As IT and business requirements change within an organisation, enterprise networks need to evolve to support the new environment.
Network managers have been adding bandwidth and splitting the network into smaller Lan segments. They have also implemented technologies such as fast ethernet, Layer 2 switching and virtual Lans (VLans) to improve the performance of their networks. However, the take-up of high-speed technologies such as asynchronous transfer mode (ATM) and gigabit ethernet still falls far behind the marketing hype of vendors.
Mark Iliffe, European sales support manager of Foundry Networks, says: "Lots of companies don't need gigabit ethernet, and I freely admit that only a small percentage of companies in the UK have moved to gigabit ethernet.
"But the network manager of any company that moves to a centralised server infrastructure without adding bandwidth should be shot. Generally, ethernet is the cheapest solution to implement, and it provides a strategy for migrating to a high-speed infrastructure without the complexity and expense of ATM."
Research among 3900 companies carried out by consultancy firm Rhetorik shows 44 per cent are using 10Mbps-switched ethernet in the backbone, an increase of 16 per cent from its last survey.
Faster and more expensive technologies such as ATM and gigabit ethernet in the backbone show only marginal progress. The main reasons for the shift to lower speeds in the backbone are the rapid decrease in price-per-port for fast ethernet switches and the relative ease of migration, says Rhetorik.
Rhetorik managing director Roger Foskett says: "There has been a lot of hype within the networking business about the accelerated growth of gigabit ethernet and the lacklustre adoption of ATM in the backbone. ATM may not be taking the UK by storm, but neither is gigabit ethernet."
The slow take-up of gigabit ethernet can be explained by understanding the basic challenges faced by network managers. The continuous evolution of the network and the applications and services it supports present managers with three main challenges, which are:
- support for increased link speeds within the network
- adapting to evolving traffic patterns
- need to contain broadcasts.
Increased link speeds
First-generation networks were based on shared-media Lan technologies, such as 10Mbps ethernet or 4/16Mbps Token Ring.
These are still the primary Lan technologies used by most enterprise networks today. However, managers recognise that shared bandwidth Lans are becoming inadequate.
The need for increased performance, combined with the low cost of 10/100Mbps ethernet network interface cards (Nics), cheap 10/100 ethernet switches and even cheaper hubs, is leading many organisations to migrate their user base from 10Mbps ethernet to 100Mbps ethernet.
In the backbone, 16Mbps Token Ring and Fiber Distributed Data Interface (FDDI) networks were initially installed to support low-speed, shared-media Lans. But network managers are technology fashion victims too, as Neil Wilkins, European solutions marketing director at Enterasys Systems (formerly the enterprise division of Cabletron), confirms.
He describes an Italian banking customer who was running a switched FDDI network that had had the investment paid off years ago, and only saw a maximum of five per cent traffic load. However, the customer still replaced it with a gigabit ethernet network out of embarrassment, because he didn't want to admit to his colleagues that he was still running FDDI, when the IT department was supposed to be at the leading edge of technology.
Nevertheless, the fact is that a backbone designed to support multiple networks of 10Mbps with perhaps 50 users may now be required to support far more users and therefore traffic. Because of this, backbones need higher performance to cope with the increased bandwidth available at the network edge.
For small and medium-sized businesses, which represent 95 per cent of all installations, a switched fast ethernet backbone fed by low-speed switched or shared ethernet satisfies requirements. Only large networks have the need for speed.
Most of reseller Scalable Networks' customers fall into this category. So there was little surprise when managing director Alan McGibbon says: "Our customers range from those that have a fast ethernet core to those with a gigabit ethernet backbone fed by switched fast ethernet for their clients and mission-critical servers.
"The only place where you cannot have contention for bandwidth, or blocking, is in the server room. Gigabit ethernet switches from some vendors are in danger of getting a bad name because many of their architectures are blocking." Let us note here that Scalable is an Extreme Networks reseller, which may have some bearing.
But according to Wilkins, for most users this is an impressive but meaningless argument. "The requirement for higher port gigabit ethernet densities has not come from the UK market, but from France and Germany.
"This indicates the customer is not particularly concerned whether a switch has blocking or non-blocking architecture. Essentially, the customer wants backbone gigabit ethernet at an affordable price-point."
Ethernet desktop victory
There is no question that 10/100 ethernet has won the desktop from a price perspective, and that ethernet layer 3 switches can now deliver the reliability and performance of technologies such as ATM, FDDI, and Token Ring. At the same time, these other technologies (particularly ATM, in campus backbone networks) represent a large installed base that continues to serve its purposes well, but not without its own set of problems.
Roger Hockaday, marketing director of Alcatel IND, says: "Large organisations that committed to ATM several years ago, before gigabit ethernet appeared, find it highly reliable and are staying with the technology as a backbone. Their problem is that major network vendors are saying to them they can no longer have ATM, and should take gigabit ethernet from them instead. At which point, the user tells the vendor to go away.
"IBM used to be a major ATM proponent, now it's a Cisco house. Marconi/Fore has lost its way. There are very few vendors left that are committed to ATM in the Lan. It is now in the same situation as FDDI was several years ago."
