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rfc:rfc3049

Network Working Group J. Naugle Request for Comments: 3049 K. Kasthurirangan Category: Standards Track IBM

                                                            G. Ledford
                                                    Zephyr Development
                                                          January 2001
           TN3270E Service Location and Session Balancing

Status of this Memo

 This document specifies an Internet standards track protocol for the
 Internet community, and requests discussion and suggestions for
 improvements.  Please refer to the current edition of the "Internet
 Official Protocol Standards" (STD 1) for the standardization state
 and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2001).  All Rights Reserved.

Abstract

 This document discusses the implementation of Service Location
 Protocol (SLP) and session balancing with a TN3270E emulator in a
 client server implementation with a TN3270E server.
 Application program developer's can locate TN3270E services and load
 balance among those services (3270 host sessions), by using this SLP
 support.

Table of Contents

 1. Introduction and Terminology .................................  2
    1.1 Terminology ..............................................  2
 2. An Overview of RFC 2165 ......................................  3
    2.1 SLP Agents ...............................................  3
    2.2 Service Agents ...........................................  3
    2.3 User Agents ..............................................  4
 3. TN3270E Server Environment and Load ..........................  4
    3.1 TnN3270E Server Load .....................................  4
 4. TN3270E Client Configuration .................................  6
    4.1 SLP Scope ................................................  6
    4.2 DA-Discovery Time-Out ....................................  6
    4.3 SA-Discovery Time-Out ....................................  7
 5. TN3270E Client Implementation Information ....................  7
    5.1 Overview .................................................  7

Naugle, et al. Standards Track [Page 1] RFC 3049 TN3270E Location & Balancing January 2001

    5.2 How to Obtain List of TN3270E Servers Supporting SLP .....  8
    5.3 TN3270E Sample Client Flow ...............................  9
       5.3.1 Open the SLP connection .............................  9
       5.3.2 Query the list of TN3270E servers ...................  9
       5.3.3 Forward Looking Example using SLPv2 ................. 10
       5.3.4 Determine loading of each TN3270E server ............ 10
    5.4 Recommendations .......................................... 11
 6. Sample Trace Flow of SLP and Session Balancing ............... 11
 7. Service Templates and Service Registration ................... 12
    7.1 The TN3270E Service Type Template ........................ 12
    7.2 The Server Service Template .............................. 16
    7.3 Template Contact Information ............................. 17
    7.4 Security Considerations .................................. 17
    7.5 Sample TN3270 Service Registration Message ............... 18
    7.6 Sample Server Service Registration Message ............... 19
 8. References ................................................... 19
 9. Authors' Addresses ........................................... 20
 10. Full Copyright Statement .................................... 21

1. Introduction and Terminology

 This document will provide information on Service Location Protocol
 implementation to discover TN3270E servers in a network and session
 balance among those servers.  This implementation follows the
 standards track RFC 2165, Service Location Protocol [1] but also
 provides some examples when using Service Location Protocol version 2
 to be forward looking.  Service Location Protocol version 2 is
 documented in RFC 2608 [4] and RFC 2609 [2].

1.1 Terminology

 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
 document are to be interpreted as described in RFC 2119  [1].
 Session Balance - This refers to the ability of TN3270E client to use
 server load information to establish a TN3270E connection to the
 TN3270E server with the least load at that time.  The purpose is to
 distribute the connection of TN3270E sessions among more than one
 TN3270E server, and one server will not be excessively loaded.  The
 term "load balance" is a more general term, with respect to server
 load, and in this document we are focusing on the TN3270E session
 connections to least loaded servers.
 SNA Gateway - A Systems Network Architecture (SNA) gateway allows
 multiple LAN-attached workstations to access SNA hosts through one or
 more physical connections to one or more hosts.  A SNA gateway acts
 as a protocol converter between workstations attached to a LAN and a

Naugle, et al. Standards Track [Page 2] RFC 3049 TN3270E Location & Balancing January 2001

 WAN host line.  It typically would support the SNA protocols LU 0, 1,
 2, 3, and dependent LU 6.2 (APPC).  SNA gateways typically include a
 TN3270E server capability.
 LU Pool - The Logical Units (LUs) defined in the gateway can be
 dedicated to a particular workstation or pooled among multiple
 workstations.  Pooling allows workstations to share common Logical
 Units (LUs), which increases the efficiency of the LUs and reduces
 the configuration and startup requirements at the host.  When a
 client connects to the gateway, the gateway retrieves an LU from the
 pool to establish a session.  The LU is returned to the pool for
 access by other workstations when the session is ended.
 Commserver Service Type Template - Commserver service type is defined
 as an SNA Gateway server as previously defined above in this
 terminology section.  A template describing the attributes for this
 service type is in section 7.2.

