Page 1
Configuring X.25
Gateway Services
BayRS V ersion 12.00
Site Manager Software Version 6.00
Part No. 117378-A Rev. A
September 1997
Page 2
4401 Great America Parkway 8 Federal Street
Santa Clara, CA 95054 Billerica, MA 01821
Copyright © 1997 Bay Networks, Inc.
All rights reserved. Printed in the USA. September 1997.
The information in this document is subject to change without notice. The statements, configurations, technical data,
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117378-A Rev. A
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Contents
About This Guide
Before You Begin .............................................................................................................. ix
Conventions ....................................................................................................................... x
Acronyms .......................................................................................................................... xi
Ordering Bay Networks Publications ................................................................................xii
Bay Networks Customer Service ......................................................................................xii
How to Get Help ..............................................................................................................xiii
Chapter 1
X.25 Gateway Overview
X.25 Gateway Topology ..................................................................................................1-2
Network Interfaces ..........................................................................................................1-3
X.25 Level 3 (PLP) Interface ....................................................................................1-3
X.25 Level 2 (LAPB-Only) Interface .........................................................................1-3
TCP Interface ...........................................................................................................1-4
What X.25 Gateway Does ..............................................................................................1-4
Protocol Translation ..................................................................................................1-4
Establishing Connections from the X.25 Equipment ................................................1-6
SVCs With a Called X.121 Address ...................................................................1-6
SVCs Without a Called X.121 Address ..............................................................1-7
Permanent Virtual Circuits (PVCs) ....................................................................1-7
Establishing Connections from the X.25 Level 2 (LAPB) Terminal ...........................1-7
Establishing Connections During Failure Conditions for
PVC/TCP Translation ...............................................................................................1-8
Reestablishing the X.25 Connection .................................................................1-8
Reestablishing the TCP/IP Connection .............................................................1-9
Establishing Connections from the TCP/IP Host ......................................................1-9
Connection Summary ...................................................................................................1-11
Handling Large Data Messages ...................................................................................1-12
117378-A Rev. A
v
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How X.25 Handles Large Data Messages .............................................................1-12
How TCP Handles Large Data Messages ..............................................................1-12
X.25 Gateway Message Block Options ..................................................................1-13
Chapter 2
Enabling X.25 Gateway
Preparing a Configuration File ........................................................................................2-1
Configuring X.25 IPEX Services .....................................................................................2-1
Enabling X.25 Gateway Services ...................................................................................2-2
Adding an Entry to the IPEX Mapping Table ............................................................2-2
Configuring Mapping Parameters ............................................................................2-7
IPEX Mapping Parameters Windows .......................................................................2-7
Parameters for PVC and SVC Connections .............................................................2-9
Parameters for TCP Connections ...........................................................................2-11
Replicating a Configuration ..........................................................................................2-12
Parameters for Replicating Connections ......................................................................2-18
Index
vi
117378-A Rev. A
Page 7
Figures
Figure 1-1. Sample Network Topology Using X.25 Gateway ......................................1-2
Figure 1-2. How X.25 Gateway Establishes a Session (X.25 Initiated) ......................1-5
Figure 1-3. Reestablishing X.25 Connections ............................................................1-8
Figure 1-4. Reestablishing TCP/IP Connections ........................................................1-9
Figure 1-5. How X.25 Gateway Establishes a Session (TCP Initiated) ....................1-10
Figure 1-6. Role of the X.25 and TCP Protocol Stacks in X.25 Gateway .................1-11
Figure 2-1. IPEX Mapping Add Window for Source PVC ...........................................2-3
Figure 2-2. IPEX Mapping Parameters Window for PVC ...........................................2-8
Figure 2-3. IPEX Mapping Parameters Window for SVC ...........................................2-8
Figure 2-4. IPEX Mapping Parameters Window for TCP ............................................2-9
Figure 2-5. IPEX Mapping Table Configuration Window ...........................................2-13
Figure 2-6. IPEX Mapping Replication Window ........................................................2-15
Figure 2-7. IPEX Mapping Table Configuration Window After Replicating a
PVC-to-TCP Connection ........................................................................2-16
Figure 2-8. IPEX Mapping Table Configuration Window After Replicating a
TCP-to-PVC Connection ........................................................................2-17
117378-A Rev. A
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Page 8
Page 9
About This Guide
If you are responsible for configuring X.25 Gateway services, you need to read
this guide.
If you want to Go to
Learn about the X.25 Gateway protocol and special aspects of the Bay
Networks implementation of X.25 Gateway
Start X.25 Gateway on a router and configure Gateway parameters Chapter 2
Before Y ou Begin
Before using this guide, you must complete the following procedures. For a new
router:
• Install the router (refer to the installation manual that came with your router).
• Connect the router to the network and create a pilot configuration file (refer to
Quick-Starting Routers, Configuring BayStack Remote Access
ASN Routers to a Network)
Make sure that you are running the latest version of Bay Networks Site Manager
and router software. For instructions, refer to
7–11.xx to Version 12.00
Chapter
, or
1
Connecting
.
Upgrading Routers from Version
.
117378-A Rev. A
ix
Page 10
Configuring X.25 Gateway Services
Conventions
bold text
Indicates text that you need to enter, command names,
and buttons in menu paths.
Example: Enter
Example: Use the
Example: ATM DXI > Interfaces >
wfsm &
dinfo
command.
PVCs
identifies the
PVCs button in the window that appears when you
select the Interfaces option from the ATM DXI menu.
italic text
Indicates variable values in command syntax
descriptions, new terms, file and directory names, and
book titles.
quotation marks (“ ”) Indicate the title of a chapter or section within a book.
screen text
Indicates data that appears on the screen.
Example:
Set Bay Networks Trap Monitor Filters
separator ( > ) Separates menu and option names in instructions and
internal pin-to-pin wire connections.
Example: Protocols > AppleTalk identifies the
AppleTalk option in the Protocols menu.
