SLOW ADSL TROUBLESHOOTING GUIDE

Transcription

1 SLOW ADSL TROUBLESHOOTING GUIDE This guide will assist you in determining the reason for any reported slowness on ADSL services provided by AfriCentral ISP. A Reference for resellers. By Zeyn Khan

2 Document Contents: Section 1. Internal Network Checks Page 2 Section 2. Physical ADSL Line Checks Page 2 Section 3. Confirming ADSL Service Performance Page 5 Section 4. Comparing ADSL services and Speed Page 6 Section 5. Providing Investigation Tests to AfriCentral ISP for Further Investigation Purposes Page 6 Section 6. Disclaimer Page 8 Section 7. Contact Information- Page 8 1

3 Section 1. Internal Network Checks 1. POTS Filter: What is the current POTS filter state? Check for possible wear and tear. 2. RJ11 Sockets and Cables: What is the quality and length of the telephone line leading to the router? It should also be noted as a matter of importance that should your phone socket or cabling be located near stoves, toasters, kettles, microwaves, fridges, speakers or in general any electronic devices, you might experience definite EM interference on your line. Make sure that both socket and cable is installed well clear of such devices. 3. Wall Socket: Is the primary wall socket from the phone line damaged? Check for possible wear and tear. 4. Network Cables: Line length and quality. 5. Wireless signal: Strength and distance. 6. Faulty Router: Routers hit by lightning or general power surges could still be left operational, but still damaged. Even a fall to the ground might still allow the device to work, but with degrading performance. When doing support to a client s premises it is always advised to bring our own test router. This should be part of any technician s tool kit. 7. Specific Slowness: Is the reported slowness from a specific site or download? Not all download servers allow for your maximum download speed. 8. Active Flows: Is there more active flows then the account allows, see the technical specifications. Consider that each tab open in your browser like Facebook or Gmail is an active flow. Standard low cost uncapped ADSL has a maximum of 200 flow limit. Or an estimated 20 user network each with ten activities. 9. Overutilisation: Is there a user on the network downloading or uploading at a speed exceeding the ADSL line capacity? Torrents for example. 10. DNS Services: Please make sure you enter the correct DNS for the type of service you are using. Some network technicians sometimes enter the network gateway as the DNS and this is incorrect. Are you using the correct DNS? Examples of Internet Service Providers: a. Internet Solutions: Primary ; Secondary b. SEACOM: Primary ; Secondary c. SAIX: Cape Town Rosebank Johannesburg Pretoria Cape Town Pretoria Durban Durban Section 2. Physical ADSL Line Checks 1. Noise: Is there any measureable noise or interface on the line? 2. Line Quality: Is there any wear and tear on the line? When was the last maintenance check on the line? 3. ADSL Exchange: What is the distance from the exchange? Check the physical line length, not to be more than 3000m. Remember! As the amount of users increase over time on a specific exchange, quality of service might start degrading if no further system upgrades are completed. 4. Peering Points: Distances from the closest service provider peering point. The further away your ISP peering point is the higher the latency. Example: A user might by physically located closer to an INTERNET SOLUTIONS peering point than a SAIX based service, and thus will experience better access speeds from the IS service. 5. DSL Routing: Associated with distances from peering points. The method TELKOM approached with the physical line placing. Remember! DSL routing is not constant in South Africa and may change due to new infrastructure developments or repairs. 2

4 Fig Temporary DSL Routing: If in a large service area weather damage or infrastructure failure occurs, services might be routed to different ADSL areas. The load of this modification can result in slowness. 7. Concurrent connections: Are there multiple TELKOM circuits connected with the same ADSL service? Access speed is lost exponentially with the increasing amount of connected circuits. 8. Business Hours: Certain areas in South Africa experience heavy latency due to infrastructure overutilization based on an overload of activity, also known as the bottleneck effect. 9. International Issues: It is possible for international fibre lines to be disabled due to maintenance or damage, although very rarely. If this occurs, all traffic is routed through secondary infrastructures that might not necessarily be as fast as the primary. 10. Performing a Line Test: Most modern ADSL routers come with a series of diagnostic tools. These tools will assist you with determining the problem. (See Fig. 1. For an example of a Telkom circuit test results on a Billion Router) 11. Understanding Line Test Results: The accepted average interference measured in Decibel (db) on a Telkom circuit for optimum performance margin during business hours is around 15dB (depending on area). Signal-to-noise Ratio: Often abbreviated SNR or S/N is an electrical engineering measurement defined as the ratio of a signal power to the noise power corrupting the signal. In less technical terms, signal-to-noise ratio compares the level of a desired signal (such as music) to the level of background noise. The higher the ratio, 3

