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• State Pattern - should a state know about its context?

  - by Extrakun

  I am referring to the state pattern as described in this link. In the example class diagram, a context has numerous states. However, it does not show how does a state communicates with a context (perhaps an input in a state has impact on a setting in the context). The two examples on the page shows either passing the context to the state via a function, or storing a reference to the context. Are those advisable? Are there other ways for a state to communicate with a context? Update to an edit: For instance, I am doing a remote control which can have several states. Say, the context has a setting for Volume, and I am in one of the states which allow me to tweak the volume. How should the state communicates with the context that the volume is being changed?

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• Saving State of Objects in GXT

  - by 8EM

  Is there a way to store the state of objects in GXT? That is, having a dynamically configurable GUI built in GXT, you can add your own widgets 'on-the-fly' in any order you like - with your own custom everything. Is there a way to save the state of all the objects, so one can load the profile back at a later date?

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• Is ASP.Net State Server an elegant solution?

  - by alchemical

  We have an ASP.Net MVC project that will start with a single web server but likely soon scale into a small web farm. As ASP.Net Authentication stores a UserID, and data caching may also be useful, we would likely need to make the jump to state server fairly soon. I'd like to hear from others how State Server has been to work with and how it scales from a performance perspective. Alternateively, we could architect it as completely stateless by not using data caching and tracking sessions with an encrypted cookie.

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• asp.net state server session - cross appDomain?

  - by newone1

  When using a State server for session, are sessions still appDomain specific? So for example, I have two different IIS applications(virtual directories) on a web server, and they both point to one state server for session. The session guid from the cookie will be the same across requests from both applications, so will the same session be accessible across both of these applications? Thanks.

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• JSF 2.0: Preserving component state across multiple views

  - by tlind

  The web application I am developing using MyFaces 2.0.3 / PrimeFaces 2.2RC2 is divided into a content and a navigation area. In the navigation area, which is included into multiple pages using templating (i.e. <ui:define>), there are some widgets (e.g. a navigation tree, collapsible panels etc.) of which I want to preserve the component state across views. For example, let's say I am on the home page. When I navigate to a product details page by clicking on a product in the navigation tree, my Java code triggers a redirect using navigationHandler.handleNavigation(context, null, "/detailspage.jsf?faces-redirect=true") Another way of getting to that details page would be by directly clicking on a product teaser that is shown on the home page. The corresponding <h:link> would lead us to the details page. In both cases, the expansion state of my navigation tree (a PrimeFaces tree component) and my collapsible panels is lost. I understand this is because the redirect / h:link results in the creation of a new view. What is the best way of dealing with this? I am already using MyFaces Orchestra in my project along with its conversation scope, but I am not sure if this is of any help here (since I'd have to bind the expansion/collapsed state of the widgets to a backing bean... but as far as I know, this is not possible). Is there a way of telling JSF which component states to propagate to the next view, assuming that the same component exists in that view? I guess I could need a pointer into the right direction here. Thanks! Update 1: I just tried binding the panels and the tree to a session-scoped bean, but this seems to have no effect. Also, I guess I would have to bind all child components (if any) manually, so this doesn't seem like the way to go. Update 2: Binding UI components to non-request scoped beans is not a good idea (see link I posted in a comment below). If there is no easier approach, I might have to proceed as follows: When a panel is collapsed or the tree is expanded, save the current state in a session-scoped backing bean (!= the UI component itself) The components' states are stored in a map. The map key is the component's (hopefully) unique, relative ID. I cannot use the whole absolute component path here, since the IDs of the parent naming containers might change if the view changes, assuming these IDs are generated programmatically. As soon as a new view gets constructed, retrieve the components' states from the map and apply them to the components. For example, in case of the panels, I can set the collapsed attribute to a value retrieved from my session-scoped backing bean.

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• state server session - cross appDomain?

  - by newone1

  When using a State server for session, are sessions still appDomain specific? So for example, I have two different IIS applications(virtual directories) on a web server, and they both point to one state server for session. The session guid from the cookie will be the same across requests from both applications, so will the same session be accessible across both of these applications? Thanks.

