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4 Basic Networking Technologies ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Terms you’ll need to understand: Media Access Control (MAC) addressing Ethernet 802.3 Ethernet_II Fast Ethernet Gigabit Ethernet Token Ring 802.5 Fiber Distributed Data Interface (FDDI) Copper Distributed Data Interface (CDDI) Techniques you’ll need to master: Describing layer 2 MAC addresses Working with Ethernet,Token Ring, and FDDI characteristics and limitations Carrier Sense Multiple Access with Collision Detect (CSMA/CD) Beaconing Ring insertion Ring monitor Dual homing H.323 Signaling System 7 (SS7) Realtime Transport Protocol (RTP) RTP Control Protocol (RTCP) Quality Of Service (QOS) Understanding basic multiservice theory 1 2 Chapter 4 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ This chapter concentrates on the characteristics and limitations of the different types of Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) technologies. After reviewing each of these technologies, the chapter briefly turns to voice and video communications that can be delivered over existing data net-works.These topics are called Multiservice Services by Cisco. The following CCIE blueprint objectives as determined by the Cisco Systems CCIE program are covered in this chapter: Data Link layer—MAC addressing and IEEE 802.2 standards Ethernet/Fast Ethernet/Gigabit Ethernet—Encapsulation, Carrier Sense Mul-tiple Access with Collision Detect (CSMA/CD), topology, speed, controller errors, limitations, and the IEEE 802.3 standards Token Ring—Token passing, beaconing, active monitor, ring insertion, soft and harderrors, topology, maximum transmission unit (MTU), speed, limitations FDDI/CDDI—Dual ring, encapsulation, class, redundancy, dual homing, medium (including copper and fiber), claims, station management (SMT), limitations Voice/Video—H.323, codecs, Signaling System 7 (SS7), Realtime Transport Protocol (RTP), RTP Control Protocol (RTCP), Quality Of Service (QOS) Additional information is provided for completeness and in preparation for addi-tional subjects as the CCIE program expands.We will begin by discussing what makes up a MAC address. MAC Addressing All devices that operate over a physical LAN medium require a unique address, called the Media Access Control (MAC) address.The MAC address is also some-times referred to as the physical address, burned-in address (BIA), or hardware address. A MAC address is assigned to each hardware device that connects to a LAN, such as an Ethernet NIC. In Token Ring networks, the MAC address can be set in software. In IEEE 802 networks, the Data Link Control (DLC) layer of the OSI reference model is divided into two sublayers: the Logical Link Control (LLC) layer and the Media Access Control (MAC) layer. Figure 4.1 displays the location of the LLC sublayer and the MAC sublayer in relation to the OSI model. LLC Sublayer Functions The LLC sublayer provides networks with connection or connectionless enviroments. The LLC sublayer simply sits on top of all 802.x protocols and provides a service to the Network layer. Basic Networking Technologies 3 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ OSI Model IEEE 802 Network Network Logical Link Control Data Link Media Access Control Physical Figure 4.1 IEEE 802 DLC. Using IP as an example, we know that IP is a connectionless service, but the role of the LLC sublayer is to identify that an IP packet is carried in the data portion of the frame. The IP software then looks further into the frame to locate the header information and the IP address. MAC Sublayer Functions The MAC sublayer simply provides access to the Physical layer, whether Ethernet or any other medium is in use. To allow this communcaition each device must have a unique address. To enable all devices to have a unique address or MAC address, the network interface cards have a unique MAC address located in Read Only Memory (ROM).This unique address allows communication between devices regardless of the physical medium. Let’s now describe the format of the MAC address. MAC addresses are 48 bits long, and they are expressed primarily in two formats: 0060.7015.5e4d 00-60-70-15-5e-d4 The first byte, or octet, of a MAC address also contains two reserved bits that are used to identify what destination device or devices are intended to be the recipent of the frame: I/G—Individual/Group L/G—Local/Global Layer 2 frames can be directed to one (I bit) or more devices (G bit).The Local/ Global bit defines whther the address is the burned in address or a locally as-signed address. 4 Chapter 4 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Canonical vs. Non-Canonical The IEEE refers to MAC addresses as Universal Addresses.The IEEE also specified that when the bits are sent across the Ethernet Physical layer the least significant bit is transmitted first.This is referred to as non-canonical.Token Ring is canonical, which means that the most significant bit is transmiited first. Let’s look at a simple example of sending the number 1 (decimal) across an Ethernet network.The num-ber 1 in binary is 00000001. The non-canonical format of this is 10000000. This means that on the Ethernet wire the bits 10000000 will be reversed by the receiving device back to 00000001. The majority of modern networks use a 48-bit addressing scheme or plan. MAC addresses are represented using the hexadecimal numbering system.The first 24 bits represent the manufacturer’s identification, vendor’s code, or the organiza-tion unique identifier (OUI).The next 24 bits typically provide a serial number assigned by the vendor.To illustrate, here is an example of a Cisco MAC address: 006070-155e4d In the preceding address, 00-60-70 (24 bits) identifies Cisco as the manufacturer or vendor code, and 15-5e-4d (24 bits) identifies the serial number assigned by Cisco. Manufacturers such as Cisco may have more than one OUI. For instance, Cisco Systems has more than 20 OUIs from the IEEE. Frames sent to MAC addresses can be classified as being sent to either unicast, multicast, or broadcast addresses: Unicast Frame—A frame destined for a specific device. In the destination address, a unicast frame will appear as 0xxxxxxx in the first byte. Multicast Address—A special address reserved for communication among a group of devices. For example, 1xxxxxxx in the first byte. Broadcast Address—An address destined for all devices on the wire. For ex-ample, FF-FF-FF-FF-FF-FF in the destination field indicates all devices must read the frame. Note that all frames will have their source MAC address as a single node (unicast). Ethernet, Fast Ethernet, and Gigabit Ethernet Ethernet is one of the most popular local area network (LAN) technologies used today. Ethernet can operate at three speeds: Basic Networking Technologies 5 ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ ○ Ethernet—Allows transmission speeds of 10Mbps Fast Ethernet—Allows transmission speeds of 100Mbps Gigabit Ethernet—Allows transmission speeds of 1,000Mbps 10 Gigabit Ethernet is coming soon.The networking industry has formed a coalition to make 10G a reality. Originally, Ethernet started when the Xerox Corporation released a method of allowing devices to share a common medium and communicate together.Table 4.1 shows a summary of Ethernet’s recent evolution. In this section, we’ll review the three main Ethernet types, starting with a discus-sion about traditional Ethernet. Ethernet 802.3 and Ethernet_II Ethernet has two versions available—Ethernet 802.3 and Ethernet_II.The main difference between Ethernet 802.3 and Ethernet_II can be found within the frame formats, as discussed later in this section. Original Ethernet and then the second version called Ethernet_II was jointly developed by the Digital Equip-ment Corporation, Intel, and Xerox Corporation, also know as the DIX Consor-tium. Ethernet 802.3 is the standard defined by the IEEE. The Ethernet specifications also define the frame sizes as follows: Minimum Ethernet Frame Size—64 bytes Maximum Ethernet Frame Size—1,514 bytes Table 4.1 Date 1972 1980 1982 1985 1994 1995 1998 Ethernet history. Timeline Event Work begins on Ethernet by Xerox Ethernet released Version II released by DIX (Digital, Intel, and Xerox) IEEE 802.3 Ethernet Standard is released Transmission of Ethernet over twisted pair wiring is released Fast Ethernet Gigabit Ethernet ... - tailieumienphi.vn
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