Ebook Computer network A systems approach (3rd edition) Part 1

(BQ) Part 1 book Computer network A systems approach has contents: Applications, implementing network software, performance, hardware building blocks, reliable transmission, network adaptors, switching and forwarding, switching and forwarding, bridges and LAN switches,...and other contents.

THIRD EDITION COMPUTER NETWORKS A Systems Approach The Morgan Kaufmann Series in Networking Series Editor, David Clark, M.I.T Computer Networks: A Systems Approach, 3e Larry L Peterson and Bruce S Davie Network Architecture, Analysis, and Design, 2e James D McCabe MPLS Network Management: MIBs, Tools, and Techniques Thomas D Nadeau Developing IP-Based Services: Solutions for Service Providers and Vendors Monique Morrow and Kateel Vijayananda Telecommunications Law in the Internet Age Sharon K Black Optical Networks: A Practical Perspective, 2e Rajiv Ramaswami and Kumar N Sivarajan Internet QoS: Architectures and Mechanisms Zheng Wang TCP/IP Sockets in Java: Practical Guide for Programmers Michael J Donahoo and Kenneth L Calvert TCP/IP Sockets in C: Practical Guide for Programmers Kenneth L Calvert and Michael J Donahoo Multicast Communication: Protocols, Programming, and Applications Ralph Wittmann and Martina Zitterbart MPLS: Technology and Applications Bruce Davie and Yakov Rekhter High-Performance Communication Networks, 2e Jean Walrand and Pravin Varaiya Internetworking Multimedia Jon Crowcroft, Mark Handley, and Ian Wakeman Understanding Networked Applications: A First Course David G Messerschmitt Integrated Management of Networked Systems: Concepts, Architectures, and their Operational Application Heinz-Gerd Hegering, Sebastian Abeck, and Bernhard Neumair Virtual Private Networks: Making the Right Connection Dennis Fowler Networked Applications: A Guide to the New Computing Infrastructure David G Messerschmitt Modern Cable Television Technology: Video, Voice, and Data Communications Walter Ciciora, James Farmer, and David Large Switching in IP Networks: IP Switching, Tag Switching, and Related Technologies Bruce S Davie, Paul Doolan, and Yakov Rekhter Wide Area Network Design: Concepts and Tools for Optimization Robert S Cahn Frame Relay Applications: Business and Technology Case Studies James P Cavanagh For further information on these books and for a list of forthcoming titles, please visit our website at http://www.mkp.com THIRD EDITION Larry L Peterson & Bruce S Davie COMPUTER NETWORKS A Systems Approach Senior Editor Rick Adams Publishing Services Manager Simon Crump Developmental Editor Karyn Johnson Cover Design Ross Carron Design Cover Image Vasco de Gama Bridge, Lisbon, Portugal Composition/Illustration International Typesetting and Composition Copyeditor Ken DellaPenta Proofreader Jennifer McClain Indexer Steve Rath Printer Courier Corporation Designations used by companies to distinguish their products are often claimed as trademarks or registered trademarks In all instances in which Morgan Kaufmann Publishers is aware of a claim, the product names appear in initial capital or all capital letters Readers, however, should contact the appropriate companies for more complete information regarding trademarks and registration Morgan Kaufmann Publishers An Imprint of Elsevier Science 340 Pine Street, Sixth Floor San Francisco, CA 94104-3205 www.mkp.com © 2003 by Elsevier Science (USA) All rights reserved Printed in the United States of America 07 06 05 04 03 No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means—electronic, mechanical, photocopying, or otherwise—without the prior written permission of the publisher Library of Congress Control Number: xxxxxxxxxx ISBN: 1-55860-832-X (Casebound) ISBN: 1-55860-833-8 (Paperback) This book is printed on acid-free paper To Lee Peterson and Robert Davie This Page Intentionally Left Blank F O R E W O R D David Clark Massachusetts Institute of Technology T his third edition represents another major upgrade to this classic networking book The field continues to change fast, and new concepts emerge with amazing speed This version expands its discussion of a lot of important new topics, including peer-to-peer networks, Ipv6, overlay and content distribution networks, MPLS and switching, wireless and mobile technology, and more It also contains an earlier and stronger focus on applications, which reflects the student and professional’s increased familiarity with a wide range of networked applications The book continues its tradition of giving you the facts you need to understand today’s world But it has not lost track of its larger goal, to tell you not only the facts but the why behind the facts The philosophy of the book remains the same: to be timely but timeless What this book will teach you in today’s networked world will give you the insight needed to work in