Example: Pin 7 > 19 > 20
vertical line (|) Indicates that you enter only one of the parts of the
command. The vertical line separates choices. Do not
type the vertical line when entering the command.
Example: If the command syntax is
show at routes
show at routes
x
nets
, you enter either
|
show at nets
or
, but not both.
117378-A Rev. A
Page 11
Acronyms
About This Guide
CCITT International Telegraph and Telephone Consultative Committee
(now ITU-T)
DCE data circuit-terminating equipment
DDN Defense Data Network
DTE data terminal equipment
FDDI Fiber Distributed Data Interface
IP Internet Protocol
IPEX IP Encapsulation of X.25
ITU-T International T elecommunications Union–Telecommunications
(formerly CCITT)
LAN local area network
LAPB Link Access Procedure Balanced
LCN logical channel number
MAN metropolitan area network
MIB Management Information Base
MCT1 Multichannel T1
MTU maximum transmission unit
PDN Public Data Network
PLP Packet Layer Protocol
PPP Point-to-Point Protocol
PToP Point-to-Point (Bay Networks proprietary)
PVC permanent virtual circuit
SNMP Simple Network Management Protocol
SVC switched virtual circuit
TCP Transmission Control Protocol
TCP/IP Transmission Control Protocol/Internet Protocol
Telnet Telecommunication Network
TFTP Trivial File Transfer Protocol
WAN wide area network
117378-A Rev. A
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Page 12
Configuring X.25 Gateway Services
Ordering Bay Networks Publications
To purchase additional copies of this document or other Bay Networks
publications, order by part number from Bay Networks Press
numbers:
• Phone--U.S./Canada: 888-422-9773
• Phone--International: 510-490-4752
• FAX--U.S./Canada and International: 510-498-2609
The Bay Networks Press catalog is available on the World Wide Web at
support.baynetworks.com/Library/GenMisc
available on the W orld W ide Web at
support.baynetworks.com/Library/tpubs
Bay Networks Customer Service
You can purchase a support contract from your Bay Networks distributor or
authorized reseller, or directly from Bay Networks Services. For information
about, or to purchase a Bay Networks service contract, either call your local Bay
Networks field sales office or one of the following numbers:
™
at the following
. Bay Networks publications are
.
xii
Region Telephone number Fax number
United States and
Canada
Europe 33-4-92-96-69-66 33-4-92-96-69-96
Asia/Pacific 61-2-9927-8888 61-2-9927-8899
Latin America 561-988-7661 561-988-7550
800-2LANWAN; then enter Express
Routing Code (ERC) 290, when prompted,
to purchase or renew a service contract
978-916-8880 (direct)
978-916-3514
Information about customer service is also available on the World Wide Web at
support.baynetworks.com
.
117378-A Rev. A
Page 13
How to Get Help
If you purchased a service contract for your Bay Networks product from a
distributor or authorized reseller, contact the technical support staff for that
distributor or reseller for assistance.
If you purchased a Bay Networks service program, call one of the following Bay
Networks Technical Solutions Centers:
Technical Solutions Center Telephone number Fax number
Billerica, MA 800-2LANWAN 978-916-3514
Santa Clara, CA 800-2LANWAN 408-495-1188
Valbonne, France 33-4-92-96-69-68 33-4-92-96-69-98
Sydney, Australia 61-2-9927-8800 61-2-9927-8811
Tokyo, Japan 81-3-5402-0180 81-3-5402-0173
About This Guide
117378-A Rev. A
xiii
Page 14
Page 15
Chapter 1
X.25 Gateway Overview
X.25 Gateway lets you send and receive messages between X.25 and
Transmission Control Protocol/Internet Protocol (TCP/IP) networks. It maps TCP
sockets to X.25 virtual circuits (and vice versa) or to Link Access Procedure
Balanced (LAPB) point-to-point connection identifiers.
The Gateway software supports X.25 permanent virtual circuits (PVCs) and
switched virtual circuits (SVCs), as well as TCP/IP over all interface types
supported in the Bay Networks router.
117378-A Rev. A
X.25 Gateway supports:
• TCP/IP over Fiber Distributed Data Interface (FDDI), Ethernet, and token
ring LAN media, or over X.25, frame relay, Asynchronous Transfer Mode
(ATM), and switched multimegabit data service (SMDS), wide area network
(WAN), or metropolitan area network (MAN) media
• X.25 Levels 2 and 3 over synchronous interfaces (6 MB/s and below) or
Multichannel T1 (MCT1) interfaces
• 10 VCs per logical channel for the FRE2-040-32MB platform, for a total of
240VCs per slot
• 32 VCs per channel for the FRE1-060-64MB, for a total of 310VCs per slot
Use Site Manager’s Configuration Manager to configure a system for X.25
Gateway services.
1-1
Page 16
Configuring X.25 Gateway Services
X.25 Gateway Topology
igure 1-1 shows a topology consisting of two Bay Networks router systems and a
F
TCP/IP network. The top system serves as a TCP/IP-to-X.25 gatew ay. The bottom
system serves as a TCP/IP-to-LAPB gateway. In this example, terminals
connected to X.25 networks can exchange messages with host systems on a
TCP/IP network through the Bay Networks routers using the X.25 Gateway
service.
X.25
terminals
Physical
(V.35) links
X.25
concentrator
LAPB
concentrator
X.25 Level 3
connections
V.35 or
T1 links
V.35 or
T1 links
X.25 Level
(LAPB)
connections
X.25
gateway
router
X.25
gateway
router
TCP
connections
TCP/IP
Figure 1-1. Sample Network Topology Using X.25 Gateway
The router translates data received from X.25 virtual connections into TCP data
packets and forwards those packets out through TCP connections. The router also
translates data received from TCP connections into X.25 data and forwards the
data out through X.25 connections. You can connect the equipment to the router
by a leased line, an X.25 packet-switched network, or a T1 or E1 circuit-switched
network.
