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• Improving TCP performance over a gigabit network lots of connections and high traffic for storage and streaming services

  - by Linux Guy

  I have two servers, Both servers hardware Specification are Processor : Dual Processor RAM : over 128 G.B Hard disk : SSD Hard disk Outging Traffic bandwidth : 3 Gbps network cards speed : 10 Gbps Server A : for Encoding videos Server B : for storage videos andstream videos over web interface like youtube The inbound bandwidth between two servers is 10Gbps , the outbound bandwidth internet bandwidth is 500Mpbs Both servers using public ip addresses in public and private network Both servers transfer and connection on nginx port , and the server B used for streaming media , like youtube stream videos Both servers in same network , when i do ping from Server A to Server B i got high time latency above 1.0ms , the time range time=52.7 ms to time=215.7 ms - This is the output of iftop utility 353Mb 707Mb 1.04Gb 1.38Gb 1.73Gb mqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqqvqqqqqqqqqqqqqqqqqqqqqqqqqqq server.example.com => ip.address 6.36Mb 4.31Mb 1.66Mb <= 158Kb 94.8Kb 35.1Kb server.example.com => ip.address 1.23Mb 4.28Mb 1.12Mb <= 17.1Kb 83.5Kb 21.9Kb server.example.com => ip.address 395Kb 3.89Mb 1.07Mb <= 6.09Kb 109Kb 28.6Kb server.example.com => ip.address 4.55Mb 3.83Mb 1.04Mb <= 55.6Kb 45.4Kb 13.0Kb server.example.com => ip.address 649Kb 3.38Mb 1.47Mb <= 9.00Kb 38.7Kb 16.7Kb server.example.com => ip.address 5.00Mb 3.32Mb 1.80Mb <= 65.7Kb 55.1Kb 29.4Kb server.example.com => ip.address 387Kb 3.13Mb 1.06Mb <= 18.4Kb 39.9Kb 15.0Kb server.example.com => ip.address 3.27Mb 3.11Mb 1.01Mb <= 81.2Kb 64.5Kb 20.9Kb server.example.com => ip.address 1.75Mb 3.08Mb 2.72Mb <= 16.6Kb 35.6Kb 32.5Kb server.example.com => ip.address 1.75Mb 2.90Mb 2.79Mb <= 22.4Kb 32.6Kb 35.6Kb server.example.com => ip.address 3.03Mb 2.78Mb 1.82Mb <= 26.6Kb 27.4Kb 20.2Kb server.example.com => ip.address 2.26Mb 2.66Mb 1.36Mb <= 51.7Kb 49.1Kb 24.4Kb server.example.com => ip.address 586Kb 2.50Mb 1.03Mb <= 4.17Kb 26.1Kb 10.7Kb server.example.com => ip.address 2.42Mb 2.49Mb 2.44Mb <= 31.6Kb 29.7Kb 29.9Kb server.example.com => ip.address 2.41Mb 2.46Mb 2.41Mb <= 26.4Kb 24.5Kb 23.8Kb server.example.com => ip.address 2.37Mb 2.39Mb 2.40Mb <= 28.9Kb 27.0Kb 28.5Kb server.example.com => ip.address 525Kb 2.20Mb 1.05Mb <= 7.03Kb 26.0Kb 12.8Kb qqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqqq TX: cum: 102GB peak: 1.65Gb rates: 1.46Gb 1.44Gb 1.48Gb RX: 1.31GB 24.3Mb 19.5Mb 18.9Mb 20.0Mb TOTAL: 103GB 1.67Gb 1.48Gb 1.46Gb 1.50Gb I check the transfer speed using iperf utility From Server A to Server B # iperf -c 0.0.0.2 -p 8777 ------------------------------------------------------------ Client connecting to 0.0.0.2, TCP port 8777 TCP window size: 85.3 KByte (default) ------------------------------------------------------------ [ 3] local 0.0.0.1 port 38895 connected with 0.0.0.2 port 8777 [ ID] Interval Transfer Bandwidth [ 3] 0.0-10.8 sec 528 KBytes 399 Kbits/sec My Current Connections in Server B # netstat -an|grep ":8777"|awk '/tcp/ {print $6}'|sort -nr| uniq -c 2072 TIME_WAIT 28 SYN_RECV 1 LISTEN 189 LAST_ACK 139 FIN_WAIT2 373 FIN_WAIT1 3381 ESTABLISHED 34 CLOSING Server A Network Card Information Settings for eth0: Supported ports: [ TP ] Supported link modes: 100baseT/Full 1000baseT/Full 10000baseT/Full Supported pause frame use: No Supports auto-negotiation: Yes Advertised link modes: 10000baseT/Full Advertised pause frame use: No Advertised auto-negotiation: Yes Speed: 10000Mb/s Duplex: Full Port: Twisted Pair PHYAD: 0 Transceiver: external Auto-negotiation: on MDI-X: Unknown Supports Wake-on: d Wake-on: d Current message level: 0x00000007 (7) drv probe link Link detected: yes Server B Network Card Information Settings for eth2: Supported ports: [ FIBRE ] Supported link modes: 10000baseT/Full Supported pause frame use: No Supports auto-negotiation: No Advertised link modes: 10000baseT/Full Advertised pause frame use: No Advertised auto-negotiation: No Speed: 10000Mb/s Duplex: Full Port: Direct Attach Copper PHYAD: 0 Transceiver: external Auto-negotiation: off Supports Wake-on: d Wake-on: d Current message level: 0x00000007 (7) drv probe link Link detected: yes ifconfig server A eth0 Link encap:Ethernet HWaddr 00:25:90:ED:9E:AA inet addr:0.0.0.1 Bcast:0.0.0.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:1202795665 errors:0 dropped:64334 overruns:0 frame:0 TX packets:2313161968 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:893413096188 (832.0 GiB) TX bytes:3360949570454 (3.0 TiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:2207544 errors:0 dropped:0 overruns:0 frame:0 TX packets:2207544 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:247769175 (236.2 MiB) TX bytes:247769175 (236.2 MiB) ifconfig Server B eth2 Link encap:Ethernet HWaddr 00:25:90:82:C4:FE inet addr:0.0.0.2 Bcast:0.0.0.2 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:39973046980 errors:0 dropped:1828387600 overruns:0 frame:0 TX packets:69618752480 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:3013976063688 (2.7 TiB) TX bytes:102250230803933 (92.9 TiB) lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:1049495 errors:0 dropped:0 overruns:0 frame:0 TX packets:1049495 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:129012422 (123.0 MiB) TX bytes:129012422 (123.0 MiB) Netstat -i on Server B # netstat -i Kernel Interface table Iface MTU Met RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth2 9000 0 42098629968 0 2131223717 0 73698797854 0 0 0 BMRU lo 65536 0 1077908 0 0 0 1077908 0 0 0 LRU I Turn up send/receive buffers on the network card to 2048 and problem still persist I increase the MTU for server A and problem still persist and i increase the MTU for server B for better connectivity and transfer speed but it couldn't transfer at all The problem is : as you can see from iperf utility, the transfer speed from server A to server B slow when i restart network service in server B the transfer in server A at full speed, after 2 minutes , it's getting slow How could i troubleshoot slow speed issue and fix it in server B ? Notice : if there any other commands i should execute in servers for more information, so it might help resolve the problem , let me know in comments

