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• In a web app, is it wise to give log files ".txt" suffix?

  - by Pekka

  I am building a logging mechanism in a web application. Being a Windows man, I tend to give files with textual content the .txt ending. The suffix is automatically registered to be opened in a text editor in any Windows environment, and is just a nice convention. The app is going to be redistributed, and running mostly on Linux, though. The Linux convention for log files is .log. Is there any good reason on the Linux end, besides convention, why I should use .log? Any filters, real-life applications that could become relevant and that will work only with a .log suffix? Or can I merrily call it error_log.txt?

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• Is it not wise to always expect semantically correct mark-up, in my own and others code?

  - by metal-gear-solid

  Is it bad to be semantic purist all the time, at work? is it not achievable all the time ? when i saw code of any other person/interviewee. I know selection of element for a purpose is most important thing. what i should judge person ability from his code; from a good written, managed, optimized css or how he wrote class and id names? Or both every time.

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• How to manage images (dimension-wise) in iPhone OS 3.1x / 3.2 / 4.0?

  - by Horace Ho

  iPhone is 480 x 320, iPad is 1024 x 768, iOS 4 is 960 x 640. What is the good practice of managing images for 3 resolutions? Say the app wallpaper as an example, the iPhone is probably a 50%-reduction of the iOS4 one. But it is also tempting to design one dimension (1024 x 768) for both devices (iPad and iOS 4 phones). Any suggestions? thanks

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• Is it wise to rely on default features of a programming language?

  - by George Edison

  Should I frequently rely on default values? For example, in PHP, if you have the following: <?php $var .= "Value"; ?> This is perfectly fine - it works. But what if assignment like this to a previously unused variable is later eliminated from the language? (I'm not referring to just general assignment to an unused variable.) There are countless examples of where the default value of something has changed and so much existing code was then useless. On the other hand, without default values, there is a lot of code redundancy. What is the proper way of dealing with this?

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• Is the moq project dead? Is it wise for me to invest in learning it?

  - by NimsDotNet

  I am fairly new to mocking frameworks and was trying to decide which one will be a good bet to start working on. I have been looking at this question about the best mocking framework, and I can see a lot of people preferring moq, but when i saw the moq project's change list, i can see that it has not been updated for almost an year now. Is moq project dead? if yes, which will be a good mocking framework to start with today?

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• Is it a wise decision to go from dev to third line/Tier 3 dev support?

  - by dotnetdev

  Hi, I am an experienced, mid-level developer. However, I recently spotted a job for a company which is small but has a lot of emphasis on training(beyond the basic technical training, but also mentoring, leadership training, etc). The role is 3rd line so still very technical. It's in app support so it's post implementation development rather than pure out-and-out development like I do now (or don't, as the senior devs do all of the interesting work). However, and this is the question - is this sort of career move common? Also, wouldn't a tech support role be a big shock to the system because I've never dealt with customers? I therefore think it's a bad move? Working in dev, I am used to the lack of customer contact and it is all filtered through by my manager. But in tech support, contacting customers/rude customers could be scary. I don't mind fixing other people's mistakes (better than me making mistakes!) and doing post-implementation dev for production systems (will give me a lot of discipline), and I do get bored sitting in the same place looking/talking to the same people in suits (I work in a corporate environment). The company puts A LOT of emphasis on training and prospects, which I don't get in the current (big) company I work at. Any advice on how to handle tech support is appreciated! Thanks

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• Best way to run multiple queries per second on database, performance wise?

  - by Michael Joell

  I am currently using Java to insert and update data multiple times per second. Never having used databases with Java, I am not sure what is required, and how to get the best performance. I currently have a method for each type of query I need to do (for example, update a row in a database). I also have a method to create the database connection. Below is my simplified code. public static void addOneForUserInChannel(String channel, String username) throws SQLException { Connection dbConnection = null; PreparedStatement ps = null; String updateSQL = "UPDATE " + channel + "_count SET messages = messages + 1 WHERE username = ?"; try { dbConnection = getDBConnection(); ps = dbConnection.prepareStatement(updateSQL); ps.setString(1, username); ps.executeUpdate(); } catch(SQLException e) { System.out.println(e.getMessage()); } finally { if(ps != null) { ps.close(); } if(dbConnection != null) { dbConnection.close(); } } } And my DB connection private static Connection getDBConnection() { Connection dbConnection = null; try { Class.forName(DB_DRIVER); } catch (ClassNotFoundException e) { System.out.println(e.getMessage()); } try { dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER,DB_PASSWORD); return dbConnection; } catch (SQLException e) { System.out.println(e.getMessage()); } return dbConnection; } This seems to be working fine for now, with about 1-2 queries per second, but I am worried that once I expand and it is running many more, I might have some issues. My questions: Is there a way to have a persistent database connection throughout the entire run time of the process? If so, should I do this? Are there any other optimizations that I should do to help with performance? Thanks

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• How costly performance-wise are these actions in iPhone objective-C?

  - by Alex Gosselin

  This is really a few questions in one, I'm wondering what the performance cost is for these things, as I haven't really been following a best practice of any sort for these. The answers may also be useful to other readers, if somebody knows these. (1) If I need the core data managed object context, is it bad to use #import "myAppDelegate.h" //farther down in the code: NSManagedObjectContext *context = [(myAppDelegate.h*)[[UIApplication sharedApplication] delegate] managedObjectContext]; as opposed to leaving the warning you get if you don't cast the delegate? (2) What is the cheapest way to hard-code a string? I have been using return @"myString"; on occasion in some functions where I need to pass it to a variety of places, is it better to do it this way: static NSString *str = @"myString"; return str; (3) How costly is it to subclass an object i wrote vs. making a new one, in general? (4) When I am using core data and navigating through a hierarchy of some sort, is it necessary to turn things back into faults somehow after I read some info from them? or is this done automatically? Thanks for any help.

