Technical Note 12.0 Dial-up X.25: Access to Networks This technical note describes how to use the dial-up X.25 (CCITT X.32) capability of Hayes V-series products. Dial-up X.25 connections using packet switch networks provide users of Hayes V-series X.25 product with flexible multisession and multipoint communications capabilities. In the US there are several x>25 public carriers including Telenet and Tymnet (as well as many private carriers), while Datapac is available in Canada. There is also X.25 support in Europe and Japan with each country's PTT (Postal, Telephone, Telegraph bureau) offering it's own service. In addition, international carriers such as Infonet and Tymnet are also available to provide global X.25 links. Many private host systems, databases, and information services are already connected to these packet switched networks and may be accessed given the proper authorization. 12.1 Placing Virtual Calls To use the X.25 product to communicate with a host system, it is necessary to firts establish a synchronous carrier connection to the network, then place the virtual call. To establish the modem carrier connection, one should first issue the string "AT&F" to place the modem in factory configuration, then type "ATS46=134 S48=0" to set up for X.25 operations. You may then issue the "ATDTnnnnnnn" command to dial the network. Once a modem carrier connection has been established to the X.25 network, a virtual channel (sometime referred to as a virtual call or virtual circuit) must be established. In the Hayes X.25 product, this call is established by using the CALL command. 12.1.1 X.25 Addressing Schemes When using the Call command with the Hayes X.25 product, a network address must be supplied to ensure that the virtual call is routed through to it's proper destination within the network. For public networks this address format is specified in X.121 (the CCITT standard for X.25 addressing conventions) as consisting of either 14 or 15 digits of the form: P Z CC I NNNNNNNNNN Where P = International Prefix (used only when calling out of country) Z = World Zone C = Country Code I = Network ID N = Terminal Number However,this scheme is not mandatory for the variuos X.25 networks which are free to come up with their own particular addresses. Some are very similiar to X.121, others are very dissimilar. 12.1.2 X.25 Addresses - Telenet The following is a list of some often-used Telenet X.25 addresses: Telemail: 311090900407 OAG: 311031200159 Dialog: 311021300290 Dow Jones News Retrieval: 311060900042 12.1.3 X.25 Addresses - Tymnet In general, Tymnet follows an address formula similiar to that of Telenet with the exception that the first four digits are "3106" rather than "3110". However, Tymnet also allows one (in most cases) to simply use an address of "31069" in conjunction with an appropriate entry in the NUI field (see the examples for details of this usage). 12.1.4 X.25 Addresses - Datapac Examples of public hosts available include the Datapac Information Service and the Envoy electronic mail service. Should you be in Canada and wish to access an information service via Telenet or Tymnet, simply call into a local Datapac number and place the international prefix "1" before the regular Tymnet or Telenet address in the CALL command. This procedure will route the call from the Datapac network to Telenet/Tymnet and then on to the appropriate destination. 12.2 Examples In the following examples, all commands issued to the modem will be in "quotes", while al responses will be in CAPS. 12.2.1 Calling OAG via Telenet: "AT S46=134 S48=0" OK This sets up the modem for an X.25 only link and disables Automatic Feature Negotiation "ATDTnnnnnnn This sets up the physical (modem carrier) link to the network where nnnnnnn is the telephone number. CONNECT xxxx - The hyphen is the PAD prompt, and indicates that the modem is in the PAD command state. "SET 2:1,13:4,15:1" - This enables Pad echo, inserts line feeds after carriage returns, and enables line editing. While these settings are not mandatory, they are recommended. See section 12.4 for full details on PAD settings with various networks. "CALL R-311031200159" This sets up the virtual call (or virtual circuit if you prefer). CON COM The CON COM stands for Connect Confirm and may optionally include a facilities string showing window size, packet size. etc. At this point you are connected to The Source and will be able to get the familiar "->" prompt. The "R-" prefix is the indication to request reverse charging facilities. This is required when using Telenet, and is optional for other services. Other less common options may be used as well. If for some reason the network does not accept the call, refer to the V-series Users Guide section on PAD Result Code Fields. 