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• How can I stop a bot attack on my site?

  - by tnorthcutt

  I have a site (built with wordpress) that is currently under a bot attack (as best I can tell). A file is being requested over and over, and the referrer is (almost every time) turkyoutube.org/player/player.swf. The file being requested is deep within my theme files, and is always followed by "?v=" and a long string (i.e. r.php?v=Wby02FlVyms&title=izlesen.tk_Wby02FlVyms&toke). I've tried setting an .htaccess rule for that referrer, which seems to work, except that now my 404 page is being loaded over and over, which is still using lots of bandwidth. Is there a way to create an .htaccess rule that requires no bandwidth usage on my part? I also tried creating a robots.txt file, but the attack seems to be ignoring that. #This is the relevant part of the .htaccess file: RewriteCond %{HTTP_REFERER} turkyoutube\.org [NC] RewriteRule .* - [F]

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• How much configurability to give to users regarding concurrency?

  - by rwong

  This question is a narrowing-down of these related questions: How much effort should we spend to programming for multiple cores? Concurrency: How do you approach the design and debug the implementation? Given that each user's computers may have different performance characteristics with respect to calculations, memory, disk I/O bandwidth and network I/O bandwidth, and that it is difficult to implement an automated self-tuning system in your software, how much configurability should we give to the end-users so that they can find ways (by trial-and-error?) to improve our software's efficiency? If we give users the ability to change these settings, how do we give visual feedback to users so they can measure the performance changes?

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• Windows Azure CDN(Content Delivery Network)

  - by kaleidoscope

  Windows Azure CDN caches your Windows Azure blobs at strategically placed locations to provide maximum bandwidth for delivering your content to users. You can enable CDN delivery for any storage account via the Windows Azure Developer Portal. The CDN provides edge delivery only to blobs that are in public blob containers, which are available for anonymous access. Windows Azure CDN has 18 locations globally (United States, Europe, Asia, Australia and South America) and continues to expand. The benefit of using a CDN is better performance and user experience for users who are farther from the source of the content stored in the Windows Azure Blob service. In addition, Windows Azure CDN provides worldwide high-bandwidth access to serve content for popular events. Current CDN locations in US. For more details please refer to the link.  http://blogs.msdn.com/windowsazure/archive/2009/11/05/introducing-the-windows-azure-content-delivery-network.aspx Sarang

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• A little gem from MPN&ndash;FREE online course on Architectural Guidance for Migrating Applications to Windows Azure Platform

