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Multitech MTASR3-200, User Manual

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Remote Access Device

200-Series

Remote Access Server with

Integrated WAN Devices

Model MTASR3-200

User Guide

Summary of Contents for MTASR3-200

Page 1: ...Remote Access Device 200 Series Remote Access Server with Integrated WAN Devices Model MTASR3 200 User Guide ...

Page 2: ...t obligation of Multi Tech Systems Inc to notify any person or organization of such revisions or changes Record of Revisions Revision Description A Manual revised All pages at revision A 3 23 98 Patents This Product is covered by one or more of the following U S Patent Numbers 5 301 274 5 309 562 5 355 365 5 355 653 5 452 289 5 453 986 Other Patents Pending TRADEMARK Trademark of Multi Tech System...

Page 3: ...and Port 14 WAN Links 14 Electrical Physical 14 Requirement 14 Chapter 2 Installation Introduction 16 Unpacking 16 Installation 17 Adding Additional RAM 18 Chapter 3 Software Loading and Configuration Introduction 20 Loading your Software 20 Setting Up Your Remote User Database 24 Chapter 4 MultiRouter Software Introduction 28 Before You Begin 28 Setup Menu 28 IP Setup 29 IPX Setup 31 Spanning Tre...

Page 4: ... Limited Warranty 48 On line Warranty Registration 48 Tech Support 49 Recording RASFinder Information 49 Service 50 The Multi Tech BBS 50 To log on to the Multi Tech BBS 50 To Download a file 50 About CompuServe 52 About the Internet 52 About the Multi Tech Fax Back Service 52 Appendices Appendix A Cabling Diagrams 54 Appendix B Script Language 55 Appendix C Regulatory Information 57 Appendix D AT...

Page 5: ...Remote Access Device 200 Series Chapter 1 Introduction and Description ...

Page 6: ...Finder 200 Series is a remote access device that supports up to three concurrent dial in sessions and IP or IPX remote access The RASFinder 200 Series features a 10BaseT or 10Base2 port for local LAN connection Command Port for configuration and three internal K56flexTM modems System management is provided through the command port using bundled Windows based software which provides easy to use con...

Page 7: ...can be used to automate certain operations Regulatory Information a summary of AT Commands and a Glossary of Terms Related Documentation The complete documentation package for the RASFinder 200 Series includes this User Guide a Quick Start Guide a Client Setup User Guide and a Remote Access Server Dial Out Redirector User Guide The printed version of the Quick Start Guide shipped with the unit pro...

Page 8: ...intended receiver Unfortunately the IP process may not know the MAC address of the receiver The Address Resolution Protocol ARP described in RFC 826 located at ftp ds internic net rfc rfc826 txt provides a mechanism for a host to determine a receiver s MAC address from the IP address In the process the host sends an ARP packet in a frame containing the MAC broadcast address and then the ARP reques...

Page 9: ...rtext Markup Language HTML an ASCII based platform independent formatting language per IETF RFC 1866 ftp ds internic net rfc rfc1866 txt Finger used to determine the status of other hosts and or users per IETF RFC 1288 ftp ds internic net rfc rfc1288 txt POP the Post Office Protocol defines a simple interface between a user s mail reader software and an electronic mail server the current version i...

Page 10: ...twork and host Network addresses come in five classes A B C D and E Each class of network address is allocated a certain number of host addresses For example a class B network can have a maximum of 65 534 hosts while a class C network can have only 254 The class A and B addresses have been exhausted and the class D and E addresses are reserved for special use Consequently companies now seeking an ...

Page 11: ...cess shared services on the LAN and access the internet via a shared internet port Internet WinNT Web Server Router or T1 IP Address 206 16 196 254 T1 MUX IP Address 199 24 15 244 IP Address 206 16 196 252 Novell File Server IP Address 206 16 196 250 Unix Host IP Address 206 16 196 253 PPP Client Trumpet Win95 IP Address 206 16 196 102 Remote Node with TCP IP IP Address 206 16 196 101 IP Address 2...

Page 12: ... Front Panel ETHERNET RD Receive Data indicator blinks when packets are being received from the local area network TD Transmit Data indicator blinks when packets are being transmitted to the local area network CL Collision indicator lights when a collision is in progress that is when two nodes are transmitting packets at the same time LK Link indicator lights indicating that the RASFinder is conne...

