lecture notes chapter 2
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1/30/2011
Lecture Notes Chapter 2
LABS: 2, 2.5, and 2.16 (Maybe more) Might be in book and might be online.
When “Take Assessments” is highlighted in CISCO, youneed to take the online quizzes
Check out “Networks” too because it is the companionmanual.
Turn in Labs using the “Messages” folder. Your Packet Tracer Labs are on the CISCO site, too.
Down side of segmentation and multiplexing:- A lot of breaking down and addressing to do so it becomes quite complex.- A lot of times, the packets can become lost.- The many tables create latency
Each gets its own amount of time (TTL) if not used in that time, they arediscarded.
What makes up components of the network?-Devices (PCs, intermediary devices)-Media (Cable or wireless)-Services and processes (software – RULES)
KNOW IEEE (what it stands for!)Know the other organizations also.
CCNA is more concerned with the lower layers of the OSI model because that’s wherethe action happens.
TRANSPORTNETWORK DLLPHYSICAL
End devices = hostsHost can be either sender (source) or receiver (destination)Server (source allocator) Client (receiver)
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Intermediary devices:-Internetwork = (2 different types of networks)-Network Access Devices (hubs, switches, and wireless access points).- Look at slide for more*NIPS (lookup)
FUNCTIONS OF INTERMEDIARY SERVICES:Lookup the jobs of switches, hubs, repeaters, bridges …. (Slide starts with “Processesrunning on the intermediary network …”Remember: The packets are TIME STAMPEDBetween internetwork, routers use interfaces with IP addresses to identify thesources.Look up switch.*Note that the early levels of OSI are critical because they set the standard of transmission, whether it be addressing or whatever.
3 Types of Media:
CopperGlass or plastic (single mode or dual mode ?)Wireless transmissionDoesn’t matter how much bandwidth is offered if the medium can’t handleit.Know the differences between “g”, “n”, etc …. Bluetooth (just peachy when you’realone but not in public … Example: His bar story where he turns on Bluetooth andpicks up information from people.)
Signaling: Depending on the channel type … there will be a difference in quality.Single mode = 62 miles
Criteria for choosing a network media are:- Distance- Environment (mountains, train tracks, … EMF interference …)- Amount of data carried and the speed it can be transmitted- Cost
LAN and WAN:LAN (Harford) Owned individually. Spans single geographical area … single business,campus, or region …WAN (Not owned individually)
Internetworks: Interconnected
Intranet (Within network)
Internet/Extranet:Use inter to access extra.
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NIC: (or LAN adaptor). 48 –bit hexadecimal number (48 may not be right). NICidentifies each address on internet. It is the only way out.Physical Port: Just the connector or outlet where media is connected to a host orother networking device.Interface: Routers deal with interfaces. Because routers are used to interconnectnetworks, the ports on router are referred to network interfaces.
Rules that Govern Communications:Predefined rules = protocolsName two of the protocols that make up TCIP protocol switch (TCP/IP)
Network protocol suites describe processes such:-Format or structure of message-How and when error and system messages are passed between devices-The setup and termination of data transfer sessions.
Protocol Suites and Industry Standards:IEEE, IETF
Interaction of Protocols:HTTP
TCPIPEthernet
See Slide
Using Layer Models (OSI):Before you can see the letter “t” you type, it has gone through all 7 layers.
Top 3 layers walk together, Bottom 4 walk together. TRANSPORTNETWORK DLLPHYSICAL
Benefits of using layer models:Assists in protocol design because protocols that operate at specific layer havedefined interface to the layers above and below.Fosters competitionPrevents technology or capability changes in one layer from affecting other layersabove and below
(One more … Look)Protocol and Reference Model:Protocol model (Use this guy)
Reference model is not meant to be implemented
TCP (Top 3 are application_ Transport is transport
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Network is internetBottom 2 is access to network.
OSI is just an illustration(please don’t throw sausage pizza away).
COMMUNICATION PROCESS (Using OSI):
Create Data = Application
Segmentation
& Encapsulate = Transport as well as Internet
Generate on to the media = Network Access
Then to the next … (See Slide)
Email Message
DATA DATA DATA
HEADER DATA
HEADER DATA TRAILER
WHEN IT ARRIVES AT DESTINATION
APPLICATIONSTRANSPORT
INTERNETNETWORK ACCESS
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(SEE PROTOCOL DATA UNITS AND ENCAPSULATION SLIDE)
APPLICATION TRANSPORTINTERNETNETWORK ACCESS
MISTAKE ON PAGE 51!
TRANSPORT IS SUPPOSED TO BE DATA NOT PACKETS
OSI (Created by ISO in 1972) IN 1984 the OSI layer was introduced
The idea was to break down the network communication into smaller, more
manageable parts.
REMEMBER, It is NOT a protocol. It is only a reference.
Take a look at the slide that says OSI Model – Example – FYI (not part of the CISCO
curriculum, though)
Application (layer 7)
Presentation (6)
Session (5)
Transport (4)
Network (3)
Data Link (2)
Physical (1)
Not commonly referred to.(DOUBLE CHECK)
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Application and Presentation and Session (Usually referred to as upper layers)
Trans = process
Network = Logical
Data Link = Device
Physical = Timing and sychronizing
ADDRESSING ALWAYS INCLUDES BOTH THE SOURCE AND DESTINATION
ADDRESSES.
ENCODED
PROCESS
LOGICAL
PHYSICAL
Layer 2 addressing:
- Move data from one local network to another
- Addresses must id both the network and the host on that network
- Used by routers to determine the best path to the destination host
- At Network (Header and Data)
Layer 4 Addressing:
- Identifies the specific process or svc runing on the destination host that willact
on the data
- Multiple, simultaneous processes
Dest. MAC SourceMAC
Dest.LogicAddress
SourceLogicalAddress
Destination ProcessAddress
SourceProcessAddress
Data
See the putting it all together interactive slide.
