Download Week_Six_Net_Design

Week Six Agenda
•
•
•
•
•
Attendance
Announcements
Review Week Five
Current Week Information
Upcoming Assignments
Review Week Five
Routing in the Enterprise Architecture
Routing in the Enterprise Architecture
Notice that RIP is not a part of an enterprise
design
• It is considered to be too slow to converge
• It is not recommended for large networks
• However, it may be adequate for small
networks and may exist in legacy networks.
EIGRP
The Enhanced Interior Gateway Routing
Protocol (EIGRP) represents an evolution from
its predecessor IGRP.
Key capabilities that distinguish EIGRP from
other routing protocols include fast
convergence, support for variable-length
subnet mask, support for partial updates, and
support for multiple network layer protocols.
EIGRP
A router running EIGRP stores all its
neighbors' routing tables so that it can quickly
adapt to alternate routes. If no appropriate
route exists, EIGRP queries its neighbors to
discover an alternate route. These queries
propagate until an alternate route is found.
OSPF
OSPF protocol was developed due to a need in the
Internet community to introduce a high functionality
non-proprietary Internal Gateway Protocol (IGP) for
the TCP/IP protocol family.
The OSPF protocol is based on link-state technology,
which is a departure from the Bellman-Ford vector
based algorithms used in traditional Internet routing
protocols such as RIP. OSPF has introduced new
concepts such as authentication of routing updates,
Variable Length Subnet Masks (VLSM), route
summarization, and so forth.
BGP
The Border Gateway Protocol (BGP) is the
routing protocol used to exchange routing
information across the Internet. It makes it
possible for ISPs to connect to each other and
for end-users to connect to more than one ISP.
BGP is the only protocol that is designed to
deal with a network of the Internet's size, and
the only protocol that can deal well with
having multiple connections to unrelated
routing domains.
IP sec
Internet Protocol security (IPsec) is a
framework of open standards for protecting
communications over Internet Protocol (IP)
networks through the use of cryptographic
security services. IPsec supports network-level
peer authentication, data origin authentication,
data integrity, data confidentiality (encryption),
and replay protection.
Routers
One of the primary jobs of a router is to
determine the best path to a given destination.
A router learns paths, or routes, from the static
configuration entered by an administrator
and/or dynamically from other routers, through
routing protocols
Static Routing
Static routes in the routing table
Includes: network address and subnet mask
and IP address of next hop router or exit
interface.
Denoted with the code S in the routing table
denotes static route.
Routing tables must contain directly connected
networks used to connect remote networks
before static or dynamic routing can be used.
Static Routing
Dynamic Routing
Dynamic Routing Protocols (DRP)are used to
add remote networks to a routing table.
DRP are used to discover networks
DRP are used to update and maintain routing
tables
DRP automatically discover the network
Network discovery is the ability of a routing
protocol to share information about the
networks that it knows about with other routers
that are also using the same routing protocol.
Dynamic Routing
Maintaining routing tables
Dynamic routing protocols are used to share
routing information with other router and to
maintain and update their own routing table.
Dynamic routing protocols not only make a best
path determination to various networks, they
will also determine a new best path if the
initial path becomes unusable (or if the
topology changes)
Routing Table
Routers keep a routing table in RAM
A routing table is a list of the best known
available routes.
Routers use this table to make decisions about
how to forward a packet.
On a Cisco router the show ip route command
is used to view the TCP/IP routing table.
Routing Loops
A network problem in which packets continue
to be routed in an endless circle.
Network routining loops are caused by a
router(s) or link(s) failure, and the notification
of the downed link has not yet reached all the
other routers.
Over time, normal network growth or merging
of networks can result in routing loops.
Routing protocols utilize various techniques to
lessen the chance of a routing loop.
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 that charge a
usage fee called, a tariff.
WAN Connection Types
Connecting LANs together over a data communications
equipment (DCE) network
Dedicated WANs utilize synchronous serial
connections.
Circuit-switched WANs use telephone company
networks with asynchronous serial, and ISDN.
Packet-switched WANs use a service provider with
synchronous serial.
WAN Connection Types
Leased lines are typically point-to-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.
Excellent for constant transmission data flow.
Circuit-switching sets up a line like a phone call. No
data can transfer before the end-to-end connection is
established. Circuit switching uses dial-up modems
and ISDN. It is used for low-bandwidth data
transfers.
WAN Connection Types
Packet switching is a WAN switching method that
allows you to share bandwidth with other companies
to save money. Packet switching is excellent for bur
sty data transfers, packet switching can save you
money. Frame relay and X.25 are packet-switching
technologies . Speeds can range from 56Kbps to
2.048Mbps.
