12/11/2009 by David Slade.

IPv6 Addressing Overview.

Probably most of us have heard of IPv6 by now. And probably most if us know why IPv6 has come about. The continued growth of the internet or rather IP ready devices that, if needed, can connect to the internet has meant that the number of available standard IPv4 addresses is quickly running out. In fact today complex routing protocols are employed to keep the Internet working as a result.

There are a number of enhancements coming with IPv6. Perhaps the most obvious is the addressing standard, which has been changed dramatically in order to provide a vast number of IP addresses something in the order of 3×10 38 . This should see us all well into the future, even if every single device with electronics in has an IP address even your toaster.

Most of us recognise an IPv4 address, commonly written as dot separated decimal, for example 192.168.0.1. These addresses are 32 bits long or 4 octets (bytes). Consider for a moment that an IPv6 address is 128 bits, or 16 octets. Now imagine having to remember 192.168.1.25.17.133.145.28.201.1.99.18.6.4.33.129 as your station IP address, and now add to that a gateway address. It soon becomes obvious that you will need a lot of note paper and pens, not to mention the problems with typing errors.

With IPv6 the problem is simplified to some extent. Firstly instead of using decimal as we do today for IPv4 hexadecimal is used in the same way as MAC addresses. The second is to compress the address to remove some zeros. So an IPv6 address in long form could look like this 3ADF:1B4C:0000:0000:0000:0045:2CD2:EFA1. Now since a typical address like this might have a number of zeros this address can be displayed in short form notation, and becomes 3ADF:1B4C::45:2CD2:EFA1. Notice also that the address uses : rather than . as the separator.

The convention here is that leading zeros within the 4 digit groups can be dropped; you will notice that 0045 in the long address becomes simply 45 in the short version. Also a group of consecutive 16 bit numbers with the value of zero can be replaced with a double colon ::. It is only possible to replace one null string with the double colon, which can then be filled out to retrieve the long form address. If there are two null strings, only one can be compressed like this because if both were compressed it wouldn’t be possible to determine how long each one was so you’d end up with an ambiguous address.

Finally there is a slightly modified form of the IPv6 address for use when it’s desirable to express an IPv4 address in IPv6 format. To save having to convert constantly between base 10 and base 16 and to avoid conversion errors this convention uses the original dot separated decimal notation for the last 32 bits of the address, so the original IPv4 address of 192.168.0.1 in IPv6 long format would be 0000:0000:0000:0000:0000:0000:192.168.0.1 which compresses into the short form as ::192.168.0.1. Despite the fact that the address space in IPv6 has been quadrupled the old IP number can still be expressed unambiguously in the new format with only 2 additional characters.

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12/11/2009 by David Slade.

IP Addresses.

IP (Internet Protocol) addresses are numbers that identify Internet hosts. They provide universal addressing across all the networks of the Internet.

IP addresses are placed in the IP packet header and are used to route packets to their destinations. An IP address is a 32-bit value split into four 8-bit pieces (octets) that are separated by dots. An example of an IP address is 206.98.23.16. Each of the 4 numbers within the IP address can be between 1 and 255.

IP addresses are prefix based. The initial prefixes of the IP address can be used for generalised routing decisions. For example, the first 16 bits of an address might identify a corporation, the next 4 bits may identify a branch of that corporation, the following 6 bits may identify a particular LAN in that corporate branch, and the entire 32-bit address might identify a specific host within that LAN.

To simplify packet routing, Internet addresses are divided into five classes: Class A, Class B, Class C, Class D, and Class E. Very large corporations and entities receive Class A addresses, mid-sized companies and universities usually have Class B addresses, and most smaller companies and ISPs have Class C addresses. Class D is a multicast address and Class E is reserved.

Class A addresses are given to large organisations such as major universities and very large corporations. Class A addresses begin with a number between 1 and 126 (127 is reserved) in the first octet, leaving the 3 other octets open to split into local addresses. Although there are only 126 Class A codes, there are more than 16 million individual IP addresses within each Class A. Class B addresses are claimed by mid-sized companies, universities, and other entities that need thousands of IP addresses. Class B IP addresses begin with numbers between 128 and 191 in the first octet and have numbers from 1 through 255 in the second octet, leaving the last 2 octets open to denote local addresses. There are 16,384 Class B addresses with 65,536 individual IP addresses each.

Class C addresses —the most common—are used by most companies and ISPs. A Class C address has a number from 192 through 223 in the first octet and a number from 1 through 255 in the second and third octets, leaving only the fourth octet free for local addresses. There are more than two million Class C addresses and each contains 255 IP addresses.

Subnetting enables a network administrator to further divide the host part of the address into two or more subnets to make them easier to manage. A filter called a subnet mask is used to determine the subnet to which an IP address belongs.

Because IP addresses are difficult to remember, many also have text equivalents such as blackbox.co.uk. These text-based addresses are called domain names. A database program called Domain Name Service (DNS) keeps track of the names and translates them into their numeric equivalents.

