LAB OBJECTIVE
The objective of this lab is to gain an understanding of the functionality of a Channel Service Unit / Data Service Unit (CSU/DSU) system employed within an Internet Protocol (IP) communications network.
INTRODUCTION (Students read prior to attending lab session)
The CSU is a device that performs protective and diagnostic functions for a telecommunications line while the DSU is used to connect a terminal to a digital line. Typically, the two devices are packaged as a single unit and are required at both ends of a T-1 or T-3 connection.
One option for connecting a company’s data network between two geographically distant offices is to use a serial connection. Some of the popular serial connections have T1, Frame Relay and 56 kbps / 64 kbps data rates. To establish the data network link, a high-speed connection (such as a T1 or Digital Data Service (DDS) 56/64 kbps line), is leased from your local carrier (e.g. AT&T/Sprint/MCI) and terminated into a CSU at the customer premise location. A DSU would normally be used to terminate the slower 56/64 kbps DDS line. In most cases, the digital line will terminate into a single device that has the DSU/CSU functionality, although, DSUs and CSUs can be acquired separately.
Figure 1
The primary function of the DSU is to convert the user generated signals such as RS-232 or V.35 into the form needed for transmission over the line provided by the local carrier. This conversion conditions the user-input signal into the appropriate line code and framing format. The DSU interconnects Data Terminal Equipment (DTE) for the public switched telephone network, acting like a short-haul, synchronous-data line driver. It is normally installed at a customer’s location and connects a user's synchronous equipment, via a 4-wire circuit, to a servicing Dial Central Office (DCO). This service can be for point-to-point or multi-point operation in a Digital Data Network (DDN).
The primary function of the CSU is to protect the local carrier’s network from the users’ network. It also tracks statistics, provides loop-back testing for the local carrier, provides signal conversion and maintains the local loop's electrical characteristics. It is a line-bridging device that is the last signal regeneration point before a multiplexer or the DTE. The CSU also may perform bit stuffing; providing a framing and formatting pattern compatible with the network. Figure 1 shows the basic CSU/DSU functional diagram.
MATERIALS
Item Qty
Cray DCP 3552 CSU/DSU 1 ea.
Satellite 651 T1 DSU 1 ea.
2600 Series Router 1 ea.
RJ48S T1 Cross Cable 1 ea.
Console Cable 1 ea.
HS Serial to V.35 1 ea.
V.35 to RS422 DTE 1 ea.
HS Serial to RS449 DTE 1 ea.
Four-port Hub 1 ea.
Cat-5 Patch Cable 1 ea.
PROCEDURES
Students will configure the Cray DCP3552 CSU/DSU System and the Satellite 651 T1 DSU System to connect two geographically distant customer sites via a 1536 kbps WAN / serial link. The WAN link between two CSU/DSU Systems will replicate a commercial carrier WAN link. This practical exercise is designed to reinforce the instructional blocks that have been presented in the Data Communications classes.
This lab assignment will require you to work in two teams. You will need to identify, configure and install the equipment and networking components that are needed for each portion of the networks. The actual commands for configuring the CSU/DSUs will be provided.
The major tasks associated with this lab are:
1. Cable the network components/devices up correctly IAW the CSU/DSU network diagrams (Figures 2, 3 and 4, in that order). (15 points)
2. Configure the Cray DCP3552 CSU/DSU systems. (5 points)
3. Configure the Satellite 651 T1 DSU systems. (5 points)
4. Configure the Cisco 2600 series routers IAW the network diagram. (20 points)
5. Configure and connect computer laptops to the network. (5 points)
6. Verify end-to-end network (component) connectivity. (5 points)
7. Perform troubleshooting as appropriate. (5 points)
Install the CSU/DSU Lab network IAW diagram Figure 2. All of the required equipment that you need is on the lab benches. Remember to identify the equipment by nomenclature and vendor name to insure that you are using the correct items. You should already be broken down into your two teams to complete the remainder of this lab. Team #1 will install the left portion of the network and Team #2 will install the right portion of the network. You should install the network from the CSU/DSU components outward to the laptops.
STEP 1 – Install and configure the T1 communications link between the two Cray DCP3552 CSU/DSUs.