2. An overview of RFC 2165

 RFC 2165, Service Location Protocol (SLP) [1], provides an automatic
 way for clients to discover services within an administrative domain.
 These services have various attributes associated with them from
 which a client can base a service selection.  The basic design
 involves the use of three agent types.  These are: User Agents
 (UA's), Service Agents (SA's) and Directory Agents (DA's).

2.1 SLP Agents

 User Agents are used to query Service Agents or Directory Agents.
 They acquire/request service information based upon the desired
 attributes and service needed for the user application.
 Service Agents represent a specific service and advertise service
 information.
 Directory Agents act as a central collection point for service
 registration information by Service Agents which is later requested
 by "user agents" in "intranets".

2.2 Service Agents

 The service registers itself with the service agent so that the SA
 can start advertising this information over the network.  The process
 of registration consists of the service giving the SA all relevant
 configuration information and attribute tag/value list pairs specific
 to this service.  The Service template is an abstract schema that

Naugle, et al. Standards Track [Page 3] RFC 3049 TN3270E Location & Balancing January 2001

 applies to the service type.  The service template for TN3270E is
 shown later, contains the URL which is the address of the server with
 the port, which should be used to connect to it.  The URL also
 contains the service type which in this case is TN3270.  The template
 also contains all the other attributes associated with this service.

2.3 User Agents

 The User Agent working on the TN3270E client's behalf retrieves
 service information from the Service Agent(s) or a Directory Agent.
 Based on the gathered information and required attributes the TN3270E
 client or user can decide whether or not to connect with a particular
 server.  Based on the service advertisements from various TN3270E
 servers, the client looks at the load attribute and can decide to
 connect to the least loaded server.  If by the time it connects to
 that particular TN3270E server, the server becomes unavailable it can
 try connecting to the next server in its list (ie: the second least
 loaded server whose advertisement was retrieved by the client/user
 agent).

3. TN3270E Server Environment and Load

 TN3270E Servers are pervasive in today's networked environment.  SLP
 provides emulator clients with a way to discover TN3270E servers in
 the network and session balance among the servers.  The TN3270E
 servers could be distributed across different SNA gateways with
 different connection methods to hosts.  The use of LU pools provides
 an easy way for administrators to provide users access to hosts.
 Administrators can add users to LU pools that have pre-configured
 LU's with specific attributes, like LU types and model types.
 These LU pools would typically have LUs from several different
 gateways assigned, and as members of the LU pool make TN3270E session
 connections, they would be making connections to different TN3270E
 servers, with different load factors, so that session balancing could
 be accomplished.  The use of LU pools is not a requirement for SLP
 and session balancing.  A TN3270E client could obtain a session by
 using SLP and session balancing to locate the least loaded server in
 the network.  On a service request a wild card "*" could be used when
 asking for LUPOOL if the emulator doesn't care which device types are
 supported in given pools or if it can assume given pools support only
 certain device types.

3.1 TN3270E Server Load

 TN3270E servers providing load information, SHOULD include number of
 sessions available, not in current use, as part of the calculation in
 determining the total load for the server.  There can be other