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• unexplainable packet drops with 5 ethernet NICs and low traffic on Ubuntu

  - by jon

  I'm stuck on problem where my machine started to drops packets with no sign of ANY system load or high interrupt usage after an upgrade to Ubuntu 12.04. My server is a network monitoring sensor, running Ubuntu LTS 12.04, it passively collects packets from 5 interfaces doing network intrusion type stuff. Before the upgrade I managed to collect 200+GB of packets a day while writing them to disk with around 0% packet loss depending on the day with the help of CPU affinity and NIC IRQ to CPU bindings. Now I lose a great deal of packets with none of my applications running and at very low PPS rate which a modern workstation NIC would have no trouble with. Specs: x64 Xeon 4 cores 3.2 Ghz 16 GB RAM NICs: 5 Intel Pro NICs using the e1000 driver (NAPI). [1] eth0 and eth1 are integrated NICs (in the motherboard) There are 2 other PCI-X network cards, each with 2 Ethernet ports. 3 of the interfaces are running at Gigabit Ethernet, the others are not because they're attached to hubs. Specs: [2] http://support.dell.com/support/edocs/systems/pe2850/en/ug/t1390aa.htm uptime 17:36:00 up 1:43, 2 users, load average: 0.00, 0.01, 0.05 # uname -a Linux nms 3.2.0-29-generic #46-Ubuntu SMP Fri Jul 27 17:03:23 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux I also have the CPU governor set to performance mode and irqbalance off. The problem still occurs with them on. # lspci -t -vv -[0000:00]-+-00.0 Intel Corporation E7520 Memory Controller Hub +-02.0-[01-03]--+-00.0-[02]----0e.0 Dell PowerEdge Expandable RAID controller 4 | \-00.2-[03]-- +-04.0-[04]-- +-05.0-[05-07]--+-00.0-[06]----07.0 Intel Corporation 82541GI Gigabit Ethernet Controller | \-00.2-[07]----08.0 Intel Corporation 82541GI Gigabit Ethernet Controller +-06.0-[08-0a]--+-00.0-[09]--+-04.0 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | | \-04.1 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | \-00.2-[0a]--+-02.0 Digium, Inc. Wildcard TE210P/TE212P dual-span T1/E1/J1 card 3.3V | +-03.0 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) | \-03.1 Intel Corporation 82546EB Gigabit Ethernet Controller (Copper) +-1d.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #1 +-1d.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #2 +-1d.2 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB UHCI Controller #3 +-1d.7 Intel Corporation 82801EB/ER (ICH5/ICH5R) USB2 EHCI Controller +-1e.0-[0b]----0d.0 Advanced Micro Devices [AMD] nee ATI RV100 QY [Radeon 7000/VE] +-1f.0 Intel Corporation 82801EB/ER (ICH5/ICH5R) LPC Interface Bridge \-1f.1 Intel Corporation 82801EB/ER (ICH5/ICH5R) IDE Controller I believe the NIC nor the NIC drivers are dropping the packets because ethtool reports 0 under rx_missed_errors and rx_no_buffer_count for each interface. On the old system, if it couldn't keep up this is where the drops would be. I drop packets on multiple interfaces just about every second, usually in small increments of 2-4. I tried all these sysctl values, I'm currently using the uncommented ones. # cat /etc/sysctl.conf # high net.core.netdev_max_backlog = 3000000 net.core.rmem_max = 16000000 net.core.rmem_default = 8000000 # defaults #net.core.netdev_max_backlog = 1000 #net.core.rmem_max = 131071 #net.core.rmem_default = 163480 # moderate #net.core.netdev_max_backlog = 10000 #net.core.rmem_max = 33554432 #net.core.rmem_default = 33554432 Here's an example of an interface stats report with ethtool. They are all the same, nothing is out of the ordinary ( I think ), so I'm only going to show one: ethtool -S eth2 NIC statistics: rx_packets: 7498 tx_packets: 0 rx_bytes: 2722585 tx_bytes: 0 rx_broadcast: 327 tx_broadcast: 0 rx_multicast: 1504 tx_multicast: 0 rx_errors: 0 tx_errors: 0 tx_dropped: 0 multicast: 1504 collisions: 0 rx_length_errors: 0 rx_over_errors: 0 rx_crc_errors: 0 rx_frame_errors: 0 rx_no_buffer_count: 0 rx_missed_errors: 0 tx_aborted_errors: 0 tx_carrier_errors: 0 tx_fifo_errors: 0 tx_heartbeat_errors: 0 tx_window_errors: 0 tx_abort_late_coll: 0 tx_deferred_ok: 0 tx_single_coll_ok: 0 tx_multi_coll_ok: 0 tx_timeout_count: 0 tx_restart_queue: 0 rx_long_length_errors: 0 rx_short_length_errors: 0 rx_align_errors: 0 tx_tcp_seg_good: 0 tx_tcp_seg_failed: 0 rx_flow_control_xon: 0 rx_flow_control_xoff: 0 tx_flow_control_xon: 0 tx_flow_control_xoff: 0 rx_long_byte_count: 2722585 rx_csum_offload_good: 0 rx_csum_offload_errors: 0 alloc_rx_buff_failed: 0 tx_smbus: 0 rx_smbus: 0 dropped_smbus: 01 # ifconfig eth0 Link encap:Ethernet HWaddr 00:11:43:e0:e2:8c UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:373348 errors:16 dropped:95 overruns:0 frame:16 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:356830572 (356.8 MB) TX bytes:0 (0.0 B) eth1 Link encap:Ethernet HWaddr 00:11:43:e0:e2:8d UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:13616 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:8690528 (8.6 MB) TX bytes:0 (0.0 B) eth2 Link encap:Ethernet HWaddr 00:04:23:e1:77:6a UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:7750 errors:0 dropped:471 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:2780935 (2.7 MB) TX bytes:0 (0.0 B) eth3 Link encap:Ethernet HWaddr 00:04:23:e1:77:6b UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:5112 errors:0 