Network Layer

FDDI Fault Tolerance

FDDI provides a number of fault-tolerant features. In particular, FDDI's dual-ring environment, the implementation of the optical bypass switch, and dual-homing support make FDDI a resilient media technology. FDDI's primary fault-tolerant feature is the dual ring. If a station on the dual ring fails or is powered ciown, or- if the cable is damaged, the dual ring is automatically wrapped (doubled back onto itself) into a single ring. When the ring is wrapped, the dual-ring topology becomes a...

MPLSBased Layer 2 VPN

The IETF PPVPN group and the PWE3 group are working to define a framework and standards for provider-provisioned Layer 2 VPN. The L2VPN lets the service provider provide Layer 2 transport for Layer 2 services, such as Ethernet, Frame Relay, and ATM, to customers over an IP MPLS backbone. This keeps the service provider from having to maintain IP, Frame Relay, and ATM networks. It also gives service providers a feasible migration path from Frame Relay and ATM infrastructures to an MPLS-based IP...

Example 41 Cisco 3640 Router Console Output at Startup

System Bootstrap, Version 11.1(20)AA2, EARLY DEPLOYMENT RELEASE SOFTWARE (fc1) Copyright (c) 1999 by Cisco Systems, Inc. C3600 processor with 98304 Kbytes of main memory Main memory is configured to 64 bit mode with parity disabled program load complete, entry point 0x80008000, size 0xa8d168 Self decompressing the image OK Use, duplication, or disclosure by the Government is subject to restrictions as set forth in subparagraph (c) of the Commercial Computer Software - Restricted Rights clause...

Figure 552 SCSI Communication Model

FC PC SCSI Fetjric iniiiaKH Tenjer FC PC SCSI Fetjric iniiiaKH Tenjer A SAN is built from a se ries of Fibre Channel or Ethern et switeh es, networked in different topo logies to build la rger networks with higher port densities . I n Fibre Ch annel, an indivtdu al wcli is ca lled a fabnia, and a connecte d group of switches is also called a fabric. The term Ethernet fabric is often used to refer to an Ethernet network used to build an iSCSI SAN. This chapter uses the te rm fabric to reees to a...

LAN Switch and the OSI Model

LAN switches can be categorized according to the OSI layer at which they filter and forward, or switch, frames. These categories are Layer 2, Layer 2 with Layer 3 features, or multilayer. A Layer 2 LAN sw itc h is operationally similar to a multiport bridge but has a much higher capacity and supports many new features, such as full-duplex operation. A Layer 2 LAN switch performs switching and filtering based on the O SI data link layer (Layer 2) MAC address. As with bridges, it is completely...

Figure 558 Fibre Channel Frame Header Format

Data field The data field consists of the actual upper-layer protocol data. It can range from 0 to 2112 bytes. CRC The Cyclical Redundancy Check is a 4-byte field used to verify the frame's integrity. The CRC is only calculated using the frame header and the Data field. EOF The End of Fra me is a 4-byte ordered set that immediately precedes the frame content. The EOF also indicates the class of the Fibre Channel frame. The following is a brief description of each field in the Fibre Channel...

Feedback Information

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Figure 2412 Sip Uac and UAS Relationship

User agents are endpoint devices in the SIP network, such as SIP phones or gateways. More recently, other UAs hnve geen added, such as chat clients wi th SIP sup> port or even wireless phones and personal digital ass tants dPDAs). Also defined in RFC 254 are SIP senvern. They tngi cally handle one or all of the following tanks SIP sessions may be set up directly between UAs or through intermediaries, such as a SIP registrar, redirect, or proxy server. A oIP registrar server manages t he...

Mbps Ethernet10BaseT

10Base-T provides Manchester-encoded 10-Mbps bit-serial communication over two unshielded twisted-pair cables. Although the standard was designed to support transmission over common telephone cable, the more typical link configuration is to use two pair of a four-pair Category 3 or 5 cable, terminated at each NIC with a n 8-pin RJ-45 connector (the MDI), as shown in Figure 8-15c Because each active pair is configured as a simplex link where transmission is in one direction only, the 10Base-T...

OSI Model Session Layer

The session layer establishes, manages, and terminates communication sessions. Communication sessions consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated by protocols implemented at the session layer. Some examples of session-layer implementations include Zone Information Protocol (ZIP), the AppleTalk protocol that coordinates the name binding process an d Session Control Protocol...

