Asus ISDNLink INET-800 Скачать руководство пользователя страница 70

Страница: 70 / 84

Internet Router User Guide

Please refer ISDNLink Router Configuration Utility
section of Chapter 2 for more information.

Access Control

Impose restrictions on the Internet Access enjoyed by
particular workstations.

Please refer ISDNLink Router Configuration Utility
section of Chapter 2 for more information.

Internet Applica-
tions

Use Virtual Servers, Special Internet Applications, or the

Exposed Computer

feature.

Please refer ISDNLink Router Configuration Utility
section of Chapter 2 for more information.

LAN-to-LAN

Use the ISDN Internet Router to connect to another
LAN, via the ISDN link.

Please refer ISDNLink Router Configuration Utility
section of Chapter 2 for more information.

ISDN

These settings allow you to use 1 B channel instead of 2,
set B channel parameters as advised by the phone com-
pany/technical support, or set the outgoing call ID.

Please refer ISDNLink Router Configuration Utility
section of Chapter 2 for more information.

Содержание ISDNLink INET-800

Страница 1: ...ISDNLink INET 800 ISDN Router User s Guide ...

Страница 2: ......

Страница 3: ...any interference received including interfer ence that may cause undesired operation CE Marking Warning This is a Class A product In a domestic environment this product may cause radio interference in which case the user may be required to take adequate measures Copyright 1998 All Rights Reserved Document Version 1 0 All trademarks and trade names are the properties of their respective owners ...

Страница 4: ......

Страница 5: ... Hardware Installation 7 Internet Router Configuration 8 Web Browser Configuration 8 Home Setup Screen 11 Configuration Utility 15 Quick Setup Screen 17 Status Screen 21 Password Screen 25 LAN Screen 27 Dial In Access Screen 30 Access Control Screen 34 Internet Application Screen 39 LAN to LAN Screen 46 ISDN Screen 50 CHAPTER 3 PC CONFIGURATION 55 PC Configuration 55 Operation Internet Access 56 C...

Страница 6: ...ii CHAPTER 5 ROUTING 641 Overview 641 Router Configuration 61 Routing Example 62 Routing Table Entries 64 ...

Страница 7: ...iii About Internet Router CHAPTER 6 STATUS MONITORING 67 Overview 67 Status Screen 67 APPENDIX A TROUBLESHOOTING 70 APPENDIX B SPECIFICATIONS 73 ...

Страница 8: ......

Страница 9: ...rk easy access to the vast resources available on the Internet Figure 1 Office to Internet Internet Router Features The Internet Router incorporates many advanced features carefully designed to provide sophisticated functions while being easy to use LAN Features Ø 10 100 BaseT Support The LAN connection will auto detect 10BaseT and 100BaseT connections Ø DHCP Server Support Dynamic Host Configurat...

Страница 10: ... users to access Internet serv ers on your LAN The required setup is quick and easy ü User Defined Virtual Servers Internet users can access non standard Internet Servers on your LAN by using this feature ü Special Internet Applications Internet applications such as Internet Vid eoconferencing Telephony Games Servers and other special purpose Servers are supported ü Exposed Computer One 1 PC on yo...

Страница 11: ...access LAN re sources Ø LAN to LAN Connectivity Using 2 ISDN Internet Routers 2 LANs can be connected via the ISDN link The ISDN Internet Router will dial the remote LAN whenever required Operation is completely automatic and transparent Security Features Ø Configuration Data Optional password protection is provided to prevent unauthorized users from modifying the configuration Ø Firewall Protecti...

Страница 12: ...n impregnable barrier against ma licious attacks Requirements PCs with Ethernet Network cards and 10 100 BaseT connectors 10 100 BaseT network ISDN line fitted with a NT 1 Network Termination 1 termination and RJ45 sockets for S T connection Internet Access account with a local ISP Internet Service Provider Package Contents The following items should be included The Internet Router Unit Power Adap...

Страница 13: ... B1 channel is in use B2 ON when a B2 channel is established Flash while the B2 channel is in use LK ON while the ISDN control signal is established All 7 LEDs will light briefly on power on This is normal Rear Panel Connectors Switches 1 Power port Connect the power adapter here Use only the unit provided 12VDC 1Amp 2 10 100BaseT ports Connect 10 100 BaseT cabling here and the other end to the PC...

