DOCSLIB.ORG

Classless Inter-Domain Routing

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Classless Inter-Domain Routing APPenDIx n Classless Inter-domain Routing The chapters in Part IV of the book work through the fundamentals of IPv4 addressing. However, most of the discussion about starting with a big block of addresses, and then cre- ating smaller blocks called subnets, begins with a classful network (that is, a Class A, B, or C network). A thorough understanding of how to take a classful network and subdivide it into subnets is very important, because most enterprises do exactly that: They start with some private IPv4 network, often network 10.0.0.0, and divide it into subnets. However, most enterprises also use Classless Inter-domain Routing (CIDR) with regard to the public IPv4 addresses used by the company. CIDR defines many ideas, including how an enterprise can be assigned a block of public IPv4 addresses called a classless prefix. Like Class A, B, or C networks, a CIDR classless prefix is a block of consecutive IP addresses. However, CIDR classless prefixes can be a variety of sizes—any power of 2—rather than the three sizes of classful networks based on Class A, B, and C rules. This appendix uses three major sections to introduce the topics. The first discusses the meaning and use of CIDR when a classless prefix is assigned to an enterprise. The second major section then examines subnetting of a classless prefix inside an enterprise. The chap- ter ends with a section about terminology and calculations to help you connect the terms and math you learned in Part IV with the details covered in this appendix. Foundation Topics Using CIDR Classless Prefixes Originally, classful IP networks played a big role in the design of the global Internet. The Internet relied on the idea that every computer would use a globally unique IPv4 address. To achieve that goal, the early administrators for the Internet created an administrative process. Each company, government branch, or other organization would be assigned one public IP network (a Class A, B, or C network). Only that company could use that particular Class A, B, or C network, preventing overlapping IP addresses between two companies. The one-classful-network-per-company strategy worked well as long as there were enough classful networks. However, the Internet grew, and it reached a stage where it grew very quickly, to the point that it was clear that the world would run out of IPv4 addresses. The long-term solution is to migrate from IPv4 to IPv6, with a 128-bit address. At the same time, the IETF came up with two other very useful tools to make better use of the existing IPv4 address space: NAT (as discussed in Chapter 27, “Network Address Translation”) and CIDR (as discussed in this appendix). 2 CCENT/CCNA ICND1 100-105 Official Cert Guide That original strategy of assigning each company an entire classful IP network worked well to ensure unique addresses, but the three-sizes-fits-all approach happened to waste address- es. That is, a company would receive an address block of the size of either a Class A, Class B, or Class C of size 224, 216, and 28, respectively. Sometimes those sizes matched the true needs of the company, but often those sizes did not. CIDR allows blocks of consecutive addresses—called classless prefixes—that come in sizes of powers of 2. Basically, CIDR lets us continue to assign IPv4 address so that they are unique but better match the size of the address block to the needs of each company. This first major section of this appendix discusses the ideas surrounding how the number- ing authorities assign a public CIDR classless prefix to an enterprise. First, this section explains the administrative process to assign public IP address blocks. Second, this section shows why the old methods wasted too many IPv4 addresses and why CIDR wastes fewer addresses. Then, once you know the terms and ideas, this section reviews the math that lets you better understand what a company receives when it is assigned a classless prefix. Note that the math works much like the math from Parts IV and VI in the book. The Public IPv4 Address Assignment Process and Players Originally, way back in the history of IP, the Internet Assigned Numbers Authority (IANA) performed all public address assignments. Each enterprise contacted IANA and applied for a block of public addresses. IANA then considered the request. Once approved, IANA provided some documentation. And in those days, the assigned address block was some Class A, B, or C network, with that public network number now assigned to that company. Simple enough. You can still see some of those original assignments of Class A networks listed on the IANA.org website. Just go to the site and find the IP Address Allocations link, and you will find the list. Figure N-1 shows a few of those Class A networks for perspective. General Electric AT&T Bell Labs 3.0.0.0/8 12.0.0.0/8 IBM The HP 9.0.0.0/8 Internet 15.0.0.0/8 US DoD Apple Computer 11.0.0.0/8 17.0.0.0/8 Figure n-1 Example Class A Assignments from IANA As the Internet grew in popularity, IANA changed the address assignment process, in part due to growth and in part to better support the global nature of the process. Rather than having all requests come to IANA (whose offices were and still are in the United States), IANA distributed the address assignment work around the world to five different regional organizations called Regional Internet