Transcript Understanding Wide Area Networks

Understanding Wide Area Networks
Lesson 7
Objectives
Skills/Concepts
Objective Domain
Description
Objective Domain
Number
Understanding routing
Understanding routers
2.2
Defining common WAN
technologies and
connections
Understanding wide area 1.3
networks (wan’s)
Routing
• Routing is the process of managing the flow of data between network
segments and between hosts or routers
• Data is sent along a path according to the IP networks and individual
IP addresses of the hosts
• A router is a network device that maintains tables of information about
other routers on the network or internetwork
Static and Dynamic Routing
• A static route is a path that is manually configured and remains
constant throughout the router’s operation
• A dynamic route is a path that is generated dynamically by using
special routing protocols
Static
Dynamic
Dynamic Routing
• Dynamic routing method has two conceptual parts:
• Routing protocol used to convey information about the network environment
• Routing Algorithm that determines paths through the network
• Common Dynamic routing protocols:
• Distance vector routing protocols: Advertise the number of hops to a network destination (distance)
and the direction a packet can reach a network destination (vector). Sends updates at regularly
scheduled intervals, and can take time for route changes to be updated
• Link state routing protocols: Provide updates only when a network link changes state
• Distance Vector Routing
• Routing Information Protocol (RIP)
• Link State Routing
• Open Shortest Path First (OSPF)
Interior Gateway Protocols (IGPs)
• Routing protocols that enable elements that comprise an autonomous
system (AS) to exchange routing information
• For very large networks it is necessary to divide the internetwork into
entities known as autonomous systems (AS)
• IGPs exchange routing information within a single AS that operates
common routing protocols
• RIP and OSPF are examples of IGPs
AS
AS
RIP
OSPF
RIP
OSPF
Routing Information Protocol (RIP and RIPv2)
• Distance vector routing protocol that enables the exchange of IP
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•
•
•
routing information
Calculates the direction or interface that packets should be forwarded
to, as well as the distance from the destination
Each router maintains a database of the number of hops to a network
destination (distance) and the direction a packet can reach a network
destination (vector)
RIP is easy to implement and has a large installed base
Updates are sent periodically
Open Shortest Path First (OSPF)
• A link-state protocol that monitors the network for routers that have a
change in their link state
• Each router maintains a database of router advertisements called Link
State Advertisements (LSAs)
• An LSA consist of a router, attached networks and their configured
costs
• Updates are sent when the status of a route is updated
Exterior Gateway Protocols (EGPs)
• A routing protocol that was designed and intended for use between
autonomous systems
• Border Gateway Protocol (BGP) is an EGP that enables autonomous
systems (AS) to exchange routing information
• BGP is used to enable routing on the Internet
BGP
AS
AS
RIP
OSPF
RIP
OSPF
DEMO: Configuring RRAS Server (verify RIP)
Wide Area Network
• Wide area networks (WANs) connect multiple local area networks
together
• WANs connect multiple LANs that can include a home, school, or
buildings
• WANs enable network to function without concern to a location
• WAN technologies can include:
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Packet Switching: Devices transport packets via shared links
Leased Line: Dedicated point to point connection
Circuit Switching: Dedicated circuit path is created between end points (dial up)
Cell Relay: Similar to packet switching but uses fixed packet lengths
Packet Switching
• WANs utilize some type of packet switching technology
• Packet switching services include X.25 and Frame Relay
• Before packet switching, technology such as direct dial-up connections
was used
X.25
• X.25 communications protocol was one of the first implementations of
packet switching
• Data Terminal Equipment (DTEs) or a network device, connect to Data
Communications Equipment (DCEs), a modem is a DCE enabling
communication to the X.25 network
• Dummy terminals can connect to the network using Packet
Assembler/Disassembler (PADs) which connect to the DCE
DTE
Modem (DCE)
X.25 Network
Virtual Circuits
• Telecommunication companies have thousands of shared circuits /
connections from which to select a path
• These are known as a circuit set
• The chances of the entire message of packets taking one circuit are slim
• Multiple circuits are being used, and not just one, the entire circuit set is
known as the virtual circuit
• This method of data transmission is the core technology for the Internet
and most LANs
Hops
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•
•
•
There could be several PSE stops along the way
These PSEs disassemble and reassemble the packets
These stops are also known as hops
At the receiving office, the packet is reassembled and the overhead
(header and trailer) is discarded
X.25 Advantages
• If data fails, X.25 automatically recovers and sends it again
• X.25 allows shared access among multiple users on the LAN
• X.25 has full error and flow control
• There is also protection from intermediate link failure
• X.25 is not completely fault tolerant, but it is 70% effective
• Pricing is per shared packet sent, not per minute
• X.25 is a synchronous, digital transmission. There is less overhead per
file
Frame Relay
• Frame Relay is the advancement of X.25 packet switching
• A standardized wide are network protocol using a form of packet
switching designed for faster connections
• It also uses a virtual circuit, but one that is more advanced. Frame
Relay created the “virtual network” that resides in the cloud