Страница 14: ...switches is this position the Internet Router will function normally ISDN Terminators Please leave them as default Reset the device If the Internet Router s IP Address or password is lost the following procedure can be used to recover from this situation 1 Turn the power to the Internet Router OFF 2 Set DIP switch 1 ON and DIP switch 2 OFF 3 Turn the power to the Internet Router ON 4 Operate DIP s...

Страница 15: ...7 About Internet Router 6 You can now connect to the Internet Router and make any configuration change required ...

Страница 16: ...o a 10BaseT or 100BaseT hub The ISDN Internet Router will auto detect the network speed 10M or 100M and full half duplex mode 2 Connect ISDN Phone Line Using a cable fitted with RJ45 plugs connect the ISDN port on the Internet Router to the S T interface on the ISDN NT 1 Network Termination 1 3 Power On and Check the LEDs Connect the supplied power adapter to the Internet Router When the Internet ...

Страница 17: ...screen and an extra utility provides more powerful configuration for users But first of all please make sure that the default IP address 192 168 0 1 is used by Internet Router ONLY at the first stage until you change it to another one after configuration Web Browser Configuration Preparation Ensure Internet Router is in the LAN your PC is using the TCP IP protocol and configure PC to use the Inter...

Страница 18: ... 3 TCP IP Properties 4 On the IP Address tab click the radio button for Obtain an IP address auto matically as above then reboot Your PC will obtain an IP Address from the Internet Router If you do not want to use the DCHP Server in Internet Router You may set DIP switch 2 ON to disable the DHCP server in the Internet Router or leave it as Default DHCP ON Enter a fixed IP Address on your PC as sho...

Страница 19: ...nstalled LAN connections are OK and it is powered ON Your PC and the Internet Router are on the same network segment If there is no router this must be the case If another PC or device is using the same IP address 192 168 0 1 as the Internet Router turn the other device OFF until you assign a new address to the Internet Router That your PC has a compatible IP address either static or obtained as a...

Страница 20: ...nge 192 168 0 2 to 192 168 0 254 and the Network mask must be 255 255 255 0 Ensure that your PC is NOT configured to use a Proxy Server In Internet Explorer this can be checked using View Internet Options Connection In Netscape check Options Network Preferences Prox ies ...

Страница 21: ...13 Setup Internet Router Home Setup Screen Figure 5 Home Setup Screen ...

Страница 22: ...ed upon connection DNS IP Address The DNS Domain Name Server translates names e g microsoft com to IP Addresses Enter the DNS IP address supplied or recom mended by your ISP Telephone Enter the telephone number used to connect to your ISP ISDN Details Country Select your country from the drop down list Note that there are 5 entries for the USA If in the USA select the entry to match the Switch Typ...

Страница 23: ... If your LAN already has a DHCP server Set DIP switch 2 ON to disable the DHCP server in the Internet Router Give the Internet Router an IP address compatible with the addresses allo cated by the DHCP server i e the last 3 digit number is NOT within the addresses allocated by the DHCP server the other numbers are the same as the addresses allocated by the DHCP server The Network Mask must be the s...

Страница 24: ...tting At this time your PC may be not in the same network mask as Internet Router if you change it to another segment You need to re configure your PC to the same segment as Internet Router Then you can access Internet Router again If you forget the IP address network mask or password of Internet Router please refer the RESET THE DEVICE section in Chapter 1 for more information ...

Страница 25: ...alues for the ISDN link do not suit your installation l You wish to use a password to protect the configuration data l You wish to take advantage of some of the advanced features of the ISDN Internet Router Preparation 1 Insert the supplied CD ROM into your drive 2 If the Setup program does not start automatically run SETUP EXE in the root directory 3 Follow the prompts to complete the installatio...

Страница 26: ...ngs The screen will display suggested values rather than current values Change the suggested values only if you know they will not work for ex ample the IP Address is already allocated to a PC which is powered off Otherwise click No Change to continue 4 If a password has been set for the ISDN Internet Router you will be prompted for the password as shown below If no password has been set you will ...

Страница 27: ...g Leave the User Name blank and enter the password you assigned to the ISDN Internet Router 5 Configure the Quick Setup tab as described below Quick Setup Screen The Quick Setup tab is displayed by default You will see a screen like the example below ...