Naugle, et al. Standards Track [Page 4] RFC 3049 TN3270E Location & Balancing January 2001

 factors that might have an effect on server load.  An example would
 be if a server is not dedicated to only SNA traffic, and is handling
 other processes, like file services and print services, etc.  It is
 beyond the scope of this document to standardize the method of
 individual server load calculations.  Different vendors server's may
 calculate load information based upon factors they consider
 important, and methods for calculating load may change over time.
 If the TN3270E server coexists in a network with other TN server
 implementations using SLP for session balancing, TN3270E server load
 could be adjusted to compensate for differences in load calculations.
 One way to allow TN3270E server administrators to compensate for
 differences in implementations of calculating server load measurement
 is to provide the ability to modify the load calculation on the
 TN3270E server.  An element of control can be provided by allowing
 the administrator to modify the load measurement, by using an
 integral number between 0 and 100 (100 being the highest) to change
 the load.  This load measurement acts as an additional factor on the
 server's actual load calculation, so that the administrator could
 bias up or down, the likelihood of that server being selected by a
 TN3270E client.
 Load MUST be defined as one of the attributes for the TN3270E server.
 The Load attribute provided at the server will allow clients to
 determine which server to make a connection.  If a UA provides only a
 Service Type, in an Attribute Request,  then the reply includes all
 attributes and all values for that Service Type, and Load would be
 included.  Attribute Requests MAY include a select clause, so you
 could be returned just load information.  For more information on
 Attribute Requests refer to Service Location Protocol [1].
 An application could issue a Service Request to locate a TN3270E
 server.  Then an application designed to perform least-load location
 of a TN3270E service, could issue a series of Attribute Requests to
 obtain the load measurement of each server specified with a URL.  It
 would specify a select clause similar to the one below to receive
 only load information.
 URL = service:tn3270://9.37.51.254:23 Attribute filter = LOAD
 The attribute LOAD would be returned along with its value.  The
 application could then issue other Attribute Request calls for each
 URL.

Naugle, et al. Standards Track [Page 5] RFC 3049 TN3270E Location & Balancing January 2001

 The application would then select the least loaded server as a
 connection target.  If it tries to connect to a server and that
 connection fails, it could then try to connect to the next least-
 loaded server.

4. TN3270E Client Configuration

4.1 SLP Scope

 Scope is a parameter used to control and manage access by clients to
 servers in a network.  It is the same as the Service Location
 Protocol scope defined in RFC 2165 [1].  The control scope provides
 is necessary for two reasons:
 As your network, the number of clients, and the number of servers
 grow, it becomes necessary to partition access to those servers by
 the growing number of clients in order to reduce overall traffic on
 the network.  It allows administrators to organize users and servers
 into administrative groups.
 The meaning of the values of scope is defined by the administrator of
 the network.  These values can represent any entity.  Commonly, they
 fall along either departmental, geographical, or organizational
 lines.
 Each TN3270E server can be assigned to a single scope or multiple
 scopes.  TN3270E clients using these servers can be configured for a
 single specific scope.  If TN3270E clients are not configured with a
 scope they MUST use the scope "default".
 SLP Service Agents and Directory Agents (DA) need to reside in the
 network that support the TN3270E server with configured scopes.
 Attribute information for Service Types pertaining to a specific
 scope can be obtained from Directory Agents (DA).  The DA will not
 return a result unless the requested scope matches.
 For more information on SLP scope refer to Service Location Protocol
 [1].

4.2 DA Discovery time-out

 The DA Discovery time-out value, is used to control how long the SLP
 API must wait to discover Directory Agents (DAs) in the network.  The
 discovery request is a multicast, and the amount of time required to
 gather all DA responses might vary depending on many factors.  If
 there are no DAs in the network, this time-out value can be set to

Naugle, et al. Standards Track [Page 6] RFC 3049 TN3270E Location & Balancing January 2001

 zero to indicate that no DA discovery is to be done.  The time-out is
 expressed in milliseconds.  Time-out intervals and default values
 should be handled as described in RFC 2165 [1].

4.3 SA Multicast time-out

 The SA Multicast time-out value, is used to control how long the SLP
 API must wait to discover services, attributes, or service types in a
 network without at least one DA that supports the scope of the
 request.  In this situation, these requests are multicast and the
 User Agent waits the time-out value to gather the multiple responses
 that are returned.  The time-out is expressed in milliseconds. Time-
 out intervals and default values should be handled as described in
 RFC 2165 [1].