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• Workflow State not changing in asp.net

  - by shail

  hi i m trying to change the state for workflow from one state to another on button click its working fine with windows but not with web application and its instance id does not persist i have used SqlWorkflowPersistenceService also. what can b the solution for this. thanks

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• The Interaction between Three-Tier Client/Server Model and Three-Tier Application Architecture Model

  The three-tier client/server model is a network architectural approach currently used in modern networking. This approach divides a network in to three distinct components. Three-Tier Client/Server Model Components Client Component Server Component Database Component The Client Component of the network typically represents any device on the network. A basic example of this would be computer or another network/web enabled devices that are connected to a network. Network clients request resources on the network, and are usually equipped with a user interface for the presentation of the data returned from the Server Component. This process is done through the use of various software clients, and example of this can be seen through the use of a web browser client. The web browser request information from the Server Component located on the network and then renders the results for the user to process. The Server Components of the network return data based on specific client request back to the requesting client.  Server Components also inherit the attributes of a Client Component in that they are a device on the network and that they can also request information from other Server Components. However what differentiates a Client Component from a Server Component is that a Server Component response to requests from devices on the network. An example of a Server Component can be seen in a web server. A web server listens for new requests and then interprets the request, processes the web pages, and then returns the processed data back to the web browser client so that it may render the data for the user to interpret. The Database Component of the network returns unprocessed data from databases or other resources. This component also inherits attributes from the Server Component in that it is a device on a network, it can request information from other server components and database components, and it also listens for new requests so that it can return data when needed. The three-tier client/server model is very similar to the three-tier application architecture model, and in fact the layers can be mapped to one another. Three-Tier Application Architecture Model Presentation Layer/Logic Business Layer/Logic Data Layer/Logic The Presentation Layer including its underlying logic is very similar to the Client Component of the three-tiered model. The Presentation Layer focuses on interpreting the data returned by the Business Layer as well as presents the data back to the user.  Both the Presentation Layer and the Client Component focus primarily on the user and their experience. This allows for segments of the Business Layer to be distributable and interchangeable because the Presentation Layer is not directly integrated in with Business Layer. The Presentation Layer does not care where the data comes from as long as it is in the proper format. This allows for the Presentation Layer and Business Layer to be stored on one or more different servers so that it can provide a higher availability to clients requesting data. A good example of this is a web site that uses load balancing. When a web site decides to take on the task of load balancing they must obtain a network device that sits in front of a one or machines in order to distribute the request across multiple servers. When a user comes in through the load balanced device they are redirected to a specific server based on a few factors. Common Load Balancing Factors Current Server Availability Current Server Response Time Current Server Priority The Business Layer and corresponding logic are business rules applied to data prior to it being sent to the Presentation Layer. These rules are used to manipulate the data coming from the Data Access Layer, in addition to validating any data prior to being stored in the Data Access Layer. A good example of this would be when a user is trying to create multiple accounts under one email address. The Business Layer logic can prevent duplicate accounts by enforcing a unique email for every new account before the data is even stored in the Data Access Layer. The Server Component can be directly tied to this layer in that the server typically stores and process the Business Layer before it is returned to the end-user via the Presentation Layer. In addition the Server Component can also run automated process through the Business Layer on the data in the Data Access Layer so that additional business analysis can be derived from the data that has been already collected. The Data Layer and its logic are responsible for storing information so that it can be easily retrieved. Typical in most modern applications data is stored in a database management system however data can also be in the form of files stored on a file server. In addition a database can take on one of several forms. Common Database Formats XML File Pipe Delimited File Tab Delimited File Comma Delimited File (CSV) Plain Text File Microsoft Access Microsoft SQL Server MySql Oracle Sybase The Database component of the Networking model can be directly tied to the Data Layer because this is where the Data Layer obtains the data to return back the Business Layer. The Database Component basically allows for a place on the network to store data for future use. This enables applications to save data when they can and then quickly recall the saved data as needed so that the application does not have to worry about storing the data in memory. This prevents overhead that could be created when an application must retain all data in memory. As you can see the Three-Tier Client/Server Networking Model and the Three-Tiered Application Architecture Model rely very heavily on one another to function especially if different aspects of an application are distributed across an entire network. The use of various servers and database servers are wonderful when an application has a need to distribute work across the network. Network Components and Application Layers Interaction Database components will store all data needed for the Data Access Layer to manipulate and return to the Business Layer Server Component executes the Business Layer that manipulates data so that it can be returned to the Presentation Layer Client Component hosts the Presentation Layer that  interprets the data and present it to the user

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• I have to make a simple app that connects devices in a network, but I have no idea of how to this

  - by Gabriel Casado

  I want to write an App for android that has only one ListView. The App will constantly search for anything (mobile devices, desktops, etc.) that is connected in the wifi network. The problem is, I have no idea how to do this. What do I need to study? I comprehend I'd need to use a Thread or a Runnable to constantly search for those devices. Also I know very little about TCP, UDP or any internet protocols. So, can someone give me a basis of what I need to learn to develop this App?

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• SARA Security Auditor Alternative

  - by bradlis7

  I have attempted to install and run Sara, but it seems that the software is broken. I could get it to run on 127.0.0.1, but it seems that no network packets ever leave the current computer that it is installed on. It tests for known security holes in a network. It was based on an older software SATAN. Is there another free alternative to this program? I did not see anything listed in this thread.