You can also configure the router as a TCP/IP-to-CCITT (now ITU-T) X.25 Level
2 gateway as in the bottom part of F
igure 1-1. This configuration allows access
from LAPB-based (X.25 Level 2) equipment with no X.25 Level 3 support. This
manual refers to this feature as
LAPB-only support.
TCP/IP
host
TCP/IP
host
X250022A
1-2
With this configuration, the router translates data received from LAPB
connections to TCP data packets and forwards those packets out through TCP
connections. It also translates data received from TCP connections to LAPB data
and forwards the data out through LAPB connections.
117378-A Rev. A
Page 17
Network Interfaces
Bay Networks routers that support X.25 Gateway services use the following
protocols:
• X.25 Level 3 Packet Layer Protocol (PLP)
• X.25 Level 2 Protocol (LAPB)
• Transmission Control Protocol (TCP)
• Internet Protocol (IP)
X.25 Level 3 (PLP) Interface
On an X.25 Level 3 interface, you can create and configure multiple virtual
circuits, including:
• Permanent virtual circuits
• Switched virtual circuits, with or without called X.121 addresses
You can create a set of either of these connections or a combination of the two. On
any X.25 interface, you can configure either X.25 Gateway service or other types
of X.25 services, such as Public Data Network (PDN), Point-to-Point (PToP), and
Defense Data Network (DDN). If you configure X.25 Gateway service on an X.25
interface, the software translates data sent and received between the X.25 netw ork
interface and the TCP/IP network interface. It uses X.25 flo w control mechanisms
to detect congestion in the X.25 connection.
X.25 Gateway Overview
X.25 Gateway uses the X.25 Level 3 client interface to:
• Open and close X.25 connections
• Send data to the X.25 module for transmission
• Process received data delivered from the X.25 module
• Control the flow of data across the client interface
X.25 Level 2 (LAPB-Only) Interface
X.25 Gateway also supports a direct LAPB interface, so terminals can transfer
data in LAPB format without using the X.25 packet layer. You can select specific
LAPB link circuits for the translation service to use instead of the X.25 PLP.
117378-A Rev. A
1-3
Page 18
Configuring X.25 Gateway Services
TCP Interface
X.25 Gateway appears to TCP as a client. As such, the software specifies one
socket
for the local TCP interface (consisting of its IP address and TCP port
number) and another socket for the remote TCP interface to establish a
connection. Each X.25 connection corresponds to only one TCP connection.
Since many TCP connections may be active concurrently to support many
Gateway sessions, a large range of TCP port numbers creates separate sockets for
individual sessions. The port numbers reserved for X.25 Gateway service are
12,304 to 16,399.
X.25 Gateway uses the TCP client interface to
• Open, close, and check the status of TCP connections.
• Send data to the TCP module for transmission.
• Process received data delivered from the TCP module.
• Control the flow of data across the client interface.
What X.25 Gateway Does
X.25 Gateway consists of a source circuit and a destination circuit. The gateway
receives the first incoming connection on the
establish an outgoing connection on the
source circuit is the one with the X.25 connection.
Protocol T ranslation
igure 1-2 shows the sequence of establishing the translation session when the
F
connection request comes from the X.25 terminal.
1-4
source circuit
destination circuit
, and attempts to
igure 1-2, the
. In F
117378-A Rev. A
Page 19
X.25 Gateway Overview
X.25
Step 1
Step 2
Step 3
Step 4
X.25
terminal
X.25
terminal
X.25
terminal
X.25
terminal
X.25
connection
requested
X.25
request
pending
X.25
request
pending
X.25
request
accepted
gateway
router
X.25
gateway
router
X.25
gateway
router
X.25
gateway
router
TCP
connection
attempt
TCP
connection
accepted
TCP
connection
established
TCP/IP
host
TCP/IP
host
TCP/IP
host
TCP/IP
host
X250023A
117378-A Rev. A
Figure 1-2. How X.25 Gateway Establishes a Session (X.25 Initiated)
If the router detects congestion on the receiving side of the network, it controls the
data flow by queuing the requests on the sending side until the congestion lifts or
the connection terminates.
1-5
Page 20
Configuring X.25 Gateway Services
Establishing Connections from the X.25 Equipment
Either the X.25 equipment or the TCP/IP-based system can request a connection.
The software relies on a set of configured
X.25 connection on one side of the router to the TCP connection on the other side.
In response to a connection request from the X.25 equipment, the router
establishes a connection to a TCP/IP server. When this TCP connection is
established, the router accepts the X.25 connection attempt. This one-to-one
connection mapping creates a consistent and reliable Gateway session.
The types of X.25 connections that X.25 Gateway supports include:
• Switched virtual circuits (SVCs)
• Switched virtual circuits with no X.121 called address
• Permanent virtual circuits (PVCs)
With an X.25 Level 3 interface, you can establish a switched virtual circuit or a
permanent virtual circuit between the X.25 equipment and the TCP-based system.
An SVC is a temporary logical connection. It may or may not have a “called
address” associated with it (depending on whether the type of connection that you
configured required an X.121 called address). The following sections describe
what you configure for each of these connections.
mapping
parameters to associate the
1-6
SVCs With a Called X.121 Address
To establish an SVC connection that contains a specified X.25 called address
(X.121 address), you configure mapping information that X.25 Gateway uses to
set a path for forwarding data traffic receiv ed on an X.25 SVC to a specific remote
TCP/IP peer. The remote TCP/IP peer has an IP address and TCP port number that
correspond to the X.25 called address. This correspondence is the mapping
information that you must configure for X.25-to-TCP conversion. The mapping
information consists of:
• The point of attachment (that is, the circuit interface) on the Gateway system
at which the SVC establishes the connection
• The X.25 called address of the incoming connection
• The associated remote TCP socket (IP address and TCP port number) that
identifies the remote end of the TCP connection
117378-A Rev. A
Page 21
X.25 Gateway Overview
SVCs Without a Called X.121 Address
When the X.25 SVC connection does not contain an X.121 called address in the
incoming call request packet, you specify the SVC service on that circuit to be a
“special” SVC service interface by configuring:
• The circuit interface in X.25 Gateway at which the SVC establishes the
connection
• The SVC service interface on that circuit, which is “special” in that it must be
set up as a data terminal equipment (DTE) interface, instead of as a data
circuit-terminating equipment (DCE) interface
• The associated remote TCP socket (remote IP address and TCP port number)
that identifies the remote end of the TCP connection
The router uses this information to form a translation session by accepting this
connection and establishing an associated TCP connection.