Page 13: ... to a WAN These connectors are RJ11 connectors EtherNet 10Base T Connector The EtherNet 10Base T connector is used to connect the RASFinder to a LAN using unshielded twisted cable This connector is an RJ45 jack EtherNet 10Base 2 Connector The EtherNet 10Base 2 connector is used to connect the RASFinder to a LAN using thin Coax cable Command Connector The Command connector is used to configure the ...

Page 14: ... EtherNet Port One Ethernet Interface 10Base T twisted pair RJ45 connector or 10Base 2 ThinNet BNC connector Command Port Single 19 2K bps asynchronous Command Port using a short RJ45 to DB25 cable with a DB25 female connector WAN Links Three internal K56flexTM modems Electrical Physical Voltage 115 VAC Standard 240 VAC Optional Frequency 47 to 63 Hz Power Consumption 10 Watts Dimensions 1 625 hig...

Page 15: ...Remote Access Device 200 Series Chapter 2 Installation ...

Page 16: ...describing how to install a second SIMM Unpacking The shipping box contains the RASFinder external power supply a plastic bag containing cables your Quick Start Guide and two diskettes i e the RASFinder 200 Series User Guide and the MultiRouter Software Inspect the contents for signs of any shipping damage If damage is observed do not power up the unit contact Multi Tech s Technical Support for ad...

Page 17: ...ions 3 Connect the RASFinder to a PC using the short RJ45 to DB25 female cable provided with your unit Plug the RJ45 end of the cable into the Command Port of the RASFinder and the other end into the PC s serial port or RS232 cable from the PC serial port See Figure 2 2 4 To make the network connection connect either an RJ45 UTP cable to the 10 BASE T connector shown in Figure 2 2 or a Coax BNC ca...

Page 18: ...osition the base so the front panel LEDs are toward you as in Figure 2 4 5 Slant the SIMM at a 450 angle to the back of the base and align the centering notch of the SIMM with the center tab on the SIMM connector 6 Gently press down on the ends of the SIMM until the two short vertical white pins enter the holes at the ends of the SIMM and the two metal side clips snap in place over the SIMM lockin...

Page 19: ...Remote Access Device 200 Series Chapter 3 Software Loading and Configuration ...

Page 20: ...epending on the location of your floppy disk drive in the Command Line field and then click on OK Win95 users Click on the Start button and then click on Run In the Run dialog box click on the down arrow and choose a install and then click on OK 4 Click on Install to continue installation at any time you may click on Abort if you wish to cancel the install Follow the on screen instructions to inst...

Page 21: ...is off before you click on the Yes button Click on Yes to set up the default parameters If you click on No the installation is complete 9 To configure your RASFinder a series of default dialog boxes MultiRouter Novell IPX Protocol Default Setup MultiRouter IP Protocol Default Setup MultiRouter WAN Port Default Setup will be displayed If your network protocol is IPX continue with the following step...

Page 22: ...o the WAN network numbers must be the same as the RASFinder on the other end of the link The WAN network numbers have to be assigned by the network administrator and must be unique throughout the entire internetwork Highlight the WAN 2 and or WAN 3 network number and change its Network Number Note The WAN ports do not have the capability of learning the network number unlike the LAN port i e the W...

Page 23: ...ocket Modem K56flex If either selection needs to be changed click on the down arrow and click on your new selection 22 Repeat the above step for WAN 2 and WAN 3 23 Click on OK when you are satisfied with your selections The WAN port can be further configured once the installation of the software is completed by clicking on the MultiRouter Configuration icon and clicking on the WAN button 24 The Ch...

Page 24: ...s from the database or you can edit information in the database 1 Win3 1 users From the Program Manager click on the Remote User Data Base icon Win95 users From your desktop click on the Start button point to Programs then MultiRouter and then click on Remote User Data Base The Users List dialog box is displayed 2 Click on the Add User button and the Add Users dialog box is displayed ...

Page 25: ... if the user is to be allowed to choose the call back number and the call back delay Call Back Number The call back number field is editable only if call back security is enabled checked This is the number where the user will be called back If call back security is enabled the user cannot choose the call back number Call Back Delay Call back delay is editable only if call back security is enabled ...

Page 26: ...RASFinder User Guide MTASR3 200 26 ...