Registries (RIR). IANA ultimately owns all the IPv4 Appendix N: Classless Inter-domain Routing 3 address spaces worldwide, but the RIRs ask IANA to allocate address blocks to the RIR. The RIR in turn assigns blocks of addresses to enterprises for them to use when connect- ing to the Internet (or further allocates addresses to Internet service providers [ISP], which in turn assign the addresses for use by their customers). Figure N-2 shows the names of the RIRs and the general flow of assignments of public IP addresses. IANA ARIN LACNIC RIPE AFRINIC APNIC ISP ISP ISP ISP ISP N Enterprise Enterprise Enterprise Enterprise Enterprise Figure n-2 IANA, RIRs, ISPs, and Organizations That Use IPv4 Addresses The figure shows the process as it normally works today. For example, ISPs can (and typi- cally do) receive the allocation of an address block from one of the RIRs. Then, the ISP can assign subsets of its address block to its customers. In the end, each enterprise can choose to apply for a block of globally unique IPv4 addresses to use; it can apply to its RIR or to any ISP that serves its geography. The need for More Granular Block Size Assignment The process shown in Figure N-2 helped to distribute the administrative effort to assign IPv4 addresses worldwide. However, the process itself did nothing to prevent the waste that occurred by assigning only Class A, B, and C address blocks. So, how did the process of using only three sizes of public IP address blocks cause waste? To understand, you need to connect a couple of points. First, recall the size of Class A, B, or C networks, as listed here. Then notice how huge the difference is between the number of addresses in each. Class A: 16,777,216 Class B: 65,536 Class C: 256 Second, focus on the fact that public addresses assigned to one company cannot be used by another. Suppose, for example, that an enterprise is assigned some Class B network. It uses 10,000 or so IPv4 addresses. What about the other 55,000 or so in that Class B network? Wasted. No other company can use them. Or imagine a company has a Class A network and uses even 1 million addresses (that would be a pretty large company). How much waste? About 15.7 million addresses. 4 CCENT/CCNA ICND1 100-105 Official Cert Guide nOTe Here is an analogy that might make the two main points more memorable. Imagine that the grocery store sold bread in loaves of two sizes: 2 slices or 1000 slices. You need more than two slices of bread, but for some reason, you are only allowed to buy one loaf— either the one with 2 slices or the loaf with 1000 slices. And they cost about the same. What do you do? You might just buy the loaf with 1000 slices, knowing that most of that bread will go to waste. CIDR attacked the problem of wasted public IP addresses with several interrelated features. Most importantly for this appendix, CIDR allowed the assignment of address blocks of any power of 2. In comparison, think of Class A, B, and C networks as address blocks of size 224, 216, and 28, respectively. CIDR defines rules for any useful power of 2. For example: ■ A company needed 1000 addresses and received an entire Class B network, wasting 64,000+ addresses. With CIDR, the company received an address block with 1024 (210) addresses, with little waste. ■ A company needed 10,000 addresses and received an entire Class B address, wasting 55,000+ addresses. With CIDR, the company received an address block with 16,384 (214) addresses, wasting about 6,000 addresses. ■ A company needed 50 addresses and received an entire Class C network, wasting about 200 addresses. With CIDR, the company received an address block with 64 (26) address- es, wasting about 14 addresses. CIDR Address Assignment These next few pages take material you should know well by now—how a Class A, B, and C network works—and contrast that with the classless prefixes defined by CIDR.
Load more

Recommended publications
  • Building a Network
    Building a network Data Communications and Computer Networks Lab EP1100 Ezzeldin Shereen Ming Zeng Peiyue Zhao Version 7.0 (2018) Department of Network and Systems Engineering School of Electrical Engineering and Computer Science KTH, Royal Institute of Technology Laboratory Manual 2 Chapter 1 Introduction 1.1 Purpose of the laboratory The main goal of this laboratory is to give you an overview of the different processes involved in building a network, such as a corporate network. You will have to plan the IP address scheme, configure and test the equipment, as well as configure several applications and servers typical of any corporate network (DNS servers for example). After you have completed the laboratory exercises, you should be familiar with the practical issues of the different concepts explained in the course, as well as with the real equipment used nowadays in computer networks. 1.2 Duties before the lab starts Students are required submit the homeworks before the lab starts. Students missing the homework submission will not be accepted to the lab. 1.2.1 Preparatory quizzes Each student has to complete two online lab entry quizzes, which can be found at the course web page. The quizzes are due on the first lab session, and the third. Their purpose is to check that you have enough theoretical knowledge of the tasks that you will perform in the lab. Since these tasks are not part of the course book, you will have to read this manual and its references carefully to pass the quizzes. 1.3 Rules of behavior in the laboratory 1.