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Comparing the OSI and TCP/IP Models:
(See and copy this slide)
Chapter 3 Lecture Notes
1/30/2011
ON BLACKBOARD, CHECK OUT “REVIEW” AND DO AS MANY LABS AS YOU
CAN
The CISCO work will expire on the 6th.
No Lecture on WEDNESDAY. READ CHAPTERS 4 &5
SEND ALL EMAILS THROUGH BLACKBOARD
Focusing on the Application Layer
Application provides the 1st step of the data getting to the network.
- People creat the communication
- (see slide)
Presentation layer:
3 funtions:
- Coding and conversion of application layer data to ensure that data from the
source device can be interpreted byt the appropriate application on the
destination device
- Compression of the date in a manner that can be decompressed by the
destination device (encryption and security)
- Encryption of the data for transmission and decryption
Session Layer:
- Creates and maintains dialogs between souce and destination applications
- Handles the expchange of info. To initiate dialogs and keeps them active
- Restarts sessions that are disrupted or idel for a long period of time.
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(when session is done, session layer closes and waits until it is needed again)
If man in the middle tries to connect in, the session will
end and then restart (purposeful) This means that the
medium disconnects and then reconnects. Also happens
with CSMA.
Some application Layer Protocols:
-Domain Name Service (DNS)
(Used to resolve internet name to IP addresses)
*Example:
- Hypertext Transfer Protocol (HTTP) - Port 80 ( OR 20, 21)
(Used to transfer files that make up the web pages of the world
wide web)
- SMTP (Port 25)
- Telnet
- FTP
(interactive file …)
See page 69
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User applications, services and Protocols
-User applications provide the user with a way to create msgs.
-Services establish an interface to the network
-Protocols provide the rules and formats that govern how data is treated
-Establish consistent rules for exchanging data between applications and services
-Specity how data inside the msg. is structured and the types of messages that are
sent between the source and destination.
See last two …
Client-Server Model:
- The device requesting the info in the client
- The device responding to the request is called a server
- Application layer protocols describe the format of the requests and responses
between the clients and servers.
Resource requestor and resource provider.
TACACAS+ is a type of CISCO Server
The server runs daemon and daemon:
-runs in background
-listens for …. (see slide)
APPLICATION LAYER SERVICES AND PROTOCOLS:
Application layer processes and services rely on support from lower layer funtions to
successfully manage the multiple conversations.
Private ports are used a lot and they mix up the ports to confuse would be spies.
Peer-to-Peer:
2+ computers connected via a network and can share resources without having a
dedication server.
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-every connected end device, known as a peer, can function as a standalone, a
server, or a client.
-Info can be located anywhere on any connected device
- User accounts and access rights are set individually on each peer-to-peer
- Difficult to enforce security.
- Most current operating systems support file and print …
(See More)
DNS SERVICE AND PROTOCOL:
-DNS uses TCP/UDP (Port 53)
- Domain names were cerated to convert the numeric IP addres into a simple,
recognizable name
- Domain names are easier to remember than actual numeric addresses
-Any change to the address is transparent to the user since it is the same
(MEANING THAT IT IS EASIER TO TYPE: WWW.CISCO.COM RATHER THAN 192.83.80)
See next slide:
DNS Message Format:
(See slide)
DNS Resource Records:
How many root DNSs? THERE ARE 13
LOOK UP A DEMONSTRATION ON HOW ADDRESSING HAPPENS.
A an end device address
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NS (Look up on slide)
WWW Service and Protocol:
-HTTP uses TCP 80 Port
URL has 3 parts (look at slide)
Browsers can interpret and present many data types (look at slide and next one)
HTTP Protocol
Uses GET, POST, AND PUT
LOOK UP THE PORT NUMBERS AND BEGIN TO MEMORIZE THEM.
Email Svcs. And SMTP/POP3
- Usere composes an email using an application called a Mail User Agent (MUA)
or email client.
- Client sends emails to a server using SMTP and receives emails using
POP3smtp uses tcp portst
- Pop uses UDP port 110
Mail Transfer Agent:
- MTA is just a transfer agent (MTS receives msgs from MUA or another MTA)
- Based on the message header, it determines how a message has to be fwd …
See rest of slide
Mail Delivery Agent:
- The MDA receives the inbound (see rest)
SMTP AND POP:
See slide
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SMTP Commands:
HELO
EHLO
MAIL FROM
RCPT TO
DATA
FTP:
Uses TCP 20 (for downloading and uploading on internet
21 is for control traffic search
DHCP uses UDP ports 67 (server) and 68 (client)
Preferred on large LANs (see slide)
DHCP Process
- I need this address (broadcast)
- I have this one avlble (said from many servers)
- Thanks but I’ll use this one
- Acknowledge the lease is finalized (provided that IP address is still valid)
(Default is one day … CISCO is 1 month) at the end, it goes back to the server
or you can renew it.
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File sharing Services:
SMB (Server Message Block) --- see slide
SMB Protocol:
- All SMB messages share a common format
- - a fixed sized header … (see slide)
P2P:
Based on Gnutella protocol
-Gnutella – compatible client software allows users to connect to Gnutella svcs over
the internet to locate and access resources shared by other Gnutella peers
-BearShare, Gnucleus, LimeWire, Morpheous, WinMX and Xolox
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Gnutella Protocol:
All share using another resource to access yours. (See slide)
Telnet:
-Uses Port 23
-Text based terminals over the network
-A connection using Telnet is called VTY (
-TELNET IS NOT SAFE BECAUSE IT IS NOT ENCRYPTED
-Telnet runs service called Telnet Daemon