hellhollowreadingΔίκτυα και Επικοινωνίες

26 Οκτ 2013 (πριν από 5 χρόνια και 5 μήνες)

490 εμφανίσεις

Week Five Agenda



Review Week Three

Current Week Information

Upcoming Assignments

Review Week Three

Designing an Enterprise Campus

The Enterprise Campus is the foundation for delivering
the applications, services, and user requirements.

Network application characteristics (requirements)

Organizational requirements



Environment characteristics (requirements)


Transmission media

Infrastructure device characteristics (requirements)

High availability

High throughput

Network Application Characteristics

Peer Applications

The peer
peer applications are designed with the
majority of users in mind. It is likely to be
most heavily traffic path from one network
edge device to another through the
organizational network.

Instant messaging

IP phone calls (strict network requirements

for QoS)

File sharing

Videoconferencing systems (requirements

similar to IP phone QoS)

Network Application Characteristics

Quality of Service (QoS)

A set of metrics used to measure the quality of
transmission and service availability of any
given transmission system.

Network Application Characteristics

Local Server Applications

80/20 Workgroup Rule

Because the traffic on corporate networks has

typically increased, it has resulted in more

isolated segments. These isolated segments

resemble departments within a corporate

structure, where segments have their own local

servers, users, and applications. This design

configuration usually has the local servers and

users in the same VLAN. The traffic leaving the

network segment will connect to the campus

backbone to connect to other VLANs or


Network Application Characteristics

Server Farm Applications

Large organizations require their users to have

fast, and reliable access to critical applications.

Today, banks, state, and other governmental

organizations needed this access in order to verify

and maintain the integrity of individuals.

Because of this high accountability requirement,

performance multilayer switches are

implemented, increased network bandwidth, and

locating the servers in a central location rather

than a workgroup has been achievable due to

scale of economies. These configurations require

end LAN switches connected to the fastest

LAN technologies, such as Gigabit Ethernet.

Network Application Characteristics

Server Farm Applications

20/80 Rule

Server farms include the following:

Organizational mail servers (Microsoft


File servers (Microsoft and Sun)

Database servers (Oracle)

Network Application Characteristics

Enterprise Edge Application

The Enterprise Edge application is used to

transmit data between the organization and its

public servers. Data transmission exchange can

come from web based technologies, external

mail, and DNS servers.

Communications with these servers is crucial,

because two
way replication of data. In order to

sustain this high accountability, redundancy and

security are the most important requirements for

these applications.

Network Application Characteristics

Enterprise Edge Application


has increased the use of LAN

switching at Layer 2. LAN switching has resulted

in increased performance and more bandwidth for

specific applications requirements of new

organizational applications.


is the average rate of successful

message delivery over a communication channel.

This data may be delivered over a physical link,

and/or pass through a certain network node. The

throughput is usually measured in bits per second

(bit/s or bps), and sometimes in data packets per

second or data packets per time slot. Throughput

varies between user workgroups and high capacity

links to servers, and/or server farms.

Network Application Characteristics

Enterprise Edge Application

High Availability
is a function of the application

and the entire network between the client

workstation and server(s) located in the network.


Project costs are driven by it’s size and

applications used. If your implementing a peer

peer environment, normally the cost will be low.

If your designing a network with redundancy and

with high end application(s), your costs will be

significantly higher. The types of applications

used will also raise the cost

Environment Characteristics

Environmental characteristics play a significant role
in determining the location of the Enterprise Campus,
the distance between buildings, the size and shapes of
the buildings, and which technology to use to
maximize the organizations investment.

Normally, the distance between nodes and their
locations within an Enterprise Campus drive the type
of technology utilized. In addition to the node (s)
proximity, organizational requirements also influence
the type of technology to be used.

Environment Characteristics


campus network structure provides

connectivity for all terminating nodes located in the


building and provides external access to network

resources. The Building Access and Building

Distribution layers are located in the same building.

User workstations are usually connected to the

Building Access switches in the floor wiring closet with

pair copper cable
technology can also

be used to provide connectivity within the building and/or

between buildings without the use of UTP and cables.

