New Applications
Product Report: chartware, vaporware or hardware?
Gigabit Ethernet - A Core Competence Industry Report
by David M. Piscitello
This white paper is revised periodically.
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Gigabit Ethernet uses the same frame format,
frame size, and when shared, the same (CSMA/CD) protocol as 10
Megabit and 100 Megabit (Fast) Ethernet. The same Simple Network Management Protocol
managed objects defined for 10 Mbps Ethernet also apply to Gigabit Ethernet, including
remote monitoring (RMON) objects. Proponents of Gigabit Ethernet identify the
commonalities of protocol, framing, management and scalability as
key factors to consider when evaluating an Ethernet or
alternative (e.g., ATM) LAN solutions.
Gigabit Ethernet operates either switched
(full-duplex from switch to switch or switch port to end node)
or shared (half-duplex using CSMA/CD). Switched Gigabit Ethernet
is appealing for its very high aggregation and low latency characteristics.
Shared Gigabit Ethernet may be attractive for very high-performance
applications, e.g., collaborative computing or parallel tasking
across an Ethernet workgroup, rather than a HIPPI, environment.
Gigabit Ethernet can be operated over Category
5 Unshielded twisted pair, coax, multi-mode or single-mode fiber.
The following table describes the maximum recommended cable/fiber
distances for what is expected to emerge as the industry (IEEE
802.3z) standard.
Some companies operate proprietary Gigabit Ethernet
at 10 kilometers, and have indicate they expect to push the distance
to perhaps 20 kilometers by 1998.
To increase throughput and reduce CPU processing, some companies offer
extended or jumbo frames. This feature is proprietary, and usually
requires that you use
switches and network interfaces from a single vendor, but for certain
applications (e.g., NFS operating over unfragemented UDP datagrams)
the performance gains realized using jumbo frames can be significant.
The initial applications for, and early deployment experience
with Gigabit Ethernet included the following:
National Network Access Points (NAPs) and similar co-location
points for Internet Service Providers served by ATM, FDDI,
and SMDS, are likely applications for
Gigabit Ethernet.
Gigabit Ethernet is an attractive technology on which to deploy
Intranets, Extranets, and enterprise client-server applications
on a very large scale. Such environments demand enormous CPU cycles
from servers, and vast amounts of storage and bus-like characteristics
from LAN technologies. Applications of Gigabit Ethernet in such
environments have produced a new wave of acronyms and terminology.
Here are three of the more interesting terms you'll come across.
Server-switching is a term used to describe
a highly optimized Gigabit Ethernet LAN interconnect for servers that
comprise a server farm. By analogy, if conventional LAN switching were
a mountain bike, server switching
might be a mountain bike customized for Exteme Team bikers. Your basic
and Extreme Team mountain bikes might begin with the same standard frame,
but the latter is outfitted for the specific purpose
of not merely enduring, but excelling, in a race
down a mountain at a breakneck pace. If it works for bikes, why not for switching?
Server-switching removes the general-purpose
features of a conventional LAN switch (multiprotocol routing, packet filtering,
and other level 3 functions), replaces them with functions that
can enhance server performance (large Ethernet frame support,
server load-balancing), and provides NICs for your servers that support these
features and offload CPU in the process.
Layer-4 switching? You bet. Alteon Networks uses this term to describe
how a server-switch can use layer 3 and layer 4 protocol information to
implement a variety of load-balancing schemes. In Alteon's model, the switch
behaves like a front-end processor for a group of servers that support a
common application. A special IP address that is treated much like a "hunt
group address" is DNS-registered. The switch maintains a state-full
relationship with all the servers, and establishes connections to the
least-busy server based on load information. Curious? Read the
white paper at Alteon.
I/O switching is a "NIC-bypass" technique. The conventional
LAN I/O path for data on a server is from system bus to a LAN NIC,
where the data are Ethernet-framed and forwarded to a
switch. I/O switching basically eliminates Ethernet framing between server
and switch. A special PCI or SBus NIC is used on the server, and data are
passed between server and switch at native bus rates in native I/O requests, i.e.,
without Ethernet framing. A Gigabit switch that supports I/O switching only
Ethernet-frames data emitted by the switch onto LAN media.