Permanent Virtual Circuits (PVCs)
For each permanent virtual circuit connection between the X.25 system and X.25
Gateway, there is a corresponding TCP connection set up between X.25 Gateway
and the TCP/IP peer. This connection remains established until either:
117378-A Rev. A
• The X.25 equipment resets the PVC connection.
• The X.25 interface is restarted.
• The TCP peer terminates the TCP connection.
The mapping information that you must configure is:
• The circuit interface for the PVC connection
• The logical channel number (LCN) of the PVC connection
• The associated remote TCP socket (IP address and TCP port number) that
identifies the remote end of the TCP connection
1-7
Page 22
Configuring X.25 Gateway Services
Establishing Connections from the X.25 Level 2 (LAPB) Terminal
The router uses a similar procedure for establishing LAPB-to-TCP connections.
You must specify the mapping information needed to configure the connection,
specifically:
• The circuit interface through which X.25 Gateway will establish a LAPB
connection
• Its associated remote TCP socket, which identifies the remote end of the TCP
connection
This mapping information sets up the path for forwarding data traffic receiv ed in a
LAPB circuit to a specific remote TCP/IP server and for forwarding data traffic
received from a TCP connection to a specific LAPB circuit.
When it has established this LAPB-to-TCP translation session, X.25 Gateway
translates the LAPB information frames it receives from the LAPB terminals into
TCP data segments, and vice versa.
Establishing Connections During Failure Conditions for PVC/TCP T ranslation
1-8
The X.25 Gateway software running on X.25 PVC devices is able to reestablish a
connection when a fault occurs at the TCP/IP or X.25 physical layer. You do not
have to enable or configure this feature. The figures below show how the software
reestablishes a connection between X.25 and TCP/IP.
Reestablishing the X.25 Connection
When a physical layer fault occurs (a disconnected cable) at the X.25 interface
(Figure 1-3), X.25 Gateway disconnects the associated TCP connections. It
reestablishes the TCP connections to the mapped X.25 virtual circuits when the
X.25 interface is again available.
117378-A Rev. A
Page 23
X.25 Gateway Overview
X.25
TCP/IP
host
gateway
router
X.25
terminal
TCP
connections
reset
X.25
interface
down
X250024A
Figure 1-3. Reestablishing X.25 Connections
Reestablishing the TCP/IP Connection
In the event of a physical layer fault on the TCP/IP interface (F
igure 1-4), X.25
Gateway resets any established TCP connections as well as the X.25 connections
associated with each TCP connection. The software attempts to reestablish a TCP
connection until the TCP interface is again available. When TCP connections are
available, the software resets the X.25 connections to an operational state.
Examples of physical layer faults include a disconnected cable or a failure at
either the X.25 Gateway or remote TCP/IP host interface.
X.25
TCP/IP
host
gateway
router
X.25
terminal
X.25
interface
down
TCP
connections
reestablished
Figure 1-4. Reestablishing TCP/IP Connections
Establishing Connections from the TCP/IP Host
When a TCP/IP-based system issues a connection request, X.25 Gateway
performs the sequence of actions shown in 1-
117378-A Rev. A
5
X250025A
1-9
Page 24
Configuring X.25 Gateway Services
TCP/IP
host
Step 1
Connection
requested
TCP/IP
host
Step 2
Request
pending
TCP/IP
host
Step 3
Request
pending
TCP/IP
host
Step 4
Request
accepted
X.25
gateway
router
X.25
gateway
router
X.25
connection
X.25
gateway
router
X.25
gateway
router
attempt
X.25
connection
accepted
X.25
connection
established
X.25
terminal
X.25
terminal
X.25
terminal
X.25
terminal
X250026A
Figure 1-5. How X.25 Gateway Establishes a Session (TCP Initiated)
After establishing the X.25 connection, X.25 Gateway accepts the TCP
connection. This one-to-one connection mapping provides another consistent and
reliable session. The mapping information you need to configure is:
• The circuit interface on which X.25 Gateway establishes the TCP connection
• The TCP port number that uniquely identifies the translation session
• The type of connection, SVC or PVC, at the X.25 end of the connection
• The logical channel number (LCN) of the PVC connection, or the pair of
calling and called X.121 addresses of the SVC connection
1-10 117378-A Rev. A
Page 25
After establishing this X.25-to-TCP session, X.25 Gateway translates X.25 Level
3 data packets received from the X.25 client terminals to TCP data segments, and
vice versa.
Connection Summary
To set up a reliable X.25 Gateway session, both sides must successfully establish
the connections. When one side receives a connection indication, the other side
initiates a connection attempt. If the connection attempt fails on the far side, the
near side rejects the connection request it received.
igure 1-6 shows how X.25 Gateway mediates the interaction between the two
F
protocol stacks as the data flows between the X.25 client terminals and the
TCP-based hosts.
Information
from/to other
X.25 terminals
X.25 Gateway Overview
Information
from/to other
TCP hosts
or other Gateway
routers
X.25 Gateway
TCP
IP
IEEE 802.2
FDDI
IEEE 802.5
IEEE 802.3
TCP
IP
SNMP
IEEE 802.2
IEEE 802.3
X.25 level 3
X.25 level 2
V.35
SNMP SNMP
X.25 level 3
X.25 level 2
MCT1/E1
SYNC
Figure 1-6. Role of the X.25 and TCP Protocol Stacks in X.25 Gateway
117378-A Rev. A 1-11
Page 26
Configuring X.25 Gateway Services
The TCP and X.25 communication stacks share the responsibility for maintaining
reliable and efficient data flow. If data loss occurs on one side, that side
retransmits the lost data. In addition, both sides independently maintain protocol
flow control.