  - by Eric Nelson

  I know a lot of technical people who work in partners (ISVs, System Integrators etc). I know that virtually none of them would think of going to the Microsoft Partner Network (MPN) learning portal to find some deep and high quality technical content. Instead they would head to MSDN, Channel 9, msdev.com etc. I am one of those people :-) Hence imagine my surprise when i stumbled upon this little gem Architectural Guidance for Migrating Applications to Windows Azure Platform (your company and hence your live id need to be a member of MPN – which is free to join). This is first class stuff – and represents about 4 hours which is really 8 if you stop and ponder :) Course Structure The course is divided into eight modules.  Each module explores a different factor that needs to be considered as part of the migration process. Module 1:  Introduction:  This section provides an introduction to the training course, highlighting the values of the Windows Azure Platform for developers. Module 2:  Dynamic Environment: This section goes into detail about the dynamic environment of the Windows Azure Platform. This session will explain the difference between current development states and the Windows Azure Platform environment, detail the functions of roles, and highlight development considerations to be aware of when working with the Windows Azure Platform. Module 3:  Local State: This session details the local state of the Windows Azure Platform. This section details the different types of storage within the Windows Azure Platform (Blobs, Tables, Queues, and SQL Azure). The training will provide technical guidance on local storage usage, how to write to blobs, how to effectively use table storage, and other authorization methods. Module 4:  Latency and Timeouts: This session goes into detail explaining the considerations surrounding latency, timeouts and how to assess an IT portfolio. Module 5:  Transactions and Bandwidth: This session details the performance metrics surrounding transactions and bandwidth in the Windows Azure Platform environment. This session will detail the transactions and bandwidth costs involved with the Windows Azure Platform and mitigation techniques that can be used to properly manage those costs. Module 6:  Authentication and Authorization: This session details authentication and authorization protocols within the Windows Azure Platform. This session will detail information around web methods of authorization, web identification, Access Control Benefits, and a walkthrough of the Windows Identify Foundation. Module 7:  Data Sensitivity: This session details data considerations that users and developers will experience when placing data into the cloud. This section of the training highlights these concerns, and details the strategies that developers can take to increase the security of their data in the cloud. Module 8:  Summary Provides an overall review of the course.

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• Polycom Lowers Bar for High-Def Videoconferencing

  Implements improved protocol for dramatically lower bandwidth requirements, launches low-cost telepresence bundle.

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• Cloud computing cost savings for large enterprise

  - by user13817

  I'm trying to understand whether cloud computing is meant for small to medium sized companies OR also for large companies. Imagine a website with a very large user base. The storage and bandwidth demands as well as the number of database transactions are incredibly high. The website might be hosting videos, music, images, etc. that keep the demands high. Does it make sense to be in the cloud when you know you need huge volumes of storage, bandwidth, and GET,PUT,etc. requests? (Each of these variables costs money in the cloud) OR does it make sense to build your own infrastructure? I can see the cost savings of cloud computing if you are a small business, but if you were aiming at the next big thing on the Internet, I can't quite see the benefits.

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• FatCow and iPage real deal?

  - by Tribbey

  I need a cheap host that I can upgrade if needed for a startup. From searching, FatCow and iPage seem reliable and inexpensive web hosting services with a Unix OS and good bandwidth + disk space. I suspect they were bought from the same company. They propose to offer unlimited bandwidth/disc space and perks like AdSense/Facebook credit however, they're packages range from 1-3 years @ 3.15 USD/mo, there isn't a monthly package but they do allow you to cancel at anytime and there servers run on wind-mill generated energy which is a plus. I was suspicious because I couldnt seem to find one negative review about them, just affiliate pages until I read a review explaining they're strict policies on copywritten data. Has anyone experience with one of these two hosts?

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• How does having assets saved on a secondary domain(s) reduce the load time of the website?

  - by AAA

  I went for an interview yesterday where I was asked this question: "How does having assets (images/videos) stored on a secondary domain (assets.example.com) reduce the load time of example.com?" To that I answered that by having the code "call" those assets from a secondary website it reduces the traffic that is coming to the main domain and therefore only applying bandwidth to the main domain vs having to also serve bandwidth to request assets. Is that correct? Also, If i am correct, would you say it makes sense to start new websites with this in mind or do you prefer having it done after large traffic rates are achieved?

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• Apple Mail clones Gmail account folders and gets out of sync when tracking unread emails

  - by Petruza

  The Gmail (fc.mm.mp.lh is Gmail also) accounts that I've set up with Mail, automatically created a second folder for each of the accounts, the ones you can see in ALL CAPS at the bottom. I guess this folders represent the web mail accounts, while the folders inside Inbox represent the pop accounts, despite them being the same account. The thing is, as you can see, while the inbox accounts have no unread mails, their "all caps" counterparts show as if they had some unread mails. This is not the normal behavior; when I mark an email as read, it is "read" in both versions of the account, but from time to time, they kind of get "out of sync" and the bottom folders start to show unread emails that were actually read. Have you seen this behavior before? What can I do? I don't use the bottom "folders" but I can't get rid of them anyway. It's just that their unread messages notification annoys me because there aren't actually any unread mails.

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• Capslock turns on intermittenly on Windows Login Screen

  - by NoCarrier

  At first I thought it was a coworker playing a joke on me.. I have a habit of locking my workstation whenever I leave my desk. however i have noticed over the last several years that sometimes the capslock key would be on when I return. I don't notice this until i try typing in my password (which would fail because its in ALL CAPS) and then glance at the now illuminated caps lock key. This has happened on and off across half a dozen workstations on 2000, XP, Vista, and Windows 7. Possible causes I'm losing my mind "feature" in windows? some sort of institutional domain policy at my workplace someone has been messing with me for many many years ?