WAN Connection Types
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.
WAN Connection Types
WAN Protocols
Point-to-Point Protocol (PPP) is an industry standard
protocol. PPP can be used to create point-to-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-bytes
long.
WAN Protocols
An ATM cell consists of a 5-byte header and a 48byte payload. The payload size of 48 bytes was
chosen as described above.
ATM defines two different cell formats: NNI
(Network-Network Interface) and UNI (UserNetwork Interface). Most ATM links use UNI cell
format.
WAN Protocols
High-Level Data Link Control (HDLC)
HDLC is a Data Link protocol.
Designates a method for data encapsulation on
synchronous serial links
Default encapsulation for Cisco routers
Bit oriented layer protocol created by ISO.
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 equipment.
WAN Protocols
HDLC frames can be transmitted over synchronous
or asynchronous links.
Those links have no mechanism to mark the
beginning or end of a frame, so the beginning and end
of each frame has to be identified. This is done by
using a frame delimiter, or flag, which is a unique
sequence of bits that is guaranteed not to be seen
inside a frame. This sequence is '01111110', or, in
hexadecimal notation, 0x7E. Each frame begins and
ends with a frame delimiter. A frame delimiter at the
end of a frame may also mark the start of the next
frame. A sequence of 7 or more consecutive 1-bits
within a frame will cause the frame to be aborted.
WAN Protocols
Link Access Procedure, Balanced (LAPB)
Connection-oriented protocol at the Data Link layer
Possesses much overhead because of strict timeout
and windowing techniques
LAPB is used instead of the lower-overhead HDLC if
your link is very error prone
WAN Protocols
Integrated Services Digital Network (ISDN)
is a service offered by telephone companies, It is a
communication protocol that allows telephone
networks to carry data, voice, and other digital traffic.
ISDN network is a digital communication system
that is capable of producing the maximum
transmission speed of 1.4Mbps. 128Kbps speed is
however more common in the digital technology. It's
a international standard for sending data, voice, video
over regular digital telephone lines. ISDN uses UTP
(unshielded twisted pair cable) for transmission.
WAN Protocols
Frame Relay is a packet switching protocol for
connecting devices on a Wide Area Network (WAN).
Frame Relay is a protocol standard for LAN
internetworking which provides a fast and efficient
method of transmitting information from a user
device to LAN bridges and routers.
WAN Protocols
Frame Relay networks in the U.S. support data
transfer rates at T-1 (1.544Mbps ) and T-3 (45 Mbps)
speeds. In fact, you can think of Frame Relay as a
way of utilizing existing T-1 and T-3 lines owned by a
service provider. Most telephone companies now
provide Frame Relay service for customers who want
connections at 56 Kbps to T-1 speeds. (In Europe,
Frame Relay speeds vary from 64 Kbps to 2 Mbps.
WAN Protocols
Multiprotocol Label Switching (MPLS) replaces the
hop-by-hop, individually routed packet model with a
connection-oriented model that establishes ‘paths’ to
destinations. Instead of routing each packet based
upon its destination address, each packet is labeled
such that it can be switched along a pre-defined
path. Thus, a single destination may have multiple
paths leading to it, with one path used for voice, one
for video, and one for data.
MPLS integrates Layer 2 information about network
links (bandwidth, latency, utilization) into Layer 3
(IP) within a particular autonomous system or ISP in
order to simplify and improve IP packet exchange.
WAN Protocols
Multiprotocol Label Switching (MPLS)
MPLS is a highly scalable, protocol agnostic, datacarrying mechanism. In an MPLS network, data
packets are assigned labels. Packet-forwarding
decisions are made solely on the contents of this
label, without the need to examine the packet itself.
This allows one to create end-to-end circuits across
any type of transport medium, using any protocol.
The primary benefit is to eliminate dependence on a
particular Data Link Technology, such as ATM,frame
relay, SONET or Ethernet, and eliminate the need for
multiple Layer 2 networks to satisfy different types of
traffic.
WAN Protocols
Multiprotocol Label Switching (MPLS)
MPLS operates at an OSI Model layer that is
generally considered to lie between traditional
definitions of Layer 2 (Data Link Layer ) and Layer 3
(NetworkLayer ), and thus is often referred to as a
"Layer 2.5" protocol. It was designed to provide a
unified data-carrying service for both circuit-based
clients and packet-switching clients which provide a
datagram service model. It can be used to carry many
different kinds of traffic, including IP packets, as well
as native ATM, SONET, and Ethernet frames.