Session Layer

DECnet OSI implements all the standard OSI session layer implementations. DECnet OSI also supports all the protocols implemented by DECnet Phase IV at the session control layer of the DNA. The primary session control layer protocol is the Session Control Protocol (SCP). The OSI session layer protocol turns the data streams provided by the lower four layers into sessions by implementing various control mechanisms. These mechanisms include accounting, conversation control, and session-parameter...

SNMPv2 Protocol Operations

The Get, GetNext, and Set operations used in SNMPvl are exactly the same as those used in SNMPv2. However, SNMPv2 adds and enhances some protocol operations. The SNMPv2 Trap operation, for example, serves the same function as that used in SNMPvl, but it uses a different message format and is designed to replace the SNMPvl Trap. SNMPv2 also defines two new protocol operations GetBulk and Inform. The NMS uses the GetBulk operation to efficiently retrieve large blocks of data, such as multiple...

ISO Hierarchy of Networks

Large networks typically are organized as hierarchies. A hierarchical organization provides such advantages as ease of management, flexibility, and a reduction in unnecessary traffic. Thus, the International Organization for Standardization (ISO) has adopted a number of terminology conventions for a dd ressing network entities. Key terms defined in this section include end system (ES), intermediate system (IS), area, and autonomous system (AS). AnES is a network device that does not perform...

Trap PDU Format

Figure 58-9 illustrates the fields of the SNMP Trap PDU. The following descriptions summarize the fields shown in Figure 58-9 e EntejpV se identifies t hie type og managed object generating the trap. Agent Address provides the address of the managed object generating the trap. Geneei c Teap Type indicates one of a number of generic trap types. Nfeec ific Ttap Code indites on e of a numlne r of sisecific trap cod es. Time amp puovide e the amount of time t hat has elapsed twee n the last network...

Figure 88 A Gigabit Frame Burst Sequence

Bursi limit 2 max mum-length frames ' FiJttenslon bils are sent during interframe gaps to ensure an uninterrupted carrier during the entire burst sequence If the length of the first frame is less than the minimum frame length, an extension field is added to extend the frame i engt h to the value indi catnci in Tnble Si- Subsequent frames i n a frameo burst se quegee d o not need eutensioa fields, an d a frame burst may continu as long as the bu est limi t hns not been reached. If the bunst Mm...

FIFO Basic Storeand Forward Capability

(n its sim est foam, FIFO queuing involves ston ng packefs wlaen the network is congested and fotwardihg sh em in o rder ol am val when t he neiwork is no longer conges ted. FIFO 1 s the default queuing algonthm in some ir-tanceS thus eequirihg no configosation , but it has seaml ahortcomi ngs. Most impDrtnntly, FI O que umg makes no decisi on about packet priority- the inader of arrival deter m1 nes r> andeedth promprnessr aod (auffei -3llocation. Not does it provide frotection against...

OSI Protocols Presentation Layer

The presentation layet im plementarion of1 the OSI otoco suite cons ists of1 a presentation protoeoi and a presentation service. The reesen tation protocol enaWes presenta tionese rvice us ers (PS -userst to communicate with the presentsrion dei'vice. A -use r is an ent i ay thae requests the services of the prese ntation laye r. Such requests wre made at inresentatioe-service access points (PSAPs). PS-users are uniquely identified by using pSAP addresses. Presentation service negotiates...

Skinny Client Control Protocol SCCP

SCCP, also referred to as Skinny, is a Cisco Systems proprietary signaling and control protocol used for call establishment, tearlown, and control in VoIP environments. It is the heart of ths Cisco AVVID solution. It is widely deployed in VoIP enterprise solutions and is increasingly supported by third- party solutions in service provider environments. It is a simple, lightweight stimulos pjotocol that is very feature-rich deployed in conjunction with Cisco IP Phones. The signaling path uses...

User Datagram Protocol

TheUser Datagram Protocol (UDP) is a connectionless transport layer protocol (Layer 4) that belongs to the Internet protocol family. UDP is basically an interface between IP and upper-layer processes. UDP protocol ports distinguish multiple applications running on a single device from one another. Unlike the TCP, UDP adds no reliability, fl ow control, or error-recovery functions to IP. Because of UDP's simplicity, UDP headers contain fewer bytes and consume less network overhead than TCP. UDP...