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• Bad DMA/do_IRQ errors on suspend/resume, with occasional freezing

  - by Steve Kroon

  Every time I suspend or resume my laptop (Dell Latitude E6520, bought this year), I get 2 messages of the form displayed on the console just before shutting down/starting up: [ 407.107610] ehci_hcd 0000:00:1d.0: dma_pool_free buffer-128, f6f18000/36f18000 (bad dma) On occasion, I get a message of the form: [ 3753.979066] do_IRQ: 0.177 No irq handler for vector (irq -1) On occasion, my machine freezes with a flashing Caps Lock button when suspending, after which I need to do a hard shutdown. This never happened before the messages started appearing (a while back), and I think it never happens without a do_IRQ message appearing (although I'm not sure about that). [There's nothing in the owner's manual on a flashing Caps Lock button; apparently it may be a kernel panic if the scroll lock also flashes, but the laptop doesn't have a scroll lock light, and there's no message on the console saying kernel panic.] Are these bad DMA/do IRQ messages serious, and what can I do to investigate/troubleshoot them and the freezing? Edit: I've also now received the following error messages a few times: [246943.023908] JBD: I/O error detected when updating journal superblock for sdb1. [246943.023958] Buffer I/O error on device sdb1, logical block 0 [246943.023996] EXT3-fs (sdb1): I/O error while writing superblock Edit: Output of dmesg at http://pastebin.com/ra7MTQEj ; contents of /var/log/kern.log at http://pastebin.com/i6jf0Md9 Edit: the output of some smartctl (-a, -x, --log=error, --log=xerror) instructions is available at http://paste.ubuntu.com/1088488/ . Edit (31/8/2012): Output of dmesg|grep -i ehci available at http://paste.ubuntu.com/1177246/ .

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• QoS basics on a Cisco ASA

  - by qbn

  Could someone briefly explain how to use QoS on Cisco ASA 5505? I have the basics of policing down, but what about shaping and priorities? Basically what I'm trying to do is carve out some bandwidth for my VPN subnets (in an object-group called priority-traffic). I've seen this Cisco QoS document, however configuring shaping and priority-queue don't seem to have any effects in my test. A full download of the linux kernel from kernel.org will boost a ping to a server via VPN sky high. Policing has been successful in passing this test, although it doesn't seem as efficient (I cap non-vpn traffic at 3 of my 4.5 megabits of bandwidth). Am I misunderstanding the results of the test? I think there is some simple concept I'm not grasping here. EDIT: Here is my config thus far (I have 4.5 megabits of bandwidth): access-list priority-traffic extended permit ip object-group priority-traffic any access-list priority-traffic extended permit ip any object-group priority-traffic access-list priority-traffic extended permit icmp object-group priority-traffic any access-list priority-traffic extended permit icmp any object-group priority-traffic access-list non-priority-traffic extended deny ip object-group priority-traffic any access-list non-priority-traffic extended deny ip any object-group priority-traffic access-list non-priority-traffic extended permit ip any any priority-queue outside queue-limit 440 class-map non-priority-traffic match access-list non-priority-traffic class-map priority-traffic match access-list priority-traffic class-map inspection_default match default-inspection-traffic policy-map type inspect dns preset_dns_map parameters message-length maximum 512 policy-map global_policy class inspection_default inspect dns preset_dns_map inspect ftp inspect h323 h225 inspect h323 ras inspect rsh inspect rtsp inspect sqlnet inspect skinny inspect sunrpc inspect xdmcp inspect sip inspect netbios inspect tftp policy-map outbound-qos-policy class non-priority-traffic police input 2500000 police output 2500000 class priority-traffic priority service-policy global_policy global service-policy outbound-qos-policy interface outside

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• Are Colocation Cross Connects Worth While

  - by SvrGuy

  We currently operate three clusters of collocated machines in different data centers. Recently, I became aware that our newest data center will offer to cross connect us to a bandwidth provider free of charge. In the past, I never really investigated a cross connect for bandwidth because I figured that the rates would be similar to what we are paying the colo now and that it would reduce our resiliency (because we would only be using one or two carriers for IP, where as the colo uses, say 8 different providers). Then I saw an ad for hurricane electric internet services (http://he.net/cgi-bin/ip_transit_quote) that gave a price for IP transit at $1/Mbs, which is much better than the $30/Mb we pay for the blended bandwidth. What are people out there typically paying for bandwith via cross connect and how hard is to setup? Is my understanding that what you do is open agreemetns with two or three ISPs, cross connect to them and then configure your top of rack router on their network. Can you really get IP transit down to a couple of dollars per megabit per month just by doing the routing yourself? Or, is my understanding of cross connection fundamentally wrong?

