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Protocols

ITEC 370

George Vaughan

Franklin University

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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.

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TCP/IP and OSI ModelsTCP/IP and OSI Models (OSI-Model, n.d.) and (Tomsho, 2007)

TCP/IP Layers

PDU OSI Layers Function Devices - Apps Standards

7 Application Network process to application, Initiates or accepts a request to transfer data

Browsers, servers, Gateways

HTTP, SNMP, FTP, Telnet

6 Presentation Adds formatting, display, and encryption of information

Gateways ASCII, MPEG

Application Data

5 Session Adds communication session control information, Login/Logout

DNS, Gateways

NetBIOS

Transport Segments 4 Transport Adds End-to-end connections and reliability, re-sequencing, flow control

Gateways TCP, UDP

Network Packets 3 Network Path determination and logical addressing (IP), translates MAC address to logical address

Routers IP, ICMP, ARP, NetBEUI

LLC Frames 2 Data Link

MAC

Adds error checking and physical addressing (MAC & LLC)

Switches, Bridges, NICs

802.3, 802.11, FDDI

Link

Bits 1 Physical Media, signal and binary transmission, sends data as a bit stream

Hubs, Repeaters

10Base-T, T1, E1

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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).

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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

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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)

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TCP/IP and OSI ModelsTCP/IP and OSI Models (OSI-Model, n.d.) and (Tomsho, 2007)

TCP/IP Layers

PDU OSI Layers Function Devices - Apps Standards

7 Application Network process to application, Initiates or accepts a request to transfer data

Browsers, servers, Gateways

HTTP, SNMP, FTP, Telnet

6 Presentation Adds formatting, display, and encryption of information

Gateways ASCII, MPEG

Application Data

5 Session Adds communication session control information, Login/Logout

DNS, Gateways

NetBIOS

Transport Segments 4 Transport Adds End-to-end connections and reliability, re-sequencing, flow control

Gateways TCP, UDP

Network Packets 3 Network Path determination and logical addressing (IP), translates MAC address to logical address

Routers IP, ICMP, ARP, NetBEUI

LLC Frames 2 Data Link

MAC

Adds error checking and physical addressing (MAC & LLC)

Switches, Bridges, NICs

802.3, 802.11, FDDI

Link

Bits 1 Physical Media, signal and binary transmission, sends data as a bit stream

Hubs, Repeaters

10Base-T, T1, E1

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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.

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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)1. Computer A sends out ARP broadcast message to

all devices.2. Computer B recognizes IP address in ARP and

sends back MAC address to computer A3. Computer A now has 2 addresses necessary for

send message to computer B.

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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

1. A sends ‘Synchronize’ (SYN) message to B2. B sends ‘Synchronize Acknowledgement’ (SYN-ACK) message

back to A3. A sends a ‘Forward Acknowledgment’ (ACK) to B4. 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

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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.

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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)

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TCP/IP Application Layer Protocols

Tomsho, 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)

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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

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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).

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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.

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Class Based IP Addressing

(Cisco – IP Addressing, n.d.).

Used less frequently now, CIDR preferred

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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

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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:

Bits # of 16-bit fields Purpose Example 48 3 Public Topology Backbone Provider 16 1 Site Toplogy Business, Local ISP 64 4 Interface identifier Based on MAC address

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Other Protocol Suites

Tomsho, 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

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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