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• stuck with enable session state

  - by Shrewd Demon

  hi i have an application wherein i am accessing the Session object in the CommonCode.cs file that resides in the App_Code folder. But when the session object is accessed the application throws me an error: Session state can only be used when enableSessionState is set to true, either in a configuration file or in the Page directive. Please also make sure that System.Web.SessionStateModule or a custom session state module is included in the \\ section in the application configuration. Now i have already enabled the session state property in the web.config file, here is my code from the web.config file: <pages enableSessionState="true" autoEventWireup="true"> <controls> <add tagPrefix="asp" namespace="System.Web.UI" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> <add tagPrefix="asp" namespace="System.Web.UI.WebControls" assembly="System.Web.Extensions, Version=3.5.0.0, Culture=neutral, PublicKeyToken=31BF3856AD364E35"/> </controls> </pages> I dont understand why am i still getting that error !! please help ! thanks a lot.

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• How to display over state of a SimpleButton at up state

  - by Hasan Gürsoy

  I have a menu with button objects in As3. I want to display the page where user is and for this I must show buttons' over state (which is mc) when flash loads. I'm sending the page parameter to flash. I just need to play the movie clip inside the specific button. Looking for something like: btn1.m1.gotoAndPlay(1); or btn1.m1.play();

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• OS X won't see Windows 7 in network (and vice versa)

  - by meds

  I've enabled SMB sharing in OS X Lion and have added folders to share, it says 'Windows Sharing: On' with a green circle next to it (from the sharing window) and that to access the volume I will need to to go to \\192.168.0.17. It also says that the OS X should be visible as 'macbook' in the network. Both my WIndows 7 and OS X are connected to the same network, yet when I try to go to \\192.168.0.17 or from the Mac try to go to my Windows system (smb://192.168.0.6) the two OSs don't see each other. Any ideas why? Attempting to ping the Mac from Windows results in this output in the command prompt: Pinging 192.168.0.17 with 32 bytes of data: Reply from 192.168.0.6: Destination host unreachable. Request timed out. Request timed out. Request timed out. Ping statistics for 192.168.0.17: Packets: Sent = 4, Received = 1, Lost = 3 (75% loss), ipconfig in Windows is: Wireless LAN adapter Wireless Network Connection: Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::8918:efd1:b05c:890f%21 IPv4 Address. . . . . . . . . . . : 192.168.0.6 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : 192.168.0.1 Ethernet adapter Bluetooth Network Connection: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Ethernet adapter VMware Network Adapter VMnet1: Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::98ab:63fc:3c07:d837%13 IPv4 Address. . . . . . . . . . . : 192.168.74.1 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : Ethernet adapter VMware Network Adapter VMnet8: Connection-specific DNS Suffix . : Link-local IPv6 Address . . . . . : fe80::80ff:c575:7b50:3a10%14 IPv4 Address. . . . . . . . . . . : 192.168.21.1 Subnet Mask . . . . . . . . . . . : 255.255.255.0 Default Gateway . . . . . . . . . : Tunnel adapter isatap.{2E97D0AE-9E18-4072-AC23-1979BA0DCB79}: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Tunnel adapter isatap.{E260CE43-E9A7-4DE0-A88E-4EAFF68ACDDB}: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Tunnel adapter isatap.{A5130812-59CE-4DDF-9C35-9433BCED9831}: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Tunnel adapter Teredo Tunneling Pseudo-Interface: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Tunnel adapter isatap.{134BCAE7-CFFF-4A98-8DA0-3708806AABEB}: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : Tunnel adapter isatap.{8D9E3B8F-161C-4ACE-B211-3EDD694416B2}: Media State . . . . . . . . . . . : Media disconnected Connection-specific DNS Suffix . : in OS X: lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384 options=3<RXCSUM,TXCSUM> inet6 fe80::1%lo0 prefixlen 64 scopeid 0x1 inet 127.0.0.1 netmask 0xff000000 inet6 ::1 prefixlen 128 gif0: flags=8010<POINTOPOINT,MULTICAST> mtu 1280 stf0: flags=0<> mtu 1280 en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 options=2b<RXCSUM,TXCSUM,VLAN_HWTAGGING,TSO4> ether c8:2a:14:01:24:c1 media: autoselect (none) status: inactive en1: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500 ether e0:f8:47:0c:fe:04 inet6 fe80::e2f8:47ff:fe0c:fe04%en1 prefixlen 64 scopeid 0x5 inet 192.168.0.17 netmask 0xffffff00 broadcast 192.168.0.255 media: autoselect status: active p2p0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 2304 ether 02:f8:47:0c:fe:04 media: autoselect status: inactive fw0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 4078 lladdr 70:cd:60:ff:fe:d8:f1:32 media: autoselect <full-duplex> status: inactive