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• Cisco ASA 5510 Time of Day Based Policing

  - by minamhere

  I have a Cisco ASA 5510 setup at a boarding school. I determined that many (most?) of the students were downloading files, watching movies, etc, during the day and this was causing the academic side of our network to suffer. The students should not even be in their rooms during the day, so I configured the ASA to police their network segment and limit their outbound bandwidth. This resolved all of our academic issues, and everyone was happy. Except the resident students. I have been asked to change/remove the policing policy at the end of the day, to allow the residents access to the unused bandwidth at night. There's no reason to let bandwidth sit unused at night just because it would be abused during the day. Is there a way to setup Time of Day based Policies on the ASA? Ideally I'd like to be able to open up the network at night and all day during weekends. If I can't set Time based policies, is is possible to schedule the ASA to load a set of commands at a specific time? I suppose I could just setup a scheduled task on one of our servers to log in and make the changes with a simple script, but this seems like a hack, and I'm hoping there is a better or more standard way to accomplish this. Thanks. Edit: If there is a totally different solution that would accomplish a similar goal, I'd be interested in that as well. Free/Cheap would be ideal, but if a separate internet connection is my only other option, it might be worth fighting for money for hardware or software to do this better or more efficiently.

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• maximum number of connections Squid

  - by Isaac

  I have a Squid proxy server that controls all internet traffic for my network. I need a way to stop users from downloading big files (say 50MB) in my network. I banned some famous ports (e.g. torrent) but some downloads are possible by HTTP port. Obviously I cannot ban port 80! A simple solution is limiting maxmimum number of the simultaneous connections for each IP (e.g. 3 connections). It's possible in Squid with this config: acl ACCOUNTSDEPT 192.168.5.0/24 acl limitusercon maxconn 3 http_access deny ACCOUNTSDEPT limitusercon But this solution has really bad impact in web browsing, because any smart browser get different parts of a website by several connections simultaneously to speedup web browsing. But if we have a maximum number of connections, the browsers will fail to get some parts and the website will be shown partially and some parts/images/frames will not be shown. So, can we limit maximum number of persist connections? I think this policy will works: Specify Maximum number of connections that is alive for 10 seconds But Number of simultaneous connections for every IP is unlimited But how can we implement this policy when Squid? With which config? UPDATE: artifex and Tom Newton offered using a bandwidth-limiting approach to fight against downloaders. But bandwidth-limiting in Squid has a shortcoming: It's static and cannot dynamically change. So a person has a limited bandwidth not matter how many people are using internet (maybe nobody!) Also, this solution cannot help to stop people from downloading. They still can download but in a lower speed. But if we find a way to terminate persist connections (or any connection that is alive more than a specific time), downloading big files will be almost impossible (always there is some way!)

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• Cisco configuration for public library internet

  - by AlternateZ

  I'm a C/C++ computer programmer turned IT support guy working for a public library. My day is usually spent helping random grandparents learn how to use email, so my networking knowledge is limited to what I can glean from google. Here's the situation. We have a public library with 20 PCs on a LAN and also public wifi access. Previously we were running all of this on 1 ADSL connection and people complained about low speeds. We hired a networking company to set up a Cisco dual-WAN router for us, and purchased an additional ADSL connection. The intention was to give the LAN PCs a guaranteed amount of bandwidth each, and then let the wifi users split the rest. The results were far worse than what we expected, and all we got from the company was excuses and they've since washed their hands of us. During busy periods, net performance on the LAN PCs are so poor that attaching files to gmail etc often times out and fails - far from the "guaranteed amount of bandwidth each" that we hope for! Sometimes it feels like performance is worse than before when we had 1 ADSL link and an unconfigured router? Anyways, surely this is a problem encountered a million times over across the world? (Sharing internet across many users effectively.) What are standard solutions for something like this? I admit to not even knowing the right jargon to google for (load balancing?) I'd appreciate any links to resources/guides that might help me get a better understanding of the problem/solutions, and perhaps some stories of your own experience in solving similar problems. This will help us evaluate and negotiate with network consultants in the future. If its relevant, our router config contains a section "policy-map" with "bandwidth percent" for each class of user (LAN, wifi), and "fair queue".

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• Alternative to Amazon’s S3 service?

  - by Cory

  Just wondering if there is good alternative to Amazon's S3 service? I like S3 but the bandwidth cost is high. I looked at CouldFiles from Rackspace but the cost is even higher. I don't mind prepaying or having monthly payment in order to reduce the bandwidth cost greatly. Thank you for any help

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• Animated Notify Icon like the task manager graph

  - by Blind Trevor

  Hi guys, I'm trying to create a bandwidth monitor - I've done most of it, but I want to have a notifyicon that changes dependent on the bandwidth. The same as when you open task manager and then minimise it, there is a little animated bar graph by the clock showing CPU usage... How do I do that??? Any help would be appreciated.

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• How to achieve Database Synchronization in Adobe Air with out LCDS

  - by Thirst for Excellence

  i designed one application which pulls data from DB once its stated,if all the clients pulls data at a time from server, there is a lot of bandwidth, and one more worse case is one client may close & open his application many time a days, so there is a lot of bandwidth consumption on serve... Is there any database Sync technique to implement in AIR desktop application ? Please if anybody know please let me know..plz dont suggest LCDS(this is bit cost) Advance Thanking, Cheers, vasu

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• Controlling youtube traffic path ingoing to multihoming network

  - by Hamdy Ali

  Scenario: I've network multihoming (dual ISP) setup. each ISP bandwidth 500Mbps Currently ISP-A link bandwidth almost fully utilized then the second ISP-B link From our investigation, it is because youtube server cache response to link ISP-A. Some time the utilization of link ISP B increased because at that time youtube server cached is response to ISP B. My question how/Why did this happen? how do I force youtube cache server using ISP link B?

