AR24027 Operator’s Manual Rev: A September, 2003 AFAR Communications Inc.
FCC Notice This equipment has been tested and found to comply with the limits for a Class B digital device, pursuant to Part 15 of the FCC Rules. These limits are designed to provide reasonable protection against harmful interference in a residential installation. This equipment generates, uses, and can radiate radio frequency energy and, if not installed and used in accordance with the instructions, may cause harmful interference to radio communications.
AR24027 Operator’s Manual (rev E) STATEMENT OF WARRANTY AFAR COMMUNICATIONS INC. products, except as otherwise stated in an applicable price list, are warranted against defects in workmanship and material for a period of one (1) year from date of delivery as evidenced by AFAR COMMUNICATIONS INC.’s packing slip or other transportation receipt. AFAR COMMUNICATIONS INC.
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AR24027 Operator’s Manual (rev E) TABLE OF CONTENTS 1 INTRODUCTION ........................................................................................................................................1 2 PRODUCT DESCRIPTION........................................................................................................................3 2.1 RADIO COMPONENTS ..............................................................................................................................3 2.
AR24027 Operator’s Manual (rev A) 6.1.1 General ........................................................................................................................................ 55 6.1.2 Starting a Telnet Session.............................................................................................................. 55 6.1.3 Telnet Security ............................................................................................................................. 56 6.2 SNMP ...................
AR24027 Operator’s Manual (rev E) 1 INTRODUCTION The AR24027 Wireless Ethernet Bridge is a license free radio that can be used to bridge Ethernet LAN’s (Local Area Networks) across distances ranging from a few hundred feet to 50 miles (80 Km) and beyond. In a standalone configuration the radio provides an Ethernet interface to the user.
AR24027 Operator’s Manual (rev A) The AR24027 can be configured over a local serial interface or over the Ethernet using an “Ethernet console” program provided by Afar. Once a unit is configured with an IP address you can also configure and monitor the unit using Telnet or SNMP. The radio firmware in non-volatile memory can also be updated remotely.
AR24027 Operator’s Manual (rev E) 2 PRODUCT DESCRIPTION 2.1 Radio Components Table 2.1 below shows the components that are typically shipped with each AR24027 radio. Table 2.1 - AR24027 Components A AR24027 outdoor unit. B Bracket for securing the AR24027 unit to an outdoor mast. C Power Inserter Module including 110-240 VAC power supply D CD with this Operator’s Manual, Econsole program, and other application notes.
AR24027 Operator’s Manual (rev A) Table 2.2 – AR24027 Connectors CONNECTOR TYPE Function A N-FEMALE 2.4 GHz RF connector to antenna A B N-FEMALE 2.4 GHz RF connector to antenna B C Lumberg Auxiliary port (3 pin) used as an antenna alignment aid and for RS-232 console port. D Lumberg 10/100 Base-T data interface and DC power input (8 pin). Must be connected to the “Power Inserter Unit” with a CAT 5 cable.
AR24027 Operator’s Manual (rev E) Table 2.4 – Power Inserter Unit Connector/LED Type Function To LAN RJ-45 10/100 Base-T to be connected to the Local Area Network. Use a straight through cable to connect to a hub and a cross over cable to connect directly to a computer. See table 2.5 for pin assignments. To radio RJ-45 Carries the DC power and Ethernet signals to the AR24027. See table 2.6 for pin assignments.
AR24027 Operator’s Manual (rev A) Table 2.6 – “To radio” Ethernet Connector Pin Assignments Pin Signal Name Abbr. 1 Ethernet Tx Tx (+) Radio to Ethernet 2 Ethernet Tx Tx (-) Radio to Ethernet 3 Ethernet Rx Rx (+) Ethernet to Radio 4 +18 VDC DCV (+) Power Inserter to Radio 5 +18 VDC DCV(+) Power Inserter to Radio 6 Ethernet Rx 7 18 VDC ground GND(-) Power Inserter to Radio 8 18 VDC ground GND(-) Power Inserter to Radio Rx (-) Direction Ethernet to Radio 2.
AR24027 Operator’s Manual (rev E) Table 2.
AR24027 Operator’s Manual (rev E) 3 ANTENNAS, SITE SELECTION, PATH ANALYSIS 3.1 Introduction NOTE Basic instructions for connecting the antenna to the radio are given in section 4. If the system is to be used at short to moderate ranges and there are no major obstructions between antennas, the more detailed information in this section may not be necessary.
