The OSI Model (Open Systems Interconnect)
7.Application
- HTTP (Hypertext Transfer Protocol) Used for unsecured web browsing and uses TCP Port 80
- HTTPS (Hypertext Transfer Protocol Secure) Used for secured web browsing and uses TCP port 443
6.Presentation
5.Session
4.Transport-network connections – segments
Tail Drop
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Occurs when a packet is dropped when it tries to enter a queue because the queue is full
RTP (Real-time Transport Protocol)
-A Layer 4 protocol used to stream voice and video
TCP (Transport Control Protocol) Connection-Oriented Layer 4 protocol that is considered RELIABLE
UDP (User Datagram Protocol) Connectionless Layer 4 protocol that is considered UNRELIABLE
3.Network – Routers- Packets (datagrams)
2.Data Link- MAC (Media Access Control) Address – A 48-bit address ‘burned-in’ to a network
interface card (NIC) by its manufacturer – Frames –(SWITCH)
Types of Synchronization
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Isochronous: Devices look to a common external device for chocking
Asynchronous: Devices use their own internal clocks and use one or more start/stop bits
Synchronous: Clocking is shared between sender and receiver over a separate channel
1.Physical – Cables -Bits (Protocol Data Unit: The name given to data at a specific layer of the OSI
Model)
Broadband
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Different conversations can use different frequency ranges
Baseband
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One conversation uses the entire frequency range
Please Do Not Throw Sausage Pizza Away
TCP/IP Model
4.Application
- Application
- Presentation
- Session
3.Transport
2.Internet
1.Network Access
NETWORK AND TRANSPORT LAYER
Network
IP, ICMP, UDP and TCP
-IP - Router
-UDP (User Datagram Protocol)
- TCP (Transmission Control Protocol)
-ICMP – Ping (An CMP – based networking utility that can check reachability to a specified IP
address) can we ping Gateway addresses
TRANSPORT
- UDP – for Voice Tel.
- TCP-3way handshake
Headers
Layers 3 and 4
TCP Header
Source Port - Destination Port
Sequence Number
Acknowledgment Number (if the ACK flag is set)
Data Offset – Reserved – Flags - Window Size
Checksum – Urgent Pointer (if the URG flag is set)
Options (0-320 bits)
-Source Port: 16bit field that identifies the sending port
-Destination Port :16-bit Field that identifies the receiving port
-Sequence Number: 32-bit field that specifies the first sequence number if the SYN flag=1, or the
accumulated sequence number if the SYN flag=0
-Acknowledgment Number: 32-bit field that specifies the next sequence number the sender of an
ACK expects (if the ACK flag =1)
-Data Offset: 4-bit field that specifies the size of the TCP headers, with a unit of measure of 32-bit
words (the minimum value is 5, and the maximum value is 15)
-Reserved: 3-bit field reserved for future use, where each bit is set to a value of 0
-Flags: A series of nine 1-bit fields, each representing a different TCP flag (The SYN, ACK and URG
flags)
-Checksum: 15-bit field used for error -checking both the header and payload of the segment
-Urgent Pointer: 16-bit field indicating the last urgent data byte (if the URG flag=1)
-Options: A field whose size is in the range of 0-320 bits and can be used to indicate a variety of
additional TCP options
UDP Header
Source Port – Destination Port
Length – Checksum
-Source Port: 16-bit field that identifies the sending port
- Destination Port: 16-bit field that identifies the receiving port
- Length: 16-bit field that specifies the combined length of the UDP header and data
-Checksum: 16-bit field that can be used to perform error checking of the header and data (optional
for IPv4 and required for IPv6)
IPv4 Header
IPv6 Header
Maximum Transmission Unit (MTU) – The largest frame or packet that can be transmitted or
received on an interface.
Don’t Fragment (DF) Bit: A bit in an IP4 header that prevents a packet from being fragmented.
Note: IPv6 does not have a DF bit, and it uses a ‘Packet Too Big’ ICMPv6 message.
Ports and Protocols
*Well-Known Ports:0-1023 Offer well-known network services
*Registered Ports: 1024-49151 Registered with the Internet Assigned Number Authority
*Ephemeral Ports: 49152-65535 Dynamic Ports or Private Ports
Flooding – When a switch forwards a copy of a frame out all of its ports, except the port on which it
was received. We doing it when we don’t know where the destination of the MAC is!
All ports on a hub belong one collision domain!!!
Module 2: Recognizing the Pieces and Parts of a Network
Modem (Modulator/Demodulator)
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Modulates binary data into analog signals and demodulates analog signals into binary data
Carrier-Sense Multiple Access with Collision Detection (CSMA/CD)
Carrier-Sense Multiple Access with Collision Avoidance (CSMA/CA)
Flooding
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When a switch forwards a copy of a frame out all of its ports, except the port on which it
was received
Default Route
- A route that is used when a router does not have a more specific routing table entry for the
destination network.