tomorrow’s landscape And that is important, since there is no reason to believe that the evolution of networks is going to slow down anytime soon It is hard to remember what the world looked like only ten years ago Back then the Internet was not really a commercial reality Ten megabits per second was really fast We didn’t worry about spam and virus attacks—we left our computers unguarded and hardly worried Those times were simpler, but today may be more exciting And you better believe that tomorrow will be different from today: at least as exciting, with luck no less trustworthy, and certainly bigger, faster and filled with fresh innovation So I hope Larry and Bruce can relax for a little before they have to start the next revision Meanwhile, use this book to learn about today and get ready for tomorrow Have fun This Page Intentionally Left Blank F O R E W O R D T O T H E F I R S T E D I T I O N David Clark Massachusetts Institute of Technology T he term spaghetti code is universally understood as an insult All good computer scientists worship the god of modularity, since modularity brings many benefits, including the all-powerful benefit of not having to understand all parts of a problem at the same time in order to solve it Modularity thus plays a role in presenting ideas in a book, as well as in writing code If a book’s material is organized effectively— modularly—the reader can start at the beginning and actually make it to the end The field of network protocols is perhaps unique in that the “proper” modularity has been handed down to us in the form of an international standard: the seven-layer reference model of network protocols from the ISO This model, which reflects a layered approach to modularity, is almost universally used as a starting point for discussions of protocol organization, whether the design in question conforms to the model or deviates from it It seems obvious to organize a networking book around this layered model However, there is a peril to doing so, because the OSI model is not really successful at organizing the core concepts of networking Such basic requirements as reliability, flow control, or security can be addressed at most, if not all, of the OSI layers This fact has led to great confusion in trying to understand the reference model At times it even requires a suspension of disbelief Indeed, a book organized strictly according to a layered model has some of the attributes of spaghetti code Which brings us to this book Peterson and Davie follow the traditional layered model, but they not pretend that this model actually helps in the understanding of the big issues in networking Instead, the authors organize discussion of fundamental concepts in a way that is independent of layering Thus, after reading the book, readers will understand flow control, congestion control, reliability enhancement, data representation, and synchronization, and will separately understand the implications of addressing these issues in one or another of the traditional layers This is a timely book It looks at the important protocols in use today—especially the Internet protocols Peterson and Davie have a long involvement in and much experience with the Internet Thus their book reflects not just the theoretical issues in Exercises 359 A F Node Cost NextHop Node Cost NextHop B B A E C B B C D D C C E B D E F D E E Table 4.12 Forwarding tables for Exercise 18 A F Node Cost NextHop Node Cost NextHop B B A C C C B C D B C C E C D C F C E E Table 4.13 Forwarding tables for Exercise 19 18 Suppose we have the forwarding tables shown in Table 4.12 for nodes A and F, in a network where all links have cost Give a diagram of the smallest network consistent with these tables 19 Suppose we have the forwarding tables shown in Table 4.13 for nodes A and F, in a network where all links have cost Give a diagram of the smallest network consistent with these tables 20 For the network in Figure 4.48, suppose the forwarding tables are all established as in Exercise 15 and then the C–E link fails Give (a) the tables of A, B, D, and F after C and E have reported the news (b) the tables of A and D after their next mutual exchange (c) the table of C after A exchanges with it 360 Internetworking SubnetNumber SubnetMask NextHop 128.96.39.0 255.255.255.128 Interface 128.96.39.128 255.255.255.128 Interface 128.96.40.0 255.255.255.128 R2 192.4.153.0 255.255.255.192 R3 R4 Default Table 4.14 Routing table for Exercise 21 SubnetNumber SubnetMask NextHop 128.96.170.0 255.255.254.0 Interface 128.96.168.0 255.255.254.0 Interface 128.96.166.0 255.255.254.0 R2 128.96.164.0 255.255.252.0 R3 Default R4 Table 4.15 Routing table for Exercise 22 21 Suppose a router has built up the routing table shown in Table 4.14 The router can deliver packets directly over interfaces and 1, or it can forward packets to routers