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• Diving into OpenStack Network Architecture - Part 1

  - by Ronen Kofman

  v\:* {behavior:url(#default#VML);} o\:* {behavior:url(#default#VML);} w\:* {behavior:url(#default#VML);} .shape {behavior:url(#default#VML);} rkofman Normal rkofman 83 3045 2014-05-23T21:11:00Z 2014-05-27T06:58:00Z 3 1883 10739 Oracle Corporation 89 25 12597 12.00 140 Clean Clean false false false false EN-US X-NONE HE MicrosoftInternetExplorer4 /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:10.0pt; mso-para-margin-left:0in; line-height:115%; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:Arial; mso-bidi-theme-font:minor-bidi; mso-bidi-language:AR-SA;} Before we begin OpenStack networking has very powerful capabilities but at the same time it is quite complicated. In this blog series we will review an existing OpenStack setup using the Oracle OpenStack Tech Preview and explain the different network components through use cases and examples. The goal is to show how the different pieces come together and provide a bigger picture view of the network architecture in OpenStack. This can be very helpful to users making their first steps in OpenStack or anyone wishes to understand how networking works in this environment.  We will go through the basics first and build the examples as we go. According to the recent Icehouse user survey and the one before it, Neutron with Open vSwitch plug-in is the most widely used network setup both in production and in POCs (in terms of number of customers) and so in this blog series we will analyze this specific OpenStack networking setup. As we know there are many options to setup OpenStack networking and while Neturon + Open vSwitch is the most popular setup there is no claim that it is either best or the most efficient option. Neutron + Open vSwitch is an example, one which provides a good starting point for anyone interested in understanding OpenStack networking. Even if you are using different kind of network setup such as different Neutron plug-in or even not using Neutron at all this will still be a good starting point to understand the network architecture in OpenStack. The setup we are using for the examples is the one used in the Oracle OpenStack Tech Preview. Installing it is simple and it would be helpful to have it as reference. In this setup we use eth2 on all servers for VM network, all VM traffic will be flowing through this interface.The Oracle OpenStack Tech Preview is using VLANs for L2 isolation to provide tenant and network isolation. The following diagram shows how we have configured our deployment: This first post is a bit long and will focus on some basic concepts in OpenStack networking. The components we will be discussing are Open vSwitch, network namespaces, Linux bridge and veth pairs. Note that this is not meant to be a comprehensive review of these components, it is meant to describe the component as much as needed to understand OpenStack network architecture. All the components described here can be further explored using other resources. Open vSwitch (OVS) In the Oracle OpenStack Tech Preview OVS is used to connect virtual machines to the physical port (in our case eth2) as shown in the deployment diagram. OVS contains bridges and ports, the OVS bridges are different from the Linux bridge (controlled by the brctl command) which are also used in this setup. To get started let’s view the OVS structure, use the following command: # ovs-vsctl show 7ec51567-ab42-49e8-906d-b854309c9edf     Bridge br-int         Port br-int             Interface br-int type: internal         Port "int-br-eth2"             Interface "int-br-eth2"     Bridge "br-eth2"         Port "br-eth2"             Interface "br-eth2" type: internal         Port "eth2"             Interface "eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2" ovs_version: "1.11.0" We see a standard post deployment OVS on a compute node with two bridges and several ports hanging off of each of them. The example above is a compute node without any VMs, we can see that the physical port eth2 is connected to a bridge called “br-eth2”. We also see two ports "int-br-eth2" and "phy-br-eth2" which are actually a veth pair and form virtual wire between the two bridges, veth pairs are discussed later in this post. When a virtual machine is created a port is created on one the br-int bridge and this port is eventually connected to the virtual machine (we will discuss the exact connectivity later in the series). Here is how OVS looks after a VM was launched: # ovs-vsctl show efd98c87-dc62-422d-8f73-a68c2a14e73d     Bridge br-int         Port "int-br-eth2"             Interface "int-br-eth2"         Port br-int             Interface br-int type: internal         Port "qvocb64ea96-9f" tag: 1             Interface "qvocb64ea96-9f"     Bridge "br-eth2"         Port "phy-br-eth2"             Interface "phy-br-eth2"         Port "br-eth2"             Interface "br-eth2" type: internal         Port "eth2"             Interface "eth2" ovs_version: "1.11.0" Bridge "br-int" now has a new port "qvocb64ea96-9f" which connects to the VM and tagged with VLAN 1. Every VM which will be launched will add a port on the “br-int” bridge for every network interface the VM has. Another useful command on OVS is dump-flows for example: # ovs-ofctl dump-flows br-int NXST_FLOW reply (xid=0x4): cookie=0x0, duration=735.544s, table=0, n_packets=70, n_bytes=9976, idle_age=17, priority=3,in_port=1,dl_vlan=1000 actions=mod_vlan_vid:1,NORMAL cookie=0x0, duration=76679.786s, table=0, n_packets=0, n_bytes=0, idle_age=65534, hard_age=65534, priority=2,in_port=1 actions=drop cookie=0x0, duration=76681.36s, table=0, n_packets=68, n_bytes=7950, idle_age=17, hard_age=65534, priority=1 actions=NORMAL As we see the port which is connected to the VM has the VLAN tag 1. However the port on the VM network (eth2) will be using tag 1000. OVS is modifying the vlan as the packet flow from the VM to the physical interface. In OpenStack the Open vSwitch agent takes care of programming the flows in Open vSwitch so the users do not have to deal with this at all. If you wish to learn more about how to