Intranets are smoking hot...
but are you dropping more lately and enjoying it less?
If so, it may be time to switch. A new generation of switches are coming to the
rescue of IT professionals who have become the victims of their own successful
intranets.
In the course of a recent Strategic Networks custom seminar tour, over 1500 IT
managers were informally polled about their experiences with intranets, LAN
switching and related issues. When asked how many had deployed intranets within
their companies, the average response was nearly 75%. This comes as no surprise.
Intranets have been widely deployed for good reasons. Most of the managers
attending the seminars agreed that obtaining approval for an intranet was not
difficult, and unlike I-VPNs, security is no longer a deterrent to intranet
implementation.
While some of the benefits are hard to quantify, top management will always be
in favor of tools that increase productivity and reduce the cost of
communication. By October of last year, 59% of U.S. companies and 38% of
European companies had deployed intranets, and by the year 2001 the number of
users is predicted to exceed 130 million (NUA Internet Surveys & IDC).
So far, the single largest benefit of a successful intranet is an easy-to-use
global publishing system for time-sensitive information. This is important in
the data communications industry, where 15-20% of printed corporate material
becomes outdated within 30 days. With an intranet, remote branch offices and
sales forces can get the most recent information they need, 24 hours a day.
This empowers them to make decisions and respond to customer issues quickly,
with the confidence that increases their credibility and the company's
competitive advantage. Even Dilbert agrees: Real time access to information is
power.
More Work For Networks
Another question asked in the recent seminar series was: "How many of you were
ready for the impact that intranet traffic has on your network?" Only a few
hands were raised. Intranets often exhibit the "Field of Dreams" syndrome: Build
it, and they will come. Initially, you only get feedback (and traffic) from
early adopters, but eventually, even the hard-copy diehards see the light and
start clicking. Once users are empowered with a web browser, there's no turning
back. Information quests can lead them anywhere in the world, but most certainly
between subnets and across core backbone routers. This can be a serious
challenge for installed software-based routers that typically forward only
250,000 to 500,000 packets per second.
As you already know, the problem is not so much increased traffic volumes as it
is the change in the traffic patterns across the enterprise. This may be
painfully clear to you but now you have to explain the reversal of the 80/20
rule to your average user and to the CFO. And whether they understand it or
not, you're still faced with the task of maintaining acceptable response times
for the full range of intranet applications. Can Layer 3 and Layer 4 switching
help? The short answer is "Yes." The latest generation of network switches
will elevate local backbone performance to unprecedented levels. This can affect
all aspects of your network, including (indirectly) the forwarding of WAN and
legacy protocols.
Layer 3 switching
Attendees of the latest N+I in Las Vegas were inundated by Layer 3 switch
vendors and their solutions. This movement started back in 1996, when many of
that year's N+I attendees awoke in the middle of the night with visions of
strange and wonderful VLANs dancing in their heads. By now most of you are up to
speed on basic L3 switching and VLANs. The current wave of trade press
surrounding L3 switching would make you believe that if you don't hurry up,
you'll be the last kid on the block to reap the benefits. So far, that's just
not true. Layer 3 switching may no longer be considered "bleeding edge", but
among the Strategic Networks' client base it is still being embraced primarily
by early adopters. This will change quickly. Why? A new class of
internetworking device has emerged, the Layer 3 routing switch, which separates
routing functions--discovery and forwarding--and executes both in hardware.
Why is this important? In a word, speed. A properly designed L3 routing switch
is optimized for the LAN, and delivers near wire-speed routing of IP, regardless
of load. Similar to earlier Layer 2 switching debates over cut-through versus
packet by packet approaches; the latter has emerged as the winner. A true L3
routing switch runs routing protocols (e.g., RIP,OSPF) and looks at the entire
packet before forwarding. Vendor claims that routing no longer has to be slow
and expensive are becoming reality. Performance is increasing nearly as fast as
prices are declining. The latest L3 routing switches we've seen are capable of
forwarding rates in the range of 2-35 million packets per second, and consistent
latencies within 2-10 microseconds, which should go a long way toward reducing
intranet users response-time complaints.