The people at Gadzoox
define a Storage Area Network (SAN) as
"a highly scalable, managed server-storage infrastructure
that offers gigabit speed data connectivity, high system
availability, extensive fault tolerance and low cost of
ownership." SANs provide storage access, server
networking and server-storage clustering at gigabit rates over
Fibre-Channel Arbitrated Loop (where
both SCSI and IP operate over the same medium). From an
architectural perspective, I/O switching
and SAN have a lot in common, and it's hard to imagine
that only Fibre-Channel can accommodate SANs.
When asked to summarize the pro's and con's of these technologies,
I find the following comparisons between Gigabit Ethernet and
ATM most useful:
ATM gets most of the attention in discussions concerning differentiated
communications services, but ATM is not necessarily an entirely
end-to-end solution for all campus internets. Switched Ethernet
environments, when complemented with sophisticated routing and
other end-to-end transport services (RSVP, RTP, IPv6) may perform
equally well. Several switch manufacturers offer class of service
switching on Ethernet switches. These features allow priority
queueing, type of switching selection (cut-through, store-and-forward),
configurable back pressure, and latency control.
There is neither sufficient information to dismiss Ethernet and
general topology internetworks entirely
as media for integrated services, nor sweeping evidence that
integrated services can be supported in a scalable and tractable
manner.
Adopting the posture of technology agnostic is appropriate when
considering the relative merits of ATM and Gigabit Ethernet.
(You may find my column at
Interop OnLine relevant.)
Gigabit Ethernet is available as an interface on the following
hardware:
Products available today are pre-standard IEEE 802.3z.
Many vendors offer both a pre-standard and proprietary interface
(e.g., an I/O NIC, or server adapter for server-switching).
Many vendors commit to compatibility with the eventual standard
through an upgrade or replacement guarantee.
Gigalabs offers a modular
chassis backbone switch product (the Gigastar 3000,
a new product evaluation on this product for InfoWorld
can be found
online. Gigalabs has a companion switch,
the Gigastar 100, that can be used to connect servers and systems
with HIPPI into the backplane of the Gigastar 3000 using their
Gigabit I/O switching interface. Gigalabs has installed Gigabit
Ethernet using single-mode fiber over 3 Km distances, and claims
to be developing optical-electronics necessary to extend the maximum
distance over fiber to between 10-20 Km using their proprietary
gigabit Ethernet interface. The most recent product from Gigalabs
is an enterprise switch (Gigastar 8000) that supports multicasting in
hardware, layer 3 switching and VLAN capabilities.
The ACEswitch100 and compatible Gigabit Ethernet adapters
from Alteon Networks
fall into the server-switching solution
category previously described. The Alteon "network switch/adapter combo" solution provides
load-balancing across servers (see layer 4 switching).
ACEswitch 100's have eight full- or half-duplex 10/100 Mbps Ethernet ports and
two full-duplex Gigabit Ethernet ports and can be cascaded.
Prominet has recently been
acquired by Lucent Technologies. The Prominet P550™ Cajun™ switch
has performed well in testing by Strategic Networks and Network Computing.
This enterprise class switch is VLAN level 3 capable.
Hardware integrated multiprotocol routing and multicast support will
be available 1Q98. P550™ VLAN implementation is compatible with 3Com.
Extreme Networks has a level
3 VLAN stackable switch line (Summit) that supports multicast
routing protocols, RSVP and RIP. Two Summit models support
ExtremeWare™, the software through which Extreme Network's flavor of
Policy-Based QoS is implemented. Policies are based on user-defined traffic groups
(e.g., TCP sessions, UDP/RSVP flows) and QoS profiles for those groups
(minimum/maximum bandwidth allowed, relative priorities).
Extreme recently announced the Summit Virtual Chassis, a high-speed backplane that
connects Summit stackable switches. Virtual chassis is an odd monicker
for this product: it's a freestanding unit that provides eight channels, to which
you connect Summit switches. What's very newsworthy about this product is the
announced price ($8995), a very modest outlay for an external backplane.