Страница 28: ...e Figure 9 Quick Setup Screen Data Setup Screen Internet Access Account Details from ISP Account User Name Enter the account name provided by your ISP Internet Service Provider This name will be used to log in to the ISP s server ...

Страница 29: ...DN connection automati cally to save money DNS IP Address The DNS Domain Name Server translates names e g microsoft com to IP Addresses Enter the DNS IP address supplied or recommended by your ISP Telephone Enter the telephone number used to connect to your ISP Telephone 2 3 Optional Enter the telephone number to try if the first number is busy ISDN Details from Telephone Company Country Select yo...

Страница 30: ...by your phone company If your telephone company did not provide this informa tion leave this blank SPID 2nd B Channel Enter the SPID for the 2nd B Channel See above LAN Settings The TCP IP settings displayed on the screen are read only Once setup is complete Restart the ISDN Internet Router by disconnecting and reconnecting the power Refer to the next document LAN PC Setup for details on setting u...

Страница 31: ... you do not have a router in your LAN If you DO have a router it is necessary to configure BOTH the Router and the Routing table in the ISDN Internet Router correctly See Routing for details Default ISDN Settings unsuitable In rare cases it may be necessary to change the ISDN settings B Channel Speed Initialization string These settings are on the ISDN Tab screen This screen also allows you to Tem...

Страница 32: ... Router User Guide Status Screen The Status tab on the Windows utility can be used to review the current settings and operation of the ISDN Internet Router An example screen is shown below Figure 10 Status Screen ...

Страница 33: ...dware ID of this device used by the manufac turer for identification ISDN Connection Idle Dial in LAN to LAN Indicates what the ISDN link is being used for If not being used Idle will be displayed Name Dial in use The name of the user performing dial in Internet access The account name LAN to LAN connections The login name The login name could be either accepted or pro vided depending which end in...

Страница 34: ...al connection to ISP has been established Start PPP A PPP connection is now being established PPP up fail The PPP connection could not be established PPP up successfully The PPP connection was established successfully Stop PPP The PPP connection was terminated This will occur at the end of a session or an error condition Idle timer expires The Idle time out has been triggered There was no data sen...

Страница 35: ...ot set anyone can connect to the ISDN Internet Router and change its configu ration If the password is lost a DIP switch setting is provided to clear the password Refer the RESET THE DEVICE for more information Selecting the Password tab will reveal a screen like the example below Figure 11 Password Screen ...

Страница 36: ... password on this screen Passwords are case sensitive and can be up to 8 alphanumeric characters no spaces or punctuation To create or change the password enter the required password in both the New Password and Verify Password input fields ...

Страница 37: ...unnecessary to change the settings on this screen An example screen is shown below This screen has 3 sections relating to the LAN on which the ISDN Internet Router is installed DHCP Server Routing Table DNS Domain Name Server IP Addresses Figure 12 LAN Screen ...

Страница 38: ...es using fixed IP Addresses you must ensure that each of those devices uses an IP Address which is compatible with the IP Addresses allocated by the DHCP Server Compatible means o The IP Address is from the same address range as the DHCP Server By default the ISDN Internet Router uses the IP Address range 192 168 0 1 to 192 168 0 254 o The IP Address must NOT be within the group allocated by the D...

Страница 39: ...number of clients is 50 the maximum is 253 Routing Table This is a static Routing Table Entries are required only if your LAN contains 1 or more Routers See Chapter Routing for further details If you are using the ISDN Internet Router for LAN to LAN connectivity an entry will automatically appear here for the remote LAN you are connecting to Do NOT delete this entry DNS Domain Name Server IP Addre...

Страница 40: ...p the user s incoming connection and then call them back To use the Dial in Feature 1 Dial in must be Enabled on the Dial in Tab 2 User access data is required The options are as follows o Allow access by anyone and everyone not recommended If Authentication on the Dial in screen is set to None then the user name and password is not checked so anyone who dials in can gain access o All users use th...

Страница 41: ...Access Dial in Access Enable Dial in Access If checked dial in will be allowed Otherwise any attempt to dial in will be blocked Idle Time out If a dial in connection remains inactive it is terminated after this time period Allowable range is 0 99 minutes 0 means no ...