AR24027 Operator’s Manual (rev A) 3.2.1 Directionality An antenna may be designed to receive and transmit in all directions. Such antennas are omnidirectional. An example of an omnidirectional receiving antenna would be a television antenna in a metropolitan area where each television station transmits its signal from a different location relative to the receiver. Similarly, a centrally located television transmitter would use an omnidirectional transmitting antenna.
AR24027 Operator’s Manual (rev E) For omnidirectional coverage from fixed locations, AFAR Communications Inc. provides collinear antennas. The collinear design achieves gain by increased focus in comparison with the dipole design. The standard collinear antenna used with the AR24027 provides 9 dBi gain, representing an eight-fold power and sensitivity increase. 3.2.3 Polarization Another important concept for antenna performance is polarization.
AR24027 Operator’s Manual (rev A) 4. All antenna cables attenuate (reduce) signal strength in proportion to their length. Therefore, the distance between the antenna and the radio is limited to a cable length that does not exceed the maximum attenuation tolerated by the system. Since various cable types offer different attenuation levels, maximum length depends on cable type.
AR24027 Operator’s Manual (rev E) Figure 3-1. Antenna Height and Radio Horizon Graph If the radio horizon is well within maximum communication range of the system, this graph provides a reasonable guide for antenna height. However, as maximum range of the system is approached, results are less reliable because of atmospheric effects and other unpredictable phenomena. In such cases, the more thorough point-to-point path analysis described in the next section should provide more reliable results. 3.3.
AR24027 Operator’s Manual (rev A) maximum speed), a tradeoff analysis can be conducted before installation to determine if lowering the data rate will allow the radio sufficient link margin to operate. A line-of-sight is required to insure the best performance from the radio. The calculations below will allow the operator to build towers and other mounting areas to the correct height before the antennas are installed. The calculation of the RSS level is useful for two purposes.
AR24027 Operator’s Manual (rev E) An additional increment must be added to the height of each obstruction because of the earth’s curvature. For each obstruction calculate this increment using the following formula: d= d1 × d2 × C K Where: (for US units:) d d1 d2 C K = = = = = (or for metric units:) d = d1 = d2 = C = K = additional height increment in feet distance of the obstruction from the first site in miles distance of the obstruction from the second site in miles .
AR24027 Operator’s Manual (rev A) Determine ideal antenna height by drawing a line on the graph between the sites and across the top of the obstruction heights. Note the elevation at each antenna site. The following section will show how to calculate the RSS level expected at the radio and to determine the theoretical link margin at the sight. Determine free-space path loss, using either table 3-1, the graph of figure 3-2, or the formula following figure 3-2. Table 3-1. Free-Space Path Loss at 2.
AR24027 Operator’s Manual (rev E) −95 −97 −99 −101 −103 −105 Path Loss (dB) −107 −109 −111 −113 −115 −117 −119 −121 −123 −125 −127 −129 −131 Path Loss at 2.4 GHz −133 −135 −137 −139 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 Path Length (miles) −95 −97 −99 −101 −103 −105 Path Loss (dB) −107 −109 −111 −113 −115 −117 −119 −121 −123 −125 −127 −129 −131 Path Loss at 2.
AR24027 Operator’s Manual (rev A) −L = C + 20log(D) + 20 log(F) Where: (for US units) -L C D F = = = = (or for metric units) -L = C = D = F = loss in dB 6.6 for US units path length in miles 2400 (frequency in MHz) loss in dB 32.5 for metric units path length in km 2400 (frequency in MHz) For example, for a distance of 10 miles −L = 36.6 + 20(1) + 20(3.38) −L = −124 dB Calculate effective radiated power (ERP) at the transmit antenna.
AR24027 Operator’s Manual (rev E) RSS = 38 dBm - 124 dB + 24 dB = -62 dBm Calculate link margin by subtracting radio sensitivity from the calculated RSS level. Calculated RSS level at receiver = -62 dBm Sensitivity of 2411 at 11 Mbps = -81 dB link margin = +19 dB This figure, link margin, is the amount of signal received by the radio that is above the minimum required for the radio to meet its performance characteristics.
