# Compare and Contrast OSI Model Layers OSI - Open Systems Interconnection ![[OSI model.png]] 1. Physical - actual media transporting data (cant connect to the internet) - rj45, cat5, fibreoptic 2. Data Link - 3. Network - converts frames and packets, and addressing (router) 4. Transport - 5. Session - formats the packets 6. Presentation - format of packet, and rebuilds a received packet 7. Application - Use to type, what you see on screen ## Data Encapsulation and Decapsulation This happens at layer 6 (Presentation). Encapsulation is adding or (NOT) encryption and how the data is presented on the other side ## Layer 1 - Physical There is cabled and Wireless - wireless is layers 1,2,3 **Does not add headers** PHY layer features: - Physical topology and segments - Physical interface and transmission of signals - Modulation and encoding NIC converts the binary that is recieved over the network to machine language. - Layer 1, 2 Other layer 1 devices - Transceiver - repeater - hub - media converter -- like copper cabling to fiberoptic - modem ## Layer 2 - Data Link Data inside the computer from the NIC. Converts electric signals to frames (machine language), hardware addresses are being sent. Gives you **MAC address** Devices working at Layer 2: - NIC - bridge - **switch (MAC conversions)** - wireless access point ## Layer 3 - Network Houses routers, gives IP addresses. Layer 3 is super important because it gives you an **IP address**, you need this to get on the internet. DHCP, routing table, NAT, - forwarding datagrams/packets via routers using logical network addresses - Everything behind the SOHO router is the logcal network Devices: - **Router** - basic firewalls (stateless) ## Layer 4 - Transport Identify applications using port numbers. All applications that connect to the internet have a port. 65,535 ports total. The computer decides here which port to send the data on, as well as what port to receive data on. 2 separate computers communicating must be on the same port. 1024 ports are standard. like ftp, email 25, https 445, http, ssh 22, DNS 53 TLS -- transport layer security ## Upper Layers - Layer 5 - Session - establish rules for exchange of messages and sequencing - Layer 6 - Presentation - Establish data formats (such as character sets), data encapsulation / deencapsulation - encapulation is describing how the message should be packaged for transmission - Layer 7 - Application - what you see in a program ![[Pasted image 20230515094043.png]] # Configure SOHO Networks (Small office Home office) The router from the ISP at the home. (LAN) WAN scope: - businesses have these, more then 1 location connecting. SOHO router... - multifunction network appliance - Combine modem, switch, wireless access point, router, firewall - Establish a local area network and connect it the internet WAN - They are DNS, DHCP, Firewall, file transfer... They can do many many things. **Physical Layer Functions** - RJ-45 ports for cabled network connections - radio antennas for WIFI - Modem for WAN connectivity **Data Link Layer Functions** - ethernet switch (4 lan ports) - connect the RJ-45 ports - Wireless access point: - Connect stations in a wireless LAN - Connected to switch to bridge to wire and wireless segments in a single data link network - MAC hardware addresses indentify each interface **Network Layer Functions** connects us to the outside world. Gives us an IP address **Transport, application Layers, and security Functions** - Filtering between public and private zones (firewall) - application layer configures transport and security functions - Specify allow/block rulesa for IP addresses - allow/block rules for layer 4 port numbers - ACL = firewall - Authenticate access to the wireless network - Protect the SOHO router management interface ## The Internet - The public switched telephone network (PSTN) - RJ-11 (analog) - Legacy way to connect - Internet service providers (ISP) - Internet standards and authorities: - Internet Assigned Numbers and Authority (IANA) - Manages IP address allocation and namespaces - Internet Corporation for Assigned Names and Numbers (ICANN) - Regional Internet Registries (RIRs) and ISPs - Internet Engineering Taskforce (IETF) and requests for comments (RFCs) - IETF comes up with RFCs ## Hexadecimal Notation Machine language. signals over physical media is in binary. This is alpha numeric