Page 27: ...Remote Access Device 200 Series Chapter 4 MultiRouter Software ...

Page 28: ...r Configuration You can also start the Router Configuration from My Computer by selecting the following folders in turn Windows Start Menu Programs MultiRouter and finally double clicking on the Router Configuration icon Setup Menu The Router Setup menu consists of 14 buttons in which you can point and click and two status fields The 12 buttons four columns of three buttons each in the upper part ...

Page 29: ... are usually provided in what is known as the dotted decimal notation In this notation each 8 bit portion of the address is given a decimal quantity separated by a dot For example 192 2 10 1 The RASFinder expects all IP addresses to be provided in dotted decimal notation Among IP addresses address 0 0 0 0 and 127 cannot be specified as they are special case addresses not used on the internetwork f...

Page 30: ...tem DNS servers the default route filters and Static Routes In most cases you should not have to change any of the timers i e default TTL reassembly timeout RIP response time and RIP route aging time The DNS Resolver is supplied for remote Telnet clients when the router is configured for remote access and the terminal server application is enabled ...

Page 31: ...twork numbers for the WAN ports change the default RIP and SAP timers and optimize the bandwidth The IPX WAN network number has to be the same on both ends of the link and must be unique throughout the internetwork If a WAN port is configured in a point to point operation both WAN network numbers have to be the same and unique The IPX General Setup window controls the routing of the protocol and a...

Page 32: ...ant links then the Spanning Tree Algorithm must also be enabled If you use only the IP and IPX protocols leave bridging disabled to allow the RASFinder to operate more efficiently With Spanning Tree bridging the RASFinder defaults with one logical WAN port mapped to a DLCI and set for forwarding Any other WAN ports should be set for blocking When it is required the RASFinder will make the transiti...

Page 33: ...s to be entered in the Dial Number field and the correct modem type designated in the Modem Types field If the PPP SLIP mode is selected the RASFinder is configured for point to point operation in which data packets are transferred between two end points Enabling this device driver allows for either an asynchronous or synchronous device to be connected between the end points If an asynchronous dev...

Page 34: ... the end points to negotiate the use of the link and protocol parameters in a standardized way and also allows for standardized encapsulation of the packets SLIP is an older protocol which requires manual authentication using a script PPP is the default protocol If SLIP is to be used click on the PPP Enable option to disable PPP then select the SLIP Enable option Determine if the TCP header is goi...

Page 35: ...Remote Access Device 200 Series Chapter 5 Remote Configuration ...

Page 36: ...e LAN Based Remote Configuration Procedure in this chapter to configure a remote RASFinder Modem Based Remote Configuration Procedure 1 At the remote site remove the serial cable from the PC to the Command Port connector on the back panel of the RASFinder 2 At the remote site connect a special cable Remote Configuration Cable to the Command Port connector on the back panel of the RASFinder and the...

Page 37: ... remote RASFinder Refer to Chapter 4 for a description of each dialog box For a detailed description of each field within a dialog box refer to the on line helps provided within your MultiRouter software 10 After you have changed the configuration of the remote RASFinder click on the Download Setup button to update the configuration The remote RASFinder will be brought down the new configuration w...

Page 38: ...ocol Ping command for the PC host name You should also test the network interface configuration by Pinging another TCP IP device that is connected to the network 2 Install the MultiRouter software on the local PC and at the Windows Program Manager screen run the Configuration Port Setup program Windows 3 1x double click on the Configuration Port Setup Icon in the MultiFRAD program group Windows 95...

Page 39: ...tware For definitions of each dialog box or fields within a dialog box refer to the on line helps provided in the software 7 After you have changed the configuration of the remote RASFinder click on the Download Setup button to update the configuration The remote RASFinder will be brought down the new configuration written to the unit and the unit will reboot 8 Click on the Exit button when the do...

Page 40: ...RASFinder User Guide MTASR3 200 40 ...

Page 41: ...Remote Access Device 200 Series Chapter 6 Router Management ...

Page 42: ... anywhere on the Internet through its WEB interface For a detailed description of the MultiRouter software refer to Chapter 4 in this manual For a detailed description of each parameter refer to the on line helps provided in the software The TCP IP stack has to be loaded before the Telnet client a Windows application can run Double click on the Telnet icon and a blank Telnet screen is displayed Cl...