Страница 42: ...n column indicates whether or not each user currently has Dial in access Click any entry in this column to Enable Disable dial in access The user Guest is pre defined with no password or Dial in access This name will initially appear in the list Note the limitations on user names o Multiple words are NOT allowed o Punctuation and special characters must NOT be used o User names are case insensitiv...

Страница 43: ...ial up software they use for Internet access They should check the following Their ISDN TA must dial the telephone number of the ISDN Internet Router Their software should be set to obtain an IP Address from the dial in host This is the standard configuration no changes should be required Upon connection the ISDN Internet Router will allocate a suitable unused IP Address When prompted for user nam...

Страница 44: ...Access by individual workstations The process uses Packet Filtering to block or discard data packets You can apply the pre defined filters and optionally define your own filters By default filtering is disabled no packets are blocked or discarded Selecting the Access Control tab will reveal a screen like the example below ...

Страница 45: ...Access Control Screen To use the Access Control feature 1 Set the desired restrictions on the Everyone group by selecting this group and clicking Setup By default all PCs are in the Everyone group unless explicitly moved to another group ...

Страница 46: ...veryone Group 1 Group 2 Group 3 and Group 4 These names cannot be changed 2 Click the Setup button to define restrictions for the selected group An ex ample screen is shown above 3 Enter data on this screen as explained below Click OK when finished Data for each Group No restric tions No packets are blocked Use this to create an Unlimited Access group or to temporarily remove restrictions from a g...

Страница 47: ...ion to a particular security group To reserve an IP Address for this PC or device so that the DHCP Server function in the ISDN Internet Router will always allocate the same IP Ad dress to this device and never assign the reserved IP Address to any other device Use the Add Edit and Delete buttons to modify the list as required An example Add or Edit screen is shown below Figure 15 Workstation ...

Страница 48: ...ess You can use the Windows Winipcfg program or your LAN man agement program to find this address By default there is no Start Menu item for Winipcfg so you must use the Run com mand or create your own shortcut Reserve IP Address in DHCP Table Check this if you wish to reserve an IP address for this workstation This is useful if you have to provide the IP Address for other programs or users If thi...

Страница 49: ... Router Clicking the Internet Application tab will display a screen like the example below Figure 16 Internet Application Screen Special Applications This feature is only required if you wish to use Internet applications which require 2 way communication multiple connections or combined TCP UDP connections ...

Страница 50: ...n correctly At any time only one 1 PC can use each Special Application Operation To enable an existing entry On the list of special applications you can click the Enable column to toggle the Enable value On and Off If creating or editing an entry an Enable checkbox is available To create a new entry 1 Click the Add button A screen like the following will be shown Figure 17 Special Applications 2 E...

Страница 51: ... If the application uses a single port number enter it in both the Start and Finish fields Port Range Finish The end of the range of port numbers used by the application server for data you send Incoming Data Protocol The protocol TCP or UDP used when the application or service sends data to you Port Range Start The beginning of the range of port numbers used by the application server when data is...

Страница 52: ...et Router Normally Internet users would not be able to access a server on your LAN because Your Server does not have a valid external IP Address Attempts to connect to devices on your LAN are blocked by the firewall in this device The Virtual Server feature solves these problems and allows Internet users to connect to your servers However your LAN must have an existing connection to the Internet I...

Страница 53: ...ing within the Enable column to toggle the value On or Off If creating or editing an entry an Enable checkbox is available 2 Enter the IP Address of each server on your LAN 3 Click OK when finished 4 Advise Internet users of the IP Address to use The IP Address allocated by the ISP not the address on your LAN Note that because all Servers have the same IP Address the appropriate client software e ...

Страница 54: ...se is ignored IP Address The IP Address of the PC on your LAN which is running the Server software Internal Port Number Enter the port number used by the Server to connect to clients External Port Number The port number used by clients when connecting to the Server This is normally the same as the Internal Port Number If it is different this device will perform a mapping or transla tion function a...

Страница 55: ...Computer What happens after connection depends on what software both computers are using This allows connection to special purpose servers which require proprie tary client software or 2 way user connections such as Video conferencing which requires both users to run special software To allow unrestricted access the Firewall in this device is disabled creating a security risk You should use this f...

Страница 56: ... Server can be configured to initiate the connection or both can dial up as neces sary In the latter case there is a possibility that neither can connect because each is dialing the other NAT Network Address Translation the feature that allows all PCs on the LAN to share 1 external IP Address and also provides firewall protection is disabled when using the LAN to LAN function Selecting the LAN to ...