R2, R3, or R4 Describe what the router does with a packet addressed to each of the following destinations: (a) 128.96.39.10 (b) 128.96.40.12 (c) 128.96.40.151 (d) 192.4.153.17 (e) 192.4.153.90 22 Suppose a router has built up the routing table shown in Table 4.15 The router can deliver packets directly over interfaces and 1, or it can forward packets to routers R2, R3, or R4 Assume the router does the longest prefix match Describe Exercises E 361 A B Figure 4.50 Simple network for Exercise 23 what the router does with a packet addressed to each of the following destinations: (a) 128.96.171.92 (b) 128.96.167.151 (c) 128.96.163.151 (d) 128.96.169.192 (e) 128.96.165.121 23 Consider the simple network in Figure 4.50, in which A and B exchange distancevector routing information All links have cost Suppose the A–E link fails (a) Give a sequence of routing table updates that leads to a routing loop between A and B (b) Estimate the probability of the scenario in (a), assuming A and B send out routing updates at random times, each at the same average rate (c) Estimate the probability of a loop forming if A broadcasts an updated report within second of discovering the A–E failure, and B broadcasts every 60 seconds uniformly 24 Consider the situation involving the creation of a routing loop in the network of Figure 4.15 when the A–E link goes down List all sequences of table updates among A, B, and C, pertaining to destination E, that lead to the loop Assume that table updates are done one at a time, that the split horizon technique is observed by all participants, and that A sends its initial report of E’s unreachability to B before C You may ignore updates that don’t result in changes 25 Suppose a set of routers all use the split horizon technique; we consider here under what circumstances it makes a difference if they use poison reverse in addition (a) Show that poison reverse makes no difference in the evolution of the routing loop in the two examples described in Section 4.2.2, given that the hosts involved use split horizon (b) Suppose split horizon routers A and B somehow reach a state in which they forward traffic for a given destination X toward each other Describe how this situation will evolve with and without the use of poison reverse 362 Internetworking E A B and E A B D Figure 4.51 Networks for Exercise 26 A B F G C Figure 4.52 Network for Exercise 27 (c) Give a sequence of events that leads A and B to a looped state as in (b), even if poison reverse is used Hint: Suppose B and A connect through a very slow link They each reach X through a third node, C, and simultaneously advertise their routes to each other 26 Hold-down is another distance-vector loop-avoidance technique, whereby hosts ignore updates for a period of time until link failure news has had a chance to propagate Consider the networks in Figure 4.51, where all links have cost 1, except E–D with cost 10 Suppose that the E–A link breaks and B reports its loopforming E route to A immediately afterward (this is the false route, via A) Specify the details of a hold-down interpretation, and use this to describe the evolution of the routing loop in both networks To what extent can hold down prevent the loop in the EAB network without delaying the discovery of the alternative route in the EABD network? 27 Consider the network in Figure 4.52, using link-state routing Suppose the B–F link fails, and the following then occur in sequence: (a) Node H is added to the right side with a connection to G (b) Node D is added to the left side with a connection to C (c) A new link D–A is added The failed B–F link is now restored Describe what link-state packets will flood back and forth Assume that the initial sequence number at all nodes is 1, and Exercises 363 D 2 A E B C Figure 4.53 Network for Exercise 28 B A C D E Figure 4.54 Network for Exercise 29 A C B Figure 4.55 Network for Exercise 30 that no packets time out, and that both ends of a link use the same sequence number in their LSP for that link, greater than any sequence number either used before 28 Give the steps as in Table 4.9 in the forward search algorithm as it builds the routing database for node A in the network shown in Figure 4.53 29 Give the steps as in Table 4.9 in the forward search algorithm as it builds the routing database for node A in the network shown in Figure 4.54 30 Suppose that nodes in the network shown in Figure 4.55 participate in link-state routing, and C receives contradictory LSPs: One from A arrives claiming the A–B link is down, but one from B arrives claiming the A–B link is up (a) How could this happen? (b) What should C do? What can C expect? Do not assume that LSPs contain any synchronized timestamp 364 Internetworking A Provider P Provider Q B Provider R Figure 4.56 Network for Exercise 31 31 Consider the network shown in Figure 