Semesters 1

1
Semesters 1 2Concept Review

• Chapter 1Review

Instructor Mehran Dowlatshahi
2
Table of Contents

• Review the OSI Model
• LAN Devices Technologies
• IP Addressing
• CIDR Notation
• Routing
• Transport Layer

Go There!
Go There!
Go There!
Go There!
Go There!
Go There!
3
Peer-to-Peer Communications

• Peers communicate using the PDU of their layer.
  For example, the network layers of the source and
  destination are peers and use packets to
  communicate with each other.

4
TCP/IP Reference Mode

• TCP/IP Network Layer protocols layer 
• IP provides connectionless, best-effort delivery
  routing of datagrams.
• Internet Control Message Protocol (ICMP) provides
  control and messaging capabilities. 
• Address Resolution Protocol (ARP) determines the
  data link layer addresses for known IP
  addresses. 
• Reverse ARP (RARP) determines network addresses
  when data link layer addresses are known.
•  

5
Address Resolution Protocol

• In broadcast topologies, we need a way to resolve
  unknown destination MAC addresses.
• ARP is protocol where the sending device sends
  out a broadcast ARP request which says, Whats
  you MAC address?
• If the destination exists on the same LAN segment
  as the source, then the destination replies with
  its MAC address.
• However, if the destination and source are
  separated by a router, the router will not
  forward the broadcast (an important function of
  routers). Instead the router replies with its
  own MAC address.

6
IP Addressing

• Subnetting Review

Network
Table of Contents
7
1. How many bits to borrow?

• How many bits do I have to work with?
• Depends on the class of your network address.
• Class C 8 host bits
• Class B 16 host bits
• Class A 24 host bits
• Remember you must borrow at least 2 bits for
  subnets and leave at least 2 bits for host
  addresses.
• 2 bits borrowed allows 22 - 2 2 subnets

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1. How many bits to borrow?

• Class B Example 185.75.0.0
• Design goals specify no more than 126 hosts per
  subnet, so how many bits do we need to leave ?
• How many bits in the host portion do we have to
  work with ?
• 2 to the what power will insure no more than 126
  hosts per subnet and give us the most subnets?
• 27 - 2 126 hosts

9
Practice On Your Own

• Below are some practice problems. Take out a
  sheet of paper and calculate...
• Last non-zero octet
• Second usable subnet address and broadcast
  address
• 192.168.15.0/26
• 220.75.32.0/30
• Bits borrowed
• 200.39.79.0/29
• 195.50.120.0/27
• 202.139.67.0/28
• Challenge 132.59.0.0/19
• Challenge 64.0.0.0/16

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Answers
Dont Cheat Yourself!! Work them out before you
check your answers. Click the back button if
youre not done. Otherwise, click anywhere else
in the screen to see the answers.
Back
11
Routing Basics

• Path Determination Packet Switching

Network
Table of Contents
12
A Routers Functions

• A router is responsible for determining the
  packets path and switching the packet out the
  correct port.
• A router does this in five steps
• De-encapsulates the packet
• Performs the ANDing operation
• Looks for entry in routing table
• Re-encapsulates packet into a frame
• Switches the packet out the correct interface

13
Routed v. Routing Protocols

• What is a routed protocol?
• Routed protocols are protocols that enable data
  to be transmitted across a collection of networks
  or internetworks using a hierarchical addressing
  scheme.
• Examples include IP, IPX and AppleTalk.
• A routable protocol provides both a network and
  node number to each device on the network.
  Routers AND the address to discover the network
  portion of the address.
• An example of a protocol that is not routable is
  NetBEUI because it does not have a network/node
  structure.

14
Routed v. Routing Protocols

• What is a routing protocol?
• A routing protocol is a protocol that determines
  the path a routed protocol will follow to its
  destination.
• Routers use routing protocols to create a map of
  the network. These maps allow path determination
  and packet switching. Maps become part of the
  routers routing table.
• Examples of routing protocols include RIP, IGRP,
  EIGRP, OSPF

15
Multi-protocol Routing

• Routers are capable of running multiple routing
  protocols (RIP, IGRP, OSPF, etc.) as well as
  running multiple routed protocols (IP, IPX,
  AppleTalk).
• For a router to be able use different routing and
  routing protocols, you must enable the protocols
  using the appropriate commands.

16
Dynamic v. Static Routing

• Dynamic routing refers to the process of allowing
  the router to determine the path to the
  destination.
• Routing protocols enable dynamic routing where
  multiple paths to the same destination exist.

17
Dynamic v. Static Routing

• Static routing means that the network
  administrator directly assigns the path router
  are to take to the destination.
• Static routing is most often used with stub
  networks where only one path exists to the
  destination.

18
Default Routes

• A default route is usually to a border or gateway
  router that all routers on a network can send
  packets to if they do not know the route for a
  particular network.

19
Routing Protocol Classes

• Routing protocols can be divided into three
  classes
• Distancevector determines the route based on
  the direction (vector) and distance to the
  destination
• Link-state opens the shortest path first to the
  destination by recreating an exact topology of
  the network in its routing table
• Hybrid combines aspects of both

20
Convergence

• Convergence means that all routers share the same
  information about the network. In other words,
  each router knows its neighbor routers routing
  table
• Every time there is a topology change, routing
  protocols update the routers until the network is
  said to have converged again.
• The time of convergence varies depending upon the
  routing protocol being used.

21
Distance-vector Routing

• Each router receives a routing table periodically
  from its directly connected neighboring routers.
• For example, in the graphic, Router B receives
  information from Router A. Router B adds a
  distance-vector number (such as a number of
  hops), and then passes this new routing table to
  its other neighbor, Router C.

22
Link-state Routing

• Link-state protocols maintain complex databases
  that summarize routes to the entire network.
• Each time a new route is added or a route goes
  down, each router receives a message and then
  recalculates a spanning tree algorithm and
  updates its topology database.

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Comparing the Two
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Hybrid Routing

• Ciscos proprietary routing protocol, EIGRP, is
  considered a hybrid.
• EIGRP uses distance-vector metrics. However, it
  uses event-triggered topology changes instead of
  periodic passing of routing tables.

25
Transport Layer
Transport

• A Quick Review

Table of Contents
26
Transport Layer Functions

• Synchronization of the connection
• Three-way handshake
• Flow Control
• Slow down, youre overloading my memory
  buffer!!
• Reliability Error Recovery
• Windowing How much data can I send before
  getting an acknowledgement?
• Retransmission of lost or unacknowledged segments

27
Transports Two Protocols

• TCP
• Transmission Control Protocol
• Connection-oriented
• Acknowledgment Retransmission of segments
• Windowing
• Applications
• Email
• File Transfer
• E-Commerce

• UDP
• User Datagram Protocol
• Connectionless
• No Acknowledgements
• Applications
• Routing Protocols
• Streaming Audio
• Gaming
• Video Conferencing