12.2.2 Calling Dow Jones via Tymnet: "AT S46=134 S48=0" OK "ATDTnnnnnnn" CONNECT xxxx - "CALL Ndow1,W7-31069,,4 CON COM Note that this CALL statement is substantially different from the Telenet example. The "Ndow1" signifies that the code "dow1" is to be entered into the NUI field of the call request packet, while the "W7" indicates a request for a negotiated window size of 7. The ",,4" is used to ensure that the call is placed on outgoing channel 4, rather than the default channel of 16. See 12.3 Note 2 for more details on outgoing channel numbers. 12.2.3 Callling into the Datapac Information Service: "ATS46=134 S48=0" OK "ATDTnnnnnnn" CONNECT xxxx - "SET 2:1, 13:4, 15:1" - "CALL R,W3,P8-92100086,,4" CON COM If calling from inside the US, Datapac may be accessed via the local Telenet X.25 number by issuing the following CALL command: CALL R-302092100086 Alternately, you may access via Tymnet by issuing: CALL Ndpac;,W7-302092100086,,4 12.2.4 Calling into OAG via Telenet from Datapac: "ATS46=134 S48=0" OK "ATDTnnnnnnn" CONNECT xxxx - "CALL R,W3,P8-1311031200159,,4" CON COM Note the use of the "1" prefix on the network address. 12.2.5 Callling into any Tymnet service from Datapac: "ATS46=134 S48=0" OK "ATDTnnnnnnn" CONNECT xxxx - "CALL R,W3-131069,,4" CON COM You should now see the standard Tymnet prompt requiring you to log in. At thsi point you should type the information that you would ordinarily put in the NUI field if calling Tymnet direct. 12.3 Configuration Issues 1. FLOW CONTROL: PAD parameter 5 (Anvillary Device Control) should be disabled (SET 5:0) when using a terminal emulation or communications package using XON/XOFF flow control. It should be enabled (SET 5:1) when using a "dumb" terminal that supplies no flow control. The various PAD parameters and their meanings may be found in chapter 3 of the V-series X.25 Product Users Guide. 2. MULTIPLE VIRTUAL CHANNELS: When placing more than one virtual call, it is advisable to use the outgoing channels in descending order - thus, the first call should be on channel 4, the next on channel 3, etc. Alternately, you may specify the maximum channel number by setting the S78 and S79 registers as specified in the V-series X.25 Users Guide. It should be noted that, while the default value of the maximum outgoing channel is 16, some networks will not support this. Both Tymnet and Datapac support a maximum channel number of 4. 3.THE S53 REGISTER: Setting the S53 register may be desirable in some cases, particularly when multiple virtual calls are to be placed. Setting S53=3 (the default setting is S53=2) will cause the cahnnel number to appear before the hyphen in the PAD prompt. 4. PRIVATE HOST SYSTEMS: When calling some hosts (including those using 3270 emulation), it is often desirable to enable line editing (SET 15:1) and to select appropriate Data Forwarding signal, usually a Carriage Return (SET 3:2). In addition, when line editing is enabled it is usually desirable to enable echo (SET 2:1) and include line feeds after carriage returns (SET 13:4) 5. ADJUSTING WINDOW SIZES: Many X.25 networks will support a larger window size than the default of 2. It is usually desirable to use the largest possible window size supported by the network, as this will generally enhance overall throughput. To select a larger window size, use the "W" call Facility, or set National PAD Parameter 101 to the desired window size. 6. ADJUSTING PACKET SIZES: Many X.25 networks will support a larger packet size than the default of 128 bytes. It is often desirable to use the largest packet size supported by the network, particularly if you are being billed by the packet. (smaller packets are desirable on multiple virtual channel calls and/or if a quicker response time is desired). The packet size may be adjusted by either using the "P" Call Facility. or setting the National PAD Parameter 100 to the desired packet size according to the following chart: PACKET SIZE "P" Call Facility Parameter 100 Setting ----------------------------------------------------------------------- 16 Bytes P4 SET 100:4 32 Bytes P5 SET 100:5 64 Bytes P6 SET 100:6 128 Bytes P7 SET 100:7 256 Bytes P8 SET 100:8 512 Bytes P9 SET 100:9 9. TYMNET NUI FIELDS: There are many ways to route your call via Tymnet. One of the easiest is to use the "generic" address 31069 and place the appropriate identifier in the NUI (Network User ID) field, provided that this service is available at your local Tymnet node. Some NUI codes include: dow1 for Dow Jones, oag for the OAG Electronic Edition, and esl for Easylink. Contact your local Tymnet representative for all applicable codes. A partial listing may be found in section 12.4. 