QSpiders - Dod Model
- 1. DOD MODEL
- 2. The DoD Model • The Process / Application Layer • The Host-to-Host Layer • The Internet Layer • The Network Layer
- 3. The DoD & OSI Application Application Presentation Session Transport Network Data Link Physical Host-to-Host Internet Network Access DoD Model OSI Model
- 4. Process/Application Layer • The Process / Application layer defines protocols for node-to-node application communication and also controls user- interface specification. • A vast array of protocols combine at this layer of DoD’s Model to integrate the activities and duties of upper layer of OSI. • Examples for this layer are : Telnet, FTP, TFTP, NFS, SMTP, SNMP, DNS DHCP, BootP etc.
- 5. Host-to-Host Layer • The Host-to-Host layer parallels the functions of the OSIs Transport layer • It performs the following: • Defining protocols for setting up the level of transmission service for Applications • It tackles issues like creating reliable ene-to-end communication. • It ensures the error free delivery of data • It handles packet sequencing and maintains data integrity.
- 6. Internet Layer • Internet Layer corresponds to the OSI’s Network Layer. • It performs the following: • Designating the protocols relating to the logical transmission of packets over the entire network. • It takes care of the addressing of hosts by giving them an IP address. • It handles routing of packets among multiple networks.
- 7. Network Access Layer •This layer is equivalent of the Data Link and Physical Layer of OSI model. •It performs the following • It monitors the data exchange between the host and the network. • Network Access Layer overseas hardware addressing and defines protocols for the physical transmission of the Data. Lets have a look on how TCP/IP Protocol suit relates to the DoD model layers.
- 8. TCP/IP Protocol Suit at DoD DoD Model Process / Application Host-to-Host Internet Network Access TCP/IP Protocol Suit Telnet FTP LPD SNMP X WindowNFSSMTPTFTP TCP UDP ICMP Ethernet ARP RARP IP Fast Ethernet Token Ring FDDI BootP
- 10. Common LAN Technologies • Ethernet • Token Ring • FDDI FDDI Dual Ring Token Ring
- 11. Ethernet © 1999, Cisco Systems, Inc. www.cisco.com
- 12. Introduction • Ethernet is a methodology for accessing a media • It allows all hosts on a network to share the same bandwidth of a link. • It is popular because : • It is easy to implement & Troubleshoot • It is easy to add new technologies like Fast Ethernet and Gigabit Ethernet to existing infrastructure. • Ethernet uses Data Link Layer and Physical Layer Specification • It uses something called CSMA/CD
- 13. Ethernet Operation AA BB CC DD
- 14. Ethernet Operation AA BB CC DD D Data Link Network Transport Session Presentation Application Physical
- 15. Ethernet Operation AA BB CC DD D Data Link Network Transport Session Presentation Application Physical B and C Data Link Network Transport Session Presentation Application Physical
- 16. Ethernet LANs: How do they work? • Multiple workstations are connected to a “segment” • Each station has to take turns sending traffic • All stations listen to all traffic on their segment • Stations can only send data (Ethernet Frames) when no one else is sending
- 17. Ethernet LANs: MAC Addresses • Every workstation has a Network Interface Card (NIC) • Every NIC has a unique MAC address • Stations use MAC addresses to send Ethernet Frames to a specific station 0000.0c12.3456 0000.0c12.11110000.1018.321a
- 18. Ethernet LANs: Unicast Frames • Ethernet frames contain the MAC address of the station that the frame was sent to • These are called “unicast” frames • All stations receive the Ethernet frame, but ignore the frames that are not addressed to their MAC address 0000.0c12.3456 0000.0c12.11110000.1018.321a Frame To: 0000.0c12.3456
- 19. Ethernet LANs: Broadcast Frames • Some Ethernet frames are sent to all stations • These are called “broadcast” frames • All stations process this frame 0000.0c12.3456 0000.0c12.11110000.1018.321a Frame To: FFFF.FFFF.FFFF
- 20. Flow Control Mechanism on Ethernet •CSMA/CD is the mechanism that regulates the segment •Each station listens for other traffic before they transmit PacketFrame
- 21. Ethernet Collisions • Sometimes stations transmit simultaneously • Two frames on the same segment collide • Collisions require each station to wait and resend Collision! PacketFrame PacketFrame Packe t Packe tFrame Frame
- 22. Ethernet Reliability B C DA B C DA Figure 1 Figure 2 Collision
- 23. Ethernet Reliability Collision C B C DA BA D JAMJAMJAMJAMJAM JAM
- 24. Ethernet Reliability B C DA Collision B C DA JAMJAMJAMJAMJAM JAM • Carrier sense multiple access with collision detection (CSMA/CD)
- 25. CSMA/CD • CSMA/CD stands for Carrier Sense Multiple Access / Collision Detect. • It is used by all NICs in Ethernet Networking • In this method all NICs first sense whether the cable is free or not. • If it is free the request is sent otherwise it waits.