Страница 57: ...r Figure 20 LAN to LAN Screen Data LAN to LAN Enable LAN to LAN Disable Internet Access Dial in Use this to Enable and Disable the LAN to LAN feature Note that if using LAN to LAN both Internet Access and Dial in are disabled ...

Страница 58: ...LAN to LAN mode cannot function Authentication Select the desired security option Disable means no name password checking is performed No login name or password is required if this option is chosen Warning Anyone can connect this is a major security risk Enable uses the industry standard PAP security method Login Name When another ISDN Internet Router at tempts to connect to this one a log in name...

Страница 59: ...th Act as Receiver and Initiate Connection are Disabled LAN to LAN mode cannot function Telephone Telephone number to dial to connect to the remote LAN The remote site must have another ISDN Internet Router or compatible device Login using Name Password The remote ISDN Internet Router will request a Log in name and password Enter the name and password required to gain access to the remote ISDN Int...

Страница 60: ... to allow you to Use 1 B Channel for Internet access rather than both Set the outgoing call MSN Multiple Subscriber Numbering and SAD Sub address Set the B Channel line speed to 56K rather than 64K and enter an Ini tialization String for the ISDN link Note You should only do this if advised to do so by your phone company ...

Страница 61: ...53 Setup Internet Router Figure 21 ISDN Screen Data ISDN Screen Internet Access Usage Always use 1 B Channel Only 1 B Channel is used for Internet Access The 2nd B Channel is never used for Internet ...

Страница 62: ...hannel is still available for Dial in Access if enabled and configured Outgoing Call ID MSN If provided enter the MSN Multiple Subscriber Numbering which receivers of your calls will see using caller ID The phone company will bill this number SAD If provided enter the SAD SubAddress The SAD acts like an extension number to your main ISDN number You can dial up from this number instead of the main ...

Страница 63: ...ed B Channel Settings B Channel Line Speed The default is 64K Set to 56K only if advised to do so by your phone company B Channel Init String This is normally not needed If required enter the value advised by technical support staff ...

Страница 64: ...56 Internet Router User Guide Leave This Page Blank ...

Страница 65: ...figuration of PC TCP IP Settings If you use the DHCP Server function Configure each PC to be a DHCP client as shown in Preparation of Web Browser Configuration in Chapter 2 If your LAN already has a DHCP server On the LAN Tab of Utility disable the DHCP server in the ISDN Internet Router Configure your existing DHCP server to provide the Internet Router s IP Address as the Default Gateway 3 ...

Страница 66: ...l Internet When prompted select Access via LAN or click the SETUP to set this option For other application you may escape it and configure it later Operation Internet Access Once your PC is configured to use Internet access via the LAN simply use your Browser to connect to any Internet site Accessing AOL To access AOL America On Line through the Internet Router the following items are required Int...

Страница 67: ...nication software Version 2 5 3 0 or later Click the Setup button Select Create Location and change the location name from New Locality to Internet Router Click Edit Location Select TCP IP for the Network field Leave the Phone Number blank Click Save then OK Configuration is now complete Before clicking Sign On always ensure that you are using the Internet Router location ...

Страница 68: ...60 Internet Router User Guide Leave This Page Blank ...

Страница 69: ...d is used to protect the configuration data Please refer ISDNLink Router Configuration Utility section of Chapter 2 for more information LAN Use this to Enable Disable the DHCHP Server or change the IP Addresses allocated by the DHCP server or increase the number of DHCP clients sup ported Default is 50 maximum is 253 Add or Delete entries in the Routing Table Enter additional DNS Domain Name Serv...

Страница 70: ...pplications or the Exposed Computer feature Please refer ISDNLink Router Configuration Utility section of Chapter 2 for more information LAN to LAN Use the ISDN Internet Router to connect to another LAN via the ISDN link Please refer ISDNLink Router Configuration Utility section of Chapter 2 for more information ISDN These settings allow you to use 1 B channel instead of 2 set B channel parameters...

Страница 71: ...63 Advanced Port Settings ...

Страница 72: ...LAN be passed to the ISDN Internet Router so that they can be forwarded to the Internet To achieve this the Routers must be configured to use the ISDN Internet Router as the Default Route or Default Gateway Local Router The local router is the Router installed on the same LAN segment as the ISDN Internet Router This router requires that the Default Route is the ISDN Internet Router itself Typicall...

