CCNA I

SEMESTER 1

NETWORK FUNDAMENTAL

Chapter 1

- Network Elements 

• Message : what is sent
• Device : tools like router, switch, etc.
• Medium : track/lane
• Rule : regulations on the track

- Header is an additional information on the packet which control communication on the track.

- Overhead is any combination of excess or indirect computation time, memory, bandwidth, or other resources that are required to attain a particular goal.

- LAN : a set of host in the same network.

- WAN : a set of LAN.

- Modem : convert analog signal to digital signal.

- CSU/DSU(Channel Service Unit / Data Service Unit) : convert digital signal to digital signal.

- Broadband : one media is able to carry many data or services.

Service                     |   Protocol                                                                       

www                            HTTP (Hypertext Transport Protocol)

email                            SMTP (Simple Mail Transport Protocol)

Instant Message            XMPP (Extensible Messaging and Presence Protocol)

IP Telephony               SIP (Session Initiation Protocol)

Network Architecture:

1.     Fault Tolerance (Redundancy)  : Backup Track.

2.     Scalability : Planning in order to make the network efficient.

3.     QoS (Quality of Service) : Regulations which set the priority of packets. Ex : priority of Voice, Data, or Video packets.

4.     Security : To secure the filtered data.

Security Function

1.     Ensuring Confidentiality 

2.     Integrity

3.     Availability

Chapter 2

- Multiplexing : sending process (settings) many different services on the same media.

- Segmentation is a file division which is made in order to ease the delivery of files, if there is a corrupted or broken file, then redelivery is done on the broken package only so it can save the bandwidth.

Commonly, a device is divided into 2 types : 

1.     End Device : device that sends data (originating data flow). example : PC

2.     Intermediary Device : device that connects between hosts. example : router, switch.

Protocol Function : 

1.     Control data Format.

2.     Control running processes / data path.

3.     Control and solve error.

4.     Control when the path is on or off.

OSI Layers ( Open System Interconnection )

7. Application : control GUI

6. Presentation : control data format

5. Session : control communication session

4. Transport : control end to end communication / ensure that the message is delivered

3. Network : best path selection / logical addressing

2. Data Link : physical addressing / error checking

1. Physical : convert data into bit - bit into data

OSI                   |      PDU (Protocol Data Unit)

7. Application              Data

6. Presentation            Data

5. Session                   Data

4. Transport               Segment (Data + source port + dest port)

3. Network                 Packet (Segment + source IP + dest IP)

2. Data Link               Frame (Packet + source MAC + dest MAC + FCS)

1. Physical                 bit (0101)

TCP/IP 

4. Application : OSI 5.6.7

3. Transport : OSI 4

2. Internet : OSI 3

1. Network : OSI 1,2

Chapter 3

Network Models

• Client - Server : centralization, more secure, easy to manage.

• Peer to Peer : less safety but more flexible and less cost. user can become a client or server. there is no centralization point, everyone can access the data so it's less secure. we must run the same service. example : torrent.

• Hybrid : Combination between client - server and peer to peer.

- DNS (Domain Name System) : convert address domain to IP address. Port = 53. For check the DNS    use nslookup.

- DNS Hierarchical 

1.     Local DNS : there are 2 local DNS, at computer and at the network, if there is no address request on Local DNS, so DNS will search on Top Level DNS

2.     Top Level DNS : if the the address already exist, it will be saved on cache on the Local DNS, so on the next searching, only use Local DNS.

3.     Root DNS : can be used to block a website. go to system32\driver\etc find host file and write 127.0.0.1 goo*le.com. so then the website cannot be accessed.

Ports

• HTTP = 80/8080/8008 (web)
• HTTPS = 443 (HTTP with encryption)
• SMTP = 25 (send email)
• POP = 110 (get email / email office)
• FTP = 20 (file transfer), 21 (establish connection)
• DHCP = 67 (server), 68 (client)
• SMB (Server Message Block) = 445 (file sharing for windows)
• TELNET = 23 (remote access)
• SSH = 22 (remote access with encryption)

DHCP Process

Advantages and  disadvantages using DHCP

(+) Save configuration time settings

(-) less safety because the device which connected can get IP directly, so every user can access Daemon (can hear request from every user)

Application on Email

• MUA (Mail User Agent) : send message to server
• MTA (Mail Transfer Agent) : communication between server
• MDA (Mail Delivery Agent) : last post between server to destination

Server saved a file (example)

1.     Control connection : use port 21 (FTP) to establish connection

2.     Data connection : open/ file transfer port 21 to establish connection

3.     Get Data : Transfer file, DHCP server give free active IP to all host which request IP

SMB Protocol : Protocol at windows, used for data sharing, at linux named Samba.

File Sharing Function :

1.     Start and stop connection

2.     Communication between device at the network

3.     Control data sharing through network.

Chapter 4

Transport Layer : distinguish different communication with others.