Transmission Modes
Digital transmission, is binary codes of 0 and 1.for
transmission. It is necessary to notify the receiving
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
networks.
Synchronous Transmission Mode
0111111001101100110001
Synchronous Signal
01111110
Data First Char
01101100
Data Second Char
11000101
Transmission Modes
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.
Asynchronous Transmission Mode
001101100101100010110
Start
Stop
Start
Stop
0011011001
0110001011
Data First Char
Data Second Char
Packet-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-to-point
links. A logical ring topology can be configurated as a
physical star topology using a unidirectional closedloop star rather than point-to-point links. That is,
connections within the hub are arranged in an internal
ring.
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.
Packet-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.
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
conversation.
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.
Technologies
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 21meters). Most common type used.
Frequency range 100KHz to 1.1Hz. ADSL allows
PSTN telephone service concurrently on the same
line.
Technologies
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.
Technologies
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
modem.
Technologies
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
(SONET/SDH) is the ANSI standard for synchronous
transmission on fiber optic media. It specifies a base
signal rate (OC-1) of 51.84 Mbps and a set of
multiples of that rate, known as Optical Carrier
levels, up to 9.5 Gbps for OC-192.
Technologies
SONET/SDH is a circuit based technology that
provided uses high speed circuits using TDM
framing.
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 dotcom 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 Bandwidth Optimization
Compression is used to reduce the data size to
conserve transmission time.
Private Addressing
What has happened to IPv4 addresses?
In 1981, IPv4 Protocol was published. In 1985, about 1/16 of
the total IPv4 address space was in use. By mid-2001, about
2/3 of the total IPv4 address space was in use.
Since 2001, Internet service providers have been trying to
conserve IP addresses. They have assigned only a subset of
addresses to customers. Currently, the number of public IP
addresses available is insufficient for assigning addresses for
an entire network.
The answer to this problem is to assign private addresses
within a network and to translate these private addresses to
public addresses when Internet connectivity is required.
Public and Private Concerns
Are there public, private, or both types of addressing
required?
How many end systems will need access to the public
network? This includes email, file transfer, or web
browsing.
How many end systems require access to visible public
network(s). This includes e-commerce, such as web
servers, database servers, application servers, and
public servers. These end systems require globally
unambiguous IP addresses.
Where will the boundaries be between private and
public IP addresses and how will they be
implemented?
Private Addresses
• RFC 1918 sets aside three blocks of private IP
addresses:
• One (1) Class A address
• Sixteen (16) Class B addresses
• Two hundred and fifty six (256) Class C addresses
• These addresses are for private, internal network use
only
• Packets containing these addresses are not routed
over the Internet
• A router should never route RFC 1918 addresses.
Typically, ISPs configure the border routers to
prevent privately addressed traffic from being
forwarded
Private Addressing
• 172.16.0.0 –172.31.255.255: 172.16.0.0/12
• Where does the /12 come from?
• 12 bits in common
172.16.0.0 –172.31.255.255: 172.16.0.0/12
Where does the /12 come from?
• 12 bits in common
10101100 . 00010000 . 00000000 . 00000000 –172.16.0.0
10101100 . 00011111 . 11111111 . 11111111 -172.31.255.255
10101100 . 0001000 00000000 . 00000000 –172.16.0.0/12
Network Address Translation (NAT)
• NAT is defined by RFC 1631. It is the process of
swapping one address for another in the IP packet
header.
• NAT is a mechanism for conserving registered IP
addresses in large networks and simplifying IP
addressing management tasks.
• In practice, NAT is used to allow hosts that are
privately addressed, using RFC 1918 addresses, to
access the Internet
• NAT allows many hosts on an inside network to
communicate on the Internet with one valid, assigned
IP address
Network Address Translation (NAT)
• NAT provides a level of security for your inside
network from the outside world
NAT Terminology
• Inside local IP address: The IP address assigned to a
host on the inside network. The address is typically
an RFC 1918 address.
• Inside global IP address: A globally unique IP address
(typically assigned by an ISP) that represents one or
more inside local IP addresses to the outside world.
• Outside global IP address: The IP address assigned to
a host on the outside network by its owner. The
address is globally unique.
• Outside local IP address: The local IP address
assigned to a host on the outside network. In most
situations, this address will be identical to the outside
global address of that outside device
NAT Terminology
Static IP Address Assignment
• An IP address is manually assigned to a device or
host.
• The network administrator configures the IP address,
default gateway, and name servers manually by
entering them into a special file or files on the end
system with either a graphical or text interface.