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• WNDR3700 Router + Cisco SG200-08 + LACP + Dual Uplink

  - by kobaltz

  Background I have a storage server that has several virtual machine images stored on them. I would store them locally, but I have limited space on my desktop (using SSD storage). I would like to increase the bandwidth between the desktop and the storage server by using two NICs on each computer. My original configuration allowed about 55MBps between the desktop and storage server. This storage server also has several TBs of documents, pictures, movies, vms, and ISO/programs. The storage server has 8 1.5TB hard drives in a RAID 10 configuration with a hardware RAID controller. The benchmarks on the RAID 10 are about 300MBps. Configuration In short, I am trying to bridge my switch and router. The switch is a small 8 port Cisco smart switch that supports 802.3ad LACP. I have two computers plugged into the switch, each with 2 Intel Gigabit NICs. The first computer is a Windows 7 machine that has the Intel ANS software installed. I have LACP configured with the computer and now show 3 NICs (2 Physical + 1 TEAM Virtual @ 2Gbps). It looks like this computer is configured correctly. I trunked the two ports that this computer is plugged into with the switch's web interface. The second computer is a homebrew storage box running debian. I also have the bonding enabled on this machine and the switch configured with LACP. Without having the WNDR3700 router in the picture yet, I am able to communicate between the Windows 7 machine and the debian box since they both have static IP addresses. With LACP enabled on both machines I am getting about 106-108MBps speeds. Issue I plug in a network cable from the switch into the router and enable DHCP on the desktop. I saw no need to have a static address on the desktop. My transfer rates are still from 106MBps-108MBps. While this is still a boost, I am trying to figure out how to get about 140-180MBps. I am thinking that I need to increase the bandwidth from the router to the switch. My switch allows 4 groups for port trunking. I plugged in a second network cable from the router to the switch. My question is, what is the proper way to fix this issue. Should I port trunk the two ports that are going from the switch to the router? Keep in mind that the router is a WNDR3700 and is unsure whether or not it supports LACP. I do have OpenWRT installed on the router, but it still wasn't clear in any documentation that I found if it supported 802.3ad LACP standards. I am also wondering if there needs to be anything changed within the Cisco settings. [Edit] - Corrected some numbers, wasn't really paying attention. It looks like the speeds though at least two NICs are bonded with LACP is still reaching the max bandwidth of one port. Is there a way to configure the switch so that I can increase this bandwidth? Also, on the storage server, I had a couple of extra NICs laying around and threw them on there as well. Another EDIT and More Findings I happened to look at the traffic of each individual NIC and think that I see the problem. I tested with a simple transfer for a 4GB file. I noticed that only one of the NICs was taking the load of the traffic. I then copied the file back to the Storage Server and noticed that the other NIC was sending out the traffic. I have 802.3ad LACP enabled on the two NICs and I see that it gets enabled dynamically on the switch's interface. Should I be using Static Link Aggregation?

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• SQL SERVER – Core Concepts – Elasticity, Scalability and ACID Properties – Exploring NuoDB an Elastically Scalable Database System