4.56, in which horizontal lines represent transit providers and numbered vertical lines are interprovider links (a) How many routes to P could provider Q’s BGP speakers receive? (b) Suppose Q and P adopt the policy that outbound traffic is routed to the closest link to the destination’s provider, thus minimizing their own cost What paths will traffic from host A to host B and from host B to host A take? (c) What could Q to have the B−→A traffic use the closer link 1? (d) What could Q to have the B−→A traffic pass through R? 32 Give an example of an arrangement of routers grouped into autonomous systems so that the path with the fewest hops from a point A to another point B crosses the same AS twice Explain what BGP would with this situation 33 Let A be the number of autonomous systems on the Internet, and let D (for diameter) be the maximum AS path length (a) Give a connectivity model for which D is of order log A and another for which √ D is of order A (b) Assuming each AS number is bytes and each network number is bytes, give an estimate for the amount of data a BGP speaker must receive to keep track of the AS path to every network Express your answer in terms of A, D, and the number of networks N 34 Suppose IP routers learned about IP networks and subnets the way Ethernet learning bridges learn about hosts: by noting the appearance of new ones and the interface by which they arrive Compare this with existing distance-vector router learning (a) for a leaf site with a single attachment to the Internet, and (b) for internal use at an organization that did not connect to the Internet Exercises 365 A C R1 RB R2 Rest of Internet D B Figure 4.57 Site for Exercise 39 Assume that routers only receive new-network notices from other routers, and that the originating routers receive their IP network information via configuration 35 IP hosts that are not designated routers are required to drop packets misaddressed to them, even if they would otherwise be able to forward them correctly In the absence of this requirement, what would happen if a packet addressed to IP address A were inadvertently broadcast at the link layer? What other justifications for this requirement can you think of? 36 Read the man page or other documentation for the Unix/Windows utility netstat Use netstat to display the current IP routing table on your host Explain the purpose of each entry What is the practical minimum number of entries? 37 Use the Unix utility traceroute (Windows tracert) to determine how many hops it is from your host to other hosts in the Internet (e.g., cs.princeton.edu or www.cisco.com) How many routers you traverse just to get out of your local site? Read the man page or other documentation for traceroute and explain how it is implemented 38 What will happen if traceroute is used to find the path to an unassigned address? Does it matter if the network portion or only the host portion is unassigned? 39 A site is shown in Figure 4.57 R1 and R2 are routers; R2 connects to the outside world Individual LANs are Ethernets RB is a bridge router; it routes traffic addressed to it and acts as a bridge for other traffic Subnetting is used inside the site; ARP is used on each subnet Unfortunately, host A has been misconfigured and doesn’t use subnets Which of B, C, D can A reach? 366 Internetworking C A B Figure 4.58 Network for Exercise 41 40 An organization has a class C network 200.1.1 and wants to form subnets for four departments, with hosts as follows: A 72 hosts B 35 hosts C 20 hosts D 18 hosts There are 145 hosts in all (a) Give a possible arrangement of subnet masks to make this possible (b) Suggest what the organization might if department D grows to 34 hosts 41 Suppose hosts A and B are on an Ethernet LAN with class C IP network address 200.0.0 It is desired to attach a host C to the network via a direct connection to B (see Figure 4.58) Explain how to this with subnets; give sample subnet assignments Assume that an additional network address is not available What does this to the size of the Ethernet LAN? 42 An alternative method for connecting host C in Exercise 41 is to use proxy ARP and routing: B agrees to route traffic to and from C and also answers ARP queries for C received over the Ethernet (a) Give all packets sent, with physical addresses, as A uses ARP to locate and then send one packet to C (b) Give B’s routing table What peculiarity must it contain? 