Gist: Gigabit connections, which were earlier used for interconnecting network switches (hence forming the backbone connectivity) have become common to connect the desktop. Is 10 GE (10 Gigabit Ethernet) then taking over any time soon both for interconnectig switches as well as directly connecting the servers? We would explore on whether there is a need for 10 GE ports, 10 GE interconnections, standards and types of pluggable optics for 10 GE as well as salient points along with the limitations of the 10 Gigabit Ethernet, in this article.

Need for 10GE Ports:

• Consolidation and virtualization are two of the strategies that many data centers are implementing in order to lower server count, improve server utilization, reduce energy demand, reclaim floor space, and redeploy IT resources to higher value projects, while maintaining, or improving, reliability. Virtualization has enabled dynamic allocation of resources for applications which earlier used to reside in seperate servers. So, the 1GE connectivity to a single server is no longer dedicated to that single server as multiple virtual servers populate every physical server. Hence 10GE Ports on every server (whose capacity will be increasing to more multiple cores and memory in the future) is a reality today, and in certain cases, a must.
• More and more applications (some of them being real-time, requiring extremely less latency) have moved in to the IP Network. Today, HD Video Conferencing/ Streaming (Single MPEG-4 Stream consumes about 3.75 Mbps of Bandwidth), IP Video Surveillance, Centralized IP Telephony, Clustered Business continuity applications like ERP/CRM, E-Commerce etc. & Scheduled back up to SAN/ NAS networks have increased the load on existing server room environments.
• Virtualization and the advances in the storage technologies like iSCSI has enabled consolidation of storage resources like SAN/NAS and hence consolidation of different disparate SAN networks in to a centralized low-cost high speed 10 GE ethernet based storage network saves a lot of cost and management overhead.
• HPCC – High Performance Computing Cluster (which is basically an interconnection of various high capacity servers working togeather to solve big computational tasks) requires higher throughput and low latency between all the nodes in the cluster, which is offered by 10GE.
• Connecting Top of the Rack Access Switchs for Blade Servers to the Core Switch – The Aggregation layer thus formed requires fewer cables/ ports connecting to the core switch when it uses 10GE links for the same.
• High Performance Servers: The availability of next generation multi core CPU’s with multi-threaded networking stacks will be able to fully utilize a 10 GE connection directly from the network switch to the server. Single 10GE connection also avoids the need to interconnect multiple 1 Gbe NIC’s from individual servers to switches in order to acheive higher throughput – increasing server utilization and also reducing power utilization.
• In the WAN (Wide Area Networking) end, carriers have been using SONET and ATM for high capacity long distance interconnections and with the introduction of 10GE standard, the lower costs of setting up and maintaining high speed networks that are scalable is quite appealing.

Need for 10GE Interconnects:

• When a 24/48 Port 1GE Port Switch is deployed in a data centre it is imperative that the interconnecting technology (to other switches) be more than 1GE as all the aggregated throughput goes through this setup. In this case, a 10GE Interconnecting apparatus or a 40GE interconnecting apparatus might be more optimum and the later is required for non-blocking performance if crucial servers are connected through the switch.
• Interconnection of multiple vendor switches (where stacking is not possible) can be achieved through multiple such 10GE/40GE interconnects along with Link Aggregation technology to ensure that the aggregation layer has a fully non-blocking or at least 2.4:1 architecture.

10 GE Cabling / Connectors:

Standards:

• 10GBASE-SR, 10GBASE-ER, 10GBASE-LR, 10GBASE-ZR are the common standards for fiber optic interfaces for 10GE. Both single mode, multimode fiber are supported for longer, shorter distances respectively ranging from a few meters up to 80 KM.
• 10GBaseT is the copper interface standard that can go up to 100 meters using Cat 6a or Cat 7 Cables. It can support lower distances for Cat 6 Cables (55 meters). 10GBaseT is reverse compatible with the earlier 1G and 100 Mbps Base T Connections.
• 10GEBASE-CX4 is another standard that supports 10GE by using twin-axial cable with 24 Gauge wire (same cable used for infiniband) and the primary application is for stacking switches of the same vendor. This technology has distance limitations (like 15 meters max).
• DAC – Direct Attach Cable : Low cost technology, supports shorter distances (For 10 GE). SFP+ Can be used along with DAC.