    [Show full text]
  • An Internet Protocol (IP) Address Is a Numerical Label That Is
    Computer Communication Networks Lecture No. 5 Computer Network Lectures IP address An Internet Protocol (IP) address is a numerical label that is assigned to devices participating in a computer network, that uses the Internet Protocol for communication between its nodes. An IP address serves two principal functions: 1- host or network interface identification 2- location addressing. Its role has been characterized as follows: "A name indicates what we seek. An address indicates where it is. A route indicates how to get there." The designers of TCP/IP defined an IP address as a 32-bit number and this system, known as Internet Protocol Version 4 or IPv4, is still in use today. However, due to the enormous growth of the Internet and the resulting depletion of available addresses, a new addressing system (IPv6), using 128 bits for the address, was developed in 1995. Although IP addresses are stored as binary numbers, they are usually displayed in human-readable notations, such as 208.77.188.166 (for IPv4), and 2001:db8:0:1234:0:567:1:1 (for IPv6). The Internet Protocol also routes data packets between networks; IP addresses specify the locations of the source and destination nodes in the topology of the routing system. For this purpose, some of the bits in an IP address are used to designate a sub network. As the development of private networks raised the threat of IPv4 address exhaustion, RFC 1918 set aside a group of private address spaces that may be used by anyone on private networks. They are often used with network address translators to connect to the global public Internet.
    [Show full text]
  • Subnet Mask Notation
    Subnetting Subnetting is the process of breaking down an IP network into smaller sub- networks called “subnets.” Each subnet is a non-physical description (or ID) for a physical sub-network (usually a switched network of host containing a single router in a multi-router network). In many cases, subnets are created to serve as physical or geographical separations similar to those found between rooms, floors, buildings, or cities. There could be more than one definition for subnetting but perhaps the best explanation is that by default a network id has only one broadcast domain. Subnetting is a process of segmentation of a network id into multiple broadcast domains. Subnetting originally referred to the subdivision of a class-based network into many subnetworks, but now it generally refers to the subdivision of a CIDR block in to smaller CIDR blocks. Subnetting allows single routing entries to refer either to the larger block or to its individual constituents. This permits a single routing entry to be used though most of the Internet, more specific routes only being required for routers in the subnetted block. Most modern subnet definitions are created according to 3 main factors. These include: 1. The number of hosts that needs to exist on the subnet now and in the future. 2. The necessary security controls between networks. 3. The performance required for communications between hosts. Subnet Mask Notation There are two forms of subnet notation, standard notation and CIDR (Classless Internet Domain Routing) notation. Both versions of notation use a base address (or network address) to define the network’s starting point, such as 192.168.1.0.
    [Show full text]
  • Understand Ipv4
    LESSON 3.2 98-366 Networking Fundamentals UnderstandUnderstand IPv4IPv4 LESSON 3.2 98-366 Networking Fundamentals Lesson Overview In this lesson, you will learn about: APIPA addressing classful IP addressing and classless IP addressing gateway IPv4 local loopback IP NAT network classes reserved address ranges for local use subnetting static IP LESSON 3.2 98-366 Networking Fundamentals Anticipatory Set 1. Write the address range and broadcast address for the following subnet: Subnet: 192.168.1.128 / 255.255.255.224 Address Range? Subnet Broadcast Address? 2. Check your answer with those provided by the instructor. If it is different, review the method of how you derived the answer with your group and correct your understanding. LESSON 3.2 98-366 Networking Fundamentals IPv4 A connectionless protocol for use on packet-switched Link Layer networks like the Ethernet At the core of standards-based internetworking methods of the Internet Network addressing architecture redesign is underway via classful network design, Classless Inter-Domain Routing, and network address translation (NAT) . Microsoft Windows uses TCP/IP for IP version 4 (a networking protocol suite) to communicate over the Internet with other computers. It interacts with Windows naming services like WINS and security technologies. IPsec helps facilitate the successful and secure transfer of IP packets between computers. An IPv4 address shortage has been developing. LESSON 3.2 98-366 Networking Fundamentals Network Classes Provide a method for interacting with the network All networks have different sizes so IP address space is divided in different classes to meet different requirements. Each class fixes a boundary between the network prefix and the host within the 32-bit address.