- 26. Half Duplex Ethernet • It is defined in 802.3 Ethernet specifications • It uses only one wire pair for signals running in both direction. • CSMA/CD is used to prevent collision. • Half Duplex typically 10base T is 50-60 % efficient. (Depends on network size) • In a large 10 base T network you only get 3 to 4 MBPS at most.
- 27. Full Duplex • Full Duplex Ethernet uses two pairs of wires. • It uses Point-to-Point connection • There is no collision in Full Duplex • Full Duplex is suppose to offer 100% efficiency in both direction • Means you can get 20 MBPS in 10 MBPS or 200 MBPS in Fast Ethernet running Full Duplex.
- 28. Auto Detect Mechanism • When a Full Duplex port is powered on, it first checks with remote end and decides whether it can run on 10 or 100 MBPS. • Then it checks to see whether it can run Full duplex or half duplex. • This is called Auto Detect Mechanism.
- 29. Ethernet Addressing • Ethernet Addressing uses MAC Address • MAC addresses are burned on every NIC • It is a 48-bit address • It is written in the same format even if different LAN Technologies are used. Organizationally Unique Identifier (OUI) (Assigned by IEEE) Vender Assigned 24 bits 24 bits Ethernet Addressing using MAC Addresses
- 30. Ethernet and IEEE 802.3 • Benefits and background • Ethernet is the most popular physical layer LAN technology because it strikes a good balance between speed, cost, and ease of installation • Supports virtually all network protocols • Xerox initiated, then joined by DEC & Intel in 1980 • Revisions of Ethernet specification • Fast Ethernet (IEEE 802.3u) raises speed from 10 Mbps to 100 Mbps • Gigabit Ethernet is an extension of IEEE 802.3 which increases speeds to 1000 Mbps, or 1 Gbps
- 31. • Ethernet and IEEE 802.3 • Several framing variations exist for this common LAN technology
- 32. Ethernet Frames • Frames are used at the Data Link Layer to encapsulate packets coming down for transmission on a type of Media Access • Types of Media Access • Contention (Ethernet) • Token Passing (Token Ring or FDDI) We will be covering only “Contention”, as rest all are beyond the scope of our course.
- 33. DataSource add FCSLengthDest add Variable266 4 0000.0C xx.xxxx Vendor assigned IEEE assigned MAC Layer - 802.3 MAC SUB-LAYER Preamble Ethernet II uses “Type” here and does not use 802.2. MAC Address 8# Bytes
- 34. Ethernet Local Area Network • Ethernet was first created and implemented by a group called DIX (Digital, Intel and Xerox). • The first Ethernet specification was modified by IEEE and IEEE 802.3 was created. • This was a 10Mbps network running on co-axial, twisted pair and fiber physical media. • IEEE 802.3 was further modified by IEEE only and 802.3u (Fast Ethernet) and 802.3z (Gigabit Ethernet) was created. • 802.3u and 802.3z are specified only on twisted pair and fiber physical media.