Common Pluggable optics for 10GE through MSA’s:

• SFP+ (For 10 GE) and SFP Standards use the same physical dimensions and SFP transceivers are supported by SFP+ equipment – So, it supports 1GE Optics as well. This standard supports up to 80 KM. Lower latency, lower power, lower heat when compared to equivalent standards.
• XFP, XENPAK, X2 are the other common types of pluggable optics supporting 10 GE primarily through MSA’s.
• Interoperability between multiple vendor transceivers are governed mostly by MSA – Multi Source Agreement between the various vendors.

Salient Points about 10GE

• 10 GE is an 1EEE 802.3ae Standard
• 10 GE Supports Full Duplex Communication – Hence lower latency and faster response than 1 GE Connections.
• Same frame format, frame size and MAC protocol as previous ethernet versions
• Computer/ Server expansion interface – PCI Express can support up to 12.5 Gbps of bandwidth to accomodate a 10GE Network Interface Card.
• Intelligent Ethernet NIC cards offload protocol (TCP/IP) processing from the host processor and hence has reduced the CPU utilization parameter for 10GE connections and the latency is also lesser for 10GE when compared to 1GE.
• Ethernet based switches and interconnects can be managed by the same Network Management System and protocols currently being used in data centres. For, newer protocols, need for a seperate management interface increases the cost of management.

Challenges in moving to 10GE:

• Cost of 10GE NIC cards as well as the price per port for 10 GE switches / Optical interfaces remain very high.
• The options for connecting 1GE ports alongside with 10GE ports are limited in most of the switches.
• 10GE NIC cards do not come built-in on most of the servers.
• Latency/ server utilization is higher and hence an issue with ethernet, especially with higher throughput applications, when compared with parallel technologies like Infiniband.
• Packet loss due to buffer overflows on congested ports is an issue in ethernet – the IEEE 802.1Q au is working on enhanced congestion management techniques for ethernet.

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Required Infrastructure: PC, Webcam, Headset/Mic (or) speakers/mic, broadband/leased line internet connectivity and a messenger software like Gtalk, Skype etc.
Pros: Cheap, Available anywhere, IM service is free of cost, Uses the internet which is commonly available.
Cons: Average Picture quality (as most webcams come with a lower resolution) and delayed reception/display of images.

Before we move on, we need to know about an important video compression format called H.264. Also called MPEG 4 Part-10, H.264 is a compression technology used by video transmission/ storage systems to give a good compression ratio for transmitted/ stored videos. Since it is a standard, any manufacturers device at one end can compress and send the video files and the same can be de-compressed by another manufacturers device at the other end. The advantage of H.264 is the achievement of better video quality at a lower bandwidth (when compared to uncompressed video). Do look for this H.264 compression format enabled devices if you choose any of the below video conferencing devices – it really helps and is crucial for a good quality video conference especially over the internet.

IP Video Phones:

IP Video phones are not very popular, but offer a good and an effective choice for personal video calling between two persons, sometimes even three. Interestingly, the video phones use open standard VOIP protocol called SIP. That makes it easier for them to integrate in to business VOIP System as an IP extension and hence can receive voice only calls as well as video calls. Some video phone manufacturers also offer an unique phone number that can be used anywhere (over the internet) to call another phone of the same manufacturer/ model. That makes it easier than having to procure a static IP address at each end or having to register them with an IP PBX. Interestingly, you can also call from an IP Video Phone to any standard Professional Video conferencing system if the latter supports video over SIP (or) IP-SIP protocol. And yes, some of the video phones support H.264. Click here to go through a detailed feature list supported by IP Video Phones.

Required Infrastructure: IP Video Phones (at both ends) and internet connectivity (preferably an Internet leased line/ high speed broadband) as at least 128 Kbps upload and download is required for a single channel of video to be transmitted at 15 frames/ second. Some manufacturers of the IP video phones include Polycom, Grandstream etc.
Pros: Can work independently or with an IP PBX, can be used with video conferencing systems that support SIP, relatively cost effective, can work with broadband as well, supports H.264.
Cons: The interoperability between IP Video phones of different manufacturers is not widely tested, smaller screen, limited audio (over speaker phone/ handset), average quality of images over broadband connections operating at lower speeds.

Software/PC based Personal Video Conferencing Systems:

As an interesting alternative to video chatting, there are certain software’s that are provided by professional video conference system manufacturers that can be downloaded to any standard PC (at both ends) and can be used along with any standard web-cams and headset/mic or speakers/mic. The crucial thing that the provided software does in addition to giving a user interface is that it can do H.264 compression/ decompression of the video using the PC hardware/processor which gives excellent quality of images even at lower bit rates. You can also call a professional video conference system from the PC equipped with the personal VC software edition. Click here for a detailed description of PC based Video Conference systems.

