- Network Design

1. NETWORK DESIGN
TIJ3053
Chapter 4 : High-Speed Network
Design

2. Outline
• ATM
• VLAN/LANE
• X.25
• Frame Relay
• FDDI
• CDDI
• ISDN
• SONET/SDH

3. ATM - Overview
• ATM is a high-bandwidth switching and
multiplexing technology that combines the
benefits of circuit switching (ensuring
minimum transmission delay and guaranteed
bandwidth) with the benefits of packet
switching (providing flexibility and efficiency in
handling intermittent traffic).

4. ATM - Overview
• ATM technology supports the following types of communications services:
– Circuit emulation (CE) services—CE service is an on-demand, connection-
oriented, constant bit rate ATM transport service. This service has stringent
end-to-end timing requirements, and the user chooses the desired bandwidth
and quality of services during connection setup. CE services traditionally
provide the equivalent of a dedicated line for such communications
applications as video conferencing and multimedia.
– Frame Relay services—Frame Relay is an industry-standard, switched data link
layer protocol used for handling multiple virtual circuits by means of HDLC
encapsulation between connected devices. Due to its relative efficiency,
Frame Relay has to some extent superseded X.25 packet-switching
technologies.
– Switched Multimegabit Data Services (SMDS)—SMDS is a high-speed, packet-
switched, datagram-based WAN technology offered typically by telephone
companies.
– Cell relay services (CRS)—CRS is a networking technology based on the use of
small, fixed-length packets (cells) that can be processed and switched in
hardware at very high speeds. CRS is the basis for several high-speed
networking protocols, including ATM, SMDS, and IEEE 802.6.

5. ATM Technology
• Frame Relay, SMDS, and CRS are "fastpacket" transmission technologies
that are playing a prominent role in communications of the 1990's. A
generic ATM platform can support all three of these fastpacket
technologies, as well as CE services.
• A network that supports cell relay services is based on user data units
called cells. Such cells are formatted according to a standard layout and
sent sequentially in a connection-oriented manner (by means of an
established communications path) to remote destinations in the network.
• Cell relay services are being used for emerging multimedia and video
conferencing applications that require both high transmission capacities
and a guaranteed quality of service (QoS). For such applications, cell relay
technology provides the most efficient means for transporting data
expediently and reliably through the network.
• Hence, cell relay services are generally regarded as the best data
multiplexing technology available for today's current and emerging
communications needs. ATM combines its unique strengths with those
inherent in existing data communications and telecommunications
applications.

6. ATM – Cell Relay Sevices
• Typically, cell relay services support two types of network connections:
– Permanent virtual connections (PVCs)—A PVC is a logical (rather than
a physical) connection between two communicating ATM peers. Such
a connection is typically established by a network administrator.
Thus, a PVC is a non-switched connection that is established
beforehand (pre-provisioned manually) to satisfy a standing need for
network services. User applications that require an on-going, specific
level of transmission bandwidth typically use PVCs for
interconnectivity. Such connections are static in nature, that is, they
remain in service until changed by the user, a network administrator,
or a network management application.
– Switched virtual connections (SVCs)— An SVC is a switched
connection that is established by means of a defined and standardized
ATM signaling protocol. Such connections are set up dynamically ("on
demand") across the network, as required by the user's
communications applications.

7. ATM Technology
• The power and flexibility of ATM derive from two primary
attributes:
– ATM supports very high-speed interfaces in a single data
transmission and switching fabric
– ATM supports the multiplexing of multiple traffic types—data,
voice, and video.
• Consequently, ATM affords the following benefits to
network users:
– Provides flexible access to and efficient use of network
resources
– Provides scalable framework for growing the network
– Enables highly integrated communications capabilities and
services

8. ATM Network Interface Types

9. Benefits of ATM
• ATM Benefits ATM technology offers the following primary
benefits:
– Bandwidth efficiency—ATM efficiently supports the
aggregate transmission requirements of a network by
allocating bandwidth on demand, based on actual user
needs. Bandwidth allocation is accomplished without
administrative intervention. Furthermore, network
bandwidth is scalable to meet future user needs for higher
transmission rates.
– Scalability —ATM is highly flexible, accommodating a wide
range of traffic types, traffic rates, and communications
applications. ATM interface standards exist for data rates as
low as 1.544 Mbps (DS1) and as high as 2.4 Gbps (SONET).
– Application transparency—The fixed-length size of an ATM
cell is an effective compromise between the typically lengthy
packets of data communications applications and the short,
repetitive frames of telecommunications (voice)
applications.