43 Propose a plausible addressing plan for IPv6 that runs out of bits Specifically, provide a diagram such as Figure 4.33, perhaps with additional ID fields, that adds up to more than 128 bits, together with plausible justifications for the size of each field You may assume fields are divided on byte boundaries and that Exercises 367 NetMaskLength NextHop C4.50.0.0/12 A C4.5E.10.0/20 B C4.60.0.0/12 C C4.68.0.0/14 D 80.0.0.0/1 E 40.0.0.0/2 F 00.0.0.0/2 G Table 4.16 Routing table for Exercise 45 the InterfaceID is 64 bits Hint: Consider fields that would approach maximum allocation only under unusual circumstances Can you this if the InterfaceID is 48 bits? 44 Suppose two subnets share the same physical LAN; hosts on each subnet will see the other subnet’s broadcast packets (a) How will DHCP fare if two servers, one for each subnet, coexist on the shared LAN? What problems might [do!] arise? (b) Will ARP be affected by such sharing? 45 Table 4.16 is a routing table using CIDR Address bytes are in hexadecimal The notation “/12” in C4.50.0.0/12 denotes a netmask with 12 leading bits, that is, FF.F0.0.0 Note that the last three entries cover every address and thus serve in lieu of a default route State to what next hop the following will be delivered (a) C4.5E.13.87 (b) C4.5E.22.09 (c) C3.41.80.02 (d) 5E.43.91.12 (e) C4.6D.31.2E (f) C4.6B.31.2E 368 Internetworking NetMaskLength NextHop C4.5E.2.0/23 A C4.5E.4.0/22 B C4.5E.C0.0/19 C C4.5E.40.0/18 D C4.4C.0.0/14 E C0.0.0.0/2 F 80.0.0.0/1 G Table 4.17 Routing table for Exercise 46 46 Table 4.17 is a routing table using CIDR Address bytes are in hexadecimal The notation “/12” in C4.50.0.0/12 denotes a netmask with 12 leading bits, that is, FF.F0.0.0 State to what next hop the following will be delivered: (a) C4.4B.31.2E (b) C4.5E.05.09 (c) C4.4D.31.2E (d) C4.5E.03.87 (e) C4.5E.7F.12 (f) C4.5E.D1.02 47 Suppose P, Q, and R are network service providers, with respective CIDR address allocations (using the notation of Exercise 45) C1.0.0.0/8, C2.0.0.0/8, and C3.0.0.0/8 Each provider’s customers initially receive address allocations that are a subset of the provider’s P has the following customers: PA, with allocation C1.A3.0.0/16, and PB, with allocation C1.B0.0.0/12 Q has the following customers: QA, with allocation C2.0A.10.0/20, and QB, with allocation C2.0B.0.0/16 Assume there are no other providers or customers Exercises 369 (a) Give routing tables for P, Q, and R, assuming each provider connects to both of the others (b) Now assume P is connected to Q and Q is connected to R, but P and R are not directly connected Give tables for P and R (c) Suppose customer PA acquires a direct link to Q, and QA acquires a direct link to P, in addition to existing links Give tables for P and Q, ignoring R 48 In the previous problem, assume each provider connects to both others Suppose customer PA switches to provider Q and customer QB switches to provider R Use the CIDR longest match rule to give routing tables for all three providers that allow PA and QB to switch without renumbering 49 Suppose most of the Internet uses some form of geographical addressing, but that a large international organization has a single IP network address and routes its internal traffic over its own links (a) Explain the routing inefficiency for the organization’s inbound traffic inherent in this situation (b) Explain how the organization might solve this problem for outbound traffic (c) For your method above to work for inbound traffic, what would have to happen? (d) Suppose the large organization now changes its addressing to separate geographical addresses for each office What will its internal routing structure have to look like if internal traffic is still to be routed internally? 50 The telephone system uses geographical addressing Why you think this wasn’t adopted as a matter of course by the Internet? 51 Suppose a site A is multihomed, in that it has two Internet connections from two different providers, P and Q Provider-based addressing as in Exercise 47 is used, and A takes its address assignment from P Q has a CIDR longest match routing entry for A (a) Describe what inbound traffic might flow on the A–Q connection Consider cases where Q does and does not advertise A to the world using BGP (b) What is the minimum advertising of its route to A that Q must in order for all inbound traffic to reach A via Q if the P–A link breaks? (c) What problems must be overcome if A is to use both links for its outbound traffic? 370 Internetworking 52 An ISP with a class B address is working with a new company to allocate it a portion of address space based on CIDR The new company needs IP addresses for machines in three divisions of its corporate network: Engineering, Marketing, and Sales These divisions plan to grow as follows: Engineering has machines as of the start of year and intends to add machine every week; Marketing will never need more than 16 machines; and Sales needs machine for every two clients As of the start of year 1, the company has no clients, but the sales model indicates that by the start of year 2, the company will have six clients and each week thereafter gets one new client with probability 60%, loses one client with probability 20%, or maintains the same number with probability 20% (a) What address range would be required to support the company’s growth plans for at least seven years if marketing uses all 16 of its addresses and the sales and engineering plans behave as expected? (b) How long would this address assignment last? At the time when the company runs out of address space, how would the addresses be assigned to the three groups? (c) If CIDR addressing were not available for the seven-year plan, what options would the new company have in terms of getting address space? 