Network Fundamentals: Ch5 - Network Layer
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This document provides an overview of the transport and network layers of the OSI model, detailing functions like end-to-end data transfer, addressing, and packet handling using protocols such as IPv4 and IPv6. It discusses key concepts like IP packet characteristics, fragmentation, and the routing of data through various network devices, particularly routers. Additionally, it emphasizes the importance of structuring large networks into smaller subnetworks for efficient communication.
Network Fundamentals: Ch5 - Network Layer
- 1. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Network Fundamentals Abdelkhalik Elsaid Mosa abdu.elsaid@yahoo.com abdelkhalik.staff.scuegypt.edu.eg
- 2. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Introduction • Transport Layer allows end-to-end transfer of application data. • Network Layer allows end-to-end device communication.
- 3. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Network Layer – Communication from host to host • Layer 3 provides services to exchange the individual pieces of data over the network between identified end devices. • To accomplish this end-to-end transport, Layer 3 uses four basic processes: 1.Addressing 2.Encapsulation 3.Routing 4.Decapsulation
- 4. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Network Layer Protocols • Routed Protocols: carry user data 1. Internet Protocol version 4(IP v4), IP v6. 2. Novell Internetwork Packet Exchange (IPX). 3. AppleTalk. 4. Connectionless Network Service (CLNS/DECNet). • Routing Protocols: direct packet to destination 1. RIP, BGP “application layer Protocols” 2. IGRP, EIGRP 3. OSPF 4. IS-IS • Other supporting protocols 1. ICMP 2. ARP
- 5. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy IP v4 Characteristics • IP v4 was designed as a protocol with low overhead. • It provides only the functions that are necessary to deliver a packet from a source to a destination over an interconnected system of networks.
- 6. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Connectionless • IP packets are sent without notifying the end host that they are coming. • Connection-oriented protocols require that control data be exchanged to establish the connection.
- 7. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Best effort «Unreliable» • Means that IP does not have the capability to manage, and recover from, undelivered or corrupt packets.
- 8. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Media Independent • IPv4 and IPv6 operate independently of the media that carry the data at lower layers of the protocol stack. • It is the responsibility of the OSI Data Link layer to take an IP packet and prepare it for transmission over the medium. • MTU: the maximum size of a packet. • The Data Link layer passes the MTU upward to the Network layer. • Intermediary device like a router usually fragments the packet
- 9. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy IP v4 Packet Header
- 10. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy IP v4 Packet Header • Version: Contains the IP version number (4) • Header Length (IHL): Specifies the size of the packet header to know where the header ends and hence data begins. • Packet Length: The entire packet size, including header and data. • Type-of-Service (TOS): reflect priority. • TTL: indicates the remaining "life" of the packet. TTL is decreased by at least one each time the packet is processed by a router. • Identification: uniquely identifies fragments of an original IP packet. • Fragment offset: identifies the order in which to place the packet fragment in the reconstruction. • MF & DF Flags • Header Checksum: used for error checking the packet header. • Protocol: Indicates the data payload type that the packet is carrying. Ex: 01 ICMP, 06 TCP, 17 UDP
- 11. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy IP Fragmentation • A router may have to fragment a packet when forwarding it from one medium to another medium that has a smaller MTU. • Packet does not get reconstructed until it reaches the host. If DF = 1, it will not fragment packet, but discards it. • Fragment Offset field and MF flag are used to reconstruct the packet at the destination host. Data = 1480 bytesIP Data = 500IP Data = 480IP IP Packet Fragments Original IP Packet IP Header = 20 bytes Data = 500IP Data = 500L2 L2
- 12. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Dividing Networks • large network should be separated into smaller networks that are interconnected. • These smaller networks are often called subnetworks or subnets.
- 13. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Grouping Hosts Geographically
- 14. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Grouping Hosts for Purpose
- 15. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Grouping Hosts for Ownership
- 16. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Layer 3 Devices Router: - Best path determination - Creating routing table - Connecting different LANs • All interfaces of the router are members in a multiple broadcast domains, and multiple collision domains. • Supports more than one technology
- 17. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy Device Parameters • IP address • Subnet Mask • Default gateway • DNS Server
- 18. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy ARP SIEMENS NIXDORF SIEMENS NIXDORF Host A Host B IP Address: 128.0.10.4 HW Address: 080020021545 ARP Reply ARP Request - Broadcast to all hosts „What is the hardware address for IP address 128.0.10.4?“ SIEMENS NIXDORF
- 19. Suez Canal University – Faculty of Computers & Informatics - Cisco Local Academy