Page 43: ...d to the WAN port When the dial out session is over the WAN port reverts to its original configuration Router Configuration The Router Configuration option Option 2 on the Router Management Menu enables a Telnet user to view and change parameters on the protocol stacks high or low level device drivers enable or disable the supported servers or view system information Protocol Stacks The Protocol S...

Page 44: ...tion 1 to enable it Following are descriptions of each server type and its use TFTP Server The TFTP server is used for transferring configuration and firmware updates across the IP internetwork TFTP is a file transfer protocol that uses User Datagram Protocol UDP to provide a simple method for transferring files between two nodes server and client Telnet Server The Telnet server allows an authoriz...

Page 45: ...ss to any available WAN port on the RASFinder The user can select either Port 1 Port 2 or Port 3 depending on what port s are currently available Remote User Database The Remote User Database option Option 4 on the Router Management Menu allows a remote user to add user information such as Name and Password callback information and which protocol stacks to enable or disable ...

Page 46: ...oad setup changes to the unit You can access RASFinder configuration by typing the IP Address of the unit into the address line of your web browser When the Welcome screen appears click on the word Login to gain access to the RASFinder The Enter Network Password screen appears Enter your User name and Password then click on OK to go to the RASFinder Configuration menu Note The first user to access...

Page 47: ...Remote Access Device 200 Series Chapter 7 Service Warranty and Tech Support ...

Page 48: ...O OTHER WARRANTY EXPRESSED OR IMPLIED AND ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE HEREBY DISCLAIMED This warranty does not apply to any products which have been damaged by lightning storms water or power surges or which have been neglected altered abused used for a purpose other than the one for which they were manufactured repaired by the customer or any...

Page 49: ...link device that is connected to your RASFinder before calling tech support Also note the status of your RASFinder including LED indicators screen messages diagnostic test results DIP Switch settings problems with a specific application etc Use the space below to note the RASFinder status ________________________________________________________________________________________________________ _____...

Page 50: ...have Internet access Multi Tech maintains a bulletin board system BBS that mirrors its FTP site Information available from the BBS includes new product information product upgrade files and problem solving tips The phone number for the Multi Tech BBS is 800 392 2432 USA and Canada or 612 785 3702 international and local The BBS can be accessed by any asynchronous modem operating at 1200 bps to 33 ...

Page 51: ...all of the files on the BBS 2 Mark each file area you would like to examine by typing its list number and pressing ENTER 3 Enter L to list all the files in the selected file areas Enter C to go forward in the file list and P to go back 4 To mark one or more files for download type M press ENTER type the list numbers of the files and press ENTER again 5 Enter D You will see a list of the files you ...

Page 52: ...site at ftp ftp multitech com The ftp server mirrors the Multi Tech BBS About the Multi Tech Fax Back Service Multi Tech s fax back system provides 24 hour access to sales marketing and technical literature Dial 612 717 5888 follow the voice prompts and request document number 10 for a catalog of available documents For convenience have your fax number handy ________________________ From the catal...

Page 53: ...Remote Access Device 200 Series Appendices ...

Page 54: ...inal TRANSMIT DATA BA RECEIVE DATA BB SIGNAL GROUND AB PIN NO To COMMAND PORT Connector LAN Cables 10BASE T 1 2 3 4 5 6 7 8 10BASE 2 ETHERNET Pin Circuit Signal Name Pin Description 1 TD Data Transmit Positive 1 Center 2 TD Data Transmit Negative 2 Shield 3 RD Data Receive Positive 4 RD Data Receive Negative WAN Cables LINK3 LINK1 LINK2 1 2 3 4 5 6 1 2 3 4 5 6 1 2 3 4 5 6 Pin Circuit 3 Tip 4 Ring ...

Page 55: ... I expression expression OPERATOR expression I expression I expression I expression I identifier expression expression OPERATOR I I I I I I I II I I I I I proc_declaration PROC identifier parameter_list vartype FORWARD proc_declaration PROC identifier parameter_list vartype declarations statement_list ENDPROC parameter_list argument_list argument_list argument_list VAR var_type identifier identifi...

Page 56: ...he statement after the ENDSWITCH If control enters one of the CASE or DEFAULT statements all the statements up to the next ENDCASE statement are executed Each CASE or DEFAULT statement should be terminated by a matching ENDCASE keyword The SWITCH statement should be terminated by a ENDSWITCH keywork The DEFAULT statement can be placed anywhere within the scope of the SWITCH statement There can be ...