Data loss may result from either software or hardware errors, or catastrophic
failures. Redundancy in network design is critical for handling these types of data
communication failures.
Handling Large Data Messages
X.25 is a message-based protocol, and TCP is an unstructured stream protocol.
They differ in the way they send outgoing traffic and deliver incoming traffic to
their clients.
How X.25 Handles Large Data Messages
When the X.25 client submits an X.25 message that is larger than an X.25 packet
size, the X.25 protocol fragments the message. X.25 then transmits the sequence
of packets containing these fragments. Within each packet, X.25 includes a flag
that indicates the fragmentation and aids in the reassembly process at the
receiving end.
How TCP Handles Large Data Messages
TCP, on the other hand, does not have a flag to mark fragmentation of messages
that are larger than the TCP maximum transmission unit (MTU) size. The portion
that does not fit into one TCP data segment is sent in a subsequent data segment.
Without the flag and any indication of the size of the message, the TCP client has
no way of determining the boundary of a message; that is, whether the complete
message is contained within one or in several data segments. When X.25 Gate w ay
receives the X.25 user data and translates it to a TCP data segment, the message
boundary is lost.
To minimize changes in the existing host applications, X.25 Gateway maintains
the X.25 message boundary . It structures the application information into message
blocks before encapsulating it in TCP data segments. Each message block
contains a header and a data portion.
1-12 117378-A Rev. A
Page 27
X.25 Gateway Message Block Options
You can configure X.25 Gateway with the following message block options.
• No message block structure in any TCP segment -- X.25 Gateway translates
each TCP data segment as a complete message.
• Message length specified -- The header portion of the message contains a
2-byte message length field. The data portion holds the actual application
information. The length field indicates the total length of the application data
portion in the message block.
• Message version, type, and length specified in the header -- The header
specifies the version of the message header format, including a More flag bit.
The Type field specifies the message type, DATA. The data portion holds the
actual application information.
The message block options that let you specify the message length allow TCP
clients to determine message boundaries. Depending on the size of the message
block, a TCP data segment can contain multiple message blocks. A lar ger message
block may be transmitted in several TCP data segments. With the 2-byte length
field, the maximum length of a message block that X.25 Gateway can send and
receive using TCP is 64 KB.
X.25 Gateway Overview
Note: While the maximum length of the X.25 message that X.25 Gateway can
send to the terminal is 64 KB, the maximum length of the X.25 message that
X.25 Gateway can receive from the terminal is 4 KB.
117378-A Rev. A 1-13
Page 28
Page 29
Chapter 2
Enabling X.25 Gateway
This chapter, as outlined in the following table, describes how to use the
Configuration Manager to set up X.25 Gateway services.
Section Page
Preparing a Configuration File 2-1
Configuring X.25 IPEX Services 2-1
Enabling X.25 Gateway Services 2-2
Adding an Entry to the IPEX Mapping Table 2-2
Complete the following steps to configure IPEX mapping parameters: 2-7
Preparing a Configuration File
Before you configure X.25 Gateway:
1. Create and save a configuration file that has at least one WAN interface.
2. Retrieve the configuration file in local, remote, or dynamic mode.
3. Specify router hardware if this is a local-mode configuration file.
Refer to Configuring and Managing Routers with Site Manager for instructions.
Configuring X.25 IPEX Services
When you enable X.25 Gateway services, you must configure X.25 IPEX
services. Refer to Chapters 3 and 4 of Configuring X.25 Services for instructions
on enabling X.25 and editing X.25 parameters. Refer to Chapter 5 of that guide
for instructions on configuring IPEX.
117378-A Rev. A 2-1
Page 30
Configuring X.25 Gateway Services
Enabling X.25 Gateway Services
To enable X.25 Gateway services:
1. Add an entry to the IPEX mapping table.
2. Choose Gateway as the IPEX Mapping Type.
3. Configure mapping parameters.
Use the following instructions to add an IPEX mapping entry and choose Gateway
as the mapping type
Adding an Entry to the IPEX Mapping Table
Complete the following steps to add an entry to the IPEX mapping table:
You do this System responds
.
Site Manager Procedure
1. In the Configuration Manager window,
select Circuits > Edit Circuits.
2. Choose an X.25 interface, then click on
Edit.
3. Choose X25 Protocol > Service. The X.25 Service Configuration window
4. Choose the network service record you
want to configure for X.25 Gateway
services.
5. Click on Add. The X.25 Service window opens.
6. Position your cursor in the Type parameter
bar, click on the Values button, and
choose IPEX as the service type.
The Circuit List window opens.
The Circuit Definition window opens.
appears. It lists all currently defined
network service records.
2-2 117378-A Rev. A
Page 31
Enabling X.25 Gateway
Site Manager Procedure
You do this System responds
7. Edit the following parameters as
appropriate to your network. Use Help or
see the parameter descriptions in
(continued)
Configuring X.25 Services.
• First PVC LCN
• Number of PVC LCN
• Service VC Type
• Window Size
• Packet Size
8. Click on OK. The IPEX Mapping Table Configuration
window opens.
9. Click on Add. The IPEX Mapping Add window opens
10.Set the following parameters. Click on
Help or see the parameter descriptions
beginning on page
• Source Connection Type
• Mapping Type
• TCP Circuit Name
• TCP Header Type
2-4.
(Figure
2-1).
117378-A Rev. A 2-3
Page 32
Configuring X.25 Gateway Services
Figure 2-1. IPEX Mapping Add Window for Source PVC
Note: This window is the same for PVC, SVC, and TCP source connections.
