TCP/IP Model

Question 1

TCP/IP Model (4 Layers)

Answer 1

Alternative to OSI model, more relevant for network designers

1) Network Interface (Physical, Data Link)
2) Internet (Network)
3) Transport (Transport)
4) Application (Session, Presentation, Application)

Question 2

Layer 1 (Network Interface)

Answer 2

Physical/electrical characteristics
Describes how to transmit bits across the network
Determines how interface uses network medium
Coax/Fiber/Copper
(Ethernet, Token Ring, FDDI, RS-232)

Question 3

Layer 2 (Internet)

Answer 3

Packages data into IP datagrams:
Contains source & destination IPs
Forwards datagrams between hosts across networks

Routes IP datagrams across networks
Connectivity occurs externally
(IP, ICMP, ARP, RARP)

Question 4

Layer 3 (Transport)

Answer 4

Provides communication session management between hosts
Defines level of service & status of connection used for transport
(TCP, UDP, RTP)

Question 5

Layer 4 (Application)

Answer 5

Defines TCP/IP application protocols
Defines how programs interface with the transport layer service
Layer with which the user interacts

(HTTP, TELNET, FTP, SNMP, DNS, SMTP, SSL, TLS)

Question 6

Data Transfer Over Networks: Ports

Answer 6

Port numbers can be 0 to 65,535

Well-known (reserved) ports: 0 to 1023

Ephemeral Ports: Short-lived transport port that is automatically selected from a predefined range
1024 to 65,535

Question 7

Data Transfer Over Networks: IPv4 Packets

Answer 7

Source address (IP of sender)
Destination address (IP of receiver)
IP Flags (Allows packet fragmentation)
Protocol (Is this packet using TCP or UDP?)

Question 8

TCP & UDP Headers (Size)

Answer 8

TCP Header = 20 bytes
UDP Header = 8 bytes

Question 9

GRE

Answer 9

Generic Routing Encapsulation Protocol:
A tunneling protocol (Cisco) to encapsulate a wide variety of network layer protocols inside a virtual point-to-point/multipoint link over an IP network.

Important to set a smaller MTU size on the tunnel.
No encryption