    [Show full text]
  • Microsoft® Official Academic Course: Networking Fundamentals, Exam
    Microsoft® Official Academic Course Networking Fundamentals, Exam 98-366 VP & PUBLISHER Barry Pruett SENIOR EXECUTIVE EDITOR Jim Minatel MICROSOFT PRODUCT MANAGER Microsoft Learning SENIOR EDITORIAL ASSISTANT Devon Lewis TECHNICAL EDITOR Ron Handlon CHANNEL MARKETING MANAGER Michele Szczesniak CONTENT MANAGEMENT DIRECTOR Lisa Wojcik CONTENT MANAGER Nichole Urban PRODUCTION COORDINATOR Nicole Repasky PRODUCTION EDITOR Umamaheswari Gnanamani COVER DESIGNER Tom Nery COVER PHOTO: © shutterstock/wavebreakmedia Copyright © 2017 by John Wiley & Sons, Inc. All rights reserved. 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, recording, scanning or otherwise, except as permitted under Sections 107 or 108 of the 1976 United States Copyright Act, without either the prior written permission of the Publisher, or authorization through payment of the appropriate per-copy fee to the Copyright Clearance Center, Inc. 222 Rosewood Drive, Danvers, MA 01923, (978) 750-8400, fax (978) 646-8600. Requests to the Publisher for permission should be addressed to the Permissions Department, John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030-5774, (201) 748-6011, fax (201) 748-6008. To order books or for customer service, please call 1-800-CALL WILEY (225-5945). Microsoft, Active Directory, AppLocker, Bing, BitLocker, Hyper-V, Internet Explorer, Microsoft Intune, Microsoft Office 365, SQL Server, Visual Studio, Windows Azure, Windows, Windows PowerShell, and Windows Server are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. Other product and company names mentioned herein may be the trademarks of their respective owners. The example companies, organizations, products, domain names, e-mail addresses, logos, people, places, and events depicted herein are fictitious.
    [Show full text]
  • IP Addressing
    Introducing TCP/IP: Host Identifiers Multiple levels of naming • Highest level: human readable names • Domain names names like www.google.com • IP level: IP addresss • Two types : V4 or V6 A unified network requires a universal communication service. • Lowest level: machine addresses • Format depends on the lin,/physical layer • Many physical layers conform to the Ethernet standard • Ethernet frame includes a 6 octet source MAC address and 6 octet dst MAC address in the MAC header •In TCP/IP terminology, a Host is a computer that communicates with another computer using TCP/IP •The network between Host 1 and Host 2 can range from •directly connected by a physical cable (serial cable or USB cable). •This type of network is ‘point-to-point’ •Directly connected to the same Local Area Network (like Ethernet) •This type of network is ‘broadcast’ network- many Hosts can attach to the network. •When one Host sends, all Hosts receive. •A Host should ‘accept’ the frame only if the destination MAC address is 1)that of Host 2; 2)A broadcast (dst MAC address of all 1’s) •Indirectly connected - this means there is >1 network which implies there is a router •The Internet - implied indirectly connected. Host 1 generates frames over each link, contained in each frame is an IP datagram. •An IP network is able to deliver an IP datagram to the destination network specified in the IP header’s destination network field •A TCP/IP network is a number of autonomous networks that operate in a manner presenting a unified network to end users Host Identifiers •Host
    [Show full text]
  • Niagaraax Networking and IT Guide; Niagaraax 3.X Drivers Guide; Niagaraax SNMP Guide; Niagaraax SMS Guide
    Network Basics Technical Documents: NiagaraAX Networking and IT Guide; NiagaraAX 3.x Drivers Guide; NiagaraAX SNMP Guide; NiagaraAX SMS Guide Network Types Network Type Description LAN Local Area Networks (LANs) are typically node-to-node communications within building or facility. Ethernet over twisted pair cabling and Wi-Fi are the two most common technologies to build LANS. RS-485 multidrop LANs are common with BACnet architectures. WAN Wide Area Networks (WANs) are used where nodes are separated by large distances (ie, region-to-region). WANs are often built using private leased lines. A Virtual Private Network (VPN) is a form of WAN where the difference is the ability to use public networks rather than private leased lines (eliminates long-distance charges). The user VPN