Transport Layer Function :

• Communication between Application
• Dividing data
• At the destination, data will be arranged (reassembling)
• Identifying different application

TCP (Transmission Control Protocol) Characteristic : 

1.     connection oriented

2.     3-way handshake

3.     overhead

4.     reliable

5.     flow control mechanism

6.     20 bytes header size

7.     sequence number for rearranging data

UDP(Unit Data Protocol) Characteristic : 

1.     connectionless

2.     fast data delivery

3.     unreliable

4.     8 bytes header size

Port Number Range          |      Port Group         

0 - 1023                                   Well Known (contact) ports

1024 - 49151                            Registered Ports

49152 - 65535                          Private / Dynamic Ports

• Well Known : registered for service or important application
• Registered Port : for application and user process / local
• Private Port : for dynamically assign port 

IANA -> Port Numbering

IETF -> Protocol = RFC(Request for Comment)

IEEE -> Electricity

3 Way Handshake (Synchronize Process)

3 Way Handshake (Termination Process)

- Windows Size : determine size of byte sent, before ACK being given (TCP mechanism). if sending process failed , on the next sending process, windows size will be reduced.

- Flow Control : control data process appropriate with windows size. Flow control is TCP mechanism that prevent congestion / overwhelm.

Chapter 5

Routing : forward packet to destination is based on destination IP address.

IP Characteristic :

1.     Connectionless : no three-way handshake process

2.     Best Effort (unreliable) : no overhead

3.     Media Independent : independent with other media.

IPv4 Header:

1.     IP Source Address

2.     IP Destination Address

3.     Time to Live : IP mechanism, if there is false configuration, the network will not be crowded, because there are hop jump limitation (Cisco = 254 , Microsoft = 128) prevent Layer 3 Looping.

4.     ToS (Type of Service) : Protocol which indicate the priority of a packet

5.     Protocol : indicate the data, TCP or UDP.

6.     Fragment Offset : Parameter that control segmentation/ reassembly packet at the layer 3 (13 bits)

7.     Hop : the number of layer 3 devices which passed to reach the destination.

Fragment Offset Flag divided into 2 :

• More Fragment (MF) : it means, if MF configured, the packet is not the last fragment.
• Don't Fragment (DF) : it means, if DF configured, fragmentation from the packet is not allowed.

IPv4 Characteristic : 

• Consist of 3 binary numbers
• Separated every 8 bit
• Consist of network portion and host portion

Parameters on Router :

• Routing Table : place that save the database of destination IP address.
• Default Route : default destination address if the destination IP address does not exist in the routing table. 

How a Router Forward a packet

1.     When a packet arrived at router, Layer 2 encapsulation dropped, then IP destination will be checked to it's Routing table, so router will re-encapsulation layer 2, packet will be forwarded to the destination IP address (it is case when there are specific route)

2.     If specific route exists, but default route also, the steps are the same, but if the specific route does not exist, default route will be used. so specific route is the first priority on checking.

3.     If default route and specific route does not exist , the packet will be DROPPED.

-Broadcast Domain : is an area which a  broadcasted packet will be forwarded. it need layer 3 devices. the way to sum the number of broadcast domain is to calculate the number of branch router. one broadcast for per branch.

Chapter 6

The Way Delivery Process on IPv4

• Unicast (one to one)
• Multicast (one to many)
• Broadcast (one to all) : limited (in the network / local), directed (out of the network/ all)

1.     Unicast : Switch look the destination IP address and MAC, sent directly into destination, it's does not send to those which don't need. (Destination IP Server)

2.     Broadcast : Running at Hub, if you want to send, the packet will be sent into all host, but only the destination host that would response to this broadcasted packet. 

3.     Multicast : Packet will be sent to many host (group) (Destination IP Group)

Kind of IPv4 :

• Private : for local host, this kind of IP cannot be used for routing to Internet.
• Public : can be used for routing to Internet.

IPv4 Classification :

• Class A : 1.0.0.0 - 127.255.255.255           SM : 255.0.0.0
• Class B : 128.0.0.0 - 191.255.255.255       SM : 255.255.0.0
• Class C : 192.0.0.0 - 223.255.255.255       SM : 255.255.255.0
• Class D : 224.0.0.0 - 239.255.255.255     -> Multicast
• Class E : 240.0.0.0 - 255.255.255.255

IP Private (RFC 1918)

• 10.0.0.0 - 10.255.255.255
• 172.16.0.0 - 172.31.255.255
• 192.168.0.0 - 192.168.255.255

- AUTO IP / APIPA : Feature in NIC (Network Interface Card) / Ethernet, used for assign IP automatically, if there is no DHCP server.

- Loopback Address : IP that refer to it self, used for check the TCP/IP, is that running correctly?

- Subneting : Method for dividing a network into smaller network, used for the efficiency of the IP addressing.