Required Infrastructure: PC/ Laptop, Internet (high speed broadband/ internet leased line at least 128 Kbps dedicated – upstream and downstream), good quality standard web-cam and microphone/headset. Some examples of such systems include Polycom PVX, Tandberg Movi, Radvision Scopia etc.
Pros: Lower cost, higher quality, uses standard PC/webcam/headsets etc, supports H.264, High Definition Formats (HD).
Cons: The video quality depends upon the web-cam quality, all of which may not be very good. Lack of external microphone means wearing the headset continuously. The in-built microphones of PC/Laptop may not provide good audio quality.

Depending on the manufacturer, some of them also offer hardware based personal video conferencing systems that range from personal VC codec/camera to personal LCD monitor with integrated camera/mic/speakers.

Professional Video Conferencing:

Professional Video Conferencing Systems (Set-Top Boxes):

These systems are more for companies/ organizations which have a requirement of one or few people from one place to see and talk to one person/few people at another place. Normally, a set-top Codec is supplied by the Video Conference vendors which connect to monitors/ projectors/ plasma etc for display, microphones (mostly supplied by the manufacturer of the video conferencing systems), ISDN/PRI(E1/T1) Lines OR Internet Leased Lines. Most of these set top boxes support H.264 and require at least 128 Kbps of Internet Leased Line (Or intranet bandwidth) to work fine. Some of them even support HD formats for superior video quality but require higher bandwidth. You can also use document cameras/ dvd players to display objects/ videos to the other end. Most of them support dual video output streams for displaying video along with data (power point presentations etc) for better collaboration. Such systems support one person at either end or many people, depending on the model of the video conference system. Some of them even allow for viewing people from multiple locations simultaneously (normally 1+3/4, and can be expanded to accommodate many sites using a multi-conference system). Click here to know more about High Definition Video Conference systems and click here to know more about multi-site video conference systems. The below block diagram for professional VC systems should be self-explanatory.

Requirements: Video Conference system (usually codec), microphone(s), monitor (TV, projector, LCD display, plasma etc), speakers, bandwidth (Internet leased lines/ MPLS/ LAN). Some manufacturers who supply such systems include Polycom, Tandberg, LifeSize, Aethra, Sony etc.
Pros: Can accommodate single to multiple persons at each side, cameras support pan/tilt/zoom/preset functions, can display data (presentations) along with video, supports H.264/HD formats.
Cons: Higher cost and higher bandwidth requirements.

Tele-Presence:

A video conference system cannot get better than Tele-Presence (at least for now). This is the ultimate in video conferencing where the users are made to feel as if the other person is sitting and talking to them from across the table, in real time. A lot of preparation goes in to such systems for giving such an experience – right from the table size, colour, shape, monitor and camera locations, lighting arrangements, display of life-size images, bandwidth etc. at both the locations. Some manufacturers also let individual Video Conference systems to inter-operate with their Tele-Presence systems. Click here to get a better idea of the components involved and requirements for Tele-Presence systems.

Click on the following Youtube link to see a demonstration of Tele-Presence system :         http://www.youtube.com/watch?v=0kd2SO1_kSA

Requirements: Click here. Some manufacturers include Polycom, Tandberg, Cisco etc.
Pros: Real-time and life-like meeting experience.
Cons: Very high cost and very high bandwidth requirements.

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When you have multiple branches across a state or a country, you would definitely be wanting to connect all these branches together to facilitate data transfer/ access between them in order to accelerate the speed of business transactions. There are various options  to be considered for creating such Wide Area Networks (WAN) like,

Point to Point Leased Lines
MPLS VPN Network Connectivity
Internet Leased Lines with Site-to-Site VPN
Broadband/ VPN over Broadband
Dial-up/ CDMA/ 3G Connectivity for small branches
Satellite (VSAT) Connectivity for remote locations

Of these, let us focus on the first two modes of connectivity in this article – Point to Point Leased Lines and MPLS VPN Network connections.

As shown in the first diagram, a point to point Leased Line is formed by connecting every site to every other site using leased lines provided by the service provider network (Or in very large organisations, their own network). This is a private network and is used primarily for site-to-site communications. So for an organisation having branches in five locations, four links need to connect each location to all other locations to complete the leased line network. For ‘n’ locations, the number of links required in each location would be ‘n-1′.