5. TN3270E Client Implementation Information

5.1 Overview

 A TN3270E client that implements TN3270E SLP session balancing does
 not need to configure an IP Host Address or TCP Port for the TN3270E
 server it desires to connect to.  Instead, the IP Host Address and
 TCP Port of the least loaded TN3270E server is discovered by using
 the SLP session balancing described in this document.
 The discovery of the least loaded TN3270E server is done entirely
 outside of and before the TN3270E telnet negotiation.  Once the IP
 Host address and TCP Port of the least loaded TN3270E server is
 discovered, the TN3270E client can then start normal TN3270E telnet
 negotiation.
 The TN3270E client MUST allow for configuration of the following
 parameters.  These SLP specific configuration items are covered by
 configuration parameters in the SLP API [5].
 Enable SLP Session Balancing
 This configuration parameter indicates whether or not SLP session
 balancing is enabled.  If it is enabled the following three
 configuration parameters MUST also be configurable.  If this
 parameter is disabled, SLP session balancing is not supported and
 normal TN3270E telnet negotiation is performed.
 Scope Name The scope name is a text string that specifies a group of
 TN3270E servers.  The scope name can be used to identify groups of
 TN3270E servers in a departmental or geographic setting.  For

Naugle, et al. Standards Track [Page 7] RFC 3049 TN3270E Location & Balancing January 2001

 example, if the scope name is Building-D, then the SLP session
 balancing would search all TN3270E servers in the Building-D scope to
 find the least loaded TN3270E server.
 If the scope name is blank, then the scope name is not used.  This is
 referred to as unscoped.  It should be noted as in section 4.1 above
 that any reference to unscoped services applies to Service Location
 Protocol version 1 only [1].  Service Location Protocol version 2
 doesn't allow unscoped services but does allow the use of default
 scope [4].  In this case all TN3270E servers, with or without scope
 names, can be used to satisfy the request for least loaded TN3270E
 servers.  In order to cut down on network overhead, it is recommended
 that either all servers be scoped or no servers be scoped.  Refer
 back to section 4.1 for more discussion of scope.
 DA Discovery Time Out Value
 This value is specified in milliseconds and is fully described in
 section 4.2 of this document.
 SA Multicast Time Out Value
 This value is specified in milliseconds and is fully described in
 section 4.3 of this document.

5.2 How to obtain the list of TN3270E servers supporting SLP

 A TN3270E client that implements SLP session balancing uses API calls
 to obtain the list of TN3270E servers supporting SLP session
 balancing.
 The following Service Location Version 2 API [5] calls, could be used
 with TN3270E SLP session balancing:
 SLPOpen - returns an SLPHandle handle to be used
 SLPFindSrvs - issues the query for services
 SLPFindAttrs - returns service attributes matching the attribute ids
 for the indicated service URL or service type.
 SLPClose - frees all resources associated with the handle.

Naugle, et al. Standards Track [Page 8] RFC 3049 TN3270E Location & Balancing January 2001

5.3 TN3270E Sample Client Flow

5.3.1 Open the SLP connection

 The TN3270E client must first open a handle with the SLP User Agent.
 For Service Location Protocol version 2, SLPOpen API call [5] The SA
 multicast time out and DA discovery time out values would be passed
 as parameters to the SLPOpen API call.

5.3.2 Query the list of TN3270E servers

 The TN3270E client then queries for the list of TN3270E servers
 supporting SLP.  This is done by using the Service Request API call.
 The request string contains information that determines which type of
 TN3270E servers that this client desires to connect to.  The request
 string can contain the scope name, pool name, session type and 3270
 screen size.
 The SLPv1 query string has the following format:
 TN3270/<scope name>/LUPOOL/ == <pool name><TAB><device type>
 The <scope name> is the name of the scope that is configured for the
 TN3270E client.  If the scope is blank or null (unscoped request),
 then the scope is not inserted into the request string.
 The <pool name> is a 1 to 8 character upper case string that
 indicates the name of the pool to which the TN3270E client desires to
 connect.  For SLP session balancing, the same pool name must be
 configured on different TN3270E servers.
 The <TAB> is the '/t' tab character which is hexadecimal 0x09.  the
 <TAB> is a literal and is used as a separator.
 The <device type> can be any of the following:
  3270DSC for TN3270E device type IBM-3287-1
  3270002 for TN3270E device types IBM-3278-2 and IBM-3278-2-E
  3270003 for TN3270E device types IBM-3278-3 and IBM-3278-3-E
  3270004 for TN3270E device types IBM-3278-4 and IBM-3278-4-E
  3270005 for TN3270E device types IBM-3278-5 and IBM-3278-5-E
  * for TN3270E device type IBM-DYNAMIC

Naugle, et al. Standards Track [Page 9] RFC 3049 TN3270E Location & Balancing January 2001

 Example:
 For a TN3270E client searching for TN3270E servers in the ENGINEERING
 scope for a model 2 screen size and LUPOOL name pool2, the following
 request SLPv1 string would be constructed:
 "TN3270/ENGINEERING/LUPOOL/ == POOL2<TAB>3270002"
 Note: The " characters before and after the string are not part of
 the request string.