program the Open vSwitch you can read more about it at http://openvswitch.org looking at the documentation describing the ovs-ofctl command. Network Namespaces (netns) Network namespaces is a very cool Linux feature can be used for many purposes and is heavily used in OpenStack networking. Network namespaces are isolated containers which can hold a network configuration and is not seen from outside of the namespace. A network namespace can be used to encapsulate specific network functionality or provide a network service in isolation as well as simply help to organize a complicated network setup. Using the Oracle OpenStack Tech Preview we are using the latest Unbreakable Enterprise Kernel R3 (UEK3), this kernel provides a complete support for netns. Let's see how namespaces work through couple of examples to control network namespaces we use the ip netns command: Defining a new namespace: # ip netns add my-ns # ip netns list my-ns As mentioned the namespace is an isolated container, we can perform all the normal actions in the namespace context using the exec command for example running the ifconfig command: # ip netns exec my-ns ifconfig -a lo        Link encap:Local Loopback           LOOPBACK  MTU:16436 Metric:1           RX packets:0 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:0 (0.0 b)  TX bytes:0 (0.0 b) We can run every command in the namespace context, this is especially useful for debug using tcpdump command, we can ping or ssh or define iptables all within the namespace. Connecting the namespace to the outside world: There are various ways to connect into a namespaces and between namespaces we will focus on how this is done in OpenStack. OpenStack uses a combination of Open vSwitch and network namespaces. OVS defines the interfaces and then we can add those interfaces to namespace. So first let's add a bridge to OVS: # ovs-vsctl add-br my-bridge Now let's add a port on the OVS and make it internal: # ovs-vsctl add-port my-bridge my-port # ovs-vsctl set Interface my-port type=internal And let's connect it into the namespace: # ip link set my-port netns my-ns Looking inside the namespace: # ip netns exec my-ns ifconfig -a lo        Link encap:Local Loopback           LOOPBACK  MTU:65536 Metric:1           RX packets:0 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:0 (0.0 b)  TX bytes:0 (0.0 b) my-port   Link encap:Ethernet HWaddr 22:04:45:E2:85:21           BROADCAST  MTU:1500 Metric:1           RX packets:0 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:0 (0.0 b)  TX bytes:0 (0.0 b) Now we can add more ports to the OVS bridge and connect it to other namespaces or other device like physical interfaces. Neutron is using network namespaces to implement network services such as DCHP, routing, gateway, firewall, load balance and more. In the next post we will go into this in further details. Linux Bridge and veth pairs Linux bridge is used to connect the port from OVS to the VM. Every port goes from the OVS bridge to a Linux bridge and from there to the VM. The reason for using regular Linux bridges is for security groups’ enforcement. Security groups are implemented using iptables and iptables can only be applied to Linux bridges and not to OVS bridges. Veth pairs are used extensively throughout the network setup in OpenStack and are also a good tool to debug a network problem. Veth pairs are simply a virtual wire and so veths always come in pairs. Typically one side of the veth pair will connect to a bridge and the other side to another bridge or simply left as a usable interface. In this example we will create some veth pairs, connect them to bridges and test connectivity. This example is using regular Linux server and not an OpenStack node: Creating a veth pair, note that we define names for both ends: # ip link add veth0 type veth peer name veth1 # ifconfig -a . . veth0     Link encap:Ethernet HWaddr 5E:2C:E6:03:D0:17           BROADCAST MULTICAST  MTU:1500 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) veth1     Link encap:Ethernet HWaddr E6:B6:E2:6D:42:B8           BROADCAST MULTICAST  MTU:1500 Metric:1           RX packets:0 errors:0 dropped:0 overruns:0 frame:0           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000           RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b) . . To make the example more meaningful this we will create the following setup: veth0 => veth1 => br-eth3 => eth3 ======> eth2 on another Linux server br-eth3 – a regular Linux bridge which will be connected to veth1 and eth3 eth3 – a physical interface with no IP on it, connected to a private network eth2 – a physical interface on the remote Linux box connected to the private network and configured with the IP of 50.50.50.1 Once we create the setup we will ping 50.50.50.1 (the remote IP) through veth0 to test that the connection is up: # brctl addbr br-eth3 # brctl addif br-eth3 eth3 # brctl addif br-eth3 veth1 # brctl show bridge name     bridge id               STP enabled     interfaces br-eth3         8000.00505682e7f6       no              eth3                                                         veth1 # ifconfig veth0 50.50.50.50 # ping -I veth0 50.50.50.51 PING 50.50.50.51 (50.50.50.51) from 50.50.50.50 veth0: 56(84) bytes of data. 64 bytes from 50.50.50.51: icmp_seq=1 ttl=64 time=0.454 ms 64 bytes from 50.50.50.51: icmp_seq=2 ttl=64 time=0.298 ms When the naming is not as obvious as the previous example and we don't know who are the paired veth interfaces we can use the ethtool command to figure this out. The ethtool command returns an index we can look up using ip link command, for example: # ethtool -S veth1 NIC statistics: peer_ifindex: 12 # ip link . . 12: veth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000 Summary That’s all for now, we quickly reviewed OVS, network namespaces, Linux bridges and veth pairs. These components are heavily used in the OpenStack network architecture we are exploring and understanding them well will be very useful when reviewing the different use cases. In the next post we will look at how the OpenStack network is laid out connecting the virtual machines to each other and to the external world. @RonenKofman