An MPLS Network is formed by connecting each location with a single link (as shown in the second diagram) to a service provider MPLS network. An MPLS network stands for Multi-Protocol Label Switching and any packet coming to the Label edge routers (from individual locations – source, to the service provider MPLS network) are encapsulated with an MPLS label which is used to identify it and route it through the MPLS network. This label is discarded when the packet comes out of the MPLS network back to individual locations – destination.

In both the above cases, a wide variety of physical hardware is used to carry the information including fiber, copper circuits, wireless connectivity, satellite connectivity etc. The MPLS core service provider network also use high capacity MPLS routers in addition to the MPLS edge routers which send and receive data from the routers located in the individual locations.

Let us now look at the Factors which have enabled MPLS VPN Networks to become more favourable for organisations that want to inter-connect their various branches when compared to Point to Point Leased Lines.

Traffic Engineering: Since the MPLS packets are being added at the MPLS Edge routers, it is possible to set the path that the traffic will have to take through the network. More specifically, each class of traffic (like data, voice, video etc) can be set individual performance characteristics.

Quality of Service: Since MPLS network enables traffic engineering, it is possible to send (for example) – data traffic over a lower priority path and real time delay sensitive voice/ video packets over a high priority/ lesser used/ shorter path. This enables network convergence (The Wide Area Network becomes more suitable for introduction of new services like voice, video, multicast traffic, hosting etc).

Network Redundancy: An MPLS core network is generally designed and built to overcome individual hardware (router) faults or line disconnections. In such cases, the data is re-routed through the next optimum path with a failover time of 50 ms or lesser. Even the last mile connections can be backed up using CDMA wireless back up etc, depending upon the options with the service provider.

Easy and Cost effective Expansion: Let us assume that the cost of connecting two sites by using Point to Point Leased Lines versus MPLS circuits comes to a ratio of 1:1 (For two sites there is only a single link required for both and hence the cost is same). But when it comes to interconnecting five sites (as shown in the above diagram), the number of links required for Point-to-Point Leased Lines would be 10 while for MPLS circuits, it would be only five and hence the corresponding cost ratio would be around 5:1 (Point to Point Leased Lines : MPLS Circuits). So, for organisations that are having a lot of branches or expanding with new branches, MPLS network would be very cost effective. MPLS also provides for instantaneous addition and deletion of sites.

Protocol Independent forwarding: MPLS networks can carry any type of packets – be it IP, frame relay or ATM using the same infrastructure. This is because, what ever type of packets comes in, MPLS labels would be attached to it for transmitting them over the MPLS network and these labels are protocol independent.

Connection oriented network: MPLS is a connection-oriented network unlike connection less networks like IP. So, it is more reliable.

Service Level Agreement (SLA): Service Providers generally provide an SLA – Service Level Agreement for MPLS networks with a guarantee of very minimum downtime during the contract period (usually one year or its multiples). This is possible because an MPLS network can be pro-actively monitored and maintained. It is possible to analyse the circuit performance continuously and provide immediate fault rectification and support.

Bandwidth Allocation: MPLS networks allow for dynamic bandwidth allocation and hence can be used to provide bandwidth on demand (for a specific period etc) to customers. Further, rate limiting and other bandwidth management parameters allow a certain bandwidth to be dedicated for mission critical applications.

Security: Service providers take full responsibility for the security of information that is sent over an MPLS network. Service providers also create IP tunnels throughout the network without the need for any encryption from user-end.

International MPLS: There are options with service providers to even connect individual locations across different countries using MPLS by sharing and inter-connectivity of their respective MPLS networks. International MPLS lines are more cost effective than dedicated IPLC’s.

Lesser Hops: With an MPLS network, there are lesser number of hops between the various network points resulting in improved response times and application performance.

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Actually, managed switches are not mandatory to make a computer network. Inexpensive unmanaged switches are sufficient in many smaller networks. The network would work just fine. But maintaining and trouble-shooting such a network becomes very cumbersome = that’s why many companies investing in managed switches even at the network edge. Let us look at some features offered by managed switches which differentiate them from their un-managed counterparts and justify the extra investment.

1. VLAN: This one is easy to guess. A manageable network switch allows the administrators to segment their network in to multiple smaller ones in order to restrict the broadcast domain. A PC or a server generally keeps communicating with every other PC/ server through broadcast packets (like ARP resolution packets etc) at regular intervals. So, if you have a single large network (running in to hundreds of PC’s, then these broadcast messages becomes so cumbersome that they can slow down the network. In such cases, it is better to restrict the broadcast domain so that these broadcasts are restricted to a smaller number of devices. A VLAN also gives an additional layer of security as the members of one VLAN cannot access the files of the members of another VLAN. Of course, exceptions can be created and Inter-VLAN routes/ multiple VLAN registration of a single port can be specified to access common resources like printers etc. It is also difficult for malicious files like viruses to spread from one VLAN to another.