  - by pinaldave

  I have been recently exploring Elasticity and Scalability attributes of databases. You can see that in my earlier blog posts about NuoDB where I wanted to look at Elasticity and Scalability concepts. The concepts are very interesting, and intriguing as well. I have discussed these concepts with my friend Joyti M and together we have come up with this interesting read. The goal of this article is to answer following simple questions What is Elasticity? What is Scalability? How ACID properties vary from NOSQL Concepts? What are the prevailing problems in the current database system architectures? Why is NuoDB  an innovative and welcome change in database paradigm? Elasticity This word’s original form is used in many different ways and honestly it does do a decent job in holding things together over the years as a person grows and contracts. Within the tech world, and specifically related to software systems (database, application servers), it has come to mean a few things - allow stretching of resources without reaching the breaking point (on demand). What are resources in this context? Resources are the usual suspects – RAM/CPU/IO/Bandwidth in the form of a container (a process or bunch of processes combined as modules). When it is about increasing resources the simplest idea which comes to mind is the addition of another container. Another container means adding a brand new physical node. When it is about adding a new node there are two questions which comes to mind. 1) Can we add another node to our software system? 2) If yes, does adding new node cause downtime for the system? Let us assume we have added new node, let us see what the new needs of the system are when a new node is added. Balancing incoming requests to multiple nodes Synchronization of a shared state across multiple nodes Identification of “downstate” and resolution action to bring it to “upstate” Well, adding a new node has its advantages as well. Here are few of the positive points Throughput can increase nearly horizontally across the node throughout the system Response times of application will increase as in-between layer interactions will be improved Now, Let us put the above concepts in the perspective of a Database. When we mention the term “running out of resources” or “application is bound to resources” the resources can be CPU, Memory or Bandwidth. The regular approach to “gain scalability” in the database is to look around for bottlenecks and increase the bottlenecked resource. When we have memory as a bottleneck we look at the data buffers, locks, query plans or indexes. After a point even this is not enough as there needs to be an efficient way of managing such large workload on a “single machine” across memory and CPU bound (right kind of scheduling)  workload. We next move on to either read/write separation of the workload or functionality-based sharing so that we still have control of the individual. But this requires lots of planning and change in client systems in terms of knowing where to go/update/read and for reporting applications to “aggregate the data” in an intelligent way. What we ideally need is an intelligent layer which allows us to do these things without us getting into managing, monitoring and distributing the workload. Scalability In the context of database/applications, scalability means three main things Ability to handle normal loads without pressure E.g. X users at the Y utilization of resources (CPU, Memory, Bandwidth) on the Z kind of hardware (4 processor, 32 GB machine with 15000 RPM SATA drives and 1 GHz Network switch) with T throughput Ability to scale up to expected peak load which is greater than normal load with acceptable response times Ability to provide acceptable response times across the system E.g. Response time in S milliseconds (or agreed upon unit of measure) – 90% of the time The Issue – Need of Scale In normal cases one can plan for the load testing to test out normal, peak, and stress scenarios to ensure specific hardware meets the needs. With help from Hardware and Software partners and best practices, bottlenecks can be identified and requisite resources added to the system. Unfortunately this vertical scale is expensive and difficult to achieve and most of the operational people need the ability to scale horizontally. This helps in getting better throughput as there are physical limits in terms of adding resources (Memory, CPU, Bandwidth and Storage) indefinitely. Today we have different options to achieve scalability: Read & Write Separation The idea here is to do actual writes to one store and configure slaves receiving the latest data with acceptable delays. Slaves can be used for balancing out reads. We can also explore functional separation or sharing as well. We can separate data operations by a specific identifier (e.g. region, year, month) and consolidate it for reporting purposes. For functional separation the major disadvantage is when schema changes or workload pattern changes. As the requirement grows one still needs to deal with scale need in manual ways by providing an abstraction in the middle tier code. Using NOSQL solutions The idea is to flatten out the structures in general to keep all values which are retrieved together at the same store and provide flexible schema. The issue with the stores is that they are compromising on mostly consistency (no ACID guarantees) and one has to use NON-SQL dialect to work with the store. The other major issue is about education with NOSQL solutions. Would one really want to make these compromises on the ability to connect and retrieve in simple SQL manner and learn other skill sets? Or for that matter give up on ACID guarantee and start dealing with consistency issues? Hybrid Deployment – Mac, Linux, Cloud, and Windows One of the challenges today that we see across On-premise vs Cloud infrastructure is a difference in abilities. Take for example SQL Azure – it is wonderful in its concepts of throttling (as it is shared deployment) of resources and ability to scale using federation. However, the same abilities are not available on premise. This is not a mistake, mind you – but a compromise of the sweet spot of workloads, customer requirements and operational SLAs which can be supported by the team. In today’s world it is imperative that databases are available across operating systems – which are a commodity and used by developers of all hues. An Ideal Database Ability List A system which allows a linear scale of the system (increase in throughput with reasonable response time) with the addition of resources A system which does not compromise on the ACID guarantees and require developers to learn new paradigms A system which does not force fit a new way interacting with database by learning Non-SQL dialect A system which does not force fit its mechanisms for providing availability across its various modules. Well NuoDB is the first database which has all of the above abilities and much more. In future articles I will cover my hands-on experience with it. Reference: Pinal Dave (http://blog.SQLAuthority.com) Filed under: PostADay, SQL, SQL Authority, SQL Query, SQL Server, SQL Tips and Tricks, T SQL, Technology Tagged: NuoDB

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• Library like ENet, but for TCP?