The Internet is expected to outgrow the number of available IP addresses eventually. A new system of IP addresses called IPv6 has been designed to extend the capacity of the Internet. To date, the uptake of IPv6 has been limited. Most people are still using IPv4 and NAT (Network Address Translation) which allows multiple devices to connect to the Internet using only one ‘real’ IP address.

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12/11/2009 by David Slade.

Convergence Solutions.

There is a lot of discussion about the merits of Voice over IP—or IP Telephony—at a technical level, but less about the business issues associated with a converged solution.

Black Box is a major supplier of infrastructure systems and is well placed to help you decide what is the best option for your business.

Black Box has experience from the largest to the most basic network. Whether this is the infrastructure for the latest generation network for a mobile operator or Motorola, or a budget network for a small business or even a complete voice installation for one of America’s biggest retailers, we have a solution.

Convergence
Convergence means having one common system to carry all forms of information (namely voice, data, video, etc.). Traditionally, each service has had its own network and associated technology. Voice utilised expensive PBX or exchange equipment with dedicated wiring to telephones. Data used a completely different set of cables and equipment, most commonly based on Ethernet. With technological advances and the growth of the Internet though, it is now possible to have one network carrying all the services.

So is it right for you, either now or for the future? Black Box can help you decide, plan your network and install the system; however, the solution will depend on a wide variety of factors. What you have now will influence the path you take.

Cost
It is a fact that a converged solution can save you money. The real savings, costs and benefits, however, are far less clear because the choices will be dictated by the need to move seamlessly to new systems without interruption of service or loss of quality. Depending on the age, facilities and performance of the existing voice equipment, you may want to consider conversion rather than replacement. Simply use a converter or special interface to allow some or all of the existing connections to utilise low-cost IP call facilities. Having one system simplifies management and support, reducing costs. Modern systems can be accessed and managed remotely, allowing the number of specialist staff on site to be minimised.

Compatibility
Any new system needs to integrate and offer compatibility both with the internal and external networks. There are international standards for IP telephony, so selecting the right equipment becomes easier. The two major techniques used are H323 and SIP. H323 is more established, especially when ISDN is used for the communication network. SIP is newer, but it is supported by major players such as Cisco and Microsoft®. Both will co-exist for some while, and work is under way to allow interoperation between them.

Capacity
Data packets can be delayed and, if necessary, retransmitted in the event of errors or problems. This is not a possibility with voice communication. Overlaying voice traffic on an old data network can create bottlenecks and delays, resulting in poor quality voice and slow data traffic. The network design needs to be checked and, if required, upgraded to support the extra traffic and ensure priority to the most critical types of traffic. If video is part of the system, this will place even greater demands on capacity.

Conversion
Starting with a clean sheet and scrapping all existing systems is an ideal unavailable in all but a few special cases. The need to provide paths to migrate from old legacy systems and procedures toward convergence is therefore paramount. Black Box has long been acknowledged as a specialist provider of products and technology that solves the problem of mismatch. Whether it’s a special cable, an interface converter or a complete change of protocol, Black Box is renowned for coming up with a solution.

Continuity
If all communication is taking place over a single converged network, then this could be considered a single point of failure. In reality, networks can be designed to be fully resilient; however, this has to be planned carefully and tested to make sure that everything continues to work smoothly in the event of problems. Having a converged network will make it considerably easier to establish disaster recovery procedures for a major critical event, such as a fire destroying an entire building. The requirements of new legislation on corporate governance also has an impact on communications, security and integrity of networks. Consolidating all systems under one management enables better control and eases problems of compliance with the requirements of legislation such as Sarbains Oxley, etc.

Confidence
Any system that involves access from the Internet has to be secure. Users have to be sure that they will not be overheard and that confidential information is not available to the outside world. Building in firewalls and other security procedures should be part of the design process, not a late fix to a leaky system. Support should be rapidly available when required and delivered in the most suitable and flexible manner to match the needs of the situation. Black Box provides on-site and on-line Technical Support on a local and global basis 24 hours a day, 365 days a year.

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12/11/2009 by David Slade.

Building a small network.

Building a small network.
Never fear-it’s easy to build a twisted-pair Ethernet network. In fact, it’s the simplest and most inexpensive network you can build, and it’s worth installing for even just two or three PCs. Your small network doesn’t have to be slow either-most of today’s Ethernet devices support 100-Mbps Ethernet as well as legacy 10baseT. These dual-speed devices sense and adjust automatically to the speed of connected devices.

Build a basic Ethernet network.
The most basic Ethernet network uses an Ethernet switch to enable two or more PCs to communicate directly with each other. This very simple network, which operates without a network server is called a peer-to-peer network. See the diagram below.

All you need are an Ethernet adaptor card for each connected PC, an Ethernet switch, and some CAT5e unshielded twisted-pair (UTP) cable. If your PCs have built-in Ethernet like many of today’s PCs do, you don’t even need Ethernet adaptors.

To build your network, connect the Ethernet port on each PC to a port on your Ethernet switch using the CAT5e cable. Snap-in, modular connectors make connecting the cable to the PCs and the switch as simple as plugging in your phone. If you need more ports, just connect another switch to the first.