2. Port Security: A manageable switch allows an administrator to enable or disable individual ports – this is very useful in case if a hugely broadcasting port needs to be shut down, without physically removing the cables or if unused ports needs to be locked.

3. Authentication/ Access Control: A manageable switch allows connection of devices based on their MAC addresses. So, administrators can specify a list of MAC addresses which can connect to the switch and even individual ports can be statically configured to allow devices with specified MAC addresses or the same can be dynamically learned (initially, up to a point of time) after which the port is locked to other devices. Some switches also integrate with Radius servers to enable 802.1x User-name/Password based authentication for individual users.

4. Web-browser based Management Interface: Manageable switches can be assigned with a unique IP address and hence can be accessed from a remote location (via a standard web browser over the internet) to monitor/ make any changes in the configuration. This remote management capability enables an administrator to remotely look in to, and make any changes to the switch configuration.

5. Cable visibility: Some manageable switches find out and display information about the cables connected with each port like approximate cable length, whether the cable is connected to the port or not, if the cable is shorted, if the cable is connected to switch only and the other end is open, approximate distance at which there might be a cable fault, etc.

6. Network performance monitoring (SNMP/ RMON Statistics): Manageable switches allow Network monitoring systems to monitor the performance of the devices connected to individual ports in the switches using the common and open-standards based SNMP protocol or RMON protocol which helps in planning for network resources, network fault diagnosis, trouble shooting etc using performance tuning data/ statistics.

7.  Quality of Service (QoS): The QoS parameters are critical for real time applications like voice/ video to run smoothly even in demanding network conditions. QoS allows an administrator to specify which type of data packets need to have greater precedence when traffic is buffered in the switch due to congestion. In such cases, the high priority data traffic queues will be transmitted before those in the lower priority queues. QoS can be specified by individual ports or by layer 2(802.1p)/layer 3(TOS or DSCP) parameters where the prioritization can be implemented based on the application / IP port numbers. automatically or manually.

8.  Rapid Spanning Tree Protocol support: Rapid Spanning Tree Protocol (RSTP) or its variants enables to have additional alternate cabling paths for redundancy while containing/ preventing any infinite loops that might arise by having such circular connections. Actually RSTP identifies alternate routes, if any, and keeps only one of them active at a given point of time. Once this primary route fails, or network topology changes, the alternate route for transferring data is taken automatically without noticeable delays.

9. IGMP Snooping: Manageable switches utilize a feature called IGMP Snooping to prevent multicast messages from chocking the network. This especially applies to bandwidth intensive applications like video which creates bandwidth hogs when broadcasted simultaneously to multiple users.

10. Port Mirroring: Some manageable switches have a feature called Port mirroring where a single or multiple ports are mapped to a single port in the switch and all the traffic passing through those ports are replicated in the mapped port. This enables applications like Intrusion detection, voice call logging etc.

11. Rate Limiting/ Rate Setting: Many manageable switches allow to limit the maximum rate of data traffic transmitted or received in an interface. This prevents a hugely broadcasting station, for example, from choking the entire network and prevents some network attacks like Denial Of Service attacks etc. Some switches even allow for setting the minimum commited rate of bandwidth that a particular port be allocated at all times – useful for critical users in the network. Manageable switches also allow to fix the transmit and receive rates of individual ports (like 10 Mbps or 100 Mbps etc) which can be useful for applications like Link Aggregation where the speeds of ports at both sides needs to be same.

12. Auto MDI/MDIX and Stacking: The MDI/MDIX ports are selected automatically, some ports can be configured as trunk ports, VLAN trunks etc. Some manageable switches can also be stacked together using stacking cables and stack ports which makes multiple switches to behave as a single switch with a higher data throughput capacity between them.

13. Link Aggregation: Administrators can configure multiple links between two manageable switches to increase the uplink throughput between them (Eg. 2 Gpbs with two individual links aggregated together instead of 1 Gpbs with one link). This feature can also be used with some servers with dual NIC cards to increase the bandwidth between the server and the switch. In both the cases, the additional link(s) can also be used for link redundancy (in case of failure of the primary link).

I have mentioned some reasons why manageable switches are required even at the network edge (they are more readily accepted at the core, distribution layers). If you have any points to add for or against the topic, you are welcome to do so in the comments section below.