AR24027 Operator’s Manual (rev A) Table 3-2. Loss at 2.4 GHz for Standard Coaxial Cable Types Cable Type Loss per 100 ft. (30 m) RG-8 A/U 14.4 dB Belden 9913 8.0 dB LMR 195 19 dB LMR 400 6.7 dB To determine total cable loss for your installation, perform the following calculation: For US units, multiply length in feet by the loss figure and divide by 100. For metric units, multiply length in meters by the loss figure and divide by 30.
AR24027 Operator’s Manual (rev E) additional advantage of effective system grounding is the minimizing of electrical noise and interference, which can significantly degrade system performance. Grounding involves providing a good, very low resistance connection from the antenna and radio to earth ground to provide a better path for lightning and electrical noise than that through the equipment.
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AR24027 Operator’s Manual (rev E) 4 INSTALLATION AND SETUP It is recommended that an initial check be performed on the bench before a field installation. For this bench check out you need two AR24027 units. One of the radios will be configured to operate as the “master” and the other as the “slave”. The first approach described below uses the “Ethernet Console Program” to emulate the terminal across an Ethernet connection.
AR24027 Operator’s Manual (rev A) 8. Once a radio is configured as the master it will establish a RF communication with the second radio. To verify this connection type: > monitor-link clear=1 Verify that the status shows “MASTER IN SYNC”, the receive packet count is increasing and no error counts are counting up. 9. Once the link is established, Econsole can be used to configure the local or the remote radio.
AR24027 Operator’s Manual (rev E) 8. Once a radio is configured as the master it will establish a RF communication with the second radio. To verify this connection type: > monitor-link clear=1 Verify that the status shows “MASTER IN SYNC”, the receive packet count is increasing and no error counts are counting up. 9. The terminal connected to each radio can be used to further modify the radio’s operating parameters. Section 5 describes the command language used to perform those functions. 4.
AR24027 Operator’s Manual (rev A) 4.3.2 Antenna Installation NOTICE The antennas for the AR24027 must be professionally installed on permanent structures for outdoor operations. The installer is responsible for ensuring that the limits imposed by the applicable regulatory agency (Federal Communications Commission, FCC, or CE) with regard to Maximum Effective Isotropic Radiated Power (EIRP) and Maximum Permissible Exposure (MPE) are not violated. These limits are described in the following sections.
AR24027 Operator’s Manual (rev E) 4.3.3 Antenna Alignment When mounting the high gain antenna (24 dBi), the proper antenna alignment is extremely important since the beam-width of the antenna is very narrow. Once you perform a rough alignment and the link is in operation, you can use the “monitor-link” and “antenna-alignment-aid” commands. Type: > monitor-link in order to update, every half second, the link statistics including the RSSI level.
AR24027 Operator’s Manual (rev A) Once a potential receive channel has been identified using the spectrum analysis tool, a “timing analysis” may also be used to confirm that the selected channel is indeed clear. The command: >time-analysis channel=xx input=a-antenna dwell=xx instructs the radio to dwell on the specified channel for the specified amount of time. After taking several samples the radio displays the signal level detected in that channel over time. 4.3.
AR24027 Operator’s Manual (rev E) 4.3.7 Maximum Permissible Exposure (MPE) Limitations The installer must mount all transmit antennas so as to comply with the limits for human exposure to radio frequency (RF) fields per paragraph 1.1307 of the FCC Regulations . The FCC requirements incorporate limits for Maximum Permissible Exposure (MPE) in terms of electric field strength, magnetic field strength, and power density.
AR24027 Operator’s Manual (rev A) LANs. The user can control this time-out with the “ethernet” command. If the table ever gets full, entries that have been least used are erased to make room for new entries. Bridging has two major advantages over routing: 1. There is absolutely no configuration required. The AR24027 learns about all stations automatically and routes the packets appropriately. 2. All layer 3 protocols (IP, IPX or others) can be bridged. 4.5 Upgrading the Firmware. 4.5.
AR24027 Operator’s Manual (rev E) and allows you to download to both radios in the link from the same PC. (2) Using a Telnet session from anywhere on the Internet. This requires the radio to have been pre-configured with an IP address. (3) Using a terminal emulator program (e.g. HyperTerminal) running on a PC connected through the serial port to the radio RS-232 auxiliary port. This method only allows you to download to that specific radio.