A. Connect the two Cray Communications CSU/DSU together via the NI LINE interface (RJ48S 8-Pin modular connection). You will use the RJ48S T1 Crossover cable to facilitate this connection. [The cable will be connected to the NI LINE ports on the back of the Cray Communications CSU.]
B. Configure the Cray CSU for network operation. Use the up and down arrows on the front panel of the CSU to view and select your configuration options. Use the up or down arrow to get to System Configuration and press ENTER to select and view the options. The selected configuration option(s) will be displayed on the 32-digit Alphanumeric Display. Use the following settings:
DTE Rate 1536
Format 306 to ESF (sync unframed)
Mode Bipolar w/ 8 Zero Substitution (B8ZS)
Interface RS422 (or V.35) – based on connection
Audible Alarm Disabled
Front Panel Enable
Density Mode FCC Part 68
Unit Address 000
Timing Internal
Keep Alive Type Type 1 – All Ones
Remote Unit Compatible
Line Build Out 0
Remote Loop Out Enable
Sync Date Mode Normal
Sync Clocking Give Both
Sync DSR On
Sync CTS On
Sync LSD On
Sync Diagnostic Off
C. The “TIMING” configuration option will be determined by the network function that is required.]
D. Once you have completed the configuration settings, select Return to MAIN MENU. You have now configured your CSU systems for network operation. Have the Lab instructor verify your configuration settings.
STEP 2 – Install and Configure the Cisco 2600 Routers for DTE Operation with the Cray CSUs.
A. Configure the required interfaces IAW Figure 1, to support DTE to NI operations.
B. Use the CISCO High Speed Serial to V.35 (CAB-SS-V35MT) cables or the Cisco 72-07901-01 V.35 à RS422 DTE Interface cables to connect the Cisco router high speed serial port to the V.35 interface on the back of the CSU.
C. Configure the routers and PCs to support Ethernet LAN clients IAW Figure 2 network diagram. Verify by pinging the distant end router. Turn in the router configurations with your lab questions.
D. Verify network connectivity via executing PINGs across the network from each PC
LAN client. Have the Lab instructor verify your non-secure network operability.
STEP 1 – Install and configure the T1 communications link between the two Satellite 651 T1 DSUs (See Figure 2).
A. Connect the two Satellite 651 T1 DSUs together via the NI LINE interface (RJ48S 8-Pin modular connection). You will use the RJ48S T1 Cross cable to facilitate this connection. [The cable will be connected to the NI LINE ports on the back of the DSUs.]
B. Configure the DSU for network operation. Use the following to configure the Satellite 651 T1 DSU.
Note 1: The configurations will be similar to the ones used in the Cray Communications CSU/DSU system.
Note 2: Holding the Next or Previous button down will scroll rapidly through the available choices.
Using the buttons on the front of the unit, configure the NI framing format.
1. Push escape until SYSTEM STATUS appears in the display.
2. Push Next or Previous until NETWORK CFG appears in the display.
3. Push Select. FRAMING FORMAT appears in the display.
4. Push Select. SF ESF appears in the display. The currently selected format is blinking.
5. Push Next or Previous until the format you want (ESF) is blinking. A question mark appears meaning the blinking value is not yet configured.
6. When the format you want is blinking, push Select. The question mark disappears.
Using the buttons on the front of the unit, specify the NI line coding.
1. Push Escape until SYSTEM STATUS appears in the display.
2. Push Next or Previous until NETWORKL CFG appears in the display.
3. Push Select. FRAMING FORMAT appears in the display.
4. Push Next or Previous until LINE CODING appears in the display.
5. Push Select. AMI B8ZS appears in the display. The currently selectred value blinks.
6. Push Next or Previous until the line coding you want (B8ZS) is blinking. A question mark appears meaning the blinking value is not yet configured.
7. When the line coding you want is blinking, push Select. The question mark disappears.
Step 2 - Install and Configure the Cisco 2600 Routers (if necessary) for DTE Operation with the Satellite 651 T1 DSUs.
Configure the routers, DSUs and PCs to support Ethernet LAN clients. Use the CISCO High Speed Serial to V.35 (CAB-SS-V35MT) cables or the Cisco 72-07901-01 V.35 à 422 DTE Interface cables to connect the Cisco router high speed serial port to the V.35 interface on the back of the DSU. Once you have completed your configurations, verify connectivity by executing a ping to the distant end router and PCs.
Note: Make sure you turn in the router configurations with your lab discussion questions.
