Transcript 109.05 Presentation File

Explain network protocols and services.
Objective 109.05 Course Weight 3%
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What are Protocols and Services?
Protocol is a set of conventions governing the
treatment and especially the formatting of data in an
electronic communications system – in this case, a
network.
Put simply, protocols are the rules and standards of
how the Internet works.
Services are also standardized on networks, but
these differ in that they are applications running
behind the scenes, usually in client-server
configurations, that help the networks function.
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Keeping Track of It All
There are a large number of protocols and services in
existence. To organize and understand them we use
two predominant models:
Open Systems Interconnect (OSI)
 A theoretical model used to explain protocol
interactions.
Transmission Control Protocol/Internet Protocol
(TCP/IP)
 A practical model that is actively maintained by
the Internet Engineering Task Force (IETF)
through the use of Request For Comment (RFC)
documentation.
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The OSI Model
 7 Layers
 Detailed for
ease of
explanation
 Shows how
data gets from
the user to a
transmitted bit
 Encapsulation
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The OSI Model
When data is
encapsulated using
this model it is
packaged in different
Protocol Data Units
(PDUs).
The names of the
PDUs are shown here
 Segment
 Packet
 Frame
 Bit
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Comparing to the TCP/IP Model
In practice, computer
networks are not so
easy to segment like
the OSI model.
The TCP/IP model
groups functions that
are closely
interrelated.
This makes
development and
documentation more
feasible.
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IPv4 and IPv6
These both reside in the network/internet layer of
the models.
They govern how devices locate one another in all
the world’s networks.
The system works similarly to the way telephone
numbers do.
“What happened to IPv5?”
 Version number was used for a protocol that
never really gained much popularity called
Internet Stream Protocol.
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IPv4 Basics
Format
 x.x.x.x
 where x can be any value from 0-255
This format is referred to as Dotted Decimal Notation
because it’s a decimal representation of an actual
binary number.
Length – each “octet” (one of the x’s) is made up of 8
bits resulting in a 32 bit address.
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IPv4 Subnetting
IP networks can communicate using three types of
messaging:



Unicast – from one device to a single other device.
Multicast – from one device to a select group of other
devices.
Broadcast – from one to device to all other devices on a
network.
When broadcast communication occurs it causes a
lot of traffic on the network.
As more devices join a network, broadcast messages
become larger and larger.
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IPv4 Subnetting
 To avoid huge messages to ridiculously large numbers of
devices, networks are subdivided or “subnetted”.
 IPv4 has two types of subnetting.
 Classless Addressing
 The old – Classful subnetting – left too many unused IPs
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IPv4 Subnetting: Transition
As we began to have more and more devices on the
public Internet, we began to run out of IPv4
addresses.
To reclaim unused addresses in existing class A and B
networks, the IETF created a new system of
addressing.
Current – Classless Inter Domain Routing (CIDR) with
Variable Length Subnet Masks (VLSMs)
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CIDR w/ VLSM
Using VLSM there are no set subnet sizes.
Subnet sizes are determined by the number of
subnets needed or the number of host IP addresses
needed, and then a subnet mask is determined.
A subnet that could support 254 hosts would look
like this:
 192.168.1.0/24
 The subnet portion of the address is 24 bits long
as indicated by the /24
 The host portions are 8 bits long (32-24=8)
• Anything from 192.168.1.1-192.168.1.254
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Reserved IPv4 Addresses and APIPA
 Loopback Address: 127.0.0.1
 Also referred to as localhost or home
 Any address from 127.0.0.1 to 127.255.255.255 works as
a loopback address.
 Private Addresses
 Class A: 10.x.x.x
 Class B: 172.16.0.0 – 172.31.255.255
 Class C: 192.168.0.0 – 192.168.255.255
 Automatic Private IP Addressing
 169.154.x.x
 Occurs when clients are set to use DHCP, but no DHCP
server is found on the network.
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IPv4 Limitations
As of January 3, 2011, the last top-level public IP
address was handed out by the Internet Assigned
Numbers Authority (IANA).
This problem was anticipated in the late 1980’s.
Two things were done to solve it:
 A stop gap was created called NAT.
 IPv6 was developed.
Network Address Translation (NAT) is a scheme that
allows one public address to be shared by many
private addresses within a LAN.
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Move on to Bigger and Better: IPv6
Instead of the 4.3 Billion addresses IPv4 uses, it has
340 undecillion addresses….that’s right,
undecillion…look that up!
Security is built in to the system
 IP Security (IPSec) was added to IPv4, but is not
mandatory.
 IPSec is built in to IPv6.
Subnetting is significantly easier.