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Actually IT Network infrastructure and applications is a very vast domain and requires quite an amount of experience to achieve a considerable amount of expertise. I am sure many readers of this website have much more experience than me, in this domain.

So, I invite readers to submit articles/ opinions related to IT Network infrastructure/ Applications via email – admin@excitingip.com . You can share anything related to this domain, and if it is informative, I will publish it on this website as a guest post and  mention your name as the author of that particular article (I could also link your website/ blog/ linkedin page, if you have one).

“Knowledge is one thing that grows when shared with others” – So, don’t forget to share what you have learnt

Administrator, excITingIP.com

What is a PRI line?

• There is only one line physically terminating on the customer PBX but still a PRI line can receive/send 30 calls simultaneously! A PRI line is end to end digital circuit.
• A PRI (Primary Rate Interface) line is a form of ISDN (Integrated Services Digital Network) line which is a telecommunication standard that enables traditional phone lines to carry voice, data and video traffic, among others.
• A PRI circuit consists of two pairs of copper lines terminating on a modem from a service provider premises to the customer premises. It uses multiplexing/de-multiplexing techniques to carry more than one channel in a single circuit. There are two common forms of PRI lines - E1 (which carry 30 channels in the two pairs of copper lines, common in Europe, India) and T1 (which carry 23/24 channels in the two pairs of copper lines, common in United States).

• Each channel in a PRI line provides 64 Kbps for data transmission.
• A PRI line can connect to both Analog/Mixed EPABX systems and also the newer IP PBX systems. A PRI Card / Interface might be required to terminate the PRI circuit on the PBX.
• A PRI line can also be used to connect two PBX systems thereby providing 30 channels between them for interoperability.

Advantages of PRI Lines:

1. If thirty separate analog trunks are taken instead of one PRI line,

• The cost of terminating all the thirty analog trunk lines becomes higher than terminating one PRI line.
• There would be thirty rentals to be paid instead of one consolidated lower rental for a PRI line.
• Some analog trunks might be used more (uneven distribution of calls) and some lines may not have even crossed the free calls limit.
• Terminating 30 analog trunks in a PBX also requires more free slots/cards than the one slot usually occupied by one or even two PRI trunk cards.

1. Direct Inward Dialing: For each PRI line, the service provider would provide more around 100-500 numbers which can be used by outsiders to call the extension directly, instead of having to go through the PBX Auto-attendant.
2. Caller ID: Since all the extensions have their own number, this unique number will be displayed in the phones that they are calling to. Some call centre applications are based on the unique caller ID number for differentiation of services.
3. It is possible to offer both voice and data in the PRI line. Some service providers have dynamic offerings where data is transmitted in all the channels that are free (not occupied by voice) at that given point of time.
4. Call hunting (Where the call lands in any channel that is free, instead of the called number specifically – For example, if there is one board number but a number of people are calling in at the same time and still a channel is allocated to them .With analog lines, if one number is busy, they need to call in another number manually) is possible by default with a PRI connection, but for the analog trunks this facility needs to be extended by the service provider and enabled on the PBX, involving additional cost at times.
5. PRI lines can be used for voice connectivity, data connectivity, video conferencing, faxing, and all the above can be done simultaneously too (on different channels).
6. PRI lines are end-to-end digital lines and hence the clarity is much better than analog trunk lines.
7. Since they are digital lines, PRI lines are more reliable and trouble shooting is also easier with them. They are mostly on a fiber core ring and hence there is some redundancy.
8. It is harder to tap into digital lines and listen to the conversations.
9. There are flexible billing options available with most of the PRI service providers. The billing can be centralized or distributed (department wise, etc).
10. PRI lines take lesser time to establish calls then analog trunk lines.
11. Some service providers offer flexible plans where instead of the full 30 channels, they provide and charge for only 20 channels etc. This makes PRI lines more economical for smaller companies.

Dis-advantages of PRI lines:

1. A PRI line is economical only if the minimum rental charged by the service provider for a PRI line is more than the average value of calls with analog trunk lines every month in an organization. Otherwise, the usage may not even cross the free call value provided by the service provider for a PRI line.
2. A PRI line is not so economical for long distance/ international calling. An ITSP or SIP trunk service provider who takes the calls over the internet might charge much lesser for international long distance calls.
3. Inter branch communication between the branches is not free of cost with PRI lines (Some PRI service providers provide this facility, but all your branches may need to have PRI lines from the same service provider and there also might be a minimum revenue commitment for the same). With VOIP systems, inter-branch communication can be done over internet/ leased lines hence reducing the cost drastically.