dropped:206 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:639472 (639.4 KB) TX bytes:0 (0.0 B) eth4 Link encap:Ethernet HWaddr 00:04:23:b6:35:6c UP BROADCAST RUNNING NOARP PROMISC ALLMULTI MULTICAST MTU:1500 Metric:1 RX packets:961467 errors:0 dropped:935 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:958561305 (958.5 MB) TX bytes:0 (0.0 B) eth5 Link encap:Ethernet HWaddr 00:04:23:b6:35:6d inet addr:192.168.1.6 Bcast:192.168.1.255 Mask:255.255.255.0 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:4264 errors:0 dropped:16 overruns:0 frame:0 TX packets:699 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:572228 (572.2 KB) TX bytes:124456 (124.4 KB) I tried the defaults, then started to play around with settings. I wasn't using any flow control and I increased the RxDescriptor count to 4096 before the upgrade as well without any problems. # cat /etc/modprobe.d/e1000.conf options e1000 XsumRX=0,0,0,0,0 RxDescriptors=4096,4096,4096,4096,4096 FlowControl=0,0,0,0,0 debug=16 Here's my network configuration file, I turned off checksumming and various offloading mechanisms along with setting CPU affinity with heavy use interfaces getting an entire CPU and light use interfaces sharing a CPU. I used these settings prior to the upgrade without problems. # cat /etc/network/interfaces # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet manual pre-up /sbin/ethtool -G eth0 rx 4096 tx 0 pre-up /sbin/ethtool -K eth0 gro off gso off rx off pre-up /sbin/ethtool -A eth0 rx off autoneg off up ifconfig eth0 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/48/smp_affinity down ifconfig eth0 down post-down /sbin/ethtool -G eth0 rx 256 tx 256 post-down /sbin/ethtool -K eth0 gro on gso on rx on post-down /sbin/ethtool -A eth0 rx on autoneg on auto eth1 iface eth1 inet manual pre-up /sbin/ethtool -G eth1 rx 4096 tx 0 pre-up /sbin/ethtool -K eth1 gro off gso off rx off pre-up /sbin/ethtool -A eth1 rx off autoneg off up ifconfig eth1 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/49/smp_affinity down ifconfig eth1 down post-down /sbin/ethtool -G eth1 rx 256 tx 256 post-down /sbin/ethtool -K eth1 gro on gso on rx on post-down /sbin/ethtool -A eth1 rx on autoneg on auto eth2 iface eth2 inet manual pre-up /sbin/ethtool -G eth2 rx 4096 tx 0 pre-up /sbin/ethtool -K eth2 gro off gso off rx off pre-up /sbin/ethtool -A eth2 rx off autoneg off up ifconfig eth2 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "1" > /proc/irq/82/smp_affinity down ifconfig eth2 down post-down /sbin/ethtool -G eth2 rx 256 tx 256 post-down /sbin/ethtool -K eth2 gro on gso on rx on post-down /sbin/ethtool -A eth2 rx on autoneg on auto eth3 iface eth3 inet manual pre-up /sbin/ethtool -G eth3 rx 4096 tx 0 pre-up /sbin/ethtool -K eth3 gro off gso off rx off pre-up /sbin/ethtool -A eth3 rx off autoneg off up ifconfig eth3 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "2" > /proc/irq/83/smp_affinity down ifconfig eth3 down post-down /sbin/ethtool -G eth3 rx 256 tx 256 post-down /sbin/ethtool -K eth3 gro on gso on rx on post-down /sbin/ethtool -A eth3 rx on autoneg on auto eth4 iface eth4 inet manual pre-up /sbin/ethtool -G eth4 rx 4096 tx 0 pre-up /sbin/ethtool -K eth4 gro off gso off rx off pre-up /sbin/ethtool -A eth4 rx off autoneg off up ifconfig eth4 0.0.0.0 -arp promisc mtu 1500 allmulti txqueuelen 0 up post-up echo "4" > /proc/irq/77/smp_affinity down ifconfig eth4 down post-down /sbin/ethtool -G eth4 rx 256 tx 256 post-down /sbin/ethtool -K eth4 gro on gso on rx on post-down /sbin/ethtool -A eth4 rx on autoneg on auto eth5 iface eth5 inet static pre-up /etc/fw.conf address 192.168.1.1 netmask 255.255.255.0 broadcast 192.168.1.255 gateway 192.168.1.1 dns-nameservers 192.168.1.2 192.168.1.3 up ifconfig eth5 up post-up echo "8" > /proc/irq/77/smp_affinity down ifconfig eth5 down Here's a few examples of packet drops, i ran one after another, probabling totaling 3 or 4 seconds. You can see increases in the drops from the 1st and 3rd. This was a non-busy time, very little traffic. # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 225 lo: 0 eth2: 505 eth1: 0 eth5: 17 eth0: 105 eth4: 1034 # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 225 lo: 0 eth2: 507 eth1: 0 eth5: 17 eth0: 105 eth4: 1034 # awk '{ print $1,$5 }' /proc/net/dev Inter-| face drop eth3: 227 lo: 0 eth2: 512 eth1: 0 eth5: 17 eth0: 105 eth4: 1039 I tried the pci=noacpi options. With and without, it's the same. This is what my interrupt stats looked like before the upgrade, after, with ACPI on PCI it showed multiple NICs bound to an interrupt and shared with other devices such as USB drives which I didn't like so I think i'm going to keep it with ACPI off as it's easier to designate sole purpose interrupts. Is there any advantage I would have using the default i.e. ACPI w/ PCI. ? # cat /etc/default/grub | grep CMD_LINE GRUB_CMDLINE_LINUX_DEFAULT="ipv6.disable=1 noacpi pci=noacpi" GRUB_CMDLINE_LINUX="" # cat /proc/interrupts CPU0 CPU1 CPU2 CPU3 0: 45 0 0 16 IO-APIC-edge timer 1: 1 0 0 7936 IO-APIC-edge i8042 2: 0 0 0 0 XT-PIC-XT-PIC cascade 6: 0 0 0 3 IO-APIC-edge floppy 8: 0 0 0 1 IO-APIC-edge rtc0 9: 0 0 0 0 IO-APIC-edge acpi 12: 0 0 0 1809 IO-APIC-edge i8042 14: 1 0 0 4498 IO-APIC-edge ata_piix 15: 0 0 0 0 IO-APIC-edge ata_piix 16: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb2 18: 0 0 0 1350 