10. ATM – User benefits
• ATM affords the following user benefits:
– Provides timely access to network resources
– Supports message traffic of variable length
– Provides higher transmission speeds
– Provides self-routing capabilities for multiple traffic types
– Supports new data communications and
telecommuncations applications
– Offers guaranteed network access for voice and video
applications
– Enables users to request a desired level and quality of
service
– Provides protection mechanisms against network
congestion conditions

11. VLAN/LANE
• What Is a VLAN?
• Well, the reality of the work environment today is that personnel is always
changing. Employees move departments; they switch projects. Keeping up
with these changes can consume significant network administration time.
VLANs address the end-to-end mobility needs that businesses require.
• Traditionally, routers have been used to limit the broadcast domains of
workgroups. While routers provide well-defined boundaries between LAN
segments,
• they introduce the following problems:
- Lack of scalability (e.g., restrictive addressing on subnets)
- Lack of security (e.g., within shared segments)
- Insufficient bandwidth use (e.g., extra traffic results when segmentation of
the network is based upon physical location and not necessarily by
workgroups or interest group)
- Lack of flexibility (e.g., cost reconfigurations are required when users are
moved)

12. VLANE
• Virtual LAN, or VLAN, technology solves these
problems because it enables switches and
routers to configure logical topologies on top
of the physical network infrastructure. Logical
topologies allow any arbitrary collection of
LAN segments within a network to be
combined into an autonomous user group,
appearing as a single LAN.

13. Virtual LANs

14. VLAN - Functionality
• A VLAN can be defined as a logical LAN segment that spans
different physical LANs. VLANs provide traffic separation and logical
network partitioning.
• VLANs logically segment the physical LAN infrastructure into
different subnets (broadcast domains for Ethernet) so that
broadcast frames are switched only between ports within the same
VLAN.
• A VLAN is a logical grouping of network devices (users) connected
to the port(s) on a LAN switch. A VLAN creates a single broadcast
domain and is treated like a subnet.
• Unlike a traditional segment or workgroup, you can create a VLAN
to group users by their work functions, departments, the
applications used, or the protocols shared irrespective of the users’
work location (for example, an AppleTalk network that you want to
separate from the rest of the switched network).
• VLAN implementation is most often done in the switch software.

15. Remove the Physical Boundaries
Conceptually, VLANs provide greater segmentation and organizational flexibility. VLAN
technology allows you to group switch ports and the users connected to them into
logically defined communities of interest. These groupings can be coworkers within the
same department, a cross-functional product team, or diverse users sharing the same
network application or software (such as Lotus Notes users).

16. VLAN Benefits
• VLANs provide many internetworking benefits that are
compelling.
– Reduced administrative costs—Members of a VLAN group can
be geographically dispersed. Members might be related because
of their job functions or type of data that they use rather than
the physical location of their workspace.
– The power of VLANs comes from the fact that adds, moves, and
changes can be achieved simply by configuring a port into the
appropriate VLAN. Expensive, time-consuming recabling to
extend connectivity in a switched LAN environment, or host
reconfiguration and re-addressing is no longer necessary,
because network management can be used to logically “drag
and drop” a user from one VLAN group to another.
– Better management and control of broadcast activity—A VLAN
solves the scalability problems often found in a large flat
network by breaking a single broadcast domain into several
smaller broadcast domains or VLAN groups. All broadcast and
multicast traffic is contained within each smaller domain.

17. X.25

18. X.25
• X.25 networks implement the internationally
accepted ITU-T standard governing the operation of
packet switching networks. Transmission links are
used only when needed.
• X.25 was designed almost 20 years ago when
network link quality was relatively unstable. It
performs error checking along each hop from source
node to destination node.
• The bandwidth is typically between 9.6Kbps and
64Kbps.
• X.25 is widely available in many parts of the world
including North America, Europe, and Asia.
There is a large installed base of X.25 devices.

19. FRAME RELAY
• Frame Relay provides a standard interface to the wide-area
network for bridges, routers, front-end processors (FEPs), and
other LAN devices.
• A Frame Relay interface is designed to act like a wide-area
LAN- it relays data frames directly to their destinations at very
high speeds.
• Frame Relay frames travel over predetermined virtual circuit
paths, are self-routing, and arrive at their destination in the
correct order.
• Frame Relay is designed to handle the LAN-type bursty traffic
efficiently.
• The guaranteed bandwidth (known as committed information
rate or CIR) is typically between 56 Kbps and 1.544 Mbps.
The cost is normally not distance-sensitive.

20. Connecting Offices with Frame Relay

21. FDDI (Fiber Distributed Data
Interface)
• FDDI (Fiber Distributed Data Interface) has found
its niche as a reliable, high-speed backbone for
mission critical and high traffic networks.
• It can transport data at a rate of 100 megabits per
second, and can support up to 500 stations on a
single network.
• FDDI was designed to run through fiber cables,
transmitting light pulses to convey information
between stations, but it can also run on copper
using electrical signals.