5.3.3 Forward Looking Example for SLPv2

 For SLPv2 the scope and service type are no longer part of the query
 string.  These are now separate fields in the message.  The service
 type name is required to have the "service:" prepended.  The service
 type field would look like "service:TN3270", and the scope field
 would be a comma separated list of scopes.  A scope name is always
 required in SLPv2, if no other name is known, the scope name
 "DEFAULT" is used.  The example below uses the same parameters as
 used in above section 5.3.2.
 Example:  Service Type: service:TN3270 Scope string: ENGINEERING The
 query string would have the following format:
         (LUPOOL=<POOL2> <32700002>)
 In SLPv2 queries, all whitespace is compressed to a single space
 character during matching, so the identity of the separator character
 does not matter.  The tab character could be added for readability,
 but it will not affect the outcome of the query.

5.3.4 Determine loading of each TN3270E server

 An attribute request for "service:tn3270e" specifying the attribute
 LOAD can be made and you will get back all the available loads.  Say
 these are 35,88,78.  You can then issue a service request for all
 tn3270E servers with "LOAD<40" for instance.  Even if the load
 changes between the time you get the attribute reply and when you
 issue the request, you will still get the best the network has to
 offer.
 The TN3270E client then uses the TN3270E server's IP Host address to
 start normal Telnet TN3270E negotiation.

Naugle, et al. Standards Track [Page 10] RFC 3049 TN3270E Location & Balancing January 2001

5.4 Recommendations

 The TN3270E client SHOULD display the IP hostname and TCP Port that
 is being used for the TN3270E connection.  This gives the user
 knowledge of which TN3270E server the session is connected to.  For
 example, the IP host address could be displayed in the window system
 status bar.
 The TN3270E client SHOULD display the resource name that is returned
 by the TN3270E server after connection and TN3270E negotiation is
 completed.  This gives the user knowledge of which LU resource name
 in the LUPOOL the session is connected to.  For example, the resource
 name could be displayed in the Windows status bar, or even in the
 3270 OIA line.
 In the event that after the TN3270E client has determined the least
 loaded server and the connection to that server fails for some
 reason, the connection should be closed and an attempt made to
 connect to other TN3270E servers in the list of least loaded servers.
 For example, a TN3270E server may reject a connection to a specific
 pool if the pool is full, or if the device type does not match what
 is available in the pool.  If this occurs, then an attempt to other
 least loaded TN3270E servers SHOULD be performed.

6. Sample Trace Flow of SLP and Session Balancing

 This sample trace flow is provided for informational purposes only.
 SLP API: Service Request: TN3270//LUPOOL == POOL2 3270002/
 SLP API: Service Reply: service:tn3270://206.109.45.139:23
 SLP API: Service Reply: service:tn3270://206.109.45.140:23
 Connecting to 206.109.45.139:23...
 TerminalType=NVT
 Connection established
 Recv <- DO TN3270E
 Send -> WILL TN3270E
 TerminalType=TN3270E
 Recv <- SEND DEVICE_TYPE

Naugle, et al. Standards Track [Page 11] RFC 3049 TN3270E Location & Balancing January 2001

 Send -> DEVICE_TYPE REQUEST IBM-3278-2-E CONNECT POOL2
 Recv <- DEVICE_TYPE IS IBM-3278-2-E CONNECT TN8003
 Send -> FUNCTIONS REQUEST BIND_IMAGE SYSREQ
 Recv <- FUNCTIONS IS BIND_IMAGE SYSREQ

7. Service Templates and Service Registration

 The Service Location Protocol uses the "service:" URL scheme name to
 define URLs called "service: URLs".  These schemes provide a way for
 clients to obtain configuration information that is needed to
 establish a 3270 session through the TN3270E server.  The Service
 Location Protocol provides for service: URLs to be registered and
 discovered.
 Service Registration These service registrations contain a service:
 URL, and possible attributes associated with that service.  The
 service registration information are shown below for the server.
 Service Templates Service templates are documents defining in a
 formal way the attributes associated with that service that a client
 may want to use.  For more information on service templates please
 refer to, Service Templates and service:  Schemes. [2].  The server
 service template and TN3270 service templates are shown below.