  - by Milo

  I'm not looking to use boost::asio, it is overly complex for my needs. I'm building a game that is cross platform, for desktop, iPhone and Android. I found a library called ENet which is pretty much what I need, but it uses UDP which does not seem to support encryption and a few other things. Given that the game is an event driven card game, TCP seems like the right fit. However, all I have found is WINSOCK / berkley sockets and bost::asio. Here is a sample client server application with ENet: #include <enet/enet.h> #include <stdlib.h> #include <string> #include <iostream> class Host { ENetAddress address; ENetHost * server; ENetHost* client; ENetEvent event; public: Host() :server(NULL) { enet_initialize(); setupServer(); } void setupServer() { if(server) { enet_host_destroy(server); server = NULL; } address.host = ENET_HOST_ANY; /* Bind the server to port 1234. */ address.port = 1721; server = enet_host_create (& address /* the address to bind the server host to */, 32 /* allow up to 32 clients and/or outgoing connections */, 2 /* allow up to 2 channels to be used, 0 and 1 */, 0 /* assume any amount of incoming bandwidth */, 0 /* assume any amount of outgoing bandwidth */); } void daLoop() { while(true) { /* Wait up to 1000 milliseconds for an event. */ while (enet_host_service (server, & event, 5000) > 0) { ENetPacket * packet; switch (event.type) { case ENET_EVENT_TYPE_CONNECT: printf ("A new client connected from %x:%u.\n", event.peer -> address.host, event.peer -> address.port); /* Store any relevant client information here. */ event.peer -> data = "Client information"; /* Create a reliable packet of size 7 containing "packet\0" */ packet = enet_packet_create ("packet", strlen ("packet") + 1, ENET_PACKET_FLAG_RELIABLE); /* Extend the packet so and append the string "foo", so it now */ /* contains "packetfoo\0" */ enet_packet_resize (packet, strlen ("packetfoo") + 1); strcpy ((char*)& packet -> data [strlen ("packet")], "foo"); /* Send the packet to the peer over channel id 0. */ /* One could also broadcast the packet by */ /* enet_host_broadcast (host, 0, packet); */ enet_peer_send (event.peer, 0, packet); /* One could just use enet_host_service() instead. */ enet_host_flush (server); break; case ENET_EVENT_TYPE_RECEIVE: printf ("A packet of length %u containing %s was received from %s on channel %u.\n", event.packet -> dataLength, event.packet -> data, event.peer -> data, event.channelID); /* Clean up the packet now that we're done using it. */ enet_packet_destroy (event.packet); break; case ENET_EVENT_TYPE_DISCONNECT: printf ("%s disconected.\n", event.peer -> data); /* Reset the peer's client information. */ event.peer -> data = NULL; } } } } ~Host() { if(server) { enet_host_destroy(server); server = NULL; } atexit (enet_deinitialize); } }; class Client { ENetAddress address; ENetEvent event; ENetPeer *peer; ENetHost* client; public: Client() :peer(NULL) { enet_initialize(); setupPeer(); } void setupPeer() { client = enet_host_create (NULL /* create a client host */, 1 /* only allow 1 outgoing connection */, 2 /* allow up 2 channels to be used, 0 and 1 */, 57600 / 8 /* 56K modem with 56 Kbps downstream bandwidth */, 14400 / 8 /* 56K modem with 14 Kbps upstream bandwidth */); if (client == NULL) { fprintf (stderr, "An error occurred while trying to create an ENet client host.\n"); exit (EXIT_FAILURE); } /* Connect to some.server.net:1234. */ enet_address_set_host (& address, "192.168.2.13"); address.port = 1721; /* Initiate the connection, allocating the two channels 0 and 1. */ peer = enet_host_connect (client, & address, 2, 0); if (peer == NULL) { fprintf (stderr, "No available peers for initiating an ENet connection.\n"); exit (EXIT_FAILURE); } /* Wait up to 5 seconds for the connection attempt to succeed. */ if (enet_host_service (client, & event, 20000) > 0 && event.type == ENET_EVENT_TYPE_CONNECT) { std::cout << "Connection to some.server.net:1234 succeeded." << std::endl; } else { /* Either the 5 seconds are up or a disconnect event was */ /* received. Reset the peer in the event the 5 seconds */ /* had run out without any significant event. */ enet_peer_reset (peer); puts ("Connection to some.server.net:1234 failed."); } } void daLoop() { ENetPacket* packet; /* Create a reliable packet of size 7 containing "packet\0" */ packet = enet_packet_create ("backet", strlen ("backet") + 1, ENET_PACKET_FLAG_RELIABLE); /* Extend the packet so and append the string "foo", so it now */ /* contains "packetfoo\0" */ enet_packet_resize (packet, strlen ("backetfoo") + 1); strcpy ((char*)& packet -> data [strlen ("backet")], "foo"); /* Send the packet to the peer over channel id 0. */ /* One could also broadcast the packet by */ /* enet_host_broadcast (host, 0, packet); */ enet_peer_send (event.peer, 0, packet); /* One could just use enet_host_service() instead. */ enet_host_flush (client); while(true) { /* Wait up to 1000 milliseconds for an event. */ while (enet_host_service (client, & event, 1000) > 0) { ENetPacket * packet; switch (event.type) { case ENET_EVENT_TYPE_RECEIVE: printf ("A packet of length %u containing %s was received from %s on channel %u.\n", event.packet -> dataLength, event.packet -> data, event.peer -> data, event.channelID); /* Clean up the packet now that we're done using it. */ enet_packet_destroy (event.packet); break; } } } } ~Client() { atexit (enet_deinitialize); } }; int main() { std::string a; std::cin >> a; if(a == "host") { Host host; host.daLoop(); } else { Client c; c.daLoop(); } return 0; } I looked at some socket tutorials and they seemed a bit too low level. I just need something that abstracts away the platform (eg, no WINSOCKS) and that has basic ability to keep track of connected clients and send them messages. Thanks

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• Emacs on Windows: how to protect built-in el files from being accidentally edited

  - by RamyenHead

  On Linux, they are all read only, so no problem. But on MS Windows, what happens is like this: I get curious about the definition of the command isearch-forward, I type C-h f isearch-forward and click on the link isearch.el from the help to get to the definition of the function, and while I am reading its definition, I press C-h or C-c many times, but I set Caps Lock as another Ctrl key, so sometimes it happens that I release Caps Lock too early, in which case C-h or C-c becomes inserting h or c, sometimes I notice that and undo it, but sometimes I don't notice it, and I even save them all with C-x s. What is a good way to protect the built-in el files from me on MS Windows?

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