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IPv6 Format
Format
 xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx:xxxx
 where x is a hexadecimal number.
Block – a set of four hexadecimal numbers
separated by a colon.
Length
 Each hex number is made up of 4 bits.
 There are 4 hex numbers in each block resulting
in 16 bit blocks.
 There are 8 blocks of 16 bits resulting in a 128
bit address.
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IPv6 Breakdown
0000:aaaa:1111:bbbb:2222:cccc:3333:dddd
The three parts of an IPv6 address are:
 Global Routing Prefix – the first three blocks –
0000:aaaa:1111 above
 Subnet ID – the fourth block – bbbb above
 Interface ID – the last four blocks –
2222:cccc:3333:dddd above
Subnetting is significantly easier than IPv4 because it
is built in to the address.
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IPv6 Representation
Addresses are compressed for easy representation by
eliminating unnecessary 0’s.
Leading 0’s are removed
 002b = 2b however 2b00 =/= 2b
A set of 0’s become one 0 or a ::
 Only one :: is allowed
 1abc:0000:0000:0000:0000:0000:0000:0000:2365
= 1abc::2365
 1abc:0000:0000:ffff:0000:0000:0000:0000:2365
= 1abc:0:0:ffff::2365
= 1abc::ffff:0:0:0:0:2365
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Reserved IPv6 Addresses
Loopback Address: 0:0:0:0:0:0:0:1 or ::1/128
Teredo Tunneled: 2001::/32
Reserved for Documentation about IPv6 Addressing:
2001:DB8::/32
Unique Local: FC00::/7
Link Local Unicast (like IPv4 APIPA): FE80::/10
Multicast: FF00::/8
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Making the Switch from IPv4 to IPv6
 Dual Stack Architecture network
 The network provides communication between the two
standards.
 Packets can travel as IPv4 or IPv6.
 How packets travel is determined by the application
sending them.
 Tunneling (Teredo, ISATAP, 6to4)
 IPv6 packets are encapsulated inside IPv4 packets and
transported across the network.
 Teredo or ISATAP virtual network adapters transparently
handle IPv6 to IPv4 translation.
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Assigning IP Addresses (IPv4 or IPv6)
Usually addresses are assigned to devices
automatically by a protocol called Dynamic Host
Configuration Protocol (DHCP) (more on this later).
No user intervention is required.
These addresses are subject to change per the DHCP
server’s settings.
Automatically assigned addresses are called
dynamic.
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Assigning IP Addresses (IPv4 or IPv6)
Not all IP addresses can be dynamic.
Some must never change.
Imagine if we wanted to go to Google.com but the
name changed every day.
If an address needs to be permanent, we must
manually assign the address.
 Manual assignment is referred to as static IP
addressing.
Static IP assignment is configured according to
device manufacturer’s instructions.
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TCP vs. UDP
Once IP network type is determined, traffic is
transmitted using the rules of two major protocols.
Transmission Control Protocol
 Connection oriented
 Checks to see if PDUs arrived as intended
 Like a webpage.
User Datagram Protocol
 Connectionless
 Does not care if the PDUs arrived safely, just
sends
 Like a live video call or live voice call.
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Support Services: DHCP, DNS, IPSec
IP addressing and the rules of TCP or UDP help to get
information where it needs to go.
To help IP, TCP, and UDP function there are many
background services.
Three heavily used services:
 Dynamic Host Configuration Protocol (DHCP)
 Domain Name System (DNS)
 Internet Protocol Security (IPSec)
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DHCP
Assigns IP addresses to
hosts on a network.
Uses a client-server
approach.
Different options
available for IPv4 and
IPv6.
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DNS
Converts Domain Names
(website names) to IP
addresses and vice versa.
Client-Server, hierarchical
lookup system.
Tries to find the info
locally, if info is
unavailable requests help
from higher authorities.
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DNS
DNS Servers store information
in tables.
Tables contain different record
types.
Common DNS record types.
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IPSec
Can secure any application traffic (upper layer data)
because it resides in the network/internet layer
(lower layer).
Uses one or all of a set of three protocols to secure
information:
 Security Association (SA) – provides keys for the
other two protocols.
 Authentication Header (AH) – provides data
origin authenticatioN.
 Encapsulating Security Payload (ESP) – like AH
but also provides confidentiality.
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Other Protocols
In addition to the Internet Protocol, TCP, UDP, and
the supporting services of DHCP, DNS, and IPSec
there are many other common protocols.
Knowing what these protocols are and the ports on
which they operate can make navigating networks
easier.
These ports can be especially helpful in configuring a
firewall and/or port forwarding (see sections 207.04
and 207.05).
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Other Protocols
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