Network Tanenbaum.pdf - Free download Ebook, Handbook, Textbook, User Guide PDF files on the internet quickly and easily. Download with Google Download with Facebook or download with email. Redes de Computadores Andrew Tanenbaum 4ed pt br com figuras. Redes de Computadores Andrew Tanenbaum 4ed pt br com figuras.
OSI model by layer |
---|
|
|
In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers.[1]
Functions[edit]
The network layer provides the means of transferring variable-length network packets from a source to a destination host via one or more networks. Within the service layering semantics of the OSI network architecture, the network layer responds to service requests from the transport layer and issues service requests to the data link layer.
Functions of the network layer include:
- Connectionless communication
- For example, IP is connectionless, in that a data packet can travel from a sender to a recipient without the recipient having to send an acknowledgement. Connection-oriented protocols exist at other, higher layers of the OSI model.
- Host addressing
- Every host in the network must have a unique address that determines where it is. This address is normally assigned from a hierarchical system. For example, you can be :
- 'Fred Murphy' to people in your house,
- 'Fred Murphy, 1 Main Street' to Dubliners,
- 'Fred Murphy, 1 Main Street, Dublin' to people in Ireland,
- 'Fred Murphy, 1 Main Street, Dublin, Ireland' to people anywhere in the world.
- On the Internet, addresses are known as IP addresses (Internet Protocol).
- Message forwarding
- Since many networks are partitioned into subnetworks and connect to other networks for wide-area communications, networks use specialized hosts, called gateways or routers, to forward packets between networks.
Relation to TCP/IP model[edit]
The TCP/IP model describes the protocols used by the Internet.[2] The TCP/IP model has a layer called the Internet layer, located above the link layer. In many textbooks and other secondary references, the TCP/IP Internet layer is equated with the OSI network layer. However, this comparison is misleading, as the allowed characteristics of protocols (e.g., whether they are connection-oriented or connection-less) placed into these layers are different in the two models.[citation needed] The TCP/IP Internet layer is in fact only a subset of functionality of the network layer. It describes only one type of network architecture, the Internet.[citation needed]
Protocols[edit]
The following are examples of protocols operating at the network layer.
- CLNS, Connectionless-mode Network Service
- DDP, Datagram Delivery Protocol
- EGP, Exterior Gateway Protocol
- EIGRP, Enhanced Interior Gateway Routing Protocol
- ICMP, Internet Control Message Protocol
- IGMP, Internet Group Management Protocol
- IPsec, Internet Protocol Security
- IPv4/IPv6, Internet Protocol
- IPX, Internetwork Packet Exchange
- OSPF, Open Shortest Path First
- PIM, Protocol Independent Multicast
- RIP, Routing Information Protocol
- WireGuard, WireGuard
References[edit]
- ^'Layer 3'. techtarget.com. Retrieved 2017-05-11.
- ^RFC 1122
- Tanenbaum, Andrew S. (2003). Computer networks. Upper Saddle River, New Jersey: Prentice Hall. ISBN0-13-066102-3.
External links[edit]
- OSI Reference Model—The ISO Model of Architecture for Open Systems Interconnection, Hubert Zimmermann, IEEE Transactions on Communications, vol. 28, no. 4, April 1980, pp. 425 – 432. (PDF-Datei; 776 kB)
Retrieved from 'https://en.wikipedia.org/w/index.php?title=Network_layer&oldid=901001186'
MODERN OPERATING SYSTEMS Third Edition
ANDREW S. TANENBAUM
Chapter 3 Memory Management
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Page Replacement Algorithms • • • • • • • •
Optimal page replacement algorithm Not recently used page replacement First-In, First-Out page replacement Second chance page replacement Clock page replacement Least recently used page replacement Working set page replacement WSClock page replacement
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Second Chance Algorithm
Figure 3-15. Operation of second chance. (a) Pages sorted in FIFO order. (b) Page list if a page fault occurs at time 20 and A has its R bit set. The numbers above the pages are their load times. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The Clock Page Replacement Algorithm
Figure 3-16. The clock page replacement algorithm. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
LRU Page Replacement Algorithm
Figure 3-17. LRU using a matrix when pages are referenced in the order 0, 1, 2, 3, 2, 1, 0, 3, 2, 3. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Simulating LRU in Software
Figure 3-18. The aging algorithm simulates LRU in software. Shown are six pages for five clock ticks. The five clock ticks are represented by (a) to (e). Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Working Set Page Replacement (1)
Figure 3-19. The working set is the set of pages used by the k most recent memory references. The function w(k, t) is the size of the working set at time t. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Working Set Page Replacement (2)
Figure 3-20. The working set algorithm. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (1)
When the hand comes all the way around to its starting point there are two cases to consider: • •
At least one write has been scheduled. No writes have been scheduled.
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (2)
Figure 3-21. Operation of the WSClock algorithm. (a) and (b) give an example of what happens when R = 1. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (3)
Figure 3-21. Operation of the WSClock algorithm. (c) and (d) give an example of R = 0. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Summary of Page Replacement Algorithms
Figure 3-22. Page replacement algorithms discussed in the text. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
ANDREW S. TANENBAUM
Chapter 3 Memory Management
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Page Replacement Algorithms • • • • • • • •
Optimal page replacement algorithm Not recently used page replacement First-In, First-Out page replacement Second chance page replacement Clock page replacement Least recently used page replacement Working set page replacement WSClock page replacement
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Second Chance Algorithm
Figure 3-15. Operation of second chance. (a) Pages sorted in FIFO order. (b) Page list if a page fault occurs at time 20 and A has its R bit set. The numbers above the pages are their load times. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The Clock Page Replacement Algorithm
Figure 3-16. The clock page replacement algorithm. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
LRU Page Replacement Algorithm
Figure 3-17. LRU using a matrix when pages are referenced in the order 0, 1, 2, 3, 2, 1, 0, 3, 2, 3. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Simulating LRU in Software
Figure 3-18. The aging algorithm simulates LRU in software. Shown are six pages for five clock ticks. The five clock ticks are represented by (a) to (e). Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Working Set Page Replacement (1)
Figure 3-19. The working set is the set of pages used by the k most recent memory references. The function w(k, t) is the size of the working set at time t. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Working Set Page Replacement (2)
Figure 3-20. The working set algorithm. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (1)
When the hand comes all the way around to its starting point there are two cases to consider: • •
At least one write has been scheduled. No writes have been scheduled.
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (2)
Figure 3-21. Operation of the WSClock algorithm. (a) and (b) give an example of what happens when R = 1. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
The WSClock Page Replacement Algorithm (3)
Figure 3-21. Operation of the WSClock algorithm. (c) and (d) give an example of R = 0. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
Summary of Page Replacement Algorithms
Figure 3-22. Page replacement algorithms discussed in the text. Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639