12.4 ACCESS TO SELECTED NETWORKS The following section contains X.25 network addresses, NUI fields, etc. for selected networks, hosts, and information services. This list is not intended to be comprehensive of all the connections allowed, but is instead a listing of some of the more popular public services. For information on services not listed, please contact your X.25 network representative. Note: All of the following refer to PAD setups A and B. Setup A refers to the default PAD settings. Setup B is defined as default with the following changes: a)Echo is enabled (SET 2:1) line feeds are inserted after carriage returns by the PAD (SET 13:4) Editing is enabled (SET 15:1). 12.4.1 ACESS VIA TELENET TO TELENET HOSTS Maximum channel number: 16 Maximum window size: 2 Maximum packet size: 7 (128 Bytes) Reverse Charging: Yes TELEMAIL Network Address: 311090900407 PAD Setup: A OAG Network Address: 311031200159 PAD Setup: B DOW JONES Network Address: 311060900042 PAD Setup: A DIALOG Network Address: 311021300290 PAD Setup: B 12.4.2 ACCESS VIA TYMNET TO TYMNET HOST Maximum Channel Number: 4 Maximum Window Size: 7 Maximum Packet Size: 7 (128 Bytes) Reverse Charging: No ONTYME Network Address: 3106002260 NUI: your account name PAD Setup: B TYMNET INFORMATION SERVICE Network Address: 31069 NUI: Information; PAD Setup: B DOW JONES Network Address: 31069 NUI: dow1 PASD Setup: A EASYLINK Network Address: 31069 NUI: esl PAD Setup: A MCI MAIL Network Address: 31069 NUI: mcimail PAD Setup: B OAG Network Address: 31069 NUI: oag PAD Setup: B DIALOG Network Address: 31069 NUI: dialog PAD Setup: A 12.4.3 ACCESS VIA DATAPAC TO DATAPAC HOSTS Maximum Channel Number: 4 Maximum Window Size: 3 Maximum Packet Size: 8 (256 Bytes) Reverse Charging: Yes DATAPAC INFORMATION SERVICES Network Address: 92100086 PAD Setup: B ENVOY Network Address: 79400900 PAD Setup: B COMPUSERV Network Address: 29400138 PAD Setup: A 12.4.4 ACCESS VIA DATAPAC TO TYMNET HOSTS Maximum Channel Number: 4 Maximum Window Size: 3 Maximum Packet Size: 7 (128 Bytes) Reverse Charging: Yes ONTYME Network Address: 131069 PAD Setup: B At the Tymnet prompt type: Your account number TYMNET INFORMATION SERVICES Network Address: 131069 PAD Setup: B At the Tymnet prompt type: information DOW JONES Network Address: 131069 PAD Setup: A At the Tymnet prompt type: dow1; MCI MAIL Network Address: 131069 PAD Setup: B At the Tymnet prompt type: mcimail OAG Network Address: 131069 PAD Setup: B At the Tymnet prompt type: oag DIALOG Network Address: 131069 PAD Setup: A At the Tymnet prompt type: dialog EASYLINK Network Address: 131069 PAD Setup: A At the Tymnet prompt type: esl 12.4.5 ACCESS VIA DATAPAC TO TELENET HOSTS Maximum Channel Number: 4 Maximum Window Size: 3 Maximum Packet Size: 7 (128 Bytes) Reverse Charging: Yes TELEMAIL Network Address: 1311090900407 PAD Setup: B OAG Network Address: 1311031200159 PAD Setup: B DOW JONES Network Address: 1311060900042 PAD Setup: A DIALOG Network Address: 1311021300290 PAD Setup: B 12.4.6 ACCESS VIA TYMNET TO DATAPAC HOSTS Maximum Channel Number: 4 Maximum Window Size: 7 Maximum Packet Size: 8 (256 Bytes) Reverse Charging: Yes DATAPAC INFORMATION SERVICE Network Address: 302092100086 NUI: dpac; PAD Setup: B ENVOY Network Address: 302079400900 NUI: dpac; PAD Setup: B 12.4.7 ACCESS VIA TELENET TO DATAPAC HOSTS Maximum Channel Number: 16 Maximum Window Size: 2 Maximum Packet Size: 8 (256 Bytes) Reverse Charging: Yes DATAPAC INFORMATION SERVICE Network Address: 302092100086 PAD Setup: B ENVOY Network Address: 302079400900 PAD Setup: B Please note that any or all of the above is subject to change by the various networks. Should you experience any difficulties with host or network access, a representative of the network in question should be consulted.