IO-APIC-fasteoi uhci_hcd:usb4, radeon 19: 0 0 0 0 IO-APIC-fasteoi uhci_hcd:usb3 23: 0 0 0 4099 IO-APIC-fasteoi ehci_hcd:usb1 38: 0 0 0 61963 IO-APIC-fasteoi megaraid 48: 0 0 1002319 4 IO-APIC-fasteoi eth0 49: 0 0 38772 3 IO-APIC-fasteoi eth1 77: 0 0 130076 432159 IO-APIC-fasteoi eth4 78: 0 0 0 23917 IO-APIC-fasteoi eth5 82: 1329033 0 0 4 IO-APIC-fasteoi eth2 83: 0 4886525 0 6 IO-APIC-fasteoi eth3 NMI: 5 6 4 5 Non-maskable interrupts LOC: 61409 57076 64257 114764 Local timer interrupts SPU: 0 0 0 0 Spurious interrupts IWI: 0 0 0 0 IRQ work interrupts RES: 17956 25333 13436 14789 Rescheduling interrupts CAL: 22436 607 539 478 Function call interrupts TLB: 1525 1458 4600 4151 TLB shootdowns TRM: 0 0 0 0 Thermal event interrupts THR: 0 0 0 0 Threshold APIC interrupts MCE: 0 0 0 0 Machine check exceptions MCP: 16 16 16 16 Machine check polls ERR: 0 MIS: 0 Here's sample output of vmstat, showing the system. Barebones system right now. root@nms:~# vmstat -S m 1 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa 0 0 0 14992 192 1029 0 0 56 2 419 29 1 0 99 0 0 0 0 14992 192 1029 0 0 0 0 922 27 0 0 100 0 0 0 0 14991 192 1029 0 0 0 36 763 50 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 646 35 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 722 54 0 0 100 0 0 0 0 14991 192 1029 0 0 0 0 793 27 0 0 100 0 ^C Here's dmesg output. I can't figure out why my PCI-X slots are negotiated as PCI. The network cards are all PCI-X with the exception of the integrated NICs that came with the server. In the output below it looks as if eth3 and eth2 negotiated at PCI-X speeds rather than PCI:66Mhz. Wouldn't they all drop to PCI:66Mhz? If your integrated NICs are PCI, as labeled below (eth0,eth1), then wouldn't all devices on your bus speed drop down to that slower bus speed? If not, I still don't know why only one of my NICs ( each has two ethernet ports) is labeled as PCI-X in the output below. Does that mean it is running at PCI-X speeds are is it showing that it's capable? # dmesg | grep e1000 [ 3678.349337] e1000: Intel(R) PRO/1000 Network Driver - version 7.3.21-k8-NAPI [ 3678.349342] e1000: Copyright (c) 1999-2006 Intel Corporation. [ 3678.349394] e1000 0000:06:07.0: PCI->APIC IRQ transform: INT A -> IRQ 48 [ 3678.409725] e1000 0000:06:07.0: Receive Descriptors set to 4096 [ 3678.409730] e1000 0000:06:07.0: Checksum Offload Disabled [ 3678.409734] e1000 0000:06:07.0: Flow Control Disabled [ 3678.586409] e1000 0000:06:07.0: eth0: (PCI:66MHz:32-bit) 00:11:43:e0:e2:8c [ 3678.586419] e1000 0000:06:07.0: eth0: Intel(R) PRO/1000 Network Connection [ 3678.586642] e1000 0000:07:08.0: PCI->APIC IRQ transform: INT A -> IRQ 49 [ 3678.649854] e1000 0000:07:08.0: Receive Descriptors set to 4096 [ 3678.649859] e1000 0000:07:08.0: Checksum Offload Disabled [ 3678.649863] e1000 0000:07:08.0: Flow Control Disabled [ 3678.826436] e1000 0000:07:08.0: eth1: (PCI:66MHz:32-bit) 00:11:43:e0:e2:8d [ 3678.826444] e1000 0000:07:08.0: eth1: Intel(R) PRO/1000 Network Connection [ 3678.826627] e1000 0000:09:04.0: PCI->APIC IRQ transform: INT A -> IRQ 82 [ 3679.093266] e1000 0000:09:04.0: Receive Descriptors set to 4096 [ 3679.093271] e1000 0000:09:04.0: Checksum Offload Disabled [ 3679.093275] e1000 0000:09:04.0: Flow Control Disabled [ 3679.130239] e1000 0000:09:04.0: eth2: (PCI-X:133MHz:64-bit) 00:04:23:e1:77:6a [ 3679.130246] e1000 0000:09:04.0: eth2: Intel(R) PRO/1000 Network Connection [ 3679.130449] e1000 0000:09:04.1: PCI->APIC IRQ transform: INT B -> IRQ 83 [ 3679.397312] e1000 0000:09:04.1: Receive Descriptors set to 4096 [ 3679.397318] e1000 0000:09:04.1: Checksum Offload Disabled [ 3679.397321] e1000 0000:09:04.1: Flow Control Disabled [ 3679.434350] e1000 0000:09:04.1: eth3: (PCI-X:133MHz:64-bit) 00:04:23:e1:77:6b [ 3679.434360] e1000 0000:09:04.1: eth3: Intel(R) PRO/1000 Network Connection [ 3679.434553] e1000 0000:0a:03.0: PCI->APIC IRQ transform: INT A -> IRQ 77 [ 3679.704072] e1000 0000:0a:03.0: Receive Descriptors set to 4096 [ 3679.704077] e1000 0000:0a:03.0: Checksum Offload Disabled [ 3679.704081] e1000 0000:0a:03.0: Flow Control Disabled [ 3679.738364] e1000 0000:0a:03.0: eth4: (PCI:33MHz:64-bit) 00:04:23:b6:35:6c [ 3679.738371] e1000 0000:0a:03.0: eth4: Intel(R) PRO/1000 Network Connection [ 3679.738538] e1000 0000:0a:03.1: PCI->APIC IRQ transform: INT B -> IRQ 78 [ 3680.046060] e1000 0000:0a:03.1: eth5: (PCI:33MHz:64-bit) 00:04:23:b6:35:6d [ 3680.046067] e1000 0000:0a:03.1: eth5: Intel(R) PRO/1000 Network Connection [ 3682.132415] e1000: eth0 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.224423] e1000: eth1 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.316385] e1000: eth2 NIC Link is Up 100 Mbps Half Duplex, Flow Control: None [ 3682.408391] e1000: eth3 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 3682.500396] e1000: eth4 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: None [ 3682.708401] e1000: eth5 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX At first I thought it was the NIC drivers but I'm not so sure. I really have no idea where else to look at the moment. Any help is greatly appreciated as I'm struggling with this. If you need more information just ask. Thanks! [1]http://www.cs.fsu.edu/~baker/devices/lxr/http/source/linux/Documentation/networking/e1000.txt?v=2.6.11.8 [2] http://support.dell.com/support/edocs/systems/pe2850/en/ug/t1390aa.htm