Replace one of the Satellite 651 T1 DSUs with a Cray Communications CSU/DSUs and re-establish communications. Have your lab instructor verify connectivity. This is to demonstrate that devices manufactured by different companies will work as long as they adhere to the same standards and are configured properly.
Please type all questions and answers.
[Q1, 5 points] What are the primary functions of a CSU?
[Q2, 5 points] What are the primary functions of a DSU?
[Q3, 3 points] Describe the difference(s) between a CSU and a DSU?
[Q4, 3 points] – There are two choices for timing when configuring the CSU/DSU. What are they? Explain the differences between the two. In your answer make sure you address where timing is drawn from.
[Q5, 5 points] – The synchronization settings of the CSU/DSUs used in this lab were “Internal” and “loop” respectively. Explain why this worked. In theory, should the network work if both CSU/DSUs are set to the same timing source? Will they work if both are set to Loop? Will they work if both are set to Internal?
[Q6, 2 points] The device that normally provides clocking in the network is considered to be the DTE or DCE? Which device provided timing in our lab network?
[Q7, 2 points] If you wanted to connect the two routers in our lab in a point-to-point configuration, without the CSU/DSUs, how would you do it? What cables would you require?
[Q8, 5 points] – Name the 3 types of timing used in telecommunication networking. Which is used in the U.S. telephone network? Explain.
[Q9, 5 points] - What LINE CODING can be implemented between the two CSU/DSUs for you to communicate across the network? What are the differences between the two? What FRAMING can be implemented between the two CSU/DSUs?
[Q10, 5 points] – What framing can be implemented between the two CSU/DSUs in the lab? What causes a frame slip? Define the two types of frame slips.
REFERENCES
Books/Manuals/Websites
· Cisco Systems, Inc. - http://www.cisco.com
· T1-ESF Channel Service Unit Installation and Operations Manual
· Satellite 651 T1 DSU Installation Guide
· Cisco Certified Network Associate Study Guide
· Comer, Douglas E. Internetworking With TCP/IP Volume One
· Huitema, Christian, Routing in the Internet
· Kessler, Andrew. Integrated Systems Testing for Network, Student Seminar Presentation, Spring 1996
· Newton, Harry. Newton’ s Telecom Dictionary
· Steinke, Steve. “Getting Data Over the Telephone Line, Lesson 92: CSUs and DSUs.” LAN, Apr 96.
APPARATUS
REQUIRED EQUIPMENT
/QTY
/ COMMENTSCray Communications DCP3552 CSU/DSU and Installation and Operation Manual / 2 / Provide the network / power cables along with the Cray Communication CSU/DSU and Installation and Operation Manual for the lab session.
Laptop / PC with Hyper-terminal application / 4 / For configuring the Cisco Routers and to serve as the network clients.
Network Interface Cable: RJ48S à RJ48S TELCO Cross cable / 2 / This will facilitate the T1 Network Interface between the two CSU/DSU units.
Network cables: Cisco 72-07950-01 RS449 DTE Cable à RS422 DTE Interface cable (serial port). / 2 / Two sets of each may be required to facilitate the CSU/DSU à Router connection / interface.
Network cables: Ethernet strait / 6 / Two sets of each will be required for to support the Ethernet host and network connections.
Cisco 2500 or 2600 Series Router / 4 / With the required Cisco 72-07950-01 RS449 DTE HSSI cable (listed above)
Netgear 4 port hub / 4 / To simulate client network
Satellite 651 T1 DSU and lab manual / 2 / Power Cables and
Network cables: Cisco 72-07901-01 V.35 Cable à 422 DTE Interface cable (serial port). / 2 / Two may be required to facilitate the CSU/DSU à Router connection / interface
CISCO High Speed Serial to V.35 (CAB-SS-V35MT) cables / 2 / Two may be required to facilitate the CSU/DSU à Router connection / interface
The Cisco Router Interface
All Cisco routers have at least a console port, a 25-pin female serial port or an 8 pin RJ45 female port. To access the router, you need to connect a serial cable between the console port of a router and a PC’s serial port. Then you can access the router through a terminal emulation program that emulates VT-100. When you first get a new router, none of the other ports are configured. The only way to access and configure a new router is through the console port. Once the router is configured, access is available over other interfaces with the standard Telnet program.