Page 57: ...e user s authority to operate the equipment FCC Regulations for Telephone Line Interconnection 1 This equipment complies with Part 68 of the Federal Communications Commission FCC rules On the outside surface of this equipment is a label that contains among other information the FCC registration number and ringer equivalence number REN If requested this information must be provided to the telephone...

Page 58: ...e equipment from the network until the problem is resolved 7 No repairs are to be made by you Repairs are to be made only by Multi Tech Systems or its licensees Unauthorized repairs void registration and warranty 8 This equipment cannot be used on public coin service provided by the telephone company Connection to Party Line Service is subject to state tariffs Contact the state public utility comm...

Page 59: ...de by the user to this equipment or equipment malfunctions may give the telecommunications company cause to request the user to disconnect the equipment Users should ensure for their own protection that the electrical ground connections of the power utility telephone lines and internal metallic water pipe system if present are connected together This precaution may be particularly important in rur...

Page 60: ...ve 89 336 EEC of 3 May 1989 on the approximation of the laws of Member States relating to electromagnetic compatibility and Council Directive 73 23 EEC of 19 February 1973 on the harmonization of the laws of Member States relating to electrical equipment designed for use within certain voltage limits both amended by Council Directive 93 68 EEC of 22 July 1993 on the harmonization of CE marking req...

Page 61: ...n This symbol placed in dialing string enables the modem to detect AT T s call card tones to access user s calling card when originating an on line connection Command A Answer Values n a Description Answer an incoming call before the final ring Command A Repeat Last Command Values n a Description Repeat the last command string Do not precede this command with AT Do not press ENTER to execute Comma...

Page 62: ...NSWER code AT T s call card tones detection Disable data calling tone transmission Command DS n Dial Stored Telephone Number Values n 0 3 Default none Description Dial a number previously stored in directory number n by the Zn x command Example ATDS 3 Command En Echo Command Mode Characters Values n 0 or 1 Default 1 Description E0 Do not echo keyboard input to the terminal E1 Do echo keyboard inpu...

Page 63: ...g handshake fallback to a lower speed can occur Command O Return Online to Data Mode Values 0 1 3 Default None Description O0 Exit online command mode and return to data mode O1 Issue a retrain and return to online data mode O3 Issue a rate renegotiation and return to data mode Command Qn Result Codes Enable Disable Values n 0 or 1 Default 0 Description Q0 Enable result codes Q1 Disable result cod...

Page 64: ...or 1 Default None Description Z0 Reset modem to profile saved by the last W command Z1 Same as Z0 Command Bn V 32 Auto Retrain Values n 1 Default 1 Description B0 Disable V 32 auto retrain Not supported B1 Enable V 32 auto retrain Command Cn Data Carrier Detect DCD Control Values n 0 or 1 Default 1 Description C0 Force Data Carrier Detect signal high C1 Let Data Carrier Detect follow carrier signa...

Page 65: ...tion S0 Force DSR high on S1 Let DSR follow CD Command Tn Self Test Commands Values n 0 1 3 or 6 Default None Description T0 Abort Stop any test in progress T1 Local analog loop test T3 Local digital loopback test T6 Remote digital loopback test Command V View Current Configuration Values n a Description Displays the active modem settings Command Wn Store Current Configuration Values n 0 Default N...

Page 66: ...V 42 MNP or non error correction same as N3 Command Qn Local Flow Control Selection Values n 0 1 or 3 Default 3 Description Q0 Disable flow control same as K0 Q1 XON XOFF software flow control same as K4 Q2 CTS only flow control Not supported responds ERROR Q3 RTS CTS hardware flow control same as K3 Command Tn Inactivity Timer Values n 0 255 Default n a Description Tn Inactivity timer setting con...

Page 67: ...y any of the following commands F M Q and N ES shows the only allowed value Command S Speaker Codec Loopback Values n a Description Provides a loopback from the microphone to the speaker For testing and debugging only Command T94 Testing External RAM Values n a Description This command is used for testing the external RAM Enter AT T94 cr to determine the status of external RAM The response you sho...

Page 68: ...RASFinder User Guide MTASR3 200 68 ...

Page 69: ...Remote Access Device 200 Series Glossary of Terms ...