Permanent Virtual Circuits
• A permanent virtual circuit is a virtual circuit established for repeated
use
• Frame Relay enables multiple sessions to be run simultaneously on the
same link
• These connections to the cloud are known as permanent logical links
or permanent virtual circuits (PVCs)
• The PVC links the sites together in the cloud, and this is accomplished
by using the PSE (packet switching exchange)
Leased Lines
• Leased lines are a connection contract between a provider and a
customer
• Frame Relay service must be purchased from an Internet services or
telecommunications provider
• With Frame Relay, you must commit to a certain amount of information
over time
• This is the CIR (committed information rate). The CIR is assigned to each PVC that services the
organization’s account
• Because this transmission is full duplex, there can be two CIRs for each PVC
T-Carrier Overview
• A T-carrier or telecommunications carrier system is a cabling and
interface system designed to carry data at high speeds
• The basic data transfer rate of the T-carrier system is 64 Kbps, which is
known as DS0, which is the digital signaling scheme
• DS1 is the digital signaling scheme for the T1-carrier
T-Carrier Systems Comparison
• Countries and their associated T-carrier systems
T-Carrier
North America
Japan
64 Kbps
Europe
Level 0 – DS0
64 Kbps
Level 1 – DS1
1.544 Mbps (T1: 24 user 1.544 Mbps (J1: 24
Channels)
user Channels)
1.544 Mbps (E1: 24 user
Channels)
Level 3 – DS3
44.736 Mbps (T3: 672
user channels)
34.368 Mbps (E3: 512 user
channels)
Level 4 – DS4
274.176 Mbps (T4: 4032 97.728 Mbps (J4:
user channels)
1440 user channels)
32.064 Mbps (J3:
480 user channels)
64 Kbps
139.264 Mbps (E4: 2048
user channels)
ISDN
A digital technology developed to offer faster communication speed than
an analog telephone line
• Integrated Services Digital Network (ISDN) is a set of communication
standards enabling simultaneous digital transmission of data, fax, voice
and video
• ISDN can be broken down into two major categories:
• Basic rate ISDN (BRI):
• 128 Kbps - two equal B channels at 64 Kbps each
• Generally, devices that connect to BRI lines can handle eight simultaneous connections to the
Internet.
• Primary rate ISDN (PRI):
• 1.536 Mbps - runs on a T-1 circuit
• 24 equal 64 Kbps B channels for data
ATM
• Asynchronous transfer mode (ATM) is a cell-based switching
technology as opposed to a packet switching technology
• ATM is a high-speed networking technology used to transmit data in
cells of a fixed length containing 53 bytes of information
• ATM is a native connection-oriented protocol comprised of a number
of related technologies for software, hardware and connectionoriented matter
SONET
• Synchronous Optical Networking (SONET) is a standardized protocol
allowing for the transmissions of signals over optical fiber in North
America
• Synchronous Digital Hierarchy (SDH) is the standard in Europe
• The standard represents a transport vehicle capable of supporting data
rates in the gigabit range, optical interfaces, network management and
testing methods
• Before the standard was released, each manufacturer designed its fiber
terminal device to its own optical signal interface
SONET Signal Hierarchy
Level
Line Rate
DS3 Channels
OC-1
51.84 Mbps
1
OC-3
155.52 Mbps
3
OC-12
622.08 Mbps
12
OC-24
1.244 Gbps
18
OC-48
2.488 Gbps
48
OC-192
9.953 Gbps
192
FDDI
• Fiber distributed data interface (FDDI) is a standard for transmitting
data on fiber optic cables at a rate of around 100 Mbps
• Supports transmission distances beyond 50 miles
• The original FDDI standard called for a physical double ring topology
• FDDI is primarily a protocol used on backbone networks
DSL
• Digital subscriber line (DSL) is a family of technologies that provides data
transmissions over local telephone networks
• DSL allows for voice and data to be run over the same line
• DSL uses higher frequency bands to transmit data
• xDSL is the standard for the various digital subscriber lines
• ADSL (asymmetric digital subscriber lines) The upload and download speed are
the different or asymmetrical
• SDSL (symmetrical digital subscriber line) The upload and download speed are the
same or symmetrical
Broadband Cable
• Broadband cable is used for cable Internet and cable television using
the cable television network
• It operates at a higher speed than DSL and rates can range from 384
kbps to 20 Mbps +
POTS/PSTN
• POTS/PSTN stands for plain old telephone system/public switched
telephone network.
• This is what we use now for “regular” phone lines, and it has been
around since the 1940s.
• POTS/PSTN is now digital at the switching office and some central
offices, but there analog lines run to people’s homes.
Summary
• The differences between static and dynamic routing.
• How to install and configure RRAS to function as a network router and how to
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•
•
•
install the Routing Information Protocol.
How to define packet switching types, such as X.25 and Frame Relay.
What T-carrier lines are, the different types of lines, and their Japanese and
European counterparts.
The basics about various other wide area networking technologies, such as ATM,
SONET, FDDI, and so on.
An introduction to different personal and small business Internet connectivity types.
Additional Resources & Next Steps
Instructor-Led Courses
• 40033A: Windows Operating System and Windows
Books
Server Fundamentals: Training 2-Pack for MTA
Exams 98-349 and 98-365 (5 Days)
• 40349A: Windows Operating System Fundamentals:
MTA Exam 98-349 (3 Days)
• 40032A: Networking and Security Fundamentals:
Training 2-Pack for MTA Exams 98-366 and 98-367
(5 Days)
• 40366A: Networking Fundamentals: MTA Exam 98366
• Exam 98-366: MTA
Networking
Fundamentals (Microsoft
Official Academic
Course)
Exams &
Certifications
• Exam 98-366:
Networking
Fundamentals