadcastno ip route-cacheno ip mroute-cachering-speed 16snasw cpname NETA.ROUTERCPsnasw dlus NETA.HOSTCMC1 backup NETA.HOSTCMC2snasw port TOK0 TokenRing0/0 conntype nohprsnasw port TOK1 TokenRing0/1 conntype nohprsnasw link HOSTCMC1 port TOK0 rmac 4000.aaaa.ccccsnasw link HOSTCMC2 port TOK0 rmac 4000.aaaa.ddddSNASw over Token Ring with HPR Configuration Example
illustrates a basic SNASw link over Token Ring with HPR support. In this figure, Port TOK0 is used for upstream links toward the host, and Port TOK1 is used for downstream devices connecting to SNASw. These devices are configured to connect to 4000.1234.abcd.
Figure 4 SNASw over Token Ring with HPR
The configuration for SNASw over Token Ring without HPR is as follows:
interface TokenRing0/0no ip addressno ip directed-broadcastno ip route-cacheno ip mroute-cachering-speed 16interface TokenRing0/1mac-address 4000.1234.abcdno ip addressno ip directed-broadcastno ip route-cacheno ip mroute-cachering-speed 16