Page 70: ... possible characters The extended ASCII file provides 255 characters Asynchronous Transfer Mode ATM A very high speed method of transmission that uses fixed size cells of 53 bytes to transfer information over fiber also known as cell relay AT Commands A standard set of commands used to configure various modem parameters establish connections and disconnect The AT is used to get the attention of th...

Page 71: ...t use the same logical link control protocol but that can use different medium access control protocols A bridge forwards a frame to another bridge based on the medium access control MAC address 3 In the connection of local loops channels or rings the equipment and techniques used to match circuits and to facilitate accurate data transmission Buffer A temporary storage register or Random Access Me...

Page 72: ... to reduce the length of the data stream to the LU LU session partner The encoded control byte is followed by the character that was repeated unless that character is the prime compression character 3 In Data Facility Hierarchical Storage Manager the process of moving data instead of allocated space during migration and recall in order to release unused space 4 Contrast with decompression COMx Por...

Page 73: ...lectrical pulses which have discrete jumps rather than gradual changes Digital Signaling Rates DSn A hierarchical system for transmission rates where DS0 is 64K bps equivalent to ISDN B channel and DS1 is 1 5 Mbps equivalent to ISDN PRI Digital Transmission A method of electronic information transmission common between computers and other digital devices Analog signals are waveforms a combination ...

Page 74: ... and EEPROM technologies Firmware becomes hard software when holding program code Foreground The application program currently running on and in control of the PC screen and keyboard The area of the screen that occupies the active window Compare with background Fractional T1 FT1 A digital data transmission rate between 56K bps DS0 rate and 1 544M bps the full T1 rate in North America FT1 is typica...

Page 75: ...xplicit congestion management In band Refers to the type of signalling over the conversion path on an ISDN call Contrast out of band Insufficient Ones A T1 error condition that is logged when fewer than one 1 in 16 0s or less than 12 5 average 1s density is received Inter Exchange Carrier IEC The long distance company LE who s central office provides the point of reference for T1 access Any common...

Page 76: ...he electronics at the ISDN network side of the user network interface that complements the NT1 at the user side The LT and the NT1 together provide the high speed digital line signals required for BRI access Listed Directory Number LDN The main number assigned by the telco the number listed in the telephone directory and also provided by Directory Assistance Some devices can have more than one LDN...

Page 77: ...ansaction processing is started N Nailed Connection A permanent or dedicated circuit of a previously switched circuit or circuits Nailed up Circuit A semi permanent circuit established through a circuit switching facility for point to point connectivity NAK Negative Acknowledgment Communications code used to indicate that a message was not properly received or that a terminal does not wish to tran...

Page 78: ...at lets a PC user access TCP IP Internet memeber using an ISDN terminal adapter or a high speed modem over a standard telephone line Port A location for input or output data exchange Computers muxes etc have ports for various purposes Primary Rate Interface PRI Used on ISDN In North America and Japan PRI is one 64Kbps D channel and 23 B channels Elsewhere it is one D channel and 30 B channels Prim...

Page 79: ...th least significant bit of each of the 24 8 bit time slots is robbed every sixth frame to convey voice related signaling information such as on hook off hook etc for each channel Router A device that connects two networks using the same networking protocol It operates at the Network Layer Layer 3 of the OSI model for forwarding decisions Routing Information Protocol RIP A distance vector based pr...

Page 80: ...ers are transmitted to confirm clocking before each packet of data is transmitted Compare to Asynchronous Transmission Systems Network Architecture SNA The description of the logical structure formats protocols and operational sequences for transmitting information units through and controlling the configuration and operation of networks T Tariff The rate availability schedule for telephone and IS...

Page 81: ...provides reliable end to end delivery of data and detects transmission sequential errors Transport Protocol Data Unit TPDU A transport header which is added to every message contains destination and source addressing information that allows the end to end routing of messages in multi layer NAC networks of high complexity They are automatically added to messages as they enter the network and can be...

Page 82: ... WATS A low cost toll service offered by most long distance and local phone companies Incoming 800 call service or IN WATS and outgoing WATS are subscribed to separately but over the same line X X 25 ITU T s definition of a three level packet switching protocol to be used between packet mode DTEs and network DCEs X 25 corresponds with layer 3 of the 7 layer OSI model Y Yellow Alarm An error indica...

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