Internet Protocols Application Layer Protocols

The Internet protocol suite includes many application layer protocols that represent a wide variety of applications, including the following File transfer protocol (FTP) Moves files between devices Simple network management protocol (SNMP) Primarily reports anomalous network conditiens and sets network threshold values Telnet Setves as a terminal emulation protocol X windows Serves as a distributed windowing and graphics system used for communication between X terminals and UNIX workstations...

Figure 225 Cable Modem Registration Sequence

The CMTS periodically transmits upstream bandwidth allocation maps (henceforth referred to as MAP) in shared time slots in the DS direction. The CMTS assigns a temporary service identifier (SID) (typically SID o) to the CM, which begins a coarse power ranging (R1 udi ng 3 dB innrements) and time synchronization p rocess be tween i tself end the CMTS on t contention brs is us ing shared time slots . The CMTS peviddically sends keepa I ive mes oa ges to verify dink continuity between itself a nd...

DECnetOSI Transport Layer

DECnet OSI supports NSP, three standard OSI transport protocols, and the Transmission Control Protocol (TCP). DECnet OSI supports Transport Protocol classes (TP) 0, TP2, and TP4. TP0 is the simplest OSI connection-oriaated transport protocol. Of the classic transport layer functions, it performs only segmentation and reassembly. This means that TP0 will note the smallest maximum-size protocol data unit (PDU) supported by the underlying subnetworks and will break the transport packet into...

Table 85 Maximum Operating Ranges for Common Optical Fibers

62.5mm multimode fiber (200 500) MHz.km 50 mm multimode fiber (400 400) MHz.km 50 mm multimode fiber (500e500) MHz.km t1 1000Base-LX transceivers may also require use of an offset-launch, mode-conditioning patch cord when coupling to some existing multimode fibers. t1 1000Base-LX transceivers may also require use of an offset-launch, mode-conditioning patch cord when coupling to some existing multimode fibers. The operati ng ranges shown in Table 8-5 are those specified in the IEEE 802.3...

SIP Messages

T e actual formatting s ses t he syntax oA HTTP version 1.1, which is an IETF standard for message encoding. Using this format, you will notice that the SIP address URLs look a lot li Ire tne addresses yon fi np on t Ire WWW. This is not by mistake. It goes back to ease of decoding, use, and troubleshooting. If host names are used instead of IP addresses, DNS servers can be queried for name resolution. SIP messages are placed in two main groups request and...

Figure 2415 SIP UAtoSip Ua Call Flow with SIP Proxy Server

When a SIP proxy is involved with a SIP session, it has the option of turning on a feature called record route. The record route header allows the proxy server to stay in the signaling path for the sessi on as long as that se ssion is active. If the call goes through more than one proxy, each subsequen t pooxy can als o be add ed to the record route header. That way, a backw ard-trace able path to the session's orig i n exists. The last call flow involves the use of a SIP redirect server. With...

Figure 483 ISIS Routing Architecture

Generally, Level 1 routers know only th e networki ng information withi n that area. If a Level 1 router cannot route a packet using the information within the area, it sends the packet to the closest Level 2 ro uter, which then routes it to th e appropriate areai At t he destination area, the packet is then forwarder by the Level 1 routers for that area. If a Level 1 2 router is connecter to another area, it alerts the Level 1 routers in its own area by setting the attached bit in the routing...

The Ethernet Physical Layers

Because Ethernet devices implement only the bottom two layers of the OSI protocol stack, they are typically implemented as network interface cards (NICs) that plug into the host device's motherboard. The different NICs are identified by a three-part product name that is based on the physical layer att rib utes. The naming convention is a concatenation of1 three terms indicating the transmission rate, the transmission method, and the media type signal encoding. For example, consider this...

LANE Components

The LANE protocol defines the operation of a single ELAN or VLAN. Although multiple ELANs can simultaneously exist on a single ATM network, an ELAN emulates either an Ethernet or a Token Ring and consists of the following components LAIN Imulati-i client (L1C) The LEC is an entity in an end system that performs data fo rwacdingr address resolution, and registration of MAC addresses with the LAN Emulation Server (LES). The LEC also provides a standard LAN interface to higher-level protocols on...