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• Solaris 11 Update 1 - Link Aggregation

  - by Wesley Faria

  Solaris 11.1 No início desse mês em um evento mundial da Oracle chamado Oracle Open World foi lançada a nova release do Solaris 11. Ela chega cheia de novidades, são aproximadamente 300 novas funcionalidade em rede, segurança, administração e outros. Hoje vou falar de uma funcionalidade de rede muito interessante que é o Link Aggregation. O Solaris já suporta Link Aggregation desde Solaris 10 Update 1 porem no Solaris 11 Update 1 tivemos incrementos significantes. O Link Aggregation como o próprio nome diz, é a agregação de mais de uma inteface física de rede em uma interface lógica .Veja agumas funcionalidade do Link Aggregation: · Aumentar a largura da banda; · Imcrementar a segurança fazendo Failover e Failback; · Melhora a administração da rede; O Solaris 11.1 suporta 2(dois) tipos de Link Aggregation o Trunk aggregation e o Datalink Multipathing aggregation, ambos trabalham fazendo com que o pacote de rede seja distribuído entre as intefaces da agregação garantindo melhor utilização da rede.vamos ver um pouco melhor cada um deles. Trunk Aggregation O Trunk Aggregation tem como objetivo aumentar a largura de banda, seja para aplicações que possue um tráfego de rede alto seja para consolidação. Por exemplo temos um servidor que foi adquirido para comportar várias máquinas virtuais onde cada uma delas tem uma demanda e esse servidor possue 2(duas) placas de rede. Podemos então criar uma agregação entre essas 2(duas) placas de forma que o Solaris 11.1 vai enchergar as 2(duas) placas como se fosse 1(uma) fazendo com que a largura de banda duplique, veja na figura abaixo: A figura mostra uma agregação com 2(duas) placas físicas NIC 1 e NIC 2 conectadas no mesmo switch e 2(duas) interfaces virtuais VNIC A e VNIC B. Porem para que isso funcione temos que ter um switch com suporte a LACP ( Link Aggregation Control Protocol ). A função do LACP é fazer a aggregação na camada do switch pois se isso não for feito o pacote que sairá do servidor não poderá ser montado quando chegar no switch. Uma outra forma de configuração do Trunk Aggregation é o ponto-a-ponto onde ao invéz de se usar um switch, os 2 servidores são conectados diretamente. Nesse caso a agregação de um servidor irá falar diretamente com a agregação do outro garantindo uma proteção contra falhas e tambem uma largura de banda maior. Vejamos como configurar o Trunk Aggregation: 1 – Verificando quais intefaces disponíveis # dladm show-link 2 – Verificando interfaces # ipadm show-if 3 – Apagando o endereçamento das interfaces existentes # ipadm delete-ip <interface> 4 – Criando o Trunk aggregation # dladm create-aggr -L active -l <interface> -l <interface> aggr0 5 – Listando a agregação criada # dladm show-aggr Data Link Multipath Aggregation Como vimos anteriormente o Trunk aggregation é implementado apenas 1(um) switch que possua suporte a LACP portanto, temos um ponto único de falha que é o switch. Para solucionar esse problema no Solaris 10 utilizavamos o IPMP ( IP Multipathing ) que é a combinação de 2(duas) agregações em um mesmo link ou seja, outro camada de virtualização. Agora com o Solaris 11 Update 1 isso não é mais necessário, voce pode ter uma agregação de 2(duas) interfaces físicas e cada uma conectada a 1(um) swtich diferente, veja a figura abaixo: Temos aqui uma agregação chamada aggr contendo 4(quatro) interfaces físicas sendo que as interfaces NIC 1 e NIC 2 estão conectadas em um Switch e as intefaces NIC 3 e NIC 4 estão conectadas em outro Swicth. Além disso foram criadas mais 4(quatro) interfaces virtuais vnic A, vnic B, vnic C e vnic D que podem ser destinadas a diferentes aplicações/zones. Com isso garantimos alta disponibilidade em todas a camadas pois podemos ter falhas tanto em switches, links como em interfaces de rede físicas. Para configurar siga os mesmo passos da configuração do Trunk Aggregation até o passo 3 depois faça o seguinte: 4 – Criando o Trunk aggregation # dladm create-aggr -m haonly -l <interface> -l <interface> aggr0 5 – Listando a agregação criada # dladm show-aggr Depois de configurado seja no modo Trunk aggregation ou no modo Data Link Multipathing aggregation pode ser feito a troca de um modo para o outro, pode adcionar e remover interfaces físicas ou vituais. Bem pessoal, era isso que eu tinha para mostar sobre a nova funcionalidade do Link Aggregation do Solaris 11 Update 1 espero que tenham gostado, até uma próxima novidade.