And don’t worry about software—if you have Windows® 95 or later, you have all the software you need for a small peer-to-peer network.

Add a print server.
Even a very small network can benefit from the convenience of a print server, a specialised network device that enables network users to share one or more printers. It accepts print jobs from users and manages these jobs on each printer. See the diagram below.

Typically, a print server is a freestanding device that’s connected between the network and the printer. A freestanding print server is very easy to install—just connect it to your Ethernet switch using CAT5e cable, then connect the printer using a parallel printer cable.

A print server for a small network may also be built into another device, such as a switch or a broadband router.

Your print server will probably come with software utilities to install on your PC, and you’ll need to do some configuration to set it up. But, once installed, it’s virtually transparent to network users.

Connect your network to the Internet.
A remote access router enables your entire network to share a single Internet connection. The small remote access routers used in small and home office networks are usually referred to as broadband routers because they connect your network to broadband DSL or cable modem Internet services. See the diagram below.

A remote access router enables two or more computers to share an Internet connection by using a technology called Network Address Translation (NAT), which enables all the computers on your network to share a single IP address.

Although the primary reason to install a remote access router is the convenience of having all network users share an Internet connection, a router also helps keep your system safe from hackers. NAT masks your true IP address, providing firewall protection between your network and the Internet.

You install the remote access router between your Ethernet switch and your DSL or cable modem. The DSL or cable modem is usually provided by your Internet service provider and has an Ethernet port, which may be a regular LAN port that can be connected by straight-pinned CAT5e cable or may be a WAN port that requires a special cross-pinned CAT5e cable for connection to the Ethernet switch.

Remote access routers normally require extensive setup and configuration but, once installed, operate transparently.

Broadband routers for small networks also often feature a built-in Ethernet switch and print server. This means you only need the broadband router plus some cable to turn a few unconnected PCs into a secure, multifeatured Ethernet network.

Posted in IT Tech explained, IT Network (power over Ethernet) | No Comments »

12/11/2009 by David Slade.

10-Gigabit Ethernet.

10-Gigabit Ethernet (10-GBE), ratified in June 2002, is a logical extension of previous Ethernet versions. 10-GBE was designed to make the transition from LANs to Wide Area Networks (WANs) and Metropolitan Area Networks (MANs). It offers a cost-effective migration for high-performance and long-haul transmissions at up to 40 kilometres. Its most common application now is as a backbone for high-speed LANs, server farms, and campuses. It also enables you to connect geographically separated LANs to new MANs and WANs via dark fibre, dark wavelengths, or SONET/SDH networks.

10-GBE supports existing Ethernet technologies. It uses the same layers (MAC, PHY, and PMD), and the same frame sizes and formats. But the IEEE 802.3ae spec defines two sets of physical interfaces: LAN (LAN PHY) and WAN (WAN PHY). The most notable difference between 10-GBE and previous Ethernets is that 10-GBE operates in full-duplex only and specifies fibre optic media. The chart (below) notes the differences between Gigabit and 10-Gigabit Ethernet.

At a glance—Gigabit vs. 10-Gigabit Ethernet

Gigabit

• CSMA/CD + full-duplex
• Leveraged Fibre Channel PMDs
• Reused 8B/10B coding
• Optical/copper media
• Support LAN to 5 km
• Carrier extension

10-Gigabit Ethernet

• Full-duplex only
• New optical PMDs
• New coding scheme 64B/66B
• Optical (developing copper)
• Support LAN to 40 km
• Throttle MAC speed for WAN
• Use SONET/SDH as Layer 1 transport

The alphabetical coding for 10-GBE is as follows:
S = 850 nm
L = 1310 nm
E = 1550 nm
X = 8B/10B signal encoding
R = 66B encoding
W = WIS interface (for use with SONET).

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12/11/2009 by David Slade.

Layer 3 switching.

In the last decade, network topologies have typically featured routers along with hubs or switches. The hub or switch acts as a central wiring point for LAN segments while the router takes care of higher-level functions such as protocol translation, traffic between LAN segments, and wide-area access.

Layer 3 switching, which combines Layer 2 switching and Layer 3 IP routing, provides a more cost-effective way of configuring LANs by incorporating switching and routing into one device. Although a traditional Layer 2 switch simply sends data along without examining it, a Layer 3 switch incorporates some features of a router in that it examines data packets before sending them on their way. The integration of switching and routing in a Layer 3 switch takes advantage of the speed of a switch and the intelligence of a router in one economical package.

There are two basic types of Layer 3 switching:

• Packet-by-packet Layer 3 (PPL3)
  PPL3 switches are technically routers in that they examine all packets before forwarding them to their destinations. They achieve top speed by running protocols such as OSPF (Open Shortest Path First) and by using cache routing tables. Because these switches understand and take advantage of network topology, they can blow the doors off traditional routers with speeds of more than 7,000,000 (that’s seven million) packets per second.
• Cut-through Layer 3
  This method of Layer 3 switching relies on a shortcut for top speed. Cut-through Layer 3 switches, rather than examining every packet, examine only the first in each series to determine destination. Once the destination is known, the data flow is switched at Layer 2 to achieve high speeds.

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