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• Persistent Issues on small business network using Cisco 871W and Catalyst Express 500

  - by Ben Campbell

  Being the most qualified (read: still not qualified) to solve our persistant network issues, I've turned to serverfault for guidance. I've done some searching, reading related documentation on cisco.com and tried a bit of troubleshooting. Here is the config: 100mb synchronous connection from a business internet provider (tested multiple times at 100meg at the source) Cisco 871W wireless point & router is where the WAN connection starts (this serves all our wireless). The only wired connection in the 871W is the Catalyst switch listed below. Cisco Catalyst Express 500 (24TT) is where all the wired connections terminate. About 20 Windows workstations and servers (AD/Webservers only). Some services in EC2 including mail and other web servers/apps. I've been TOLD cabling internally should be gigabit-ready. Here are the problems: generally slow download rates from the internet to the desktop/laptop frequent "page cannot be displayed" errors in browsers-sometimes 3 or 4 reloads are necessary... often times CSS wont load or other content requiring the browser to connect to a different server. slow speed within the LAN from workstation to workstation copying files. I would expect extremely fast data transfer workstation to workstation / server to workstation in this simple network. Several things I need to admit: I'm not primarily a network guy. Funding is relatively low, I need to be the guy that finds the solution. I understand most of the terminology and most of the technology. Implementation is where I fail due to lack of experience. Getting to the point: I'm wondering whether experienced network admins think that our small network should be sufficiently served with our current hardware if configured properly... or if we should purchase new equipment and start fresh? If starting fresh is the plan, whatever that new equipment may be is a likely different question entirely. If I haven't provided enough information, I will happily do some troubleshooting and update with the results. I have experience using wireshark and some other tools. Please let me know what you think would be most helpful and thanks in advance. EDIT: I forgot to add that the Cisco applicance will not finish loading the SDM Express console. It hangs every time at the "populating modules... DHCP". It eventually crashes and closes. I've rebooted the hardware and this still happens.

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• Share 3G connection over WiFi-LAN network

  - by kush.impetus

  This is how I have established network between my PC and my laptop at home (being novice in networking, it took me few days to achieve the feat). And it is working perfectly. I can easily share files between them. Laptop IP Address: 192.168.1.4 Subnet mask: 255.255.255.0 Default Gateway: 192.168.1.2 Desktop IP Address: 192.168.1.5 Subnet mask: 255.255.255.0 Default Gateway: 192.168.1.2 ASUS RT-N10+ Router IP Address: 192.168.1.4 Default Gateway: 192.168.1.2 I have connected the Desktop PC to the router using a LAN cable, and laptop to router over WiFi. Both, PC and laptop are running on Windows 7 OS, are on same HomeGroup, have same username / password. Also, I have connected the Ethernet cable to LAN port 1 of the router. Click here to view a graphical representation of the network. Can't post image here, because I don't have 10 reputation points. Now, what I want is use connect to Internet using a 3G USB modem on one device and share it over the network on the other. I tried Huawei and Micromax 3G USB modem. Both obtain a new IP address whenever I connect to Internet (means they have dynamic IPs). Rest, both have Subnet Mask as 255.255.255.255 and Default Gateway as 0.0.0.0. In that case, I cannot directly share Internet from the modem. Preferred DNS is blank for now in both, laptop and PC. What I am planning to do is to connect to Internet on laptop using the 3G modem and share the Internet connection over laptop's Wi-Fi (as hotspot) using Connectify, which I have done already. That, I suppose, will broadcast a static IP to connect to. Now what I can't figure out is that what changes should I make to the network settings of the router and the PC so that PC connects to the Internet broadcast by Connectify? Is that possible on the first hand? Please note that I am trying to implement the network without spending anything extra (for purchasing as USB WiFi adapter for PC, of course, which could have made the life lot easier for me). Thanks in advance