• Static address assignment is an extra burden for the
administrator—especially on large-scale networks—
who must configure the address on every end system
in the network.
• Typically, routers, switches, servers, and printers have
IP addresses statically assigned.
Dynamic IP Address Assignment
• Dynamic IP addresses are automatically assigned to the
devices.
• Dynamic address assignment relieves the administrator of
manually assigning an address to every network device
• Instead, the administrator must set up a server to assign the
addresses.
• On that server, the administrator defines the address pools and
additional parameters that should be sent to the host (default
gateway, name servers, time servers, and so forth)
• On the host, the administrator enables the host to acquire the
address dynamically; this is often the default.
• When IP address reconfiguration is needed, the administrator
reconfigures the server, which then performs the hostrenumbering task
• DHCP is the protocol used to distribute these IP addresses
Dynamic Host Configuration Protocol (DHCP)
DHCP is a superset of the BootP protocol. This means
that it uses the same protocol structure as BootP, but
it has enhancements added. Both of these protocols
use servers that dynamically configure clients when
requested. The two major enhancements are address
pools and lease time.
Dynamic Host Configuration Protocol
Dynamic Host Configuration Protocol
Dynamic Host Configuration Protocol (DHCP)
A DHCP Server can provide the following to a client:
•
•
•
•
•
•
•
•
•
IP address
Gateway address
Subnet mask
DNS server address
Subnet mask
Router
Domain Name
Domain Name Server(s)
WINS Server(s)
Dynamic Host Configuration Protocol
DHCP Operation
• A client must have DHCP configured when starting
the network membership process
• The client sends a request to a server requesting an IP
configuration
• Sometimes the client may suggest the IP address it
wants, such as when requesting an extension to a
DHCP lease
• The client locates a DHCP server by sending a
broadcast called a DHCPDISCOVER
Enterprise Network IP Address Assignments
Classless Interdomain Routing (CIDR)
• CIDR is the abbreviation for “Classless
InterdomainRouting”.
• CIDR is pronounced “cider”.
• CIDR replaced the old process of assigning addresses
based on Class A, Class B, and Class C.
Classless Interdomain Routing (CIDR)
A method supported by classless routing protocols,
such as OSPF and BGP4, based on the concept of
ignoring the IP class of address, permitting route
aggregation and VLSM that enable routers to
combine routes in order to minimize the routing
information that needs to be conveyed by the primary
routers. It allows a group of IP networks to appear to
other networks as a unified, larger entity. CIDR, IP
addresses and their subnet masks are written as four
dotted octets, followed by a forward slash and the
numbering of masking bits.
Example: 192.168.45.0/24
Classless Interdomain Routing (CIDR)
• With CIDR, addresses use bit identifiers, or bit
masks, instead of an address class to determine the
network portion of an address
• CIDR uses the /N notation instead of subnet masks
• CIDR allows for the more efficient allocation of IP
addresses
• Blocks of addresses that match an organization’s
needs can be issued
Classless Interdomain Routing (CIDR)
Classless Interdomain Routing (CIDR)
172.16.0.0 255.255.0.0 = 172.16.0.0 /16
198.30.1.0 255.255.255.0 = 198.30.1.0 /24
Note that 192.168.24.0 /22 is not a Class C
network, it has a subnet mask of 255.255.252.0
Classless Interdomain Routing (CIDR)
• CIDR allows routers to summarize, or aggregate,
routing information
• One address with mask can represent multiple
networks
• This reduces the size of routing tables
• Supernetting is another term for route aggregation
CIDR and Route Aggregation
Given four Class C Networks (/24):
192.168.16.0 11000000 10101000 00010000 00000000
192.168.17.0 11000000 10101000 00010001 00000000
192.168.18.0 11000000 10101000 00010010 00000000
192.168.19.0 11000000 10101000 00010011 00000000
Identify which bits all these networks have in common.
192.168.16.0 /22 can represent all these networks.
The router will look at the first 22 bits of the address
to make a routing decision
CIDR and Route Aggregation
CIDR and Route Aggregation
CIDR and Route Aggregation
Importance of Hierarchical Addressing
Without summarization, every small change in the
network will be propagated (spread) throughout the
entire network
Importance of Hierarchical Addressing
With summarization, small changes in the network
aren’t propagated (spread) throughout the entire
network
Benefits of Summarization
Upcoming Assignments
Assignment 5-1, Concept Question 4 is due May 30,
2011
Assignment 4-1-2, Basic Routing and LAN Switching
Configuration is due June 27, 2011
Assignment 4-1-3, Basic Network Troubleshooting is
due July 25, 2011