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• How to learn the math behind the code?

  - by Solomon Wise

  I am a 12 year old who has recently gotten into programming. (Although I know that the number of books you have read does not determine your programming competency or ability, just to paint a "map" of where I am in terms of the content I know...) I've finished the books: Python 3 For Absolute Beginners Pro Python Python Standard Library by Example Beautiful Code Agile Web Development With Rails and am about halfway into Programming Ruby. I have written many small programs (One that finds which files have been updated and deleted in a directory, one that compares multiple players' fantasy baseball value, and some text based games, and many more). Obviously, as I'm not some sort of child prodigy, I can't take a formal Computer Science course until high school. I really want to learn computer science to increase my knowledge about the code, and the how the code runs. I've really become interested in the math part after reading the source code for Python's random module. Is there a place where I can learn CS, or programming math online for free, at a level that would be at least partially understandable to a person my age?

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• Reasons to Use Version Control [closed]

  - by Solomon Wise

  Possible Duplicate: I'm a Subversion geek, why I should consider or not consider Mercurial or Git or any other DVCS? What is the value of using version control? I am a relative noob to programming, and am not going to be developing super-good software or even programming professionally anytime soon. With this predicament, is there really any reason to learn git or subversion or any other version control systems?

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• Count of memory copies in *nix systems between packet at NIC and user application?

  - by Michael_73

  Hi there, This is just a general question relating to some high-performance computing I've been wondering about. A certain low-latency messaging vendor speaks in its supporting documentation about using raw sockets to transfer the data directly from the network device to the user application and in so doing it speaks about reducing the messaging latency even further than it does anyway (in other admittedly carefully thought-out design decisions). My question is therefore to those that grok the networking stacks on Unix or Unix-like systems. How much difference are they likely to be able to realise using this method? Feel free to answer in terms of memory copies, numbers of whales rescued or areas the size of Wales ;) Their messaging is UDP-based, as I understand it, so there's no problem with establishing TCP connections etc. Any other points of interest on this topic would be gratefully thought about! Best wishes, Mike

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• Tamilnadu HSC (+2) exam results – List of Websites

  - by samsudeen

  Tamilnadu State Board HSC ( +2 ) exam  results is expected to be release around the mid of this month ( probably on May 19). School students can get their marks at the same time from their respective schools. The results are usually published on websites or can availed from  mobile phone service providers through SMS. But it is for sure  most the sites will not be accessed for at least couple hours at the  time of result announcement Below are some of the quality web sites ( includes mirror sites to directly access the results page) that publishes the result links. http://www.tnresults.nic.in/ http://www.squarebrothers.com/ http://results.sify.com/ http://indiaresults.com/ http://www.dge1.tn.nic.in/ http://www.dge2.tn.nic.in/ http://www.dge3.tn.nic.in/ http://www.tngdc.in/ http://www.collegesintamilnadu.com/ http://www.classontheweb.com/ http://www.schools9.com/ http://www.chennaivision.com/ http://www.mygaruda.com/ http://www.tnagar.com/ http://www.indiacollegefinder.com/ http://www.chennaionline.com/ http://www.nakkeeran.com/ http://www.getyourscore.in/ http://www.examresults.net/ http://results.webdunia.com/ http://www.jayanews.in/ http://www.findchennai.com/ Join us on Facebook to read all our stories right inside your Facebook news feed.

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• Bind DHCP Server to Network Bridge

  - by Luke

  My wireless router died, so I decided to route everything through my server. So I installed a second NIC and a wireless card to be my new network: 1 NIC to the Modem, 1 NIC to the switch, and the Wireless to... Well, wireless. Anyways, I got far enough to get DHCP to work on just ONE adapter when I used Internet Connection Sharing (I couldn't get RRAS set up for the life of me), then I decided to try bridging the wireless and second NIC. Now, the DHCP server won't bind to the bridge, but I can enter manual IP's in my clients and it'll connect to the Internet. I also tried changing my wireless adapter's IP to 192.168.0.2, and to 192.168.1.1 to try to set up a separate scope, but to no avail. Running Windows Server 2003

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• No compatible network card

  - by sbintcliffe

  Motherboard: Asus K8N-E Deluxe with onboard NIC (nVidia nForce) Secondary NIC: I've tried using a standard NIC (Device Manager displays this as D-Link DFE-538TX 10/100, but under manufacturer in the General tab of the properties in Windows it states Realtek Semiconductor Corp.) I have downloaded ESXi 4.0.0 build 208167 and cooked to disc. I've booted from it, the .TGZ modules load from the yellow and grey screen, the progress bar reaches to about 60% and like a second later the screen changes and I have the following information on screen; "No compatible network adapter found. Please consult the HCG." I've checked the HCG and found that my motherboard is listed. I also get the same message with the secondary NIC. Any ideas please?