AR24027 Operator’s Manual (rev A) in order to speed up the network recovery after rebooting the master radio below (this step is not necessary if the new firmware is known to be compatible with the old one but it does not hurt in either case). 9. Depress the “F4” key to log-off the session with the current radio. “Econ” displays the list of all radios from the initial discovery phase. Select the next radio and repeat steps 4 through 8. 10.
AR24027 Operator’s Manual (rev E) 4.5.3 Installing new firmware using Telnet Telnet is a protocol that allows you to conduct a remote radio command session from a local host. The radio must have been pre-configured with an IP address and be reachable, over the network, from the local host. Refer to section 6 for details on how to configure a radio IP address and initiate a Telnet session. The Telnet terminal emulation must have the capability of sending an ASCII file to the remote machine.
AR24027 Operator’s Manual (rev A) to insure the radio is running the latest version. 4.5.4 Installing new firmware using the RS-232 serial port On occasion, it may be necessary to install new firmware using the RS-232 port. This is generally a less desirable method as the download time is much longer and you can only update the radio that is directly connected to the PC, i.e., remote updates are not possible. The serial upgrade uses a PC with a terminal emulator.
AR24027 Operator’s Manual (rev E) When you get this prompt, go to “Transfer-Send Text file…” in Hyperterminal and select the file to be installed. The file must have a “.dwn” extension. 9. After the file is successfully installed issue the command: >directory to insure that the file has been loaded into memory. 10. Issue the command: >set-default-program filename=tddNN_NN where NN_NN file is new version of software being installed. 11. Issue the command: >reboot to restart the radio with the new software.
AR24027 Operator’s Manual (rev E) 5 COMMANDS 5.1 Configuration techniques There are three ways to configure the radio. One uses the auxiliary port at the bottom of the unit and consists of an asynchronous RS-232 link used for issuing configuration commands and monitoring the local radio status and performance.
AR24027 Operator’s Manual (rev A) remembered and their meaning is clear. In order to be descriptive however, those commands are sometimes long. As the operator becomes familiar with the command language, typing the complete words could become cumbersome. The AR24027 command interpreter recognizes any abbreviations to commands and parameter names, as long as they are unambiguous. If an ambiguous command is entered, the radio will output all possible choices.
AR24027 Operator’s Manual (rev E) The following sections describe the various commands grouped according to their functionality. A summary list of all commands are contained in Appendices A and B. 5.3 Configuration Management Commands A “radio configuration” consists of a set of programmable parameters that define the radio operation with regard to a variety of operating modes. The radio holds four configurations at all times, identified as “current”, “main”, “alternate”, and “factory”.
AR24027 Operator’s Manual (rev A) display-configuration source= current or main or alternate or factory Displays all the parameter values for the specified configuration. If the source is not specified it defaults to “current”. Examples: > display-configuration source=current > discon load-configuration source=main or alternate or factory Loads the specified configuration into the current set of parameters controlling the radio operation. If no source is specified it defaults to the “main” configuration.
AR24027 Operator’s Manual (rev E) 5.4 Major Configuration Parameters These commands change several operating parameters of the radio that are part of the radio “configuration”. When entering commands with multiple parameters, if a parameter is not included, that parameter keeps its current value. node name=”ASCII string” Gives the node a meaningful name for further reference. This name will be used as the command prompt. It is also used to identify the node in a variety of commands and displays.
AR24027 Operator’s Manual (rev A) rf-receive-setup channel=5..35 antenna=a, b This command configures the channel, and antenna used in the RF reception. Note that for the radio to establish a link to its peer, the channel selected by this command must match the channel selected as the transmit channel of the remote radio. Example: > rfre ch=15 rf-transmit-setup channel=5..35 speed-mbps= 1, 2, 5.5, 11 power-dbm=0..
AR24027 Operator’s Manual (rev E) 5.5 Bridge Management Commands Bridge management commands set and display the specific operating characteristics relating to the operation of the radios as a network. ethernet speed=auto or 10hdx or 10fdx or 100hdx or off Sets the ethernet port speed to auto-negotiate, 10Mbps half-duplex (10hdx), 10 Mbps fullduplex (10fdx), 100 Mbps half-duplex (100hdx) or turns the ethernet port off.