Fibre Channel Port Types

Fibre Channel is a connection-oriented protocol in that acdes must establish a channel via a login before communicating. Communication is established between Icgical elemeats, otherwise known as pcrts, existing within physical devices. A port can be one of several types, depending on the type of physica. device and the connection topology. Port types autonegotiate depending on what device or topology they are directly connected to. However, you c an restrict the port modes that can be...

Network Integrated Caches

The first step in creating a network-integrated cache engine is to ensure that the network supports traffic localization, which can be achieved by enabling content routing technology at thn system-level, and settin g speci-ic c'rametern to optimize netwopk traffic. Clsco IOS We b Cache Commu nicpeion Protocol (WCCP) is one example of content routing technology that can be set to support traffic localization. Once the right network foundation is in place, network caches are added into strategic...

WCCP Network Cac hing

In 199)7, Cisco developed WCCP, a router-cache protocol tha t localizes network traffic and provides network-intelligent load distribution across multiple network caches for maximized download performance and con tent ava i ia bi lity. a The cache component of the Cisco caching solution comprise network-integrated caching solutions the Cisco Cache Engine 500 Series. They are netwonk-integrated because they provide netwokk manogement capabiMties already availaWe on traditional Ciseo networking...

Figure 548 Overload Bypass

The overloaded cache engine will resume accepting requests when it determines that it has the resources to do so without retriggering overload bypass in the near future. The overload bypass on off trig gers are automatically determinpd by C PU and file system load. In the extreme situation that the cache engine becomes so overloaded that it is unable to respond to the basic WCCP otatus chec k messages from its home router, tlae WCCP hom e router wMl remove the cache engine from the cluster and...

Mbps Fast Ethernet

Increasing the Ethernet transmission rate by a factor of ten over 10Base-T was not a simple task, and the effort resulted in the development of three separate physical layer standards for 100 Mbps over UTP cable 100Base-TX and 100Base-T4 in 1995, and 100Base-T2 in 1997. Each was defined wit hi different encoding requirements and a different set of media-dependent sublayers, even though there is some overlap in the link cabling. Table 8-2 compares the physical layer characteristics of 10Base-T...

RIP Stability Features

RIP prevents routing loops from continuing indefinitely by implementing a limit on the number of hops allowed in a path from the source to a destination. The maximum number of hops in a path is 15. If a router receives a routing update that contains a new or changed entry, and if increasing the metr ic value by 1 causes the metric to be infinity (that is, 16), the network destination is coxsidered unreachable. The downside of this stability feature is that it limits the maximum diameter of a...

Label Distribution Protocol

With destinat ion-based rout i ng, a router makes a forward ing deci sion based on the Layer 3 destination address carried in a packet pnd the i nforma tion stored i n FIB renin tained by the routier. A router constructs its FIB using information the router receives from routing protocols, such as OSPF and BGP. To support destination-based routing with MPLS, an LSR participates in routing protocols and constructs its LFIB using information it receives from these protocols. In this way, it...

Figure 18 The Data Link Layer Contains Two Sublayers

TheLogical Link Control (LLC) sublayer of the data link layer manages communications between devices over a Single link of a network. LLC is defined in the IEEE 802.2 specification and supports both connectionless and connection-oriented services used by higher-layer protocols. IEEE 802.2 defines a number of fields in data link layer frames that enable multiple higher-layer protocols to shate a single bhysical dat a link. The Media Access Contcol (MAC) sublayer of the data linkc layer mangges...

FRF Transmission Theory

You have rea d about the wireless system, the electromagnetic spectrum, and the common frequency bands you will likely see in a networking environment. It is now time to look at the theory behind radio communications. To understand how wireless communications work, you must understand how electromagnetic energy is generated and propagated through free space. When current passes through a piece of wire, an electric field is created, which in turn creates a magnetic field. When the current is...

Figure 284 Four Fields Remain the Same in Frame Conversion Between Ethernet Type tt 0x80D5 Format and Token Ring

Figure 28-2 illustrates the frame conversion between IEEE 802.3 and Token Ring. The destination and source addresses (DASA), service-access point (SAP), Logical Link Control (LLC) information, and data are passed to the corresponding fields of the destination frame. The destination and source address bits are reordered. When bridging from IEEE 802.3 to Token Ring, the length field of the IEEE 802.3 frame is removed. When bridging from Token Ring to IEEE 802.3, the access-control byte and the...