Another factor is UK network managers' parsimonious attitude to technology. Wilkins notes that many UK firms have copper riser cabling. "Unless they recable with fibre, upgrading to gigabit ethernet will be more difficult. With a three to five year network refresh lifecycle, it's an in-built inhibitor to the take-up of gigabit ethernet in the UK."
In the past, network designers have lived by the rule that 80 per cent of all network traffic will remain on the local workgroup, with only 20 per cent flowing externally. However, new traffic patterns are emerging in most enterprise networks. Traffic patterns are beginning to move towards any-to-any connectivity within the network, revising the 80/20 rule to 20 per cent workgroup-related traffic and 80 per cent inter-workgroup traffic. However, we have yet to come across a network where the 80/20 rule has been completely reversed, despite vendors' insistence that this is the new norm.
Although corporate intranets are becoming widespread, with each department or workgroup maintaining its presence on the corporate web, they apply little stress the corporate network. Vendors say the introduction of multimedia applications and services increase the need for multicast capabilities, higher bandwidth and more stringent latency requirements.
Wilkins says: "Multimedia over the Lan is more hype than reality. These bandwidth-hungry applications are not widely deployed, so they provide no imperative to upgrade to gigabit ethernet."
The reality of these data-intensive applications is that they are few in number and carefully controlled by managers of campus networks to avoid even the slightest chance of network meltdown. The 80/20 rule has been broken, but not derailed.
As Iliffe says: "The easiest way to scale a solution is to provide bigger pipes. It certainly makes life easier than having to implement quality of service without a centralised policy manager, because multiple boxes will need to be continually re-configured manually."
But the overall effect for large organisations is for more and more traffic to be forced onto the network backbone and out of workgroup hubs or switches.
Need to contain broadcasts
Since Lan switches are basically high-speed multiport bridges, many of the negatives that are associated with bridges affect these switched networks. In particular, Lan switches create flat bridged networks. The major problem at large sites is that broadcast traffic, such as routing update protocols, can grow out of control and reduce the bandwidth available to support mission-critical applications.
Network managers have two options to address the broadcast containment issue for switched Lans in large-scale organisations. The first option is to use routers to create many subnets, logically segmenting the traffic - Lan broadcasts do not pass through routers. Alternatively, some Lan switches can be pre-set with broadcast thresholds on a per-port basis to mitigate the problem. Network managers understand the benefits of these approaches, but the relatively poor performance of traditional routers was one of the reasons why the switched Lan was implemented in the first place.
The second option is to implement VLans within switched networks, to crudely separate traffic types or large groups of users for security reasons. VLans work well within the confines of the traditional 80/20 rule. The implementation of ethernet VLans outside the backbone is extremely rare because of the management overhead incurred compared to the relatively low business benefit.
To gigabit or not to gigabit?
Even if the network manager of a small to medium business starts to overload the fast ethernet backbone, there is no compelling reason to automatically upgrade to gigabit ethernet. They can stick with their current Nics and deploy trunking software that aggregates several switch-to-server or switch-to-switch links into one fat logical pipe.
"We see a lot more demand for Smart Trunking [Enterasys' trunking variant] to concatenate fast ethernet channels with load-balancing and resilience than for gigabit ethernet in the UK," says Wilkins.
Along the way, load-balancing and fault tolerance can also be added to critical connections. Trunking is nothing new in the Wan, where it's known as inverse multiplexing or a hunt group.
Trunking together four fast ethernet links gives managers up to 800Mbps of full-duplex bandwidth, bringing them within spitting distance of gigabit ethernet, at relatively little expense. No need to buy new switches, pull new cable or worry about distance limitations.
Most of the budget for building a local network goes on Nics and desktop switches, since there are far more of these components than backbone switches or routers. As these are experiencing the sharpest price drops, organisations will end up paying considerably less for Lans, even when they deploy relatively high-performance products.
The bottom line is that virtually any enterprise will soon be able to afford a network with dedicated, switched fast ethernet to every desktop, connected via a fast or gigabit ethernet routed backbone.
So, over the next five years, where will the applications come from that will actually tax switched fast ethernet to the desktop? About the only real need will be with servers that require gigabit ethernet to support many simultaneous client connections, but they represent only a tiny fraction of all network connections.
Ian Shepherd, Lan product manager of Telindus K-NET, who is a recent convert to gigabit ethernet from a strong ATM heritage, says: "A correctly designed gigabit ethernet network based on state-of-the-art products that are capable of offering true quality of service - such as bandwidth reservation and not just traffic prioritisation - is going to be in the best possible position to handle whatever is thrown at it without breaking the bank."
It is reasonable to assume that as soon as enterprises have networks with the latest, low-cost Fast or gigabit ethernet products, they won't need to upgrade their Lans to provide more bandwidth for quite a time. So avoid the relentless 10 gig ethernet hype and, while you're at it, avoid the IP quality of service hype, too.
|Network technology in the backbone|
10Mbps switched Ethernet
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