7.1 The TN3270E Service Type Template

 The 'service:tn3270:' template defined below conforms to the grammar
 described in "Service Templates and service: Schemes".  Please refer
 to [2] for detailed explanation of the syntax.
 Name of submitters: Jim Naugle <jnaugle@us.ibm.com>
                     Gregg Ledford <gledford@zephyrcorp.com>
                     K. Kasthurirangan <kasthuri@us.ibm.com>
 Language of service template: en
 Security Considerations:
 Service Location Protocol can help clients discover security services
 supported by the TN3270E server.  If security services are important
 or required, using SLP authentication, and protected scopes in
 Service Location Protocol version 1 is recommended [1]. Well known
 ciphersuite names are used in the template [3].

Naugle, et al. Standards Track [Page 12] RFC 3049 TN3270E Location & Balancing January 2001

 Template text:
 ----------------------template begins here -------------------------
 template-type=tn3270e
 template-version=1.0
 template-description=
  The tn3270 service provides 3270 gateway access to an SNA network
  via the TN3270 protocol.  The attributes reflect the types of 3270
  devices, LU Pools, and load information available on the server.
 template-url-syntax=
 # service:tn3270://<hostname>:<port>
 # <hostname>
 # <port>
 load=integer
 # This is the load balancing quantity to use in determining the
 # least loaded TN3270E server to attach to for the service.  The
 #range of valid values is an integral 0 to 100 with 0 indicating the
 #lowest possible load and 100 the highest
 LUPool=string X M L
 # This attribute takes on one or more values as defined below.
 # The <TAB> char.  0x09 is literal and will be used as a separator.
 #
 #
 #   <pool name> = <name> / <name> "<TAB>" <dev type>
 #   <name>      = 1*ALPHANUM
 #                 "3270DSC"
 #
 #
 #
 #
 # Identifies the LU pool names of LU pools available for use on this
 # service with the associated device types supported in each pool.
 # Each value is a record where the first token is the pool name of
 # the pool and the second token is a device type supported in that
 # pool.  A pool name without a device type indicates that LUs of
 # unknown type are included in the pool.  Records associated with a
 # given pool name are repeated for each supported device type.  A
 # given pool is included in a registration request if any PU profile
 # that contributes at least one LU to the pool is active on the
 # server.  The range of valid dev_types are:
 #
 # dev_type    Meaning
 #

Naugle, et al. Standards Track [Page 13] RFC 3049 TN3270E Location & Balancing January 2001

 # 3270002     Lu Type 2 Model 2
 #
 # 3270003     Lu Type 2 Model 3
 #
 # 3270004     Lu Type 2 Model 4
 #
 # 3270005     Lu Type 2 Model 5
 #
 # 3270DSC     Printer LU
 #
 BIND=keyword
 # The server supports the SNA bind image TN3270E function.
 DATA=keyword
 # The non-SNA 3270 data stream is supported by server.
 RESPONSES=keyword
 # The server supports SNA response mode.
 SCS=keyword
 # The server supports SNA 3270 SCS data stream.
 SYSREQ=keyword
 # The SYSREQ keyboard key is supported on server.
 RFC1576=keyword
 # RFC1576 options supported.
 RFC1646=keyword
 # RFC1646 options supported.
 RFC2355=keyword
 # RFC2355 options supported.
 security=string M
 # This is the security technique supported on the server.
 # The defined values are:
 NONE
 SSLV3
 Ciphersuites=string M
 # Cipher specifications supported by this server.
 # Additional values will be defined in future templates.
 NULL_NULL,
 NULL_MD5,
 NULL_SHA,
 RC4_MD5_EXPORT,

