Physical Layer Implementations in WAN
Most physical implementation transmits data or traffic across WAN (wide Area Network). The requirement for physical implementation depends on distance of the equipment from the speed and the services itself. The selection of type of physical layer depends on distance. Speed and type of interface required to connect.
Figure below shows the lists of subset of the physical implementation which support most commonly used WAN solutions.
Serial connections are used to support wireless serial such as dedicated leased lines that run point-to-point protocol (PPP), High-Level Data Link control (HDLC) or Frame Relay. The speed of the connection varies from 56kbps to T1/E1 (1.544/2.048 Mbps).ISDN (Integrated Services Digital Network) offer dial-on-demand connections or dial backup services. ISDN BRI (Basic Rate Interface) is made up of two 64kbps Bearer channel (B channel)for data and one 16kbs Delta channel (D channel) for signaling and other link management tasks. Point-to-point protocol is transmit data over B channel.
Difference between WAN serial connections
Long distance communication in WAN is performed using serial transmission. Serial transmission is a process in which bits are sent over single channel. Unlike parallel data transmitted at a time, serial transmission is one-at-a time transmission. This provides more reliably long distance communication. Serial channels employ electromagnetic or optical frequency range to carry bits.
The Frequency defined in terms of cycles per second (Hertz), function as band or spectrum required for communication. For example: the frequency of signals send over voice grade telephone lines is 3 kHz. The size of the frequency is also known as bandwidth.
Various types of physical connection enable to connect to serial WAN services. Depending on the selection of physical implementation given by the service provider, the type of serial cable to be used with router has to be selected.
Figure shows different type of serial connector
For Cisco router, physical connectivity at the customer site is provided by one of the two types of serial connectors. The first type of serial connection is 60-pin connector which is commonly used by Cisco routers. This indicates that the router end of most adapter cable use male 60-pin connector, so the network ends of the adapter cables has to match with particular WAN service hardware.
Bandwidth can also be expressed as bits per second (bps)which indicate the quantity of data in bits transmitted by using two physical layer implementation (EIA/TIA-232 and EIA/TIA-449). Table below shows the physical standards for WAN serial connections.
Cabling Routers for serial connections
In addition to determining cable type, one more factor which is very much essential is to determine whether the device is Data-terminal Equipment (DTE) or Data Circuit-terminating Equipment (DTE) device. These are the two types of devices that can communicate over serial interface. DCE provides physical connection to the network and forwards the data to the service provider.
If the connection is made directly to a service provider or a device that provides signal clocking such as channel or data service unit (CSU/DSU), the router will be data terminal equipment (DTE) and uses a DTE serial cable. Figure below shows DTE/DCE connections. In this example router which is DTE device is connected to CSU/DSU or modem, which are DCE devices. As the serial devices are DCE, DTE cable has to be used to connect router and CSU/DSU or modem.
DTE/DCE Connections
In some cases router is required to provide the signal clocking, so it will use data communication equipment (DCE) signal cable. For example when performing back-to-back router scenario in a test environment, one router is DTE and other router is DCE.
When router has to be cabled in a serial connectivity, it may have fixed or modular ports. The type of ports either fixed or modular will have impact on the syntax which will be used to configure each interface.
Figure shows an example of 2500 Router with fixed port. Each port is assigned with port type and port number for example “serial 0”. In order to configure fixed interface has to be specified using this convention.
Fixed serial ports on 2500 router
Routers with modular serial ports are also available. Typically, each port is assigned a label of port type, slot number and port number. In order to configure port on modular card, interfaces are specified using this convention:
<Port type><slot number>/<port number>. For example serial 1/0
Note: port designation convention changes with type of router used. For example: 7500 series router has virtual interface processor. The convention of this also include VIP slot
<Port type><slot number>/<port adapter number>/<port number> (serial 1/0/0)
Note: Using label of port type and port number such as serial 0, you can configure 1603 router (which both fixed and modular serial interface) as fixed interface.
Cabling Router for ISDN BRI connection
ISDN BRI standard defines several physical wiring interfaces, but the two common types of interfaces are BRI U-Interface and BRI S/T interface. U-Interface is the 2-wire interface provided by the service provider for connection to the NTI.U-Interface has built- in internal NT-1 devices. The S/T –interface is the 4-wire interface between NT1 and the ISDU networking equipment such as router. An S/ T interface is used when NT1 is a separate device. The type of interface required is determined depending on whether service provider will provide an NT1 device.NT1 refers to network termination type 1 device.
NTI is a simple device that serves as an interface between router and ISDN equipment and it is used to connect four wire subscribes wiring to two-wire local loop.
Category 5 straight-through cables are required to interconnect ISDN BRI port to the service provider device
Note: cables from ISDN BRI port has to be properly inserted only to ISDN jack or switch. Because ISDN BRI uses high voltage and it may effect non-ISDN devices
Setting up console connection
To initially configure Cisco device, management connection has to be directly provided to a device. This management attachment is nothing but console port. Console port enables to configure Cisco hub, switch or router. The type of cable used to connect a console port and terminal is rollover or console cable with RJ-45 connector.
Figure below shows connecting device using console cable.