4. The cost of a single PRI card to connect to your EPABX/ IP PBX is still very high. Most of these cards are proprietary, meaning you can buy them only from your EPABX vendor.

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While the signals from the wireless network cannot be blocked from going to places where the general public might reach them, the following security practices make the signals almost impossible to break.

1. MAC Address Filtering Table: A MAC address is a unique code given by the manufacturer of every PC/ device connecting to the wireless network. Every wireless Access Point has a MAC Address filter table which needs to be updated with the list of MAC addresses that is allowed to connect to the wireless access point. So, enable this setting and add the MAC addresses of the PC/Laptops/Cell Phones in your home/SOHO.  Any laptop/ PC trying to connect to the wireless network (from outside) will simply be denied access to the wireless network.
2. Password: Update your Access Point’s setting to allow a computer that wants to connect to the wireless network only after verifying a password/ pass code/ pass phrase etc that was already provided by you in the settings page. This password needs to contain alphabets, numbers and special symbols to make it impossible to guess.
3. Encryption: All the data that is transmitted in the wireless network needs to be encrypted using 128 bit encryption and dynamic keys (WPA/WPA2). So, enable your encryption settings to WPA2 and if that is not supported by your computer, then – WPA to ensure that no one can simply sniff the wireless packets and make any meaningful attempts to read the data. WEP is also an encryption standard, but a weaker one. So, try avoiding it as much as possible.
4. Disable Router SSID Broadcast: SSID is the network name assigned to the wireless networks. When people try to check for all available wireless networks in the area, the SSID will be visible to everyone by default. But this SSID can be prevented from showing up while anyone is casually trying to identify wireless networks in the area by disabling the wireless SSID broadcast in the settings. Casual intruders may not even know that there is a wireless network.
5. Isolation of Wireless Clients: One way in which intruders might gain access is to try to directly communicate with the wireless client. With today’s access points, even this is prevented by the access points by disallowing communication between any of the clients connected to the access point through wireless and also with any outside laptop/PC.
6. Firewall: Wireless Access Points have built-in firewalls where certain policies can be applied. For example, certain ports (like 113) can be blocked, wireless access can be restricted only from 9 AM to 6 PM, it can be disabled after that automatically, or you can block certain applications like FTP etc. over the wireless network.  These firewall policies make the wireless network safer.
7. Disable wireless access to Access Point Settings: To access the Wireless Access Point’s settings page, secure https based web access is provided. Also, accessing of the settings can be prevented from the wireless medium totally. This makes it mandatory to access the settings through the wired port of the access point. This makes it impossible for any wireless intruders to change settings/ add MAC addresses from outside.

Ok, the seventh security tip was a bonus

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First of all, a wireless controller is a centralized Wi-Fi management device that manages all the access points in a campus. The following points illustrate why a controller is inevitable for larger networks.

Centralized Authentication: No more individual MAC address tables and updation in each access point, controller provides for a centralized authentication mechanism through individual user name-password based Radius Server/ Active Directory/ LDAP Integration , centralized MAC address filtering or certificate/ shared key based authentication for all the clients from a central location.

Centralized Radio Management for all Access Points:

1. Interference Mitigation: Adjacent Access Points are always maintained to operate in different non-overlapping channels by the controller so that there is no loss of packets due to interference in a dense wireless network.
2. Load Balancing: The users are automatically shifted to adjacent access points if the load (number of users connecting) on one access point is high and the neighboring access point is lesser.
3. Radio Balancing: 802.11n enabled clients are connected to the 802.11n radios, 802.11a enabled clients are connected to 802.11a radios; 802.11b/g enabled clients are connected to 802.11b/g radios in a multi-radio enabled access point.
4. Fail over: Clients are automatically shifted to neighboring access points if any access point suddenly fails, thereby introducing redundancy in the network.

RF Visualization: Another advantage of today’s centralized wireless networks are the visualization capabilities of the Controller. Once the Floor plan of the campus is integrated with the controller, the coverage pattern, signal strength, users associated in each access point and various parameters can be viewed LIVE over a PC monitor (through a web based application) sitting in a central location. This makes monitoring and trouble shooting of networks very easy. You can also locate any active Wireless client in the network map by just typing its MAC ID in the software.