Страница 73: ...l Router the Gateway IP Address is the address of the ISDN Internet Router s local router For routers which must forward packets to another router before reaching the ISDN Internet Router s local router the Gateway IP Address is the ad dress of the intermediate router Routing Example Figure 23 Routing Example For the LAN shown above with 2 routers and 3 LAN segments the required entries would be a...

Страница 74: ... Gateway IP Address 192 168 0 100 ISDN Internet Router s local Router Entry 2 Segment 2 Destination IP Ad dress 192 168 2 0 Network Mask 255 255 255 0 Gateway IP Address 192 168 0 100 For Router A s Default Route Destination IP Address 0 0 0 0 Network Mask 0 0 0 0 Gateway IP Address 192 168 0 1 ISDN Internet Router s IP Address ...

Страница 75: ...efault Route Destination IP Address 0 0 0 0 Network Mask 0 0 0 0 Gateway IP Address 192 168 1 80 ISDN Internet Router s local router Routing Table Entries On the LAN tab routing entries will appear as in the example screen below ...

Страница 76: ...each entry is as follows Destination IP Address The network address of the remote LAN segment For standard class C LANs the network address is the first 3 fields of this Destination IP Address The 4th last field can be left at 0 Network Mask The Network Mask used on the remote LAN segment For class C networks the standard Network Mask is 255 255 255 0 Gateway IP Address The IP Address of the Route...

Страница 77: ...69 Leave This Page Blank ...

Страница 78: ...hile it is operat ing You can monitor the operation of the ISDN link Browse the Internet Router and click the STATUS tab to get below window The other way is to use ISDNLink Router Configuration Utility and click STATUS tab please refer Chapter 2 for more information Status Screen Figure 25 Status Screen 6 ...

Страница 79: ...by this device allocated by the remote device This address is provided by the ISP if connected Or by the remote ISDN Internet Router if using LAN to LAN Connection Log This shows status to the PPP link over the ISDN line Common messages are shown in the following table Message Description Dialing Dialing the ISP Try to establish physical connection The device is trying to connect with the ISP Busy...

Страница 80: ...or condition Idle timer expires The Idle time out has been triggered There was no data sent or received for the duration of the Idle time period Buttons Dial Hang Up Dial your ISP or hang up depending on whether or not a connection exists Tech Log Display ISDN messages instead of connection messages This is only to assist technical support staff Clear Log Delete existing data in the log This makes...

Страница 81: ...y installed LAN connec tions are OK and it is powered ON Ensure that your PC and the Internet Router are on the same network segment If you don t have a router this must be the case Ensure that your PC is using an IP Address within the range 192 168 0 2 to 192 168 0 254 and thus compatible with the Internet Router s default IP Address of 192 168 0 1 In Windows this is done by using Control Panel N...

Страница 82: ...set to Enable 6 Check the ISDN Status screen and examine the Connec tion Log For details of the Log messages Problem 3 Some applications do not run properly when using the Internet Router Solution 3 The ISDN Internet Router processes the data passing through it so it is not transparent The Internet Application screen has 2 features designed to assist with running non standard applications Special ...

Страница 83: ...erver feature of the ISDN Internet Router The ISDN Internet Router must allocate an IP Address to the dial in PC even if the DHCP Server is disabled It uses the IP Address shown in the Start IP Address field for the DHCP Server on the LAN tab If this causes an IP Address conflict you can change this value as follows 1 On the LAN tab enable the DHCP Server function 2 Select an unused IP Address fro...

Страница 84: ...m H Operating Temperature 0 C to 40 C Storage Temperature 10 C to 70 C Network Protocol TCP IP Network Interface 10 100M BaseT UTP connectors ISDN Port RJ45 connector S T interface 4 wire full duplex AMI line code LEDs 1 Power indicator 3 LAN status 3 ISDN Status Power Adapter External 12V DC B ...

Результаты поиска

Содержание ISDNLink INET-800

Отзывы:

Бренды по названию

Популярные бренды

Asus ISDNLink INET-800, Руководство пользователя

Результаты поиска

Содержание ISDNLink INET-800

Отзывы:

Бренды по названию

Популярные бренды