Protocols ITEC 370 George Vaughan Franklin University
Sources for Slides • Material in these slides comes primarily from course text, Guide to Networking Essentials,Tomsho, Tittel, Johnson (2007). • Other sources are cited in line and listed in reference section.
TCP/IP and OSI Models
Function of Protocols • Protocol = Rules for communication • Protocols exist for each layer of OSI model. • Some protocols span more than one layer. • Higher layer protocols are more abstract. • When protocols work together to cover multiple OSI layers, they are referred to collectively as a protocol stack (or suite).
Connectionless and Connection-Oriented Protocols • Connectionless • No guarantee of delivery • Low overhead, faster • Connections don’t have to be setup or torn down • Rely on upper layers to provide reliable communications • Connection Oriented • Reliable but slower • Receiver sends acknowledgement to indicate successful transfer • Packets are resent in event of error • Upper layers don’t have to worry about reliable transmission
Routable and Non-routable Protocols • Routable • Operate at Network layer • Support internetworks (MAN, WAN) • Example: TCP/IP • Non-Routable • Does not operate at Network layer • Useful for small LANs • Example: NetBIOS Extended User Interface (NetBEUI)
TCP/IP and OSI Models
TCP/IP Network Layer Protocols • Internet Protocol version 4 (IPv4 or IP) • Source and Destination logical addressing, routing • Connectionless • Fast but not reliable • Internet Control Message Protocol (ICMP) • Used to send error and control messages • Used by ‘Ping’ utility • Address Resolution Protocol (ARP) • Used to resolve logical (IP) address to physical (MAC) address • Can only be used for two systems in same network.
Example of TCP/IP Network Layer Protocols • Computer A needs to send a message to Computer B • Before computer A can send message, it needs the following addresses for computer B: • IP (logical address) • MAC (physical address) • Computer A sends out ARP broadcast message to all devices. • Computer B recognizes IP address in ARP and sends back MAC address to computer A • Computer A now has 2 addresses necessary for send message to computer B.
TCP/IP Transport Layer Protocols • Transmission Control Protocol (TCP) • Accepts messages of any length from upper layers • Connection-Oriented • Uses 3-way handshake to establish connection • A sends ‘Synchronize’ (SYN) message to B • B sends ‘Synchronize Acknowledgement’ (SYN-ACK) message back to A • A sends a ‘Forward Acknowledgment’ (ACK) to B • Connection between A and B is now established. • TCP is responsible for fragmenting application into segments • TCP is responsible for reassembling the application data from segments. • TCP uses Acknowledgment messages to: • Ensure that data is properly received. • Manage flow control
TCP/IP Transport Layer Protocols (Cont.) • User Datagram Protocol (UDP) • Connectionless • Faster, but less reliable than TCP • UDP itself does not segment application data • UDP does not use acknowledgements • UDP is used by some higher layer protocols such as NFS and DNS.
TCP/IP Application Layer Protocols • Domain Name System (DNS) • Name-to-Address resolution system • einstein.franklin.edu 65.24.7.3 (try ‘nslookup einstein.franklin.edu’ • Hypertext Transport Protocol • Web-pages, browsers, servers • File Transfer Protocol (FTP) • Telnet • Simple Mail Transport Protocol (SMTP)
TCP/IP Application Layer ProtocolsTomsho, Tittel, Johnson (2007) • DHCP • Detailed configuration of devices, keeping track of assigned addresses and to which machine they were assigned, etc., is difficult in large networks • DHCP was developed to make this process easier • DHCP server must be configured with a block of available IP addresses and their subnet masks • Clients must be configured to use DHCP • Broadcast request message is sent on boot • Client leases the address the server assigns to it • If no answer is received, in an APIPA-enabled OS, the computer assigns itself an address (169.254.x.x)
IP Addressing • IP addressing is responsible for routing in TCP/IP environment. • Example: 192.203.187.0 • IP address is 32 bits long (4 bytes) • Special IP addresses: • 255.255.255.255 = Broadcast • 127.xxx.xxx.xxx = Localhost • IP address is divided into 2 parts • Network Identification • Host Identification
Scope of Transmission • Hosts in same network (same Network ID) can be connected with switches/hubs • Router is required to transmit to hosts outside of network (different Network ID). • Broadcast messages can only be transmitted to hosts within same network (broadcast domain).
Types of IP Addressing • The demarcation point in the 32 bit address between network ID and host ID depends on addressing scheme: • Class Based Addressing generally uses a byte boundary as the dividing point • Classless Based Addressing uses a bit boundary.
Class Based IP Addressing (Cisco – IP Addressing, n.d.). Used less frequently now, CIDR preferred
Internet Protocol Version 6 • Limitations with IPv4 • 32 bit address space is limited • No Quality of Service (QoS) support • IPv6 Features: • Incorporates IPSec • 128 bit address • Auto-configuration • No IP address to assign • No subnet mask to determine • 2 methods of auto-configuration • Stateless • Host creates its own IP address based on router information and MAC address • Simplest and most common • Stateful • Relies on DHCP server
IPv6 Address Scheme • Hexidecimal grouped in 16 bit sections: • 2001:1b20:302:442a:110:2fea:ac4:2b • Leading zeroes are eliminated • 2 or more 16 bit fields of all zeros can be ignored: • 2001:260:0:0:0:2ed3:340:ab (long form) • 2001:260::2ed3:340:ab (short form) • IPv6 has 3 parts:
Other Protocol SuitesTomsho, Tittel, Johnson (2007) • Other protocol suites are sometimes used on older networks, where the need to change to TCP/IP is not warranted, or in environments suited to the suite’s features • NetBIOS/NetBEUI • Used primarily on older Windows networks • IPX/SPX • Designed for use on NetWare networks • AppleTalk • Used almost exclusively on Macintosh networks
References Tomsho, Tittel, Johnson (2007). Guide to Networking Essentials. Boston: Thompson Course Technology. Odom, Knott (2006). Networking Basics: CCNA 1 Companion Guide. Indianapolis: Cisco Press Wikipedia (n.d.). OSI Model. Retrieved 09/12/2006 from http://en.wikipedia.org/wiki/OSI_Model Cisco – IP Addressing (n.d.). IP Addressing. Retrieved 09/27/2006 from http://cco.cisco.com/warp/public/701/3.html#figone IANA (n.d.) Abuse Issues and IP Addresses . Retrieved 11/11/06 from http://www.iana.org/faqs/abuse-faq.htm