Networking Revision. TCP/IP Protocol Stack & OSI reference model. Basic Protocols. TCP/IP Model ANTHONY KAO NETWORKING FINAL EXAM SPRING 2014 REVISION

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1 Networking Revision TCP/IP Protocol Stack & OSI reference model Basic Protocols TCP/IP Model 1

2 OSI (Open Systems Interconnection) Model main purpose to aid in clearer understanding of the functions and process involved. 2

3 Layer 7: Application Layer Communication partners are identified, network capacity is assessed, determine protocol and data syntax rules to ensure effective communication with another application program in a network is possible. Layer 6: The Presentation Layer Usually part of an operating system (OS) and converts incoming and outgoing data from one presentation format to another. Layer 5: The Session Layer Coordinates and terminates conversations. Authentication and reconnection after an interruption. TCP and UDP (User Datagram Protocol) provide these services for most applications. Layer 4: The Transport Layer Manages packetization of data, delivery of data (checking for errors once it arrives). Similarly as Layer 5, TCP and UDP provide these services for most applications. TCP Features artificially created SYN and ACK in datagram (reversed when packets are exchanged). UDP is a connectionless protocol Layer 3: The Network Layer Handles addressing and routing of data. IP is the networking layer for the internet. Uses IP therefore is connectionless (No connection established before sending data packets) Layer 2: The Data-Link Layer Sets up links across the physical network, putting packets into network frames. Two sub-layers Logical Link Control Layer and Media Access Control Layer. Ethernet is the main data link layer in use. Layer 1: The Physical Layer Conveys the bit stream through the network to electrical, optical or radio level. DNS operates at the application layer, UDP operates at the transport layer, ICMP operates at the internet layer, and WLAN protocols operate at the network access layer. POST is used to check the hardware functionality of the device on bootup and does not map to any of the functions of the TCP/IP model. Why use the TCP/IP and OSI model? - Assist in protocol design (protocol operate at a specific layer) - Fosters competition because products from different vendors can work together. - Prevents changes in one layer from affecting other layers. - Common language to describe networking and capabilities. 3

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6 Port Numbers The transport layer uses an addressing scheme called port number. They identify application/application layer services that are the source of destination of data. Port Number Ranges Well Known ports: Registered ports: Private/Dynamic: DNS: Client/Server service, runs as a service itself unlike other services which use client that is an application. 6

7 When a user s application requests to connect to a remote device by name, the requesting DNS client quires one of these name servers to resolve the name to a numeric address. Stores name, address and type of record. Record Type: A an end device address NS an authoritative name server CNAME the canonical name (Fully Qualified Domain Name). Used when multiple services have the single network address but each service has its own entry in DNS. MX Mail exchange record; maps a domain name to a list of mail exchange services for that domain. Uses hierarchical system to create a name database to provide name resolution. e.g. Top level domains can be.au or.com MUA: Mail user agent is basically an client e.g. Outlook, Yahoo SMTP: Internet standard for transmission. SMTP is used to messages between servers. HELO identifies SMTP client process to the SMTP server process. EHLO Is a newer version of HELO which includes services extensions. MAIL FROM Identifies the sender. RCPT TO Identifies the recipient. DATA Identifies the recipient. POP: Post Office Protocol allows the user to retrieve the form the storage facility e.g. ISP MDA: Mail Delivery Agent stores the mail in the user s mails store i.e. it responsible for delivery of to the mailbox. MTA: Mail Transport Agent is tasked with transporting and routing s to one user to another. FTP: File Transfer Protocol requires two connection. Port 21 for commands and replies whereas port 20 is used for the actual file transfer. DHCP: Dynamic Host Configuration Protocol is a standardized protocol used on IP networks for dynamically distributing networking configuration such as IP address for interfaces and services. Assigns IP Address, then releases and renews these addresses as devices leave and re-join the network. SMB: Server Message Block is a Client/Server file sharing protocol, unlike FTP clients establish a long term connection to servers. 7

8 Identifying Address Loopback Address: The IP address is called the loopback address. Pinging this address verifies that the protocol stack on the device is working correctly without actually sending a signal over the media. Has no hardware associated with it, and it is not physically connected to a network. Global Unicast Address: Described as a public IP Address in IPv4 (routed across the whole internet). To identify an global unicast address First three bits are set to 001 Address of IPv6 is 2000::/3 ( is 2000 in hex) Next 45 bits are global routing prefix Next 16 bits are Subnet ID Last 64 bits are Interface ID Link-Local Address: Devices with only link-local addresses can communicate with other devices on the same network but not with devices on any other network. A link-local prefix has the following format: fe80::interface-id/10 8