5 the less obtrusive the background noise is. The concept can also be understood as normalizing the noise level to 1 (0 db) and measuring how far the signal 'stands out'. In some instances interleaving can help raise the noise margin to an acceptable level. In general, higher signal to noise is better; the signal is cleaner. Attenuation: The gradual loss in intensity of any kind of flux through a medium (i.e. the reduction in signal strength due to length of your phone line). For instance, sunlight is attenuated by dark glasses, and X-rays are attenuated by lead. In ADSL the signal is attenuated by length of copper lines. Attenuation is normally directly linked to the length of your line. Copper is traditionally used in the local loop and the higher gauge of copper will give the best signal; however some lines may have some aluminium or aluminium joints on the line which will increase resistance... as will oxidization of joints. Attenuation is measured in db or noise. The more noise the weaker the data signal. In general, lower Attenuation is better; the signal is stronger. 12. List of comparisons SNR: 6dB or below is very bad and will experience no synch or intermittent synch problems 7dB-10dB is fair but does not leave much room for variances in conditions 11dB-20dB is good with little or no sync problems 20dB-28dB is excellent 29dB or above is outstanding Attenuation: 20dB and below is outstanding 20dB-30dB is very good 30dB-40dB is acceptable 40dB-50dB will work 50dB-60dB is poor and may experience connectivity issues 60dB or above is bad and will experience connectivity issues Distance guide: (Distance VS. attenuation VS. speed) gives you a guestimate of what you can achieve: <1km should be 23-24Mbit 1.0km = 13.81dB = 23Mbit 1.5km = 20.7dB = 21Mbit 2.0km = 27.6dB = 18Mbit 2.5km = 34.5dB = 13Mbit 3.0km = 41.4dB = 8Mbit 3.5km = 48.3dB = 6Mbit 4.0km = 56dB = 4Mbit 4.5km = 62.1dB = 3Mbit 5.0km = 69dB = 2Mbit >5.0km (ADSL not available or extremely poor performance) 13. Rule of thumb: The lower your connection speed the better your connection stability due to the fact that faster access speeds like for example 4MB/s takes more of a noise margin to obtain faster speeds! If you get bad SNR margin measurements at 384kbps, you are not likely going to be able to get any better speeds by upgrading the line. Telkom very rarely informs you of this unfortunately. 14. Upstream measurements: They differ primarily due to the ratio imposed on infrastructure upload limits. 15. Some Math: Telkom standard gauge copper wires (0.4mm) have a loss of approximately 14dB/km. You take your attenuation, and divide it by 14 and that should give you your distance from your Telkom exchange. Using the above example (Fig. 1.): Downstream Attenuation: / 14 = 2.18 km 4

6 16. Don t have a fancy router? If you are unable to get line measurements you can always give AfriCentral ISP a call on between 0700 and 2200 and we will give you this information. Just have the Telkom circuit or ADSL user name handy when you phone us. Section 3. Confirming ADSL Service Performance If after all the above checks are completed and do not result with a solution it is advised to run a test of the ADSL service from a different ADSL circuit and router. Fig Unlock the Account: If the account has a security feature enabled that locks it to a specific Telkom circuit you will first have to disable the users router and perform the account unlock via your Management Console control panel. (See Fig. 2.) 2. Workstation or Notebook: Connect your computer directly to your ADSL router with a network cable. Do not run your tests via any switches or access control servers. 3. Configure the ADSL User Name and Password on Your Router: NOTE! Certain routers have to be reset to factory default before they will accept a different username and password, especially if moving from an IS account to SEACOM and vice versa. This is due to router caching. 4. DNS Configuration: Remember to check your local DNS settings so that they match the type of ADSL service you are testing. See point 10 of the Internal Network Checks section for correct DNS parameters. 5. Results: If you are unable to replicate the reported slowness, follow through with Internal Network Tests and ADSL line quality tests. If however you experience the same slowness with the account, and you are certain the account does not run according to specifications, please report this to [email protected] and provide the required measurements taken as per section 5 of this document. 5