initiates a tunnel request through the Internet Service Provider (ISP). The VPN software encrypts the data, packages it in an IP packet (for compatibility with the Internet) and sends it through the tunnel, where is it is decrypted at the other end (the server). There are several tunneling protocols: IP security (IPsec), Point-to-Point Tunneling Protocol (PPTP) and Layer 2 Tunneling Protocol (L2TP). Network Architecture LAN Type Description Polling DDC Controllers cannot pass information directly to each other. Data must flow to a “Bus Supervisor” then to the controller. Typical cabling is RS-485 multi-drop LAN. Peer-to-Peer DDC Controllers are able to pass information directly to each other. Typical cabling is twisted- pair. Protocol examples are BACnet RS-485 MS/TP (Master-Slave/Token Passing) and LON. Client-Server Niagara Web Controllers (JACE) are client-server hosts where the Java, TCP/IP, Http and XML technologies that permit internet connectivity are hardware and O/S independent.
    [Show full text]
  • Computer Networks a Computer Network Consists of Two Or More
    Computer Networks A computer network consists of two or more computing devices that are connected in order to share the components of your network (its resources) and the information you store there. The most basic computer network (which consists of just two connected computers) can expand and become more usable when additional computers join and add their resources to those being shared. The first computer, yours, is commonly referred to as your local computer. It is more likely to be used as a location where you do work, a workstation, than as a storage or controlling location, a server. As more and more computers are connected to a network and share their resources, the network becomes a more powerful tool, because employees using a network with more information and more capability are able to accomplish more through those added computers or additional resources. The real power of networking computers becomes apparent if you envision your own network growing and then connecting it with other distinct networks, enabling communication and resource sharing across both networks. That is, one network can be connected to another network and become a more powerful tool because of the greater resources. Models of network Computing The three models for network computing are as follows: Centralized computing. Distributed computing. Collaborative or cooperative computing. Centralized Network Computing Model In the centralized network computing model, the clients use the resources of high-capacity servers to process information. In this model, the clients are also referred to as dumb terminals with very low or no processing capability. The clients only connect to the server and not to each other.
    [Show full text]
  • Chapter 8 Classful IP Addressing Classful IP Addressing
    8/19/2010 Chapter 8 Advanced TCP/IP Network Design Classful IP Addressing There are three basic classes of addresses known as class A, B, or C networks Classful IP Addressing Classful addresses are broken apart on octet boundaries. The first few bits of each segment address is used to denote the address class of the segment. The class ID plus network ID portions of the IP address are known as the network prefix, the network number, or the major network. 1 8/19/2010 Subnetting When IP address classes were established, networks were composed of a relatively small number of relatively expensive computers. As time went on and the PC exploded into LAN’s, the strict boundaries of the classful addressing address classes became restrictive and forced an inefficient allocation of addresses. Class C address with its limit of 254 hosts per network is too small for most organizations, while a Class B address with its limit of 65,534 hosts per subnet is too large. Subnetting Networks grew and needed to be divided or segmented in order to improve traffic flow. Routers join two separate networks. Networks that are separated by routers must have different network IDs so that the router can distinguish between them. This accelerated the depletion of IP addresses. RFC 950 RFC 950 gave users a way to subnet, or provide a third layer of organization or hierarchy between the existing network ID and the existing host ID. Since the network IDs could not be altered, the only choice was to “borrow” some of the host ID bits.