WLAN was developed because of the demand for LAN

connections over the air waves in


Environment Characteristics

Structural considerations within the network geography

The access layer switches connect to the Building


switches over
optical fiber.

This building configuration could have a

compressed hierarchical network
where the

Building Distribution switches and Campus Core

switches are combined.

Environment Characteristics

Structural considerations within the network geography


characterics is where there are two

or more individual buildings connected to each

other. These buildings could have the same

configuration (compressed hierarchical network)

or contain only the Building Access layer. The

distance between buildings is within close

proximity, typically within a few hundred meters

to a few kilometers apart. The medium used to

interconnect campus buildings is normally

customer owned,
speed optical fiber

Environment Characteristics

Structural considerations within the network geography

distant remote building
is when the buildings

exceed more than a few kilometers, but are in the

same metropolitan area. For this situation, the

physical media is the most important factor. The

speed and cost are directly related to the media


Some companies own their own media, like

copper lines , or fiber
. However, if they do not

have the connectivity to their remote locations,

the Enterprise Campus must connect through the

Enterprise edge using
connectivity options from

public service providers, such as WAN links or

Metro Ethernet.

Environment Characteristics

Structural considerations within the network geography

The service level agreement (SLA) and the risk of
downtime must be addressed if inexpensive and
unreliable links are used. Mission critical application(s)
demand fast
speed links and high
reliability connections.

Enterprise Campus Device Connectivity

An Enterprise Campus can use a variety of different
physical media to connect to their devices. The type of
media used will normally set the precedence for the
next 10 years. The cost of the media should be inline
with the companies budget, and the technical
requirements that would influence signal attenuation
and electromagnetic interference.

Transmission Media

pair cable of four pairs of
isolated wires that are wrapped together in
plastic cable.

Category 5, and 5e for greater for speeds of

100 megabits (Mbps) or higher

Category 6 is recommended for Gigabit


Because of the possibility of signal attenuation
in wires, the maximum cable length is usually
100 meters.

Transmission Media

Signal attenuation
affects the propagation of
waves and signals in electrical circuits, in
optical fibers, as well as in air (radio waves). It
is a damping affect on the original signal

Distances greater than 100 meters may require
Reach Ethernet (LRE). LRE is a Cisco
proprietary technology that runs on voice
grade copper wire, and it accommodates the
greater distance to access the technologies in

Transmission Media

Different types of fiber

Multimode (MM) fi
ber carries multiple


waves or modes concurrently, each at

a slightly different reflective angle within

the optical fiber

core. Because modes tends

to spread out over longer lengths,

multimode fiber id used for

. The diameter of multimode

fiber is 50 to 62.5 micrometers.

Transmission Media

Different types of fiber

mode (SM) fiber
carries a single wave

(laser) of light. The diameter of a single

fiber is 2 to 10 micrometers. Single
mode fiber

preserves the dispersion and loss of light, and

therefore is used for distant transmissions. SM is

an excellent solution for future high


In summary, optical fiber is used where the

transmission distance exceeds 100 meters


immunity to electromagnetic interference


Transmission Media


is also referred to as a radio receiver. The
term refers to without cables or cords, chiefly using
radio frequencies and inferred rays.

WLAN are useful when it comes to extending

an existing network or replacing a traditional

cabled network.

Inside buildings, the WLAN equipment includes

an access point (AP), which acts similar to a

wired hub, and PC client adapter.

Transmission Media

IEEE Standards


allow speeds up to 54 Mbps in the 2.4 GHz
band over a range of 100 feet.


supports speeds up to 11 Mbps in the 2.4
GHz band.

supports speeds up to 54Mbps in the 5 GHz

See chart on page 233 in your Designing for Cisco
Internetwork Solutions (DESIGN) text.