53 Propose a lookup algorithm for a CIDR fowarding table that does not require a linear search of the entire table to find the longest match 54 Suppose a network N within a larger organization A acquires its own direct connection to an Internet service provider, in addition to an existing connection via A Let R1 be the router connecting N to its own provider, and let R2 be the router connecting N to the rest of A (a) Assuming N remains a subnet of A, how should R1 and R2 be configured? What limitations would still exist with N’s use of its separate connection? Would A be prevented from using N’s connection? Specify your configuration in terms of what R1 and R2 should advertise, and with what paths Assume a BGP-like mechanism is available (b) Now suppose N gets its own network number; how does this change your answer in (a)? (c) Describe a router configuration that would allow A to use N’s link when its own link is down Exercises 371 R1 R2 R3 D R4 R5 R7 R6 E Figure 4.59 Example internet for Exercise 55 55 Consider the example internet shown in Figure 4.59, in which sources D and E send packets to multicast group G, whose members are shaded in gray Show the shortest-path multicast trees for each source 56 Consider the example internet shown in Figure 4.60 in which sources S1 and S2 send packets to multicast group G, whose members are shaded in gray Show the shortest-path multicast trees for each source 57 Suppose host A is sending to a multicast group; the recipients are leaf nodes of a tree rooted at A with depth N and with each nonleaf node having k children; there are thus kN recipients (a) How many individual link transmissions are involved if A sends a multicast message to all recipients? 372 Internetworking R8 R1 R7 S1 R2 R6 S2 R4 R5 Figure 4.60 Example network for Exercise 56 (b) How many individual link transmissions are involved if A sends unicast messages to each individual recipient? (c) Suppose A sends to all recipients, but some messages are lost and retransmission is necessary Unicast retransmissions to what fraction of the recipients is equivalent, in terms of individual link transmissions, to a multicast retransmission to all recipients? 58 Determine whether or not the following IPv6 address notations are correct (a) ::0F53:6382:AB00:67DB:BB27:7332 (b) 7803:42F2:::88EC:D4BA:B75D:11CD (c) ::4BA8:95CC::DB97:4EAB (d) 74DC::02BA (e) ::00FF:128.112.92.116 Exercises 373 59 Determine if your site is connected to the MBone If so, investigate and experiment with any MBone tools, such as sdr, vat, and vic 60 MPLS labels are usually 20 bits long Explain why this provides enough labels when MPLS is used for destination-based forwarding 61 MPLS has sometimes been claimed to improve router performance Explain why this might be true, and suggest reasons why in practice this may not be the case 62 Assume that it takes 32 bits to carry each MPLS label that is added to a packet when the “shim” header of Figure 4.42(b) is used (a) How many additional bytes are needed to tunnel a packet using the MPLS techniques described in Section 4.5.3? (b) How many additional bytes are needed, at a minimum, to tunnel a packet using an additional IP header as described in Section 4.1.8? (c) Calculate the efficiency of bandwidth usage for each of the two tunneling approaches when the average packet size is 300 bytes Repeat for 64-byte packets Bandwidth efficiency is defined as (payload bytes carried) ÷ (total bytes carried) 63 RFC 791 describes the Internet Protocol and includes two options for source routing Describe three disadvantages of using IP source route options compared to using MPLS for explicit routing (Hint: The IP header including options may be at most 15 words long.) ... Morrow and Kateel Vijayananda Telecommunications Law in the Internet Age Sharon K Black Optical Networks: A Practical Perspective, 2e Rajiv Ramaswami and Kumar N Sivarajan Internet QoS: Architectures... High-Performance Communication Networks, 2e Jean Walrand and Pravin Varaiya Internetworking Multimedia Jon Crowcroft, Mark Handley, and Ian Wakeman Understanding Networked Applications: A First Course David... EDITION COMPUTER NETWORKS A Systems Approach The Morgan Kaufmann Series in Networking Series Editor, David Clark, M.I.T Computer Networks: A Systems Approach, 3e Larry L Peterson and Bruce S Davie Network