AR24027 Operator’s Manual (rev A) >show ethernet Ethernet Stations: # 0 1 2 3 MAC address ff-ff-ff-ff-ff-ff 00-d0-39-00-2d-cb 00-a0-cc-66-8e-a6 00-d0-39-00-2d-c3 IP address Radio 0 -M 207.154.90.171 S S --Discard-from to 0 0 0 0 136 54 0 0 --Forward-from to 0 183 209 165 139575 172 0 0 >show ethernet times Ethernet Stations: # MAC address 0 ff-ff-ff-ff-ff-ff 1 00-d0-39-00-2d-cb 2 00-a0-cc-66-8e-a6 3 00-d0-39-00-2d-c3 IP address Radio MC Time added 0 29-Nov 16:17:08 -M 29-Nov 16:17:08 207.154.90.
AR24027 Operator’s Manual (rev E) Example: > ipconfig add=207.154.90.81 netmask=255.255.255.0 gateway=207.154.90.2 ping destination= count=0..500 size-bytes=32..1400 This command causes the radio to “ping” the destination address and display the results. The “ping” packet consists of an ICMP packet with a length specified by the “size-bytes” parameter. The destination is any valid IP address. When the destination host receives the packet it generates a reply of the same size.
AR24027 Operator’s Manual (rev A) value. authentication-traps=0 or 1 Specifies whether an “authentication trap” should be generated if a SNMP request is received that can not be honored (due to invalid IP address, community or access fields). When enabled, all IP managers that have “trap” access will receive this trap. delete=1..4 Allows deleting one entry in the SNMP table. The number 1..4 refer to the entry number as listed in the “display configuration” report. Example: > snmp manager=207.154.90.
AR24027 Operator’s Manual (rev E) monitor-link clear=0 or 1 This command continuously displays link statistics with its peer. The statistics include, for each direction of the link, the channel, speed, transmit power, RSSI, link distance and cumulative number of packets sent and lost. The “clear=1” parameter clears the cumulative counts in the report. Examples: >monitor-link clear=1 spectrum-analysis input=a-antenna or b-antenna display=graph or table dwell-time-ms=0..
AR24027 Operator’s Manual (rev A) >time-analysis input=b-antenna >tia in=a dis=t dwell=500 5.8 Event Logging Commands The AR24027 keeps track of various significant events in an “event log”. This event log holds up to 500 events. The first 100 entries in the log are filled sequentially after power up and are not overwritten. The remaining 400 entries consist of the last 400 events recorded. All events are timetagged with system time.
AR24027 Operator’s Manual (rev E) print=0..7 Events of the specified level or below will be output to the terminal as they occur. Examples: >max-event print=6 5.9 File Utilities The AR24027 maintains a file system that allows multiple programs to be stored in either non-volatile flash PROM or volatile RAM. New programs can be downloaded into the AR24027 memory through the auxiliary port, through the Ethernet port, or to remote radio across the RF link.
AR24027 Operator’s Manual (rev A) >copy-file tmp/tdd01_02 tdd01_02 delete-file filename=filename Deletes the specified file from RAM or Flash PROM. If the memory location is not defined (flash or tmp), the command assumes the flash directory. Examples: >delete-file filename=tdd01_03 directory format=short or full Lists all the files currently stored in flash PROM and RAM, their size, the sectors occupied and the MD5 checksum (full version). It also indicates which of the files is the default program.
AR24027 Operator’s Manual (rev E) >download destination=tdd01_12 method=inline After issuing the command initiate the file transfer using the terminal facilities.. run filename=filename Executes the specified file. The file is first copied into RAM and then the program is executed out of RAM. If the radio is rebooted or power cycled, the radio reverts back to the program defined as the default boot program. If the memory location is not defined (flash or tmp), the command assumes the flash directory.
AR24027 Operator’s Manual (rev A) zone=zone-code or offset Sets the time zone to be used by the radio to translate the NTP time to local time. It can be specified by an offset from GMT (-0800 or +0200 for example), or as a “zone-code”.
AR24027 Operator’s Manual (rev E) logout Closes the current Econsole session. reboot Resets the radio causing the software to perform a complete start up sequence. This is equivalent to power cycling the radio off and on. time time=hh:mm:ss date=day-month-year zone=zone-code or offset This command is identical to the “date” command explained above except for the order of the parameters.