Apple Talk Upper Layer Protocols

AppleTalk implements services at the session, presentation, and application layers of the OSI model. Four key implementations at the session layer are included in the AppleTalk protocol suite. (The session layer establishes, manages, and terminates communication sessions between presentation laye r entities). CommunicahioT sesoione consist of service requests and service responses that occur between applications located in different network devices. These requests and responses are coordinated...

Network Switches Provide a Second and Often Better Alternative to Higher Link Speeds in Csmacd Network Upgrades

Compet i nively priced network switch es decame avail'mle om the market shortly rfrer the mid-1990s and es seprially made network repeaters obsoiet e tor i arge networkSl Althoug h repeaterf can accept inny one fra me ap a time aed thm send it to all active ports (Axcept the port on which it im being rece ivew) , sw itches are equippe d with the following MAC-based ports with I O frame buffers that effectively isolate the port from traffic being senw at the srme time to or front othef po rts o...

Routing Algorithms

Routing algorithms can be differentiated based on several key characteristics. First, the particular goals of the algorithm designer affect the operation of the resulting routing protocol. Second, various types of routing algorithms exist, and each algorithm has a different impact on network and router resources. Finally, routing algorithms use a variety of metrics that affect calculation of optimal routes. The following sections analyze these routing algorithm attributes. Routin g algorithms...

ATM Connection Management Messages

A number of connection-management message types, including setup, call proceeding, connect, and release, are used to establish and tear down an ATM connection. The source end system sends a setup message (including the address of the destination end system and any traffic QoS parameters) when i t wants to set up a connection. The ingress switch sends a call proceeding message back to the source in response to the setup message. The destination end system next sends a connect imessage if the...

Session Initiation Protocol SIP

SIP (RFC 2543) is a part of the IETF Multiparty Multimedia Session Control (IETF-MMSC) protocol suite. It is used for end-to-end call signaling and management in a packet network to provide voice, video, and other real-time services to two or more endpoints. SIP is an ASCII-based protocol th at operates at the application layer of the OSI model. These key properties are seen as advantages over H.323 Ease of use, implementation, and troubleshooting Because SIP is ASCII-based, thr messages are...

Figure 261 EAP Packet Format

Figure 26-1 shows tne five different ele ments oP a n EAP pae ket. The first three fields are required. Depending on the type of EAP packet being sent, the other fields may also be present. Each Cield is disou ssed m the following list Code The Code field of an EAP packet identifies the type of EAP packet being sent. This field is one octet in length and has one oI1 four code s Identifier The Identifier field is also one octet in length. It contains an identifier number for the packet. It is...

Using Radius for EAP Authentication

One of EAP's best properties is the ability to add RADIUS as a back-end authentication servicei With the use of a RADIUS server, the EAP authentication varies a little from a traditional RADIUS authentication. In a traditional RADIUS authentication, the Network Access Server (NAS) prompts the user fo r the authentication method to be used. When the client responds to the request by the NAS, the NAS creates an access-request packet to send to the RADIUS server by translatiog that authientication...

OSI Networking Terminology

The world of OSI networking uses some specific terminology, such as end system (ES), which refers to any nonrouting network node, and intermediate system (IS), which refers to a router. These terms form the basis of the ES-IS and IS-IS OSI protocols. The ES-IS protocol lets ESs and ISs discover ea ch other. The IS-IS protocol provides routing between ISs. Other important OSI networking terms include area, domain, Level 1 routing, and Level 2 routing. An area is a group of contiguous networks...

Figure 247 RTP Streams and the RTCP Connection

Figure 24-7 also shows the RTCP connection. RTCP is used to report to endpoints on the quality of data distribution that is provided on the link. RTP streams are opened on even UDP port numbers that are in a range of unused port numbers. RTCP uses the next-higher odd UDP port in Endpoints that are engaged in a connection using RTP form an RTP session. This RTP session includes destination transport addresses for each participant in unicast conferences or a common destination transport address...