*Directly Connected
*Statically Configured
*Dynamic Routing Protocol
*Redistributed
FULL-DUPLEX
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Allows simultaneous transmission and reception of packets on a network segment.
HALF-DUPLEX
- Allows a device on a network segment to either transmit or receive packets at any one time,
but not transmit and receive packets simultaneously
BROADCAST DOMAIN
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An area of network throughout which a broadcast can travel (subnet or a VLAN)- HUB
-All ports on a hub belong one broadcast domain – HUB
It could be even VIRTUAL LOAD BALANCER
RANSOMWARE ATTACK
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Occurs when a system contains malware (software written to be intentionally malicious),
and the user is asked to pay ransom to prevent their data from being publicly posted or
permanently encrypted.
Module 3: Describing Network Topologies
- If one link fails, other links continue to function
- Centralized device is a potential single point of failure
- Popular in modern networks
N*(n-1) / 2
5*(5-1) / 2=10
FULL MESH
PARTIAL MESH
-optimal path
-Might be Suboptimal Path
-Not Scalable
-More Scalable
-More Expensive
-Less Expensive
Token Ring
-A legacy LAN technology that used a ring topology and had bandwidth options of 4 Mbps or 16
Mbps
Fiber Distributed Data Interface (FDDI)
-A legacy LAN technology that operated at 100 Mbps and used two counter-rotating rings (to
provide fault tolerance) and used fiber optic cabling for its transmission.
Physical ring topology – we can call it circle topology.
Sets a back off timer to avoid collisions!
VPN -logical tunnel connecting the two routers.
Point – To – Multipoint Topology Variants
Two topology’s at one network -in this case point-to-point and multipoint topology.
*Infrared
*Bluetooth
More advanced tech is available.
*Cloud Base Tech.
*Offers Quality of Service.
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SD-WAN Controller - intend base networking.
The Control Plane function are decoupled from the routers and performed by the SD-WAN
Controller.
Physical WAN connections can use a wide variety of technologies (4G&5G Cellular Data,
MPLS, or Cable Modem)
SD-WAN controller can simultaneously send out appropriate configuration commands to
routers to provide consistent QoS, security, and predictable performance
Sensor: A SCADA component that detects a specific characteristic (temperature, water level,
etc.) of a system
Control: A SCADA component that can alter a condition (temperature, water level, etc.)
Remote Telemetry Unit (RTU): A SCADA component that can receive information from a
SCADA sensor and send instructions to a SCADA control
SCADA Master: A SCADA component that uses a communications network to receive
information from one or more RTUs and send instructions to those RTUs
Module 4: Understanding Network Services
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Only do unicast – this could be an issue.
Transport Mode- does not encrypt the information
Tunnel Mode – encrypt everything.
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10.0.0.1 – private IP address. 192.0.2.1- public address (set up a tunnel) so we can access
Branch A
WEB SERVICES
Common HTTP Verbs
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POST- create a new record on the web server
GET – getting a WEB page
PUT – updating an existing record
DELETE – delete a record
HTTP (Hypertext Transfer Protocol): TCP Port 80
HTTPS (HTTP Secure): TCP Port 443 – passwords, credit cards information
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PBX (Private Branch Exchange) – A privately owned phone system used in large
organizations (Key systems were privately owned phone systems for smaller
installations)
Ones the connection is established the phone 3800 connect to 1012 without the Call Agent
Laptop A wants an IP address from DHCP Server and the DHCP server will communicate with
the MAC address of laptop A (IP address of laptop A will be all 0)
The way Laptop B receive an IP is the Router is set up to have DHCP Relay Agent to allow the
packet to reach the DHCP server
Laptop B Ip will be 172.16.1.100/24
FQDN (Fully Qualified Domain Name) – A complete DNS name that uniquely identifies a host
DNS – translator between fully qualified domain names and IP addresses.
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Out off Ipv4 addresses (public)
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 API- Application Programming interface
A way for one piece of software to communicate with another piece of software
 SBI – Southbound Interfaces
 Centralized Control Plane – SDN protocol (Open Flow)
 Open Flow
 NBI – Northbound Interfaces
 RESTful APIs
 JSON – java script object notation
Session Initiation Protocol (SIP) – A Session Layer protocol responsible for setting up,
maintaining, and tearing down sessions
Real-time Transport Protocol (RTP) – A Transport Layer protocol that gets encapsulated
inside UDP segments and is used to transmit voice and video media