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AR24027 Operator’s Manual (rev E) 6 NETWORK MANAGEMENT The radios operate as part of a network environment with many devices. Whether operated by an Internet Service Provider (ISP) or the Information Technology (IT) department of a business, there is often a need to supervise and manage the network from a central Network Operations Center (NOC). This chapter describes the features of the AR24027 that are useful for this purpose. 6.1 Telnet 6.1.
AR24027 Operator’s Manual (rev A) 6.1.3 Telnet Security The remote management capability through Telnet opens the possibility for an unauthorized user to login to any radio accessible through the Internet. The radio configuration can be password protected with the use of the lock and unlock commands. If further security is desired you can specify up to four source IP addresses that are authorized to initiate Telnet sessions with the radio.
AR24027 Operator’s Manual (rev E) 6.2.2 What is SNMP? The SNMP protocol is described in the following documents: • RFC1157 - Simple Network Management Protocol (SNMP) - ftp://ftp.isi.edu/in-notes/rfc1157.txt • RFC1155 - Structure and identification of management information for TCP/IP-based internets ftp://ftp.isi.edu/in-notes/rfc1155.txt • RFC1213 - Management Information Base for Network Management of TCP/IP-based internets: MIB-II - ftp://ftp.isi.edu/in-notes/rfc1213.
AR24027 Operator’s Manual (rev A) change color if they have alarms, and with provisions for activating a remote paging device if there is a problem. WhatsUp Gold (Ipswitch Inc) http://www.ipswitch.com/ USD 800 (approx) SNMPc (Castle Rock Computing, Inc) http://www.castlerock.com/ USD 900 to USD 2700 (approx, depending on options) OpenView (Hewlett-Packard) http://www.openview.hp.
AR24027 Operator’s Manual (rev E) APPENDIX A - Specifications RF Specifications RF Frequency Band 2.406 GHz to 2.474 GHz (center frequencies) RF Signal Bandwidth (-20 dBc) 4.
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AR24027 Operator’s Manual (rev E) APPENDIX B – Channel Frequency Assignment Frequency Frequency Frequency Channel (GHz) Channel (GHz) Channel (GHz) 3 2.406 15 2.430 27 2.454 4 2.408 16 2.432 28 2.456 5 2.410 17 2.434 29 2.458 6 2.412 18 2.436 30 2.460 7 2.414 19 2.438 31 2.462 8 2.416 20 2.440 32 2.464 9 2.418 21 2.442 33 2.466 10 2.420 22 2.444 34 2.468 11 2.422 23 2.446 35 2.470 12 2.424 24 2.448 36 2.472 13 2.426 25 2.450 37 2.
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AR24027 Operator’s Manual (rev E) APPENDIX C – Ethernet Console Program EConsole v2.01 for Windows Short description The ethernet console program was developed in order to accommodate the remote configuration of a radio, i.e. the configuration in cases where the physical access to the radio is not feasible, or it is cumbersome. The software consists of two parts: the client and the server. The client runs on the administrator's PC, while the server runs on the radio.
AR24027 Operator’s Manual (rev A) Input arguments You can provide the following arguments in the command line, even though none of them is required. Input file There are two sources for the input commands: the keyboard, or a text file. The second option is useful when you are running the same set of commands periodically, so you want to avoid retyping them every time you want to execute them.
AR24027 Operator’s Manual (rev E) Radio Serial Number The same functionality as above (see Radio MAC address) can be achieved by providing the radio serial number, instead of the radio physical address. Note that you should not include the initial UC characters of the serial number (i.e.
AR24027 Operator’s Manual (rev A) >econ -i in.txt -o out.txt -r 00:78:24:22:BA:4F or If you are reading from the keyboard, and you are simply interested in capturing the output of the session, use the following syntax: >econ -o out.txt Since no input file was specified, it is assumed that the keyboard will be used for input, and ALL radios will participate in the discovery process. Function Keys Currently there are 6 different function keys.
AR24027 Operator’s Manual (rev E) radio multiple times if not absolutely necessary. When the number of sessions reaches the limit the radio will ignore any new discovery messages. Another reason might be a unreliable RF link causing a high packet loss. Since during the discovery phase there isn't any retransmission mechanism, it is quite possible that you managed to "see" the radio, but you weren't able to connect to it, because the connection request packet was lost. In such case, try to connect again. 4.