Naugle, et al. Standards Track [Page 14] RFC 3049 TN3270E Location & Balancing January 2001

 RC4_MD5_US,
 RC4_SHA_US,
 RC2_MD5_EXPORT,
 DES_SHA_EXPORT,
 TRIPLE_DES_SHA_US
 platform=string X
 # This is the network operating system platform underlying the
 # advertising service.  The defined values are:
 #
 # IW          Server uses IntranetWare or NetWare operating system
 #
 # NT          Server uses the Microsoft NT operating system
 #
 # OS2         Server uses the OS2 operating system
 #
 # AIX         Server uses the AIX operating system
 #
 IW,NT,OS2,AIX
 protocol=string X
 #   This is the protocol(s) supported by the server providing this
 #   service.  The defined values are:
 #
 # IP          Server supports client connections over IP (TCP/IP or
 #             UDP/IP)
 #
 # IPX         Server supports client connections over IPX (SPX/IPX)
 #
 IP,IPX
 server name=string
 # This is the name of the server that was configured during
 # installation.
 release=string X
 # This is the version and release level of the server advertising
 # services.  Its format is vv.rr.mm where "vv" is the major version
 # number, "rr" is the minor version number, and "mm" is the
 # modification level.  All numbers are padded on the left with zeroes
 # to two characters.
 # Example: version 3, release 0, mod level 0 is "03.00.00"
  1. —————–template ends here ——————————-

Naugle, et al. Standards Track [Page 15] RFC 3049 TN3270E Location & Balancing January 2001

7.2 Server Service Type Template

 The 'service:commserver:' template defined below conforms to the
 grammar described in "Service Templates and service: Schemes".
 Please refer to [2] for detailed explanation of the syntax.
 Name of submitters: Jim Naugle <jnaugle@us.ibm.com>
                     Gregg Ledford <gledford@zephyrcorp.com>
                     K. Kasthurirangan <kasthuri@us.ibm.com>
 Language of service template: en
 Security Considerations:
 Service Location Protocol can help clients discover security
 services supported by the TN3270E server.  If security services are
 important or required, using SLP authentication, and protected
 scopes [1] is recommended.
 Template text:
  1. ——————template begins below this line——————
 template-type=commserver
 template-version=1.0
 template-description=
  The server service type is registered whenever the communications
  software is loaded on the server.  It describes generic attributes of
  the server.  These attributes are also repeated on the other service
  types provided.
 template-url-syntax=
  # service:commserver://<hostname>:<port>
  # <hostname>
  # <port>
 platform=string X
  # This is the network operating system platform underlying the
  # advertising service.  The defined values are:
  #
  # IW          Server uses Novell IntranetWare or NetWare operating
  #             system
  # NT          Server uses the Microsoft NT operating system
  #
  # OS2         Server uses the OS2 operating system
  #
  # AIX         Server uses the AIX operating system
  #
  IW,NT,OS2,AIX

Naugle, et al. Standards Track [Page 16] RFC 3049 TN3270E Location & Balancing January 2001

 protocol=string X
  #   This is the protocol(s) supported by the server providing this
  #   service.  The defined values are:
  #
  # IP          Server supports client connections over IP (TCP/IP or
  #             UDP/IP)
  #
  # IPX         Server supports client connections over IPX (SPX/IPX)
  #
  IP,IPX
 server name=string
  # This is the name of the server that was configured during
  # installation.
 release=string X
  # This is the version and release level of the commserver
  # advertising services.  Its format is vv.rr.mm where "vv" is the
  # major version number, "rr" is the minor version number, and "mm"
  # is the modification level.  All numbers are padded on the left with
  # zeroes to two characters.
  #
  # Example: version 3, release 0, mod level 0 is "03.00.00"
  1. ——————–template ends above this line———————

7.3 Template Contact Information

 Jim Naugle <jnaugle@us.ibm.com>
 Kasthuri Kasthurirangan <kasthuri@us.ibm.com>
 Gregg Ledford <gledford@zephyrcorp.com>

7.4 Security Considerations

 Service type templates provide information that is used to interpret
 information obtained by the Service Location Protocol.  If these
 templates are modified or if false templates are distributed,
 services may not correctly register themselves, or clients might not
 be able to interpret service information.
 The service: URLs themselves specify the service access point and
 protocol for a particular service type.  These service: URLs could be
 distributed and indicate the location of a service other than that
 normally wanted to used.  SLP [1] provides an authentication
 mechanism that allows service: URLs of registered services to be
 signed and for the signatures to be verified by clients.