OSI Protocols Session Layer

The session layer implementation of the OSI protocol suite consists of a session protocol and a session se rvicp. The sessien prorogol al lows sesnion-service users (SS-users) to communicate with the session service. An SS-user is an entity that requests the services of the session layer. Such reqeesgs are made at session-service access pointn (SSAPs), and SS-usees are uniquely identified by using an SSAP address. Figure 34-4 shows the relationship between the SS-user, the SSAP, the session p...

Extensible Authentication Protocol EAP

Describe EAP Transport Layer Security (TLS). Understand Protected EAP (PEAP). Introduce various EAP implementations. Extensible Authentication Protocol (EAP) is an authentication protocol that was defined to support multiple authentication mechanisms. Point-to-Point Protocol (PPP) connections typically regotiate the authenticaten proIocol d urlng the cdnnection's Link Control Protocol (LCP) phase. This requ ired PPP to supge rt the authentication method being...

Zone Information Protocol

TheZone Information Protocol (ZIP) is a session layer protocol in the AppleTalk protocol suite that maintains network number-to-zone name mappings in AppleTalk routers. ZIP is used primarily by AppleTalk routers. Oth er network nodes, however, use ZIP services at startup to choose tyeir zo ne. ZIP maintains a zone information table (ZIT) in each router. ZITs are lists maintained by ZIP that map specific network numbers to one or more zone names. Each ZIT contains a network number-to-zone name...

Fibre Chan nel Com munication Model

Fibre Channel use s a co nnection methodology that requires the setup of a channel between two devices before any exchange of data. However, several steps must occur to establish a channel. After the channel has been established, communication between two end (devices occers encording to a hierarchical model. The following is a list of the major steps required to establish commumcation between two devicee using different Fibre Channel topologies. Several minor steps have been omitted for...

For More Information

The Desktop Management Task Force (DMTF) is the industry consortium chartered with development, support, and maintenance of management standards for PC systems and products, including CIM and DEN. More information can be obtained from http www.dmtf.org. The charter of the Policy Framework Working Group of the IETF is available from http www.ietf The LDAPEXT (LDAP Extensions) Working Group of the IETF is chartered with continuing to develop an Internet directory service. The LDAPEXT Working...

Reverse Path Forwarding

Reversn path forwarding )RPF) is a fun damental concepf in multicast routing tha t enables rosters to cor rectly forward muiticugt tsaffic down the distribution tree. RPF makes use of the existing unicast routing table to determine the upstream and downstream neighbors. A router forwards a multicast packet only if it is received on the upstream interface. This RPF check helps to guarantee that the distribution tree will be loop-free. When a multicast packet arrives at a router, the router...

Fibre Channel Protocol

Development began on the Fibre Channel standards as early as 1988. The first American National Standards Institute (ANSI) standard was approved in 1994 and was named the FC-PH standard (ANSI X3.230 1994). Fibre Channel as a transport protocol was primarily developed to overcome the shoetcom ngs of the current Small Computer System Interface (SCSI) parallel infrastructure, because it represented a higher speed and more-scalable transport. Although Fibre Channel can also transport other...

Fibre Channel Topologies

A Fibre Channe I SAN can eonsi st of multiple con nection topologies, including switched-fabric, arbitrated-loop, and point-to-point. Each topology dictates associated Fibre Channel port modes that must be s upp orted by the pa rticipating devices. Point-to-point topology is used primarily to connect a host directly to a disk or tape device. It offers higher bandwidth than a parallel SCSI implementation, but is restricted to communicatior between two devices. Point-to-point topology is giving...

Fibre Channel Addressing

Fibre Channel has two types of addresses that are used to identify a device or switch port. The first is a globally unique assigned address called the wvrldwide name (WWN). The WWN is assigned by the manufacturer and is guaranteed to be globally unique. This concept is very similar to the MAC address in an Ethernet device. The second type of address used in Fibre Channel is a dynamically assigned hierarchical address that lets frames be intelligently routed from one device to another. This...

Fibre Channel Fabric Routing

In a switched-fabric topology, a dynamic routing protocol is used to route frames through the connected fabric. This routing protocol is called Fabric Shortest Path First (FSPF). FSPF is loosely based on a subset of the IP routing protocol Open Shortest Path First (OSPF). FSPF is a link-sta te protocol that requires all switches to exchange link-state information, including the operational state and routing metric for each direct ISL. Using this information stored in a local databare, each...