The Mapping Type is always Gateway. Values for the other parameters are
specific to your network.
Parameter: Source Connection Type
Default: None
Options: PVC
| SVC | TCP
Function: Specifies the type of connection at the sending end of the original
message. PVC and SVC specify an X.25 Level 3 connection, either a
permanent virtual circuit or a switched virtual circuit. TCP is a
Transmission Control Protocol connection.
Source connection types PVC and SVC send to destination connection
type TCP. Source connection type TCP sends to destination connection
type PVC or SVC.
Instructions: Select PVC to specify an X.25 connection to a permanent virtual circuit.
Select SVC to specify an X.25 connection to a switched virtual circuit.
Select TCP to specify a Transmission Control Protocol connection.
MIB Object ID: 1.3.6.1.4.18.3.5.15.2.1.4
2-4 117378-A Rev. A
Page 33
Enabling X.25 Gateway
Parameter: Mapping Type
Default: End_to_End
Options: Local
| End_to_End | Gateway
Function: Specifies whether facilities, call user data, and M-bit and Q-bit support
terminate locally or are passed end-to-end. X.25 parameters that you
configure at the packet and service record level determine which facilities
are supported. The last option is to configure X.25 Gateway services.
If you set this parameter to Local, IPEX ports can support different packet
sizes at each end. You must also configure the Source X.121 Address
parameter for an SVC source connection type, and both Source and
Destination X.121 Address parameters for a TCP source connection type.
If you configure End-to-End mapping, all IPEX ports must have the same
packet and window size, because different packet sizes cause M-bit
support to malfunction.
If you set this parameter to Gateway you use X.25 Gateway services.
X.25 terminates at the router interface, but allows you to configure one of
three message header types at the TCP application layer.
Instructions: Choose Gateway.
MIB Object ID: 1.3.6.1.4.1.18.3.5.15.2.1.16
117378-A Rev. A 2-5
Page 34
Configuring X.25 Gateway Services
Parameter: TCP Circuit Name
Default: None
Options: The name of this circuit. When you add a TCP circuit, the name is
displayed in the Add Circuit window.
Function: Identifies this TCP circuit for mapping purposes.
Instructions: Enter the name of the appropriate TCP circuit. If you do not know this
name, return to the main Configuration Manager window and click on the
connector you are configuring to reopen the Add Circuit window.
Parameter: TCP Header Type
Default: Short
Options: None
Function: Enables the Message Boundary Protocol. This bit marks the boundary of
Instructions: Choose a header type.
MIB Object ID: 1.3.6.1.4.1.18.3.5.15.2.1.22
| Short | Long
TCP application data that is consistent with Gateway operation.
None means that there is no message header; Message Boundary Protocol
is off.
Short means that the message header contains a 2-byte length field.
Long means that the message header contains a 1-byte type, a 1-byte
version, and a 2-byte length field.
2-6 117378-A Rev. A
Page 35
Configuring Mapping Parameters
Complete the following steps to configure IPEX mapping parameters:
You do this System responds
Enabling X.25 Gateway
Site Manager Procedure
1. In the IPEX Mapping Add window, click
on OK.
2. Configure the parameters appropriate to
your connection type. Clic k on Help or see
the parameter descriptions beginning on
page
2-9. Parameters include:
• Source PVC LCN
• X.121 Called Address
• Remote IP Address
• Remote TCP Port Number
• Local TCP Port
• Destination Connection Type
• Destination PVC LCN
3. Click on OK
4. Click on Done. The X.25 Gateway configuration is
5. To learn how to replicate this configuration
for other PVC/TCP connections, see the
later section of the guide, “Replicating a
Configuration.” Otherwise, click on Done.
. The IPEX Mapping Table Configuration
The IPEX Mapping Parameters window
opens. Depending on your Source
Connection T ype , Figure
or Figure
window reopens.
complete. You return to the X.25 Service
Configuration window.
You return to the main Configuration
Manager window.
2-4 opens.
2-2, Figure 2-3,
IPEX Mapping Parameters Windows
In the appropriate IPEX Mapping Parameters window, define a new mapping
entry by specifying source and destination addresses, the format of which depend
on whether the connection type is PVC, SVC, or TCP.
117378-A Rev. A 2-7
Page 36
Configuring X.25 Gateway Services
Figure 2-2. IPEX Mapping Parameters Window for PVC
Figure 2-3. IPEX Mapping Parameters Window for SVC
2-8 117378-A Rev. A
Page 37
Enabling X.25 Gateway
Figure 2-4. IPEX Mapping Parameters Window for TCP
Parameters for PVC and SVC Connections
Parameter descriptions for PVC and SVC connections follow:
Parameter: Source PVC LCN
Default: None
Options: 1 to 4095
Function: Specifies the inbound PVC LCN that you map to the TCP connection.
The port monitors the X.25 calls for this LCN to initiate the connection.
Instructions: This window appears only if you chose PVC as your source connection
type. Enter the LCN of the PVC for this IPEX connection.
MIB Object ID: 9999.109#1
117378-A Rev. A 2-9
Page 38
Configuring X.25 Gateway Services
Parameter: X.121 Called Address
Default: None
Options: Any valid X.121 address
Function: Specifies the inbound X.121 called address that you map to the TCP
connection. The port monitors the X.25 calls for this X.121 called address
to initiate the connection.
Instructions: This window appears only if you chose SVC as your source connection
type. Enter the called X.121 address (up to 15 decimal digits). The
destination address depends on the network device to which this circuit is
connected. Consult your network administrator for the correct value.
MIB Object ID: 1.3.6.1.4.18.3.5.15.2.1.6
Parameter: Remote IP Address
Default: None
Options: Any valid IP address
Function: Specifies the remote IP address used to establish a TCP connection to the
destination. You configure this parameter only when the source
connection type is SVC.
Instructions: Enter the IP address of the remote connection. Use dotted-decimal
notation (for example, 1.1.1.1). Consult your network administrator for
the correct value.