    [Show full text]
  • IP Addresses: Classful Addressing
    Chapter 4 CSC465 – Computer Networks Spring 2004 IP Addresses: Dr. J. Harrison Classful Addressing These slides were produced almost entirely from material by Behrouz Forouzan for the text “TCP/IP Protocol Suite (2nd Edition)”, McGraw Hill Publisher Classful Network Layer IP Address Space Addressing • To allow global communication, each Internet •232 = 4,294,967,296 device requires a unique identifier • Actual number much less due to self-imposed – Like unique phone number (country/area/local) restrictions • In the IP layer of TCP/IP, the ID is 32-bits • Uniquely and universally defines the connection of a host or router to the Internet • Classful addressing is one addressing mechanism of IPv4 • Classless addressing to be discussed Figure 4-1 Dotted-decimal notation Hexadecimal Notation 0111 0101 1001 0101 0001 1101 1110 1010 75 95 1D EA 0x75951DEA 1 Example 1 Change the following IP address from binary The binary, decimal, and notation to dotted-decimal notation. hexadecimal number 10000001 00001011 00001011 11101111 systems are reviewed in Appendix B. Appendix B. Solution 129.11.11.239 Example 2 Example 3 Change the following IP address from Find the error, if any, in the following IP dotted-decimal notation to binary notation. address: 111.56.45.78 111.56.045.78 Solution Solution 01101111 00111000 00101101 01001110 There are no leading zeroes in dotted-decimal notation (045). Example 3 (continued) Example 4 Find the error, if any, in the following IP Change the following IP addresses from address: binary notation to hexadecimal notation. 75.45.301.14 10000001 00001011 00001011 11101111 Solution Solution In dotted-decimal notation, 0X810B0BEF or 810B0BEF each number is less than or 16 equal to 255; 301 is outside this range.
    [Show full text]
  • Ipv4 Addressing and Subnetting V1.41 – Aaron Balchunas 1
    IPv4 Addressing and Subnetting v1.41 – Aaron Balchunas 1 - IPv4 Addressing and Subnetting - Hardware Addressing A hardware address is used to uniquely identify a host within a local network. Hardware addressing is a function of the Data-Link layer of the OSI model (Layer-2). Ethernet utilizes the 48-bit MAC address as its hardware address. The MAC address is often hardcoded on physical network interfaces, though some interfaces support changing the MAC address using special utilities. In virtualization environments, dynamically assigning MAC addresses is very common. A MAC address is most often represented in hexadecimal, using one of two accepted formats: 00:43:AB:F2:32:13 0043.ABF2.3213 The first six hexadecimal digits of a MAC address identify the manufacturer of the physical network interface. This is referred to as the OUI (Organizational Unique Identifier). The last six digits uniquely identify the host itself, and are referred to as the host ID . The MAC address has one shortcoming – it contains no hierarchy. MAC addresses provide no mechanism to create boundaries between networks. There is no method to distinguish one network from another. This lack of hierarchy poses significant difficulties to network scalability. If only Layer-2 hardware addressing existed, all hosts would technically exist on the same network. Internetworks like the Internet could not exist, as it would be impossible to separate my network from your network. Imagine if the entire Internet existed purely as a single Layer-2 switched network. Switches, as a rule, will forward a broadcast out every port. With billions of hosts on the Internet, the resulting broadcast storms would be devastating.
    [Show full text]
  • Chapter 4: Outline
    Chapter 4: outline Router two key router functions: 4.1 introduction 4.5 routing algorithms run routing algorithms/protocol (RIP, OSPF, BGP) 4.2 virtual circuit and . link state datagram networks . distance vector forwarding datagrams from incoming to outgoing link 4.3 what’s inside a router . hierarchical routing 4.4 IP: Internet Protocol 4.6 routing in the Internet . datagram format RIP . IPv4 addressing . OSPF . ICMP . BGP . IPv6 4.7 broadcast and multicast routing Network Layer 4-21 Network Layer 4-22 Router architecture overview Input port functions Main components: Line card . Input ports/Interfaces lookup, link forwarding . Switching fabric line layer switch termination protocol fabric . Output ports/Interfaces (receive) . Routing processor: (1)executing routing protocol, queueing (2)maintaining routing information, forwarding tables, etc. physical layer: bit-level reception Network layer – decentralized switching: data link layer: decapsulation, error Packet forwarding = decide which output checking, etc line to forward each packet based on packet header. queuing: if datagrams arrive faster than forwarding rate into switch fabric Network Layer 4-23 Network Layer 4-24 data link layer: Switching fabrics Output port encapsulation, physical layer: address mapping, etc bit-level forwarding Switching fabric function – transfer packets between input and output line cards datagram switch buffer link Types of switching fabric fabric layer line protocol termination . Via memory: datagram is received through input port, (send) stored
    [Show full text]