Infrastructure Device Characteristics

Today, most network end users are connected using
switched technology and not shared media segment.
The benefits of switched technology are dedicated
network bandwidth for each device on the network
Switched networks also support infrastructure
services, like QoS, security, and network

LAN switches in the recent past were for Layer 2
devices. Now, Layer 2 switching supports multiple
simultaneous frame flows.
Multilayer switching
performs packet switching and several functions at
Layer 3 and higher up in the OSI layers
. The
technology is moving in the direction of replacing
routers in the LAN switched environment.

Infrastructure Device Characteristics

Differences between Layer 2 and Multilayer

Multilayer switching provides
information inside the frame
to determine the
correct output interface.

Multilayer switching
forwards frames based on
network layer information
rather than MAC

Multilayer switching is a
hardware based
switching and routing
integrated into a single

Infrastructure Device Characteristics

IP Multicast

IP multicast technology is a way to sending
one data stream to multiple end users and
maintain required bandwidth. The data stream
is sent from one source, and replicated for the
registered users at the destination.

Class D IP address ranges from to

Cisco Protocols for Routers and Hosts

Internet Group Management Protocol (IGMP)

The IGMP protocol is used
between the router
and the registered hosts

intended to receive
multicast data. The hosts notify the router to
join or leave a specific multicast group.

Cisco Group Management Protocol (CGMP)

The CGMP protocol is used by
switches and
. The router informs the switches
directly connected to them about the IGMP
registration(s) from it’s hosts to receive
multicast data stream.

Cisco Protocols for Routers and Hosts

Internet Control Message Protocol (ICMP) is
used by IP for many different services. ICMP
is a
management protocol and messaging
service provider for IP
. Its messages are carried
as IP datagram's.

QoS Considerations

Classification and marking

Packet classification

partitioning traffic into

multiple priority levels, or class of service


changing the frame priority or class of


Congestion management


separating traffic into different queues.

The marking inside the frame or packet is used to

determine which queue


is used to determine the order in

which the queues are serviced

QoS Considerations

Policing and shaping is a process of identifying
violations of threshold levels and reduces a
stream of data to a predetermined rate or level.

Traffic shaping buffers the frames for a short period
of time. Policing drops or lowers the priority of the
frame in violation.

Traditional WAN Technologies

Introduction to WANs

A wide area network (WAN) is a computer network
that covers a broad area. Typically, it is any network
whose communications links cross metropolitan,
regional, or national boundaries. WAN transmission
facilities are generally provided by service providers
(SP), such as telephone companies.

Service provides charge for the switching and
connectivity they provide. This charge is called a
tariff, for the

provided by the WAN.

WAN Connection Types

Connecting LANs together over a data communications
equipment (DCE) network


WANs utilize synchronous serial
connections. Drawing


WANs use telephone company
networks with asynchronous serial, and ISDN.


WANs use a service provider with
synchronous serial. Drawing

WAN Connection Types

Leased line
s are typically point
point connections
or a dedicated connection. The WAN connection path
from the CPE, through the DCE switch, to the CPE of
the remote site, allowing DTE to communicate at any
time with no setup procedures before transmitting
data. It uses synchronous serial lines up to 45 Mbps.

Time Division Multiplexing (TDM) is a technique for
assigning bandwidth on a single wire, based on pre
assigned time slots, to data from several channels.
Bandwidth is allocated to each channel regardless of
a station’s ability to send data. Drawing

WAN Connection Types


sets up a line like a phone call. No
data can transfer before the end
end connection is
established. Circuit switching uses dial
up modems
and ISDN. It is used for low
bandwidth data

WAN Connection Types

Packet switching
is a WAN switching method that
allows you to

bandwidth with other companies
to save money. Packet switching is excellent for bur
sty data transfers, packet switching can save you
money. However, if you have constant data transfers,
you will need a leased line. Frame relay and X.25 are
switching technologies . Speeds can range
from 56Kbps to 2.048Mbps.

WAN Protocols

Point Protocol (PPP)
is an industry standard
protocol. PPP can be used to create point
links between different vendors’ equipment. It allows
authentication and multilink connections and can be
run over asynchronous and synchronous links.