RF Visualization in a wireless network

Network Access Control based on User Identity: With today’s centralized Controller based Wireless networks, wireless users can be further segregated in to sub-groups and each group can be given separate network access policies. For example, all the wireless users accessing the network from the finance department can be given SAP/ERP access while the sales department can be denied the same. Internet access for the junior management staff can be blocked and guests can be given temporary internet access without giving access to internal network. IT department and senior management can be given full unrestricted access to the network resources. Certain laptops/ wireless clients can even be blocked network access if they do not have the latest versions of the anti-virus/ OS patch running on their systems. You thought all this is possible only with wired networks?? Not any more.

Security: After authentication, all the wireless packets are encrypted end to end using 128 bit encryption technology making it difficult for any casual intruders to get in to your network.

Wireless Intrusion Detection/ Prevention Systems (Where dedicated access points can act as scanners for wireless threats) can identify and block a whole range of wireless attacks like:

1. Ad-hoc network
2. Mis-association of AP/Client to other network access points
3. Rogue Access Points detection and prevention
4. Multiple futile attempts to connect to the wireless network
5. Honey pot attacks/ Man-In-The-Middle Attacks
6. Denial of Service Attacks etc.

Branch offices and remote offices are also protected as the controller can form a Secure VPN tunnel between the HO and branch locations. Rogue Access Points and Laptop’s can be even located using location visualizers.

Mesh Connectivity: Now you can connect even the Access Points without Cables!!

Bandwidth Restriction per user/ per group: You can prevent a few wireless users from clogging the entire network by restricting the bandwidth available to them at any point of time. You can also reserve a minimum bandwidth to all the critical users.

QoS: Quality of Service through Traffic Prioritization: A centralized controller based wireless infrastructure can identify and differentiate between different types data packets and prioritize the critical traffic on the wireless network infrastructure – This is crucial for real time wireless traffic like voice, video etc.

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An Internet Leased Line is usually a dedicated line which offers direct connectivity to the Internet. This is done by connecting the nearest service provider nodal point and the customer premises with a dedicated copper line, optical fiber cable, radio links or any combination of the above.

While there are business broadband options available at pretty good price points, Internet Leased Lines are still preferred with a lot of customers for the following reasons:

• Internet Leased Lines offer same speed for both uploads and downloads (symmetric connectivity), while in broadband (through DSL technology) the speeds are always optimized for downloads and the upload speeds are much lesser. Symmetric connectivity is critical for applications like file sharing between two branches, hosting websites/ mail servers etc, video conferencing/ surveillance, voice over IP etc. all of which are used by medium and large businesses regularly.
• Generally, broadband connectivity is shared with multiple users in a locality. Broadband plans generally denote the best bandwidth that can be attained and not the assured bandwidth levels. But a 2 Mbps Internet Leased Line should give 2 Mbps of performance as it is a dedicated connection without any sharing.
• The backbone network and performance parameters (like latency, jitter etc) can be monitored in the case of Internet Leased Lines. So, it is easier to offer SLA (Service Level Agreements) to the customer and Internet Leased Lines generally come with an SLA. There are very few broadband plans that offer such performance guarantee. So, Internet Leased Lines are more reliable.
• There is a wider choice of bandwidth selection (64 Kbps, 128 Kbps,… 2 Mbps,… 155 Mbps etc) with Internet Leased Lines. With broadband, the selection is more restricted.
• Higher bandwidth (Greater than 8 Mbps) is possible only through Internet Leased Lines. That’s why it is the default choice for large organizations with hundreds of internet users.
• Internet Leased lines are provided through multiple media – Copper, Fiber, Radio links or a combination of the above. Optical media communication is more reliable and offers better fault tolerance/ performance/ monitoring abilities, especially for higher bandwidths.
• Internet Leased Lines come with unlimited usage plans which enables companies to add services like video, voice etc over IP in addition to the internet/ data connectivity. Most of the broadband plans offer usage based billing (based on the bandwidth consumed). Of course, there are unlimited usage plans with broadband as well.
• Internet Leased Lines offer a pool of permanent IP addresses which enables organizations to run their own mail servers, web servers and other applications.
• Internet Leased Lines offer better QoS (Quality of Service) when compared to broadband. So, it is more effective to run convergent services like voice, video etc. over Internet Leased Lines.
• Internet Leased Lines can be leveraged to form a Virtual Private Network across multiple branches more effectively than broadband connections.

Of course, broadband connectivity has its own advantages like lesser cost, wider reach, mobile internet access etc.  But the dedicated high performance Internet Leased Lines (cost of which is coming down every year) is the preferred choice for larger networks with a considerable internet user base.

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