MIB Object ID: 1.3.6.1.4.1.18.3.5.15.2.1.12
2-10 117378-A Rev. A
Page 39
Parameter: Remote TCP Port Number
Default: None
Options: The TCP port number at the remote connection, a value between 12304
and 16399.
Function: Specifies the remote TCP port number used to establish a TCP connection
to the destination. The remote TCP port originates connections to the
local TCP port. You configure this parameter only when the source
connection type is SVC.
Instructions: Enter the TCP port number for the remote connection.
MIB Object ID: 1.3.6.1.4.1.18.3.5.15.2.1.13
Parameters for TCP Connections
Parameter descriptions for TCP connections follow:
Parameter: Local TCP Port
Enabling X.25 Gateway
Default: None
Options: The local TCP port number, a value between 12304 and 16399.
Function: Specifies the TCP port in the local IPEX connection. This port accepts
inbound TCP connections from the remote TCP port. You configure this
parameter when the Source Connection Type is TCP.
Instructions: Enter the TCP port number.
MIB Object ID: 1.3.6.1.4.18.3.5.15.2.1.5
117378-A Rev. A 2-11
Page 40
Configuring X.25 Gateway Services
Parameter: Destination Connection Type
Default: None
Options: SVC
Function: Specifies either SVC or PVC as the destination connection for this TCP
Instructions: Choose the value that applies to your network.
Note: Either the source or the destination connection type (but not both)
must be TCP.
Parameter: Destination PVC LCN
Default: None
Options: 1 to 4095
Function: Specifies the PVC LCN that you map to the TCP connection. The port
Instructions: This window appears only if you chose PVC as your source connection
| PVC
source connection.
1.3.6.1.4.1.18.3.5.15.2.1.8
monitors the X.25 calls for this LCN to initiate the connection.
type. Enter the LCN of the PVC for this IPEX connection.
Replicating a Configuration
After you have configured one PVC-to-TCP or TCP-to-PVC connection, you can
copy that configuration and apply it to other connections, rather than configuring
the mappings one at a time. If you need to customize some of the connections, you
can edit them later.
Note: The Copy function works when one end of a connection is a PVC and
the other is TCP. It does not work with SVC connections.
Use the Copy button in the IPEX Mapping Table Configuration window
igure 2-5) to replicate a configuration. The window is the same for both
(F
PVC-to-TCP and TCP-to-PVC connections; the information the window displays
varies according to the configuration.
2-12 117378-A Rev. A
Page 41
Enabling X.25 Gateway
Figure 2-5. IPEX Mapping Table Configuration Window
To replicate a PVC-to-TCP or TCP-to-PVC configuration, complete the tasks in
the following table.
117378-A Rev. A 2-13
Page 42
Configuring X.25 Gateway Services
You do this System responds
Site Manager Procedure
1. Choose the configuration you want to
replicate, and click on Copy.
2. Set the following parameters. Click on
Help or see the parameter descriptions
beginning on 2-
• Number of instances
• First LCN number
• First TCP port number
• TCP port number increment
3. Click on OK. The IPEX Mapping Table Configuration
4. Click on Done. You return to the X.25 Service
5. Click on Done. You return to the main Configuration
18:
The IPEX Mapping Replication window
opens (Figure
window reopens (Figure
PVC-to-TCP, Figure
It now lists all of the connections you
have configured with the Copy button.
Configuration window.
Manager window.
2-6).
2-7 for
2-8 for TCP-to-PVC).
2-14 117378-A Rev. A
Page 43
Figure 2-6. IPEX Mapping Replication Window
Enabling X.25 Gateway
117378-A Rev. A 2-15
Page 44
Configuring X.25 Gateway Services
Figure 2-7. IPEX Mapping Table Configuration Window After Replicating
a PVC-to-TCP Connection
2-16 117378-A Rev. A
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Enabling X.25 Gateway
Figure 2-8. IPEX Mapping Table Configuration Window After Replicating
a TCP-to-PVC Connection
117378-A Rev. A 2-17
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Configuring X.25 Gateway Services
Parameters for Replicating Connections
Parameter: Number of Instances
Default: None
Options: 1 to 9 for a FRE2-040-32MB platform
1 to 31 for a FRE2-060-64MB platform
Function: Specifies the number of connections to be replicated. The maximum
number of VCs per channel for the FRE2-040-32MB platform is 10, so
you can make up to 9 replicates; for the FRE1-060-64MB platform, the
maximum is 32, so you can make up to 31 replicates.
Instructions: Enter the number of PVC-to-TCP or TCP-to-PVC replicate connections
you want to configure.
Parameter: First LCN number
Default: None
Options: 2 to 10 for a FRE2-040-32MB platform
2 to 32 for a FRE2-060-64MB platform
Function: Identifies the LCN number of the first PVC that will use the replicate
configuration. Each LCN number on a channel must be unique. The
options given above assume that you have assigned an LCN number of 1
for the PVC that you are using as the source for replicates.
Instructions: Enter the LCN number.
Parameter: First TCP port number
Default: None
Options: For a PVC-to-TCP connection, this value can be any valid port number.
For a TCP-to-PVC connection, this value must be within the range of
TCP ports reserved for Gateway service, 12,304 to 16,399.
Function: Identifies the number of the first TCP port that will use the replicate
configuration.
Instructions: Enter the first TCP port number.
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Enabling X.25 Gateway
Parameter: TCP port increment
Default: None
Options: Any integer. You can assign all of your replicates to the same port, in
which case you enter 0 for this parameter, or you can assign each its own
port by adding a value to each succeeding port number. In the example
given in F
igure 2-6, each succeeding port is incremented by a value of 1.
Function: Instructs the router how to increment port numbers assigned to each of the
replicate configurations.
Instructions: Enter a value.