3Com has announced a Gigabit Ethernet
module for its stackable switches in the SuperStack II series. The
module installs into the SuperStack II Switch 3000 Fast Ethernet
Switch and operates full-duplex over multi-mode fiber interface.
A SuperStack II Switch 9000 SX
will 8 full duplex multi-mode fiber switched Gigabit-Ethernet
ports. The SuperStack series provides class of service switching
and switch method selection (cut-through, store-and-forward, fragment-free,
and intelligent). We have evaluated the Switch 1000 and Desktop Switch,
and hope to have 3000's to evaluate in the future. A nice feature
of the SuperStack series is support for all 8 groups of RMON (many
vendors only support RMON-1, four groups).
Packet Engines began shipping
a 12-port shared Gigabit Ethernet repeater (FDR12™) and companion NIC's
mid-summer. Packet Engines' PE-4884™ Gigabit Routing Switch
is an enterprise class switch (first customer ship 1Q98) and claims to
provide "wire-speed Layer 3 routing, wire-speed layer 4 filtering
and forwarding" of IPv4, IPX, and IPv6
packets based on a set or matrix of layer 3 and 4 attributes (a policy). I can't imagine
who in world is pushing information at gigabit rates using IPv6, and to whom,
but I'm comforted to hear that switching will be ready when the demand appears:-)
Cisco Systems describes its 1998 rollout of Gigabit
Ethernet in a public
statement of direction
The (ASIC)-based Catalyst LAN switch architecture is expected to provide
100+ Gbps of switching capacity, wireline (gigabit) forwarding using
Cisco's NetFlowTM LAN Switching and Cisco IOS™ software technologies.
Gigabit Ethernet uplinks, switching modules, and high performance
route switch modules will be available
for the Catalyst 5000 LAN switch family. Gigabit Ethernet interfaces for the
Cisco 7500 and 12000 series router product families
will also be available in 1998. Visit Cisco and download a copy of their
detailed white paper
on Gigabit Networking. The paper discusses the roles of Gigabit Ethernet and ATM as highly
complementary. Cisco's position regarding Gigabit Ethernet and ATM is representative of
companies that have invested in both technologies and is an interesting contrast to position
papers you will find at web sites of companies whose product line is exclusively Gigabit Ethernet.
PCI and SBus NIC's are available from several manufacturers (Extreme,
Packet Engines, Gigalabs, Alteon). With pre-standard Gigabit Ethernet,
and proprietary extensions for specialized applications (see
server-switching and I/O switching)
interoperability is a question mark, so early adopters should choose
the safe course and use NICs and switches from a single manufacturer.
It still appears that no manufacturer will ship a router interface
in 1997.
There are now three dozen manufacturers who offer or claim to be developing
Gigabit Ethernet solutions. I have not attempted to include every
vendor, nor did every vendor I contacted communicate sufficient
information to merit discussion.
If you feel your company's products
merit discussion, please contact us .
We will be only too happy to discuss Gigabit Ethernet technology with you.
The extent to which I can assert accuracy regarding product specifications
and product availability is limited to the information provided
to me by manufacturers.
Back to the Technology Corner
Overview of Gigabit Ethernet
Gigabit Ethernet Technology Description
CAT5 UTP Coax wiring closet applications Multi-mode fiber (50 micron) Use same 850 nm short wavelength optical components, yield 1.063 Gbps.
Multi-mode fiber (62.5 micron) Use long wavelength (1300 nm) optical components, yields 1.250 Gbps
Single mode fiber Use long wavelength (1300 nm) optical components, yields 1.250 Gbps
A Wave of New Gigabit Applications
Gigabit Ethernet vs. ATM
Gigabit Ethernet Products
Gigabit Ethernet Products: chartware, vaporware or hardware?
The pace of product announcements for Gigabit Ethernet switching is fast and furious.
Whereas the products available in May 1997 were of the multi-port repeater and level
2 variety, 4Q97 products are specialized, catering to server-switching, or
enterprise-class iron, providing level 3 switching, VLAN capabilities, and fault
tolerance to compete with the ATM-centric switches in this class. Modular
Gigabit Ethernet Adapters are available for some stackable switches as well.
Caveat