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• Packet drop measured by ethtool, tcpdump and ifconfig

  - by Rayne

  Hi all, I have a question regarding packet drops. I am running a test to determine when packet drops occur. I'm using a Spirent TestCenter through a switch (necessary to aggregate Ethernet traffic from 5 ports to one optical link) to a server using a Myricom card. While running my test, if the input rate is below a certain value, ethtool does not report any drop (except dropped_multicast_filtered which is incrementing at a very slow rate). However, tcpdump reports X number of packets "dropped by kernel". Then if I increase the input rate, ethtool reports drops but "ifconfig eth2" does not. In fact, ifconfig doesn't seem to report any packet drops at all. Do they all measure packet drops at different "levels", i.e. ethtool at the NIC level, tcpdump at the kernel level etc? And am I right to say that in the journey of an incoming packet, the NIC level is the "so-called" first level, then the kernel, then the user application? So any packet drop is likely to happen first at the NIC, then the kernel, then the user application? So if there is no packet drop at the NIC, but packet drop at the kernel, then the bottleneck is not at the NIC? Thank you. Regards, Rayne

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• NAT ports - how do they work?

  - by Davidoper

  I have the following network schema: Computer A: three nics: NIC 1 (eth0): dhcp, public internet NIC 2 (eth1): static 192.168.1.1, gateway for Computer B NIC 3 (eth2): static 192.168.2.1, gateway for Computer C Computer B: static 192.168.1.2, using gateway 192.168.1.1 (NIC 2). Computer C: static 192.168.2.2, using gateway 192.168.2.1 (NIC 3). So I applied this to get NAT working: iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE Every computer can connect to the internet now. I have been applying rules to the main computer (Computer A), like dropping connections to some ports, e.g ssh: iptables -A INPUT -p tcp --dport 22 -j DROP But for instance, now I would like only allow connections for ports 20,21,22,53 and 80 in Computer C, and ignore the outside traffic if it's not related to those ports. The allowed connections should be FROM Computer C to outside, but not from outside to Computer C (I mean - Computer C is not hosting any HTTP or SSH, but it is going to use them as a client). I guess this sould be done like this: iptables -A OUTPUT -i eth2 -o eth0 -p tcp --dport 21 -m state --state NEW,ESTABLISHED -j ACCEPT iptables -A INPUT -i eth2 -o eth0 -p tcp --sport 21 -m state --state ESTABLISHED -j ACCEPT The last rule (dropping any other traffic different from those) is at the end of the configuration, so -A should be working correctly. The thing is... it is not working. If I put the last rule like this: iptables -A FORWARD -i eth2 -o eth0 -j DROP It just drops everything and, for instance, port 21 (previously opened as you can see above) is not either working. Can you tell me what could I have done wrong? I have been struggling with this problem for some time and I am unable to solve it. Thanks!

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• Server 2008 NAT Internet Not Working

  - by Jack

  I'm trying to set up Routing and Remote Access on Windows Server 2008 R2, I have a network connection that I want to share the internet from to another private network. The server has two NICs which are configured as follows: External NIC (Dynamically assigned by ISP) IP:10.175.4.150 Subnet:255.255.192.0 Gateway:10.175.0.1 DNS:10.175.0.1 Internal NIC IP:172.16.254.1 Subnet:255.255.255.0 Gateway:None DNS:None I have set the external NIC to be the public interface and enabled NAT on it in the RRAS MMC and set the internal NIC to be a private interface. I have also set up the DNS forwarding or whatever it is in the NAT section. From a client (IP:172.16.254.2) I can ping the server and access files on it, when I try to browse the web with the default gateway set to the internal NIC ip I end up getting a 404 page which is returned from the ISPs default gateway. I'm guessing it's something to do with the double NAT possibly. Trying to ping the ISPs default gateway from a private network client just times out as does accessing it directly. I've disabled and reconfigured RRAS multiple times and that doesn't seem to have made a difference, so can anyone tell me what I'm doing wrong? Thanks.

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• Moving Farm to co-location hosting - network settings requirements

  - by Saariko

  I am moving my farm (2 Dell's R620) to a co-location hosting service. I am trying to figure out the secure way to have my network settings The requirements are: VM1 is the working HOST, includes: esxi 5.1, vSphere, 4 clients (w2008r2 all) VM2 has esxi 5.1 installed, and a single machine with Veeam Backup and copy 6.5 - keeping a copy of VM1 clients on the VM2 internal storage (this solution is due to a very small budget - in case of failure on Host 1 - can redirect IP's) Only 2 VM clients require network address and access from the WWAN - ISP provides IP's range for them (with Gateway and DNS) I need connection to the iDrac's from my office (option to create a VPN-SSL tunnel) Connection to the vSphere appliances I want to be able to RDP to the VM clients The current configuration is that each host has the iDrac dedicated nic connected , and another (NIC #1) connected - with a static IP on 192.168.3.x The iDrac's have a static IP from the same network range (19.168.3.x) It will look something like this: My thoughts: On NIC#2 of both hosts I will connected a crossed cable I will give each VM clients that needs internet access a 2ndry VM network with the assigned IP from the ISP open only to web - can not access from the My Question: Should I give IP's (external) to the machines who DO NOT require WWAN Access? - I can't see a way to RDP to them directly if not. Should I use the crossed cable? or just plug NIC #2 to the switch? Will this setup even work? What do I need to verify? What Virtual nic's and/or switches should I create on the Hosts?