7 Section 4. Comparing ADSL services and Speed 1. Capped and Uncapped: Is the user comparing capped to uncapped speed? There is at least a 30% prioritization difference where capped accounts enjoy priority on the local networks. With the introduction of low cost uncapped services local infrastructure had to be adjusted to prevent complete overutilization. An uncapped account with the same priorities as capped services might start in excess of two thousand rand and more. 2. Peering Points and DSL Routing: See explanation under physical line checks. 3. Account Limitations: Does the user understand account limitations and recommended use of the account? Certain account types are more suited for downloading and others for gaming and VOIP. Many of today s online gamers have users have two accounts, one uncapped basic for downloads, and a capped account with low network latency for gaming. 4. Speed Test Services and Results: Is the client using a valid speed test destination? Remember that testing an ADSL service with a 3G providers speed test server might result with a poor performance measurement. The 3G providers test service is configured for their own network infrastructure. Be sure to choose a correct speed test destination. 5. Out-dated Services: Are you supplying your client with the latest ADSL service type? As progress is made with both cost and infrastructure, certain previously assigned services might degrade and become obsolete. An example would be uncappedhome.net (OLD) VS. uncappedbuss.net (NEW) account types or dsl512.co.za (OLD) VS. dsl1024.co.za (NEW). Section 5. Providing Investigation Tests to AfriCentral for Further Investigation Purposes In order to assist us with an investigation with your line, we require the following test results to be provided to us. 1. A screen grab of your results from speedtest.net. The screen grab must contain the following parameters (See Fig. 3.): a. The IP Address bottom left corner. b. The time indicated. c. The selected server. d. Upload and download results. Fig. 3. 6

8 2. Remember to select the appropriate test area: (Example: Cape Town or Johannesburg) and the test server, for example: SAIX (See Fig. 4.) Fig We also require a trace route to google.com: Use the following steps to obtain the trace route: Fig. 5. a. In Windows open a Command Prompt Window. b. Type in: tracert and execute the command. c. After the trace is complete right click anywhere within the Command Prompt window and choose Select All from the drop down menu that appears. Then press ENTER on your keyboard, this will copy the text of your result to the Windows clip board. You can then paste the results in a text document or . (See Fig. 5.) 7

9 4. Sample of Pasted Text from a Trace Route: C:\Users\Zirk Steyn>tracert Tracing route to [ ] over a maximum of 30 hops: ms 2 ms 1 ms ms 62 ms 76 ms dynamic.isadsl.co.za [ ] 231 ms 305 ms 257 ms cdsl2-rba-vl2563.ip.isnet.net [ ] 12 ms 13 ms 14 ms cdsl2-rba-vl150.ip.isnet.net [ ] 84 ms 71 ms 131 ms core2-pkl-t ip.isnet.net [ ] 326 ms 259 ms 399 ms ms 211 ms 211 ms ms 622 ms 704 ms ms 234 ms 525 ms ms 204 ms 279 ms * 576 ms 357 ms * * * Request timed out. 648 ms 506 ms 436 ms wb-in-f99.1e100.net [ ] Trace complete. C:\Users\Zirk Steyn> 5. Log a helpdesk call: Send all of the above information to [email protected]. Our automated help desk system will assign you a ticket. You will receive a reply within 8 work hours, or 24 standard hours. Remember! Any investigation by AfriCentral ISP cannot process without a Help Desk Ticket being logged and your test results provided according to this documents presented standard. Section 6. Disclaimer AfriCentral ISP cannot be held responsible for Telkom related problems, including Telkom DNS issues and/or Telkom DSL routing parameters and incorrectly configured devices such as routers or network terminals/devices. Section 7. Contact Information Feel free to pay us a visit or contact us should you have any questions. AfriCentral ISP 30 Starhaven Place Foresthaven - Phoenix 4068 Office Number: Emergency Line: [email protected] 8