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• RoboCopy fails with "the specified network name is no longer available"

  - by Justin Scott

  We have a scheduled task that runs robocopy periodically to mirror a rather large folder structure from one server to another (thousands of folders, 100,000+ files, 50+ GB in size). There is a share on the receiving server where the mirror gets stored. We're running the task from the origin server connecting out to the share on the receiving end. Both servers run Windows Server 2003 and are connected to the same network switch (100Mbps). The process will sometimes complete all the way through without error. More often than not, however, at some point during the process (seems random as to where), robocopy will fail with the error The specified network name is no longer available. It will wait 30 seconds and try the file again and eventually give up after a number of retries. Process will repeat at the next schedule interval and may complete... or not. When this occurs I am not able to access the share at all on the destination server from anywhere on the network for up to 30 minutes. There is nothing else on the network using this share. My question is what does this error mean specifically? Why is the share "dropping off" and becoming inaccessible? Is there a way to prevent it and get the file mirroring to be more stable?

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• Word documents very slow to open over network, but fine when opened locally - on one machine

  - by Craig H

  Windows XP, Word 2003, patched. The issue is happening with several Word documents stored on a network drive. The Word documents are clearly a bit wonky (i.e. one is 675k, but if you copy everything but the last paragraph marker into a new document, the new document is only 30k). But that's only part of the problem. On one weird machine, and one machine only, it takes ~20 seconds to open these Word documents from the network drive. Copy the file to C: on that werid machine? Opens immediately. Go to other machines (that are very similar - same patch level, etc.) and open the same document from the network? Opens immediately. Delete normal.dot? 20 seconds. Login with a different user on the weird machine? 20 seconds. Plug wonky machine into a different network port? 20 seconds. So the problem appears to be hardware related (i.e. wonky internal NIC) or related to a setting that is not profile specific. Any ideas? "Scrubbing" all the documents isn't ideal for several reasons. This is driving me nuts because I swear I ran into this before many years ago and eventually figured it out. But I appear to have lost my notes.

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• Prevent Network Printers Automatically being added to 'Devices and Printers' in Windows 7

  - by Ben

  I think my question is a duplicate of this one, but the original question was never properly answered (the steps described are for Windows XP). I am aware of the option to "Turn off Network Discovery" (under Control Panel All Control Panel Items Network and Sharing Center Advanced sharing settings); I set this option (for both Home/Work and Private) but it doesn't seem to stop the printers getting added, and has the side effect of preventing me from browsing the list of machines on the network (which I need). I've tried the Windows XP registry option - but it doesn't seem to make any difference: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced\NoNetCrawling I find it annoying having the printer list cluttered with printers from all over the office which I am never going to use (especially since lots of them no longer physically exist, users just haven't deleted them from their machines). This must be a real problem for people in massive offices with large numbers of printers - but I can't seem to find a lot of people complaining about it - which makes me think I'm missing something obvious. I don't really want to hack the firewall or turn off sharing completely, I still want to select and use network printers and file shares. Any ideas?

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• Hyper-V Network Boot Legacy Network

  - by Carl

  Hi, I am planning out a Hyper-V R2 Cluster environment. I was wondering if I went to the effort of deploying one of the few methods to network boot from iSCSI inside the guests, whether the legacy network adapter would switch to a synthetic after boot, or whether the connection could be handed to a synthetic network after boot? This is obviously for performance reasons. MS suggests that some emulated devices are capable of switching to synthetic with integration services after boot, but doesn't specifically list all which are capable.

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• Multiple network connections on a Windows 2008 domain controller (private network for NAS)

  - by Sysadminicus

  I have a Windows 2008 server connecting to an iSCSI target on an OpenSolaris box (yay ZFS!). I'd like to create a private network between the 2 boxes that is totally separate of my Windows domain. What is the best way to configure the additional network adapter on the Windows machine so it doesn't think the new subnet is part of the Windows domain? I want to make sure Windows doesn't magically start spewing active directory communications over the private wire and that it doesn't start poisoning the DNS with IPs from the private network.