Steps to connect computer to console port:
Step 1: connect the device to the computer using console cable. RJ-45 to DB-9 or RJ-45 to DB-25 adapter may be required for computer or terminal.
Step 2: configure terminal emulation software for computer with above a default COM port settings: 9600bps, 8 data bits, no parity, 1 stop bit and no flow control.
Most physical implementation transmits data or traffic across WAN (wide Area Network). The requirement for physical implementation depends on distance of the equipment from the speed and the services itself. The selection of type of physical layer depends on distance. Speed and type of interface required to connect.
Figure below shows the lists of subset of the physical implementation which support most commonly used WAN solutions.
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| WAN Physical Layer Implementations |
Difference between WAN serial connections
Long distance communication in WAN is performed using serial transmission. Serial transmission is a process in which bits are sent over single channel. Unlike parallel data transmitted at a time, serial transmission is one-at-a time transmission. This provides more reliably long distance communication. Serial channels employ electromagnetic or optical frequency range to carry bits.
The Frequency defined in terms of cycles per second (Hertz), function as band or spectrum required for communication. For example: the frequency of signals send over voice grade telephone lines is 3 kHz. The size of the frequency is also known as bandwidth.
Various types of physical connection enable to connect to serial WAN services. Depending on the selection of physical implementation given by the service provider, the type of serial cable to be used with router has to be selected.
Figure shows different type of serial connector
 |
| WAN Serial Connections Types |
For Cisco router, physical connectivity at the customer site is provided by one of the two types of serial connectors. The first type of serial connection is 60-pin connector which is commonly used by Cisco routers. This indicates that the router end of most adapter cable use male 60-pin connector, so the network ends of the adapter cables has to match with particular WAN service hardware.
Bandwidth can also be expressed as bits per second (bps)which indicate the quantity of data in bits transmitted by using two physical layer implementation (EIA/TIA-232 and EIA/TIA-449). Table below shows the physical standards for WAN serial connections.
In addition to determining cable type, one more factor which is very much essential is to determine whether the device is Data-terminal Equipment (DTE) or Data Circuit-terminating Equipment (DTE) device. These are the two types of devices that can communicate over serial interface. DCE provides physical connection to the network and forwards the data to the service provider.
If the connection is made directly to a service provider or a device that provides signal clocking such as channel or data service unit (CSU/DSU), the router will be data terminal equipment (DTE) and uses a DTE serial cable. Figure below shows DTE/DCE connections. In this example router which is DTE device is connected to CSU/DSU or modem, which are DCE devices. As the serial devices are DCE, DTE cable has to be used to connect router and CSU/DSU or modem.
 |
| DTE/DCE Connections |
In some cases router is required to provide the signal clocking, so it will use data communication equipment (DCE) signal cable. For example when performing back-to-back router scenario in a test environment, one router is DTE and other router is DCE.
When router has to be cabled in a serial connectivity, it may have fixed or modular ports. The type of ports either fixed or modular will have impact on the syntax which will be used to configure each interface.
 |
| Cisco 2500 Router |
Figure shows an example of 2500 Router with fixed port. Each port is assigned with port type and port number for example “serial 0”. In order to configure fixed interface has to be specified using this convention.
Fixed serial ports on 2500 router
Routers with modular serial ports are also available. Typically, each port is assigned a label of port type, slot number and port number. In order to configure port on modular card, interfaces are specified using this convention:
<Port type><slot number>/<port number>. For example serial 1/0
Note: port designation convention changes with type of router used. For example: 7500 series router has virtual interface processor. The convention of this also include VIP slot
<Port type><slot number>/<port adapter number>/<port number> (serial 1/0/0)
Note: Using label of port type and port number such as serial 0, you can configure 1603 router (which both fixed and modular serial interface) as fixed interface.
Cabling Router for ISDN BRI connection
ISDN BRI standard defines several physical wiring interfaces, but the two common types of interfaces are BRI U-Interface and BRI S/T interface. U-Interface is the 2-wire interface provided by the service provider for connection to the NTI.U-Interface has built- in internal NT-1 devices. The S/T –interface is the 4-wire interface between NT1 and the ISDU networking equipment such as router. An S/ T interface is used when NT1 is a separate device. The type of interface required is determined depending on whether service provider will provide an NT1 device.NT1 refers to network termination type 1 device.
NTI is a simple device that serves as an interface between router and ISDN equipment and it is used to connect four wire subscribes wiring to two-wire local loop.
Category 5 straight-through cables are required to interconnect ISDN BRI port to the service provider device
Note: cables from ISDN BRI port has to be properly inserted only to ISDN jack or switch. Because ISDN BRI uses high voltage and it may effect non-ISDN devices
Setting up console connection
To initially configure Cisco device, management connection has to be directly provided to a device. This management attachment is nothing but console port. Console port enables to configure Cisco hub, switch or router. The type of cable used to connect a console port and terminal is rollover or console cable with RJ-45 connector.
Figure below shows connecting device using console cable.
Step 1: connect the device to the computer using console cable. RJ-45 to DB-9 or RJ-45 to DB-25 adapter may be required for computer or terminal.
Step 2: configure terminal emulation software for computer with above a default COM port settings: 9600bps, 8 data bits, no parity, 1 stop bit and no flow control.
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