117378-A Rev. A 2-19
Page 48
Page 49
Index
A
adding an IPEX mapping entry, 2-2
address, called X.121, 1-6
B
Bay Networks Press, xii
block, message, 1-13
boundary, message, 1-12
C
called X.121 address, 1-3, 1-6
SVC with, 1-6
SVC without, 1-7
channel, 1-7
circuits, interface, 1-6
configuration file
preparing, 2-1
replicating, 2-12
Configuration Manager, 1-1
configuring IPEX mapping parameters, 2-7
congestion, 1-3, 1-5
connection
automatic reestablishment after a fault occurs,
1-8
from a LAPB terminal, 1-7
from a TCP/IP terminal, 1-9
from an X.25 terminal, 1-6
summary, 1-11
copying a configuration, 2-12
customer support
programs, xii
Technical Solutions Centers, xiii
D
DCE interface, 1-7
destination circuit, definition of, 1-4
Destination Connection Type parameter, 2-12
Destination PVC LCN parameter, 2-12
DTE interface, 1-7
E
Ethernet, 1-1
F
fault, physical layer, 1-8
FDDI, 1-1
flow control, 1-3
G
Gateway, definition of, 1-1
H
header, message, 1-13
I
interface
circuit, 1-6
DCE, 1-7
DTE, 1-7
117378-A Rev. A Index-1
Page 50
TCP, 1-4
IP (Internet Protocol)
address, 1-4
protocol, 1-3
IPEX
adding a mapping entry, 2-2
mapping parameters, configuring, 2-7
requirement to configure, 2-1
IPEX Mapping Add window, 2-3
IPEX Mapping Parameters window
PVC, 2-8
SVC, 2-8
TCP, 2-9
IPEX Mapping Replication Window, 2-15
IPEX Mapping Table Configuration Window,
2-13
IPEX Mapping Table Configuration Window
After Replication
PVC-to-TCP Connection, 2-16
TCP-to-PVC Connection, 2-17
L
LAN media, 1-1
LAPB (Link Access Procedure Balanced)
connection to TCP, 1-7
description of, 1-2, 1-3
point-to-point connection, 1-1
protocol, 1-3
large data message, 1-12
LCN (logical channel number), 1-7
Level 3 Packet Layer Protocol, 1-3
Local TCP Port parameter, 2-11
M
MAN (metropolitan area network) media, 1-1
mapping, 1-8, 1-10
Mapping Type parameter, 2-5
Maximum Transmission Unit (MTU), 1-12
MCT1 (Multichannel T1) interface, 1-1
message
block, 1-13
boundary, 1-12
header, 1-13
large, 1-12
message-based protocol, 1-12
MTU (Maximum Transmission Unit), 1-12
N
network topology
TCP/IP-to-LAPB, 1-2
TCP/IP-to-X.25, 1-2
P
Packet Layer Protocol See PLP
parameters, IPEX
Destination Connection Type, 2-12
Destination PVC LCN, 2-12
Local TCP Port, 2-11
Mapping T ype, 2-5
Remote IP Address, 2-10
Remote TCP Port Number, 2-11
Source Connection Type, 2-4
Source PVC LCN, 2-9
TCP Circuit Name, 2-6
TCP Header Type, 2-6
X.121 Called Address, 2-10
permanent virtual circuit. See PVC
PLP (Packet Layer Protocol), 1-3
point-to-point connection, 1-1
port, TCP, 1-4, 2-11
protocol
IP, 1-3
message-based (X.25), 1-12
TCP, 1-3
TCP stack, 1-11
unstructured stream (TCP), 1-12
X.25 Level 2, 1-3
Index-2 117378-A Rev. A
Page 51
X.25 Level 3, 1-3
X.25 stack, 1-11
publications
ordering, xii
PVC
configuring for X.25 Gateway, 1-3
description of Gateway connection, 1-7
R
Remote IP Address parameter, 2-10
Remote TCP Port Number parameter, 2-11
replicating a configuration, 2-12
S
Site Manager, 1-1
socket, 1-6, 1-7, 1-8
source circuit, definition of, 1-4
Source Connection Type parameter, 2-4
Source PVC LCN parameter, 2-9
stream protocol (TCP), 1-12
SVC
configuring for X.25 Gateway, 1-3
description of Gateway connection, 1-6
with called X.121 called address, 1-6
without called X.121 address, 1-7
T
T1 interface, 1-1
TCP
description of Gateway connection, 1-10
large data message, 1-12
port number, 2-11
protocol stack, 1-11
socket, 1-6, 1-7
unstructured stream protocol, 1-12
TCP (Transmission Control Protocol)
interface, 1-4
port number, 1-4
TCP Circuit Name parameter, 2-6
TCP Header Type parameter, 2-6
TCP/IP-to-X.25 gateway, 1-2
Technical Solutions Centers, xiii
terminal, X.25, establishing connections from,
1-6
token ring, 1-1
translation stream, 1-8
establishing (TCP initiated), 1-10
establishing (X.25 initiated), 1-5
X.25-to-TCP, 1-11
Transmission Control Protocol. See TCP
transmission unit, maximum, 1-12
V
VC (virtual circuit), 1-1
W
windows
IPEX Mapping Add, 2-3
IPEX Mapping Parameters
PVC, 2-8
SVC, 2-8
TCP, 2-9
IPEX Mapping Replication, 2-15
IPEX Mapping Table Configuration, 2-13
IPEX Mapping Table Configuration After
Duplication
TCP-to-PVC Connection, 2-17
IPEX Mapping Table Configuration After
Replication
PVC-to-TCP Connection, 2-16
X
X.121 called address, 1-3, 1-6, 1-7
X.121 Called Address parameter, 2-10
X.25
Gateway, definition of, 1-1
large data message, 1-12
117378-A Rev. A Index-3
Page 52
Level 2 (LAPB-only) interface, 1-1, 1-3
Level 3 (PLP) interface, 1-1, 1-3
message-based protocol, 1-12
networks, 1-1
protocol stack, 1-11
PVC, 1-1
SVC, 1-1
VC, 1-1
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