22. FDDI
• FDDI is highly reliable because FDDI networks
consist of two counter-rotating rings. A
secondary ring provides an alternate data
path in the event a fault occurs on the primary
ring. FDDI stations incorporate this secondary
ring into the data path to route traffic around
the fault.

23. "Dual Homed" FDDI Backbone With
Ethernet Switching

24. FDDI - Advantages
• High Speed And Deterministic Technology FDDI runs at a speed of 100 or 200 Mbps.
This results in very good performance for demanding applications which need to
transfer large amounts of data in a short amount of time. It is also excellent for
servicing the needs of a large number of users to ensure everyone has enough
bandwidth. FDDI's token-passing network results in a collision-free network which
gives excellent performance even under heavy load (80% + utilization).
• Long Distance With an overall ring length of up to 20 km (66,000 feet), FDDI is an
excellent choice for building a building-wide or campus network interconnecting
several buildings.
• Fault Tolerance FDDI's dual ring archetecture and the ability to set up a network
with the dual homing provides the ability to design networks which can continue to
operate even if a cable run is cut or a concentrator should fail. Since FDDI has been
in use for several years, the equipment has been thoroughly debugged and is
exceptionally stable.
• Management FDDI works with all of the popular network management platforms,
and most FDDI equipment has management features built-in from the factory.
• Flexibility FDDI can be used with any of four cable types, allowing the designer to
use less expensive UTP or STP cable where runs are short and fiber optic cable
where distances are longer and/or electrical noise is a concern.

25. FDDI - Disadvantage
• Cost - FDDI equipment is higher in cost than
other 100 Mbps network technologies. This is
due to the complexity of the token passing
protocol and certain royalties which must be
paid for every piece of equipment
manufactured.

26. Copper Distributed Data Interface
(CDDI)
• Copper Distributed Data Interface (CDDI) is the
implementation of FDDI protocols over twisted-pair
copper wire. Like FDDI, CDDI provides data rates of 100
Mbps and uses dual-ring architecture to provide
redundancy. CDDI supports distances of about 100 meters
from desktop to concentrator.
• CDDI is defined by the ANSI X3T9.5 Committee. The CDDI
standard is officially named the Twisted-Pair Physical
Medium-Dependent (TP-PMD) standard. It is also referred
to as the Twisted-Pair Distributed Data Interface (TP-DDI),
consistent with the term Fiber Distributed Data Interface
(FDDI). CDDI is consistent with the physical and media-
access control layers defined by the ANSI standard.

27. CDDI TP-PMD and FDDI Specifications
Adhere to Different Standards

28. Integrated Services Digital Network
(ISDN)

29. Integrated Services Digital Network
(ISDN)
• ISDN is a digital service that can use asynchronous or, more
commonly, synchronous transmission. ISDN can transmit data,
voice, and video over existing copper phone lines.
• Instead of leasing a dedicated line for high-speed digital
transmission, ISDN offers the option of dialup connectivity—
incurring charges only when the line is active.
• ISDN provides a high-bandwidth, cost-effective solution for
companies requiring light or sporadic high-speed access to
either a central or branch office.
• ISDN can transmit data, voice, and video over existing copper
phone lines. Instead of leasing a dedicated line for high-speed
digital transmission, ISDN offers the option of dialup
connectivity —incurring charges only when the line is active.

30. ISDN – BRI and PRI
• ISDN comes in two flavors, Basic Rate Interface (BRI) and
Primary Rate Interface (PRI).
• BRI provides two “B” or bearer channels of 64 Kbps each
and one additional signaling channel called the “D” or delta
channel. While it requires only one physical connection,
ISDN provides two channels that remote telecommuters
use to connect to the company network.
• PRI provides up to 23 bearer channels of 64 Kbps each and
one D channel for signaling. That’s 23 channels but with
only one physical connection, which makes it an elegant
solution- there’s no wiring mess (PRI service typically
provides 30 bearer channels outside the U.S. and Canada).
You’ll want to use PRI at your central site if you plan to have
many ISDN dial-in clients.

31. SONET/SDH
• SONET/SDH are point-to-point synchronous networks
that use TDM multiplexing across a ring or mesh
physical topology. These provide the Physical layer
foundation for FDDI, SMDS, and ATM implementations.
• SONET/SDH are true optical implementations. They
take advantage of the bandwidth and high reliability of
the fiber optic medium. Because they are typically
WAN standards, SONET/SDH use point-to-point
connection types. The point-to-point architecture
makes the standards ideal for high and centralized
systems or WAN backbones.

32. Summary
 ATM
VLAN/LANE
X.25
FRAME RELAY
FDDI
CDDI
ISDN
SONET/SDH