Asynchronous Transfer Mode (ATM)

was created for
time sensitive traffic, providing simultaneous
transmission of voice, video, and data. ATM uses
cells rather than packets that are a fixed 53

WAN Protocols

Level Data Link Control (HDLC)
was derived
from Synchronous Data Link Control (SDLC), which
was created by IBM as a Data Link layer connection
protocol. HDLC is a connection
oriented protocol at
the Data Link layer. HDLC was not intended to
encapsulate multiple Network layer protocols across
the same link. The HDLC header carries no
identification of the type of protocol being carried
inside the HDLC encapsulation. Because of this, each
vendor that uses HDLC has their own way of
identifying the Network layer protocol, which means
that each vendor’s HDLC is proprietary for their

WAN Protocols

Link Access Procedure, Balanced (LAPB)
created to be used as a connection
oriented protocol
at the Data Link layer for use with X.25. It can be
used as a simple Data Link transport. LAPB has a
tremendous amount of overhead because of its strict
timeout and windowing techniques. You can use
LAPB instead of the lower
overhead HDLC if your
link is very error prone.

WAN Protocols

Integrated Services Digital Network (ISDN)
is a set
of digital services that transmit voice and data over
existing phone lines. ISDN can offer a cost
solution for remote users who need a higher speed
connection than analog dial
up links offer. ISDN is
also a good choice as a backup link for other links.

ISDN allows voice and data to be transmitted
simultaneously across the world using end
digital connectivity. In addition, it offers increased
bandwidth, reduced call setup time, reduced latency,
and lower signal
noise ratios, compared to analog

WAN Protocols

Frame Relay

is a packet
switched technology that has
been around since the 1980s. Frame Relay is an
industry standard networking protocol that handles
multiple virtual circuits (VC) using a derivation of
HDLC encapsulation between connecting devices.
Frame Relay is a Data Link and Physical layer
specification that provides high performance. Frame
relay typically can run at speeds of 64Kbps to
1.544Mbps. Frame Relay provides features for
dynamic bandwidth allocation and congestion

WAN Protocols

Multiprotocol Label Switching (MPLS)

replaces the
hop, individually routed packet model with a
oriented model that establishes ‘paths’ to

Instead of routing each packet based
upon its destination address, each packet is labeled
such that it can be switched along a pre

In addition, MPLS defines traffic engineering
methods that enables these paths to have associated
service attributes. Thus, a single
destination may have multiple paths leading to it,
with one path used for voice, one for video, and one
for data. Drawing

WAN Protocols

Which WAN service is the best one to use?

Answer: None of them. The best WAN service is the
one you can get in your neighborhood or at your
company. Since you don’t have many options to
choose from, call your local service provider and ask
what they can provide to you.

Transmission Modes

For digital transmission, all information is converted
into binary codes of 0 and 1 for transmission. It is
necessary to notify the other end of precise
information such as where the data starts and how
long the interval of data is.

“Synchronous”and“asynchronous”are the two modes
for communicating this information, and it is
necessary to confirm which mode a each end
supports. With Synchronous Transmission Mode, 64
kbps is the highest available transmission speed,
while 57.6 kbps is the highest for Asynchronous
Transmission Mode. Drawings

Transmission Modes

Synchronous signals, signals that play the role of
signs, are added to the top of the data to be
transmitted. With these signals, computers can
precisely determine the first position of the
characters. This mode can transmit data accurately,
making it appropriate for corporate information


Asynchronous signals, instead, use a portion of the
data that has arrived as a clue, the first position of the
character is identified. Two bits are added to each
character, a start bit for the beginning and an end bit
for the end, making the transmission speed slower.


Switched Network Topologies

Star topology
is a LAN physical topology with
endpoints on the network converging at a common
central switch (known as a hub) using point
links. A logical ring topology can be configurated as a
physical star topology using a unidirectional closed
loop star rather than point
point links. That is,
connections within the hub are arranged in an internal
ring. Drawing

Full mesh
topology is where every node has either a
physical or a virtual circuit linking it to every other
network node. A full mesh supplies a great deal of
redundancy but is typically reserved for network
backbones because of its expense. Drawing

Switched Network Topologies

Partially meshed

topology is where some network
nodes form a full mesh, but others are attached to
only one or two nodes in the network. Drawing

Observe the WAN Transport Technology table on
pages 298 and 299 in your text book.