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• How do you confirm network adapter is gigabit capable?

  - by StrandedPirate

  Upgrading my network to gigabit speeds and don't know how to determine if the NIC in one of the systems is capable of gigabit speed. The documentation from the manufacturer states this: Network adapter 10/100/1000 Ethernet LAN on system board However when I go to the properties of the NIC under Speed & Duplex my only options are: 10 Mb Full 10 Mb Half 100 Mb Full 100 Mb Half Auto Is there a command line I can run that will give me more detail about the NIC? Windows 7 x64 OS New Info: The new switch I just bought has a light to indicate 1000Mbps. I can tell from the light that this NIC is indeed negotiating at 1000Mbps but I'd still like to know how to determine this from the console in windows.

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• Do all routers really must know all routes to every router?

  - by Philipili

  This is my complicated and long question. First let's talk about the context. Network topology: PC A --- RT A --- RT C --- RT B --- PC B (RT C has a WAN NIC connected to "the cloud") With this situation : PC A must send a packet to PC B Default routes direct packets to the cloud We haven't access to RT C's configuration RT C only knows how to join network A, not network B RT A knows about network B RT B knows about network A RT C's routing table: Destination NIC Gateway 0.0.0.0 WAN Cloud Network A LAN A RT A's WAN RT A's routing table: Destination NIC Gateway 0.0.0.0 WAN LAN A Network B WAN LAN A RT B's routing table: Destination NIC Gateway 0.0.0.0 WAN LAN B Network A WAN LAN B I would like to permit PC A and PC B to communicate, but I don't have access to RT C. Networks B and BC are new. Can PC A send a packet to RT B's WAN NIC (which is possible) and "ask RT B to direct the packet to PC B" ? I believe replacing RT B with a VPN server should do the trick, but I would like to know if it is possible to make it without establishing a new connection.

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• How to remove an "extra" (unwanted) network from a windows 2008 failover cluster?

  - by Trondh

  Hi, We had a severe crash on one node of our 2-node Windows 2008 / Exchange 2007 CCR Cluster the other day, and i tried to rebuild the node from scratch. I'm using this as a rough outline: http://edmckinzie.spaces.live.com/Blog/cns!687C72A5909E4230!508.entry?sa=641979772 The problem: Our cluster was originally setup with only one NIC per host, as this is supposedly supported in Win2008 (no dedicated heartbeat NIC). When I add my freshly installed node to the cluster, it shows up with two cluster networks, "Cluster Network 1" & 2. The existing node's NIC has been placed in one cluster network and my fresh installed has ended up in the other. I can't find anywhere in the GUI to choose which cluster network each physical NIC should be part of, but i KNOW I have done this before. Time is of the essence on this one, so I was hoping someone in here had the answer on the top of their head... Thanks for any pointers. regards, Trond Hindenes

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• CentOS 5.8 dig is not resolving ip-address

  - by travisbotello

  I'm running centos 5.8 on a local machine at home. Today I was trying to analyze the DNS-Lookup via dig. $ dig +trace -t A www.heise.de. This is giving me something like this as a response de. 172800 IN NS f.nic.de. de. 172800 IN NS z.nic.de. de. 172800 IN NS s.de.net. de. 172800 IN NS n.de.net. de. 172800 IN NS a.nic.de. de. 172800 IN NS l.de.net. ;; Received 344 bytes from 192.58.128.30#53(192.58.128.30) in 49 ms In contrast my dedicated CentOS machine is returning the following de. 172800 IN NS a.nic.de. de. 172800 IN NS n.de.net. de. 172800 IN NS f.nic.de. de. 172800 IN NS z.nic.de. de. 172800 IN NS l.de.net. de. 172800 IN NS s.de.net. ;; Received 344 bytes from 192.58.128.30#53(j.root-servers.net) in 32 ms As you can see, the last line is different. Any idea why my dedicated machine is giving me the host name of the responding DNS-Server and my local machine is only returning the ip-address? Thanks in advance UPDATE The reverse DNS-Lookup is working without any problems. Also, I just checked this on my local mac and...exactly the same problem occurs. Is it possible that this has to do with the local router/modem/ISP?

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• Simple Linux program that takes any HTTP/HTTPS request and returns a single page?

  - by ultrasawblade

  I have a Linux box operating as router. There's a NIC that's connected to the internet (WAN), a NIC connected to an 8-port GbE switch (LAN), and a NIC connected to a Linksys wireless N-router (WLAN). Routing between everything is working perfectly. I have security completely disabled on the wireless router, but the WLAN NIC is firewalled such that it will only accept DNS queries and PPTP VPN connections. Currently HTTP/HTTPS traffic and everything else is blocked. I would like to run something that listens on port 80/443 of the WLAN NIC, and, for non VPN'ed connections, given any HTTP/HTTPS request it will return a single webpage saying "Unauthenticated" and explain how to sign into the VPN. A transparent proxy seems to be what I need, but my searches all seem to direct me to Squid, which is already running on my server and seems overkill for this simple task. Is there a simpler, lightweight program out there that does just this or should I just suck it up and run two instances of Squid (or figure out how to configure it)? Or, is this entire VPN thing I'm doing complete nonsense and I should just enable encryption on the wireless router?

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