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• Setting up a WPA-PSK network card to connect to a WPA2 network

  - by mattshepherd

  I'm currently doing a spare-parts build to put a media computer in the living room, and having a devil of a time getting my Rosewill RNX-6300 wireless card to connect to my network. I'm trying to set it up using Windows as opposed to the proprietary Rosewill software -- the Rosewill software is a little over my head. It can find the network fine, but when I try to connect, I don't get the password prompt -- it moves straight to "validating identity," scans, and then says "Windows was not able to find a certificate to log you on to the wireless network Foo." The maddening thing is that the card was working fine a week ago, in the same box, using the same OS. I pulled everything out, swapped out the motherboard, and reinstalled Windows on a freshly wiped hard drive, and now I can't get it up and running again. Suggestions? I've taken several runs at it, including attempting to manually change the settings for the network to include WPA-PSK and AES and the password, and I'm a bit worried that I've totally boned everything. My router settings: ipconfig/all results from the XP box: Again, this card was working on this network a week ago. I can't figure out why I can't get it up and running now. There's no WPA2 on the card, just WPA and WPA-PSK: WPA-PSK was the only setting that would let me enter a network key. I had TKIP and AES as options there, but cipher type is AES on the router, so I chose that. (I tried TKIP later, when this didn't work, with the same results as described below.) So I set it to WPA-PSK / AES and entered my security key. It's mixed letters and numbers, 32 characters long. No joy. Still "waiting for reply" in the main screen, and "cannot find certificate" on the pop-up. And if I try again and return to the settings again, it is reset to Open/AES. It also re-enables 802.1x in the Authentication tab if I've deselected it with WPA-PSK. It also reshortens the password. I have no idea how I blundered into getting this working in the past. I am, as you can tell, far from proficient at this. It was working before, though. What am I getting wrong?

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• Are there any tests I can run on a network to simulate 100 heavy network users?

  - by marc.gayle

  I will be hosting a Ruby on Rails workshop at a small hotel in the near future, and while they have 'Wifi' everywhere on the property, and the property normally hosts 150 - 300 people, I am not 100% confident that they have hosted 150 tech people that tend to have heavy web surfing habits/needs. Their tech department is also 1 or 2 guys. Are there any automated tests I can download and run from my laptop, on the network, that would simulate 100 'heavy users' on the network at the same time? Their broadband pipe is a 15mbps cable connection. Would that suffice for the general surfing needs of 100 - 150 techies? I know all it takes is 1 or 2 bit torrenters to kill the entire network, but assuming we can at the very least block those ports or encourage the attendees not to file share on the network, would that speed suffice for general surfing needs? What are good resources online that would allow me to quickly get up to speed on the IT related issues, so that I can ask their sysadmins the right questions? Edit: Note that I am fairly technical, so assume I can get up to speed quickly even with technical manuals, etc.

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• Unusable network, packet losses between router and NIC

  - by KáGé

  I have this setup: Gigabyte P35-DS3P motherboard Asus NX1101 PCI network card (the one on the motherboard got fried a few years ago by a power surge) Asus RT-N16 router Windows 7 x64 I think the other specs are irrelevant here, but I'll post them if you say so. Until a week ago everything was fine, but then my network became unusable: websites start loading but timeout before anything would come through (true for the web interface of the router as well), I can't reach the computer from my notebook and Windows' ping utility measures a ~50% packet loss between the computer and the router. Pinging localhost is good. The router works completely fine when wired to my notebook. I also tested different ports on the router, different cables, different router and connecting directly to the modem, but it's still the same. Sometimes it works for a few minutes right after turning on the machine, but then it becomes crap again, but mostly it's useless from the start. I've tried updating the firmware on the router, updating the driver for the network card (after which I started getting BSoDs in every 15 minutes), reinstalling Windows, swapping to Fedora 15 but none of them changed anything. Does this mean that the network card is dying, or could it be something else? If it's the card, what model do you recommend as a replacement? (Could be PCI or PCI-Ex x1) Thanks for your help.

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• save and restore state of a tab bar controller

  - by phunehehe

  I have an application that has a UITabBarController with two tabs, each having its own navigation controller. Now I want to store the state of the application when the user closes it, so that when the user relauches the application will show the same place as the last time before it was closed. So, in applicationWillTerminate: I have [NSKeyedArchiver archiveRootObject:tabBarController toFile:@"lastVisitedTab"]; Then, in applicationDidFinishLaunching: I have UITabBarController *last= (UITabBarController *)[NSKeyedUnarchiver unarchiveObjectWithFile:@"lastVisitedTab"]; if (last) tabBarController = [last retain]; I also have an extension to UIImage to make it compliant to NSCoding. However, this doesn't work, as the state is not preserved. The first tab gets selected all the time, and no navigation is preserved either. Can someone tell me what's wrong, or show me how to do it correctly?

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