WAN Transport Technologies

DS0 Rate
is known as the base channel bandwidth of
64Kbps. A bandwidth of 64Kbps is the bandwidth
required for an uncompressed digitized phone

Standard speech less then 4KHz; analog speech is

filtered at 4KHz before being sampled.

Nyquist Theorem sample at a rate at least two

times the input frequency to obtain a signal that

represents the true signal.

Each sample is encoded into 8 bit octets. This

DS0 rate is 8KHz. Per second times 8 bits per

sample, which is 64Kbps.


Metro Ethernet
technology is based on Ethernet
technology to offer the best cost
effective, high speed
connectivity for MAN and WAN.

DSL technology is a high
bandwidth technology over
the traditional copper lines. It is designed to work
with two modems at either end of the wire. DSL is a
transmission technology that is used by SPs to deliver
a wide range of services to subscribers.

Asymmetric DSL (ADSL)
used over short distances
(less then 2Lmeters). Most common type used.
Frequency range 100KHz to 1.1Hz. ADSL allows
PSTN tetphone service concurrently on the same line.


Symmetric (SDSL) DSL
allows traffic to be
transmitted in both directions at the same speed over
a single twisted pair. The distance served with SDSL
is 10K feet or 3048.8 meters. SDSL is often referred
to as single
pair DSL. SDSL is excellent for running
applications like email and web servers.

Ling Reach Ethernet (LRE)
is a WAN access
technology which allows for greater distance than the
traditional Ethernet provides.

Cable technology
is another high
speed copper
platform that supports both analog and digital video
services over a coaxial cable.


Cabling technology makes use channels for upstream
and downstream data flow. One application channel
in the coaxial cable is used to upstream signals from
the modem to the Cable Modem Termination System
(CMTS). The output from the CMTS is handed to
either the WAN or the PSTN. A different channel is
used for the downstream signals from these Internet
Service Providers to the CMTS to the modem.

The CMTS converts signals from the modem to IP
packets prior to handing them to the IP router for
transmission across the Internet. Downstream signals
are modulated for transmission across the cable to the


Internet download bandwidth over a cable TV line is
shared 27 Mbps.

Internet upstream bandwidth over the same shared
cable is 2.5 Mbps.

Wireless technology electromagnetic waves carry RF
signals. It is the option of some, that these waves
could be harmful to humans.

Synchronous Optical Network/Digital Hierarchy
is the ANSI standard for synchronous
transmission on fiber optic media. It specifies a base
signal rate of 51,84 Mbps and a set of multiples of
that rate, known as Optical Carrier levels, up to 2.5


SONET/SDH is a circuit based technology that
provided uses high speed circuits using TDM

Dark fiber
is a fiber optic cable(s) leased from an SP.
Fiber is typically connected to a company’s own
infrastructure. Dark fiber got its name after the dot
com burst. Many of the companies that had the rights
to these fiber networks either went bankrupt, or, had
to abandon their goals of utilizing this fiber. This
resulted in hundreds of thousands of miles of “unlit”
(dark) fiber. Dark fiber is optical fiber that is lying in
the ground unutilized

WAN Design

The network designer should design the Enterprise
Edge based on the PPDIOO methodology.

Analyzing customer requirements

Characterizing the existing network and sites.

Designing the network topology and solutions.

Observe the WAN Physical Media Bandwidths table
in your text book on page 320.

WAN Bandwidth Optimization

Compression is used to reduce the data size to
conserve transmission time.

Upcoming Assignments

Assignment 5
1, Concept Question 4 is due May 31,

Assignment 4
2, Basic Routing and LAN Switching
Configuration is due June 28, 2010

Assignment 4
3, Basic Network Troubleshooting is
due July 26, 2010