So how does this help your intranet? It's that same word again: speed. It's
relatively simple to "front end" an existing router with a L3 routing switch,
preserving infrastructure investment without major disruptions. The existing
routers are now free to handle all non-IP protocols, and WAN communication tasks
for which they were designed. This off-loading of local IP routing can
considerably extend the useful life of installed routers.
So, what about routing non-IP protocols? IP has won the protocol war. By now
you should have a plan to move to 90% IP over the next 18 months. Most Layer 3
routing switches will handle those legacy protocols through VLANs; yes VLANs.
Maybe it's time to reconsider this much-maligned feature again. Using a simple
GUI you have the flexibility to group users of AppleTalk, IPX and other non- IP
protocols into VLANs, and send the traffic out a selected port to an existing
router.
Layer 4 Switching
You've probably seen a lot of the recent press regarding Layer 4 switching. It's
hard not to. Vendors are once again having a field day, assigning names ranging
from "all-layer" to "layerless" with benefit claims ranging nearly as wide.
So what, exactly, is a Layer 4 switch? Hype aside, there is no such thing as a
Layer 4 switch. It's probably more accurate to think of it as a Layer 3 routing
switch with some extra smarts. Setting up any switched connection requires both
a source and destination address, neither of which is included in Layer 4 of the
OSI model. Layer 4 is the transport layer, responsible for reliable end-to-end
communications between applications. This includes TCP and UDP port numbers that
are inserted in packet headers to uniquely identify the applications on either
end of a session. Combining this application session data with Layer 2 and Layer
3 information enables a more intelligent forwarding decision.
The use of Layer 4 information is not new. High-end routers have always had the
capability of tapping Layer 4 for security and other user-defined filtering
functions. But in general, the benefits were outweighed by the latency hit when
these features were turned on and executed in software. The new interest in
Layer 4 springs from some vendor's ability to incorporate the L4 lookup
functions in ASIC hardware, allowing the decisions to be made at near wire
speed.
After Layer 3, it's really only a matter of how deep into a packet you look, and
how the information is used. Soon we may be hearing of new devices that take
advantage of the two new OSI layers: 8 (politics) and 9 (religion). In the
writer's opinion, vendors don't yet know how to best utilize Layer 4
information; they're scrambling to differentiate themselves. In general, there
isn't much consistency in the way that vendors are implementing L4 switching,
which is to be expected with such a new technology.
It's Good Policy
If you will be buying switches in the near future, should you add Layer 4 to
your evaluation list? Are there any benefits to your intranet? Yes and Yes.
If you are beginning to feel pressure to consider policy management, switches
with Layer 4 capabilities may be a good start. Once a switch is aware of an
application, it can classify packets and map them to different priority levels.
Current products provide at least two levels of priority, which enables you to
assign latency-sensitive applications like SAP R/3 and SNA priority over HTTP or
SMTP (e-mail). If all business-critical applications are flowing across the LAN
with consistent response times and acceptable latencies, you'll get less
complaints, and have more time to figure out how to support the next wave of
network-aware intranet applications that users will be downloading.
There's a second area that may also be of value to your intranet. A new twist
on server load balancing, championed by Alteon Networks, Inc (San Jose, CA),
uses the socket (combination of IP addresses and TCP port number from Layer 4)
to identify individual application sessions and "bind" them to the most
available server within a group. Depending on traffic patterns, you create the
appropriate server groups (2-256) within the switch by assigning a virtual IP to
each group. The Alteon switch is like an intranet traffic director, providing
intelligent distribution of traffic sessions to servers.
Priorities and load balancing are only two representative examples. It's still
early in the Layer 4 skirmish, and vendors will undoubtedly continue to generate
confusion. In the evaluation process, make sure your best technical staff meets
with prospective vendors. Ask tough questions and determine what are the real
benefits for your environment. Evaluate the total impact these new devices will
have on both local backbones and the overall installed routing fabric. Natural
selection should continue to be the dominant driver in survival of new
technologies; as IT professionals you have the responsibility to play a key role
in the process.
# # #
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