Naugle, et al. Standards Track [Page 17] RFC 3049 TN3270E Location & Balancing January 2001

 Service Location Protocol can help clients discover security services
 supported by the TN3270E server.  If security services are important
 or required, using SLP authentication, and protected scopes [1] is
 recommended.

7.5 Sample TN3270 Service Registration Message

 URL: service:tn3270://<addr-spec>:<port-number> Attributes:
 [(SCOPE=<string>),]
 (RELEASE=03.00.00),
 (PLATFORM=IW),
 (PROTOCOL=IP),
 (SERVERNAME=<string>),
 (LOAD=<integer 0 to 100>),
 [(LUPOOL=pool-name0/tANY,
 pool-name1/tdevice_type1,
 pool-name2/tdevice-type2, ...
 pool-namen/tdevice-typen)]
 BIND,
 DATA,
 RESPONSES,
 SCS,
 SYSREQ,
 (SECURITY=NONE),
 RFC1576,
 RFC1646,
 RFC2355

Naugle, et al. Standards Track [Page 18] RFC 3049 TN3270E Location & Balancing January 2001

7.6 Sample Server Service Registration Message

 URL:service:commserver://<addr-spec>:<port-number>
 Attributes:  [(SCOPE=<string>),]
 (RELEASE=03.00.00),
 (PLATFORM=IW),
 (PROTOCOL=IP),
 (SERVERNAME=<string>)

8. References

 [1]  Veizades, J., Guttman, E., Perkins, C., and S. Kaplan, "Service
      Location Protocol", RFC 2165, July 1997.
 [2]  Guttman, E., Perkins, C. and J. Kempf, "Service Templates and
      service: Schemes", RFC 2609, June 1999.
 [3]  Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
      2246, January 1999.
 [4]  Guttman, E., Perkins, C., Veizades, J. and M. Day, "Service
      Location Protocol Version 2", RFC 2608, June 1999.
 [5]  Kempf, J. and E. Guttman, "An API for Service Location", RFC
      2614, June 1999.
 [6]  Bradner, S., "Key Words for Use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

Naugle, et al. Standards Track [Page 19] RFC 3049 TN3270E Location & Balancing January 2001

9. Authors' Addresses

 Jim Naugle
 IBM
 P.O. Box 12195
 Research Triangle Park, N.C. 27709-2195
 USA
 Phone:  (919) 254-8789
 EMail:  jnaugle@us.ibm.com
 Kasthuri Kasthurirangan
 IBM
 P.O. Box 12195
 Research Triangle Park, N.C. 27709-2195
 USA
 Phone: (919) 254-5721
 EMail: kasthuri@us.ibm.com
 Gregg Ledford
 Zephyr Development Corporation
 8 Greenway Plaza Suite 1400
 Houston, Texas 77046
 USA
 Phone: (713) 623-0089
 EMail:  gledford@zephyrcorp.com

Naugle, et al. Standards Track [Page 20] RFC 3049 TN3270E Location & Balancing January 2001

10. Full Copyright Statement

 Copyright (C) The Internet Society (2001).  All Rights Reserved.
 This document and translations of it may be copied and furnished to
 others, and derivative works that comment on or otherwise explain it
 or assist in its implementation may be prepared, copied, published
 and distributed, in whole or in part, without restriction of any
 kind, provided that the above copyright notice and this paragraph are
 included on all such copies and derivative works.  However, this
 document itself may not be modified in any way, such as by removing
 the copyright notice or references to the Internet Society or other
 Internet organizations, except as needed for the purpose of
 developing Internet standards in which case the procedures for
 copyrights defined in the Internet Standards process must be
 followed, or as required to translate it into languages other than
 English.
 The limited permissions granted above are perpetual and will not be
 revoked by the Internet Society or its successors or assigns.
 This document and the information contained herein is provided on an
 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Acknowledgement

 Funding for the RFC Editor function is currently provided by the
 Internet Society.

Naugle, et al. Standards Track [Page 21]

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