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Lecture CCNA Exploration 4.0 (Kỳ 1) - Chapter 5: OSI Network Layer

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Identify the role of the Network Layer, as it describes communication from one end device to another end device; Examine the most common Network Layer protocol, Internet Protocol (IP), and its features for providing connectionless and best-effort service;... Inviting you to refer.

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Nội dung Text: Lecture CCNA Exploration 4.0 (Kỳ 1) - Chapter 5: OSI Network Layer

Network Fundamentals – Chapter 5 OSI Network Layer CCNA Exploration version 4.0
Objectives • Identify the role of the Network Layer, as it describes communication from one end device to another end device • Examine the most common Network Layer protocol, Internet Protocol (IP), and its features for providing connectionless and best-effort service • Understand the principles used to guide the division or grouping of devices into networks • Understand the hierarchical addressing of devices and how this allows communication between networks • Understand the fundamentals of routes, next hop addresses and packet forwarding to a destination network Học viện mạng Bách Khoa - Website: www.bkacad.com 2
Introduction End-to-End connections Host-to-Host Học viện mạng Bách Khoa - Website: www.bkacad.com 3
Introduction • The protocols of the OSI model Network layer specify: – addressing and processes that enable Transport layer data to be packaged and transported. • The Network layer encapsulation allows its contents to be passed to the destination within a network or on another network with minimum overhead. Học viện mạng Bách Khoa - Website: www.bkacad.com 4
Introduction IPv4 IPv4 addresses are 32 bits long, written in dotted decimal, and separated by periods. Học viện mạng Bách Khoa - Website: www.bkacad.com 5
Network Layer – Communication from Host to Host 5.1.1.1 • The Network layer, or OSI Layer 3, provides services to exchange the individual pieces of data over the network between identified end devices. Học viện mạng Bách Khoa - Website: www.bkacad.com 6
Network Layer – Communication from Host to Host Layer 3 uses 4 basic processes: 1.Addressing 2.Encapsulation 3.Routing Communication between The role of the networks router isrouting is called to select paths for and direct packets toward their destination. This process is known as routing. 4.Decapsulation Học viện mạng Bách Khoa - Website: www.bkacad.com 7
Network Layer – Communication from Host to Host • Each route that a packet takes to reach the next device is called a hop. • As the packet is forwarded, its contents (the Transport layer PDU), remain intact until the destination host is reached. Học viện mạng Bách Khoa - Website: www.bkacad.com 8
Network Layer – Communication from Host to Host Compare role between Layer 3,4 • Transport layer (OSI Layer 4): manages the data transport between the processes running on each end host • Network layer (OSI Layer 3): specify the packet structure and processing used to carry the data from one host to another host Học viện mạng Bách Khoa - Website: www.bkacad.com 9
Network Layer – Communication from Host to Host Học viện mạng Bách Khoa - Website: www.bkacad.com 10
Network Layer – Communication from Host to Host Học viện mạng Bách Khoa - Website: www.bkacad.com 11
Network Layer Protocols • Internet Protocol version 4 (IPv4) • Internet Protocol version 6 (IPv6) • Novell Internetwork Packet Exchange (IPX) • AppleTalk • Connectionless Network Service (CLNS/DECNet) Học viện mạng Bách Khoa - Website: www.bkacad.com 12
The IPv4 Protocol – Example Network Layer Protocol • The Internet Protocol 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. • The protocol was not designed to track and manage the flow of packets. Học viện mạng Bách Khoa - Website: www.bkacad.com 13
The IPv4 Protocol – Example Network Layer Protocol Basic characteristics 5.1.2 Học viện mạng Bách Khoa - Website: www.bkacad.com 14
The IPv4 Protocol – Connectionless 5.1.3 Học viện mạng Bách Khoa - Website: www.bkacad.com 15
The IPv4 Protocol – Connectionless Connectionless vs. Connection-oriented Protocols? Học viện mạng Bách Khoa - Website: www.bkacad.com 16
The IPv4 Protocol – Best Effort 5.1.4 . Học viện mạng Bách Khoa - Website: www.bkacad.com 17
The IPv4 Protocol – Best Effort • Unreliable means simply that IP does not have the capability to manage, and recover from, undelivered or corrupt packets. • Since protocols at other layers can manage reliability, IP is allowed to function very efficiently at the Network layer. Học viện mạng Bách Khoa - Website: www.bkacad.com 18
Extra: Reliable vs. Best-effort Protocols Protocol: In a reliable I have the mechanism to know protocol, the if the packet is received. Receiver: receiver Sender: I confirm that confirms (ACK) I’ve sent the I’ve received packet #n. the packet #n. the packet it’s received. Example: TCP. Protocol: In a “best I do not have the mechanism to effort” or know if the packet is received. non-reliable Receiver: protocol, Sender: I keep silence the receiver I’ve sent the upon receiving keeps silent packet #n. packets. instead. Example: IP, UDP. •This is a classification of networking protocols. •“Non-reliable” does not mean inaccurately data delivery. Học viện mạng Bách Khoa - Website: www.bkacad.com 19
The IPv4 Protocol – Media Independent 5.1.5 MTU (Token Ring, Ethernet,PPP…) ? • In some cases, an intermediary device - usually a router - will need to split up a packet when forwarding it from one media to a media with a smaller MTU. This process is called fragmenting the packet or fragmentation. Học viện mạng Bách Khoa - Website: www.bkacad.com 20

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