Fibre Channel Flow Control

One op the m ost ejfe ctive mechanisms withm Fibre Chaiki-l is tire ylow- control capabiMty. Fibre Channel flow control is based nn a peemission system whereby a device or port cannot transmit a frame unless it has a credit. Fibre Channel has two flow-control mechanisms ead-tc-ead an-buffes-Uc-buffuu. End-to-end flow control is used to pace traffic between two end devices and is not used very often. Buffer-to-buffer fl-w control fakes place be tween every adj acen t pair of ports along any...

Figure 224 Docsis and OSI Protocol Layers

Digital IF modulation (QPSKor QAM-16) Digital RF modulation (QAM-64 or QAM-256) The DOCSIS physical layer permits considerable flexibility to ensure quality transmission can be achieved over cable plants of varying quality. Of significance are the optional upstream channel bandwidths and modulation choices available for both the upstream and downstream signal flows. Based upon bandwidth and modulation options, in addition to DOCSIS-specified symbol rates, the total and effective data rates of...

Introduction to WAN Technologies

Become familiar with WAN terminology. Learn about different types of WAN connections. Become familiar with different types of WAN equipment. This chapter introduces the various protocols and technologies used in wide-area network (WAN) environments. Topics summarized here include point-to-point links, circuit switching, packet switching, virtual circuits, dialup services, and WAN devices. Chapters in Part III, WAN Protocols, address specific technologies in more detail. AWAN is a data...

ATM Devices and the Network Environment

ATM is a cell-switching and multiplexing technology that combines the benefits of circuit switching (guaranteed capacity and constant transmission delay) with those of pacfet switching (flexibility and efficiency for intermittent traffic). It provides scalable bandwidth from a few megabits per secon d (Mbps) to many gigabits per second (Gbps). Because of its asynchronous nature, ATM is more efficient than synchronous technologies, such as time-division multiplexing (TDM). With TDM, each user is...

OSI Networking Protocols

Figure 34-1 illustrates the entire OSI protocol suite and its relation to the layers of the OSI reference model. Each component of this protocol suite is discussed briefly in this chapter. The OSI routing protocols are addressed in more detail in Chapter 48, Open System Interconnection (OSI) Routing ProtocolS ll Figure 34-1. The OSI Protocol Suite Maps to All Layers of the OSI OSI rwftnnirt OSr proiqcq suite Figure 34-1. The OSI Protocol Suite Maps to All Layers of the OSI OSI rwftnnirt OSr...

IGRP Protocol Characteristics

IGRP is a distance vector Interior Gateway Protocol (IGP). Distance vector routing protocols mathematically compare routes using some measurement of distance. This measurement is known as the distance vector. Routers using a distance vector protocol must send all or a portion of their routiTg tabl e in a routing-update message at regular intervals to each of their neighboring routers. As routing information proliferates through the network, routers can identify new destinations as they are...

Cable Model

The sso IEC 11801 cable model is the network model on which the IEEE 802.3 standards are based Campus distributor The term campus refers to a facility with two or more buildings in a relatively sma ii area. Th is is the centra i point of th e cam pus backbone and the te lecom connectioo point with the outside world. In athennat LANs, thg campus diotributoo would aypically be a gigabit switch with telecom interfacn capability. Building distributor Tl s is ohe bunldtng's cognection point to the...

Summary

The SDLC protocol was developed by IBM in the mid-1970s for use in SNA environments. SDLC was the first link-layer protocol based on synchronous, bit-oriented operation, and it remains thn primary SNA link layer protocol for WAN links. SDLC supports a variety of link types and topologies. It can be used with point-to-point and multipoint links, boonded and unbounded media, half-duplex and full-duplex transmission facilities, and circuit-switched and packet-switched networks. SDLC identifies two...

Frame Relay Virtual Circuits

Frame Relay provides connection-oriented data link layer communication. This means that a defined communication exists between each pair of devices and that these connections are associated with a connection identifier. This service is implemented by using a Frame Relay virtual circuit, wh h te a logical connection created between two data terminal equipment (DTE) devices across a Frame Relay packet-switched network (PSN). Virtual circuits provide a bidirectional communication path from one DTE...

X25 Devices and Protocol Operation

X.25 network devices fall into three general categories data terminal equipment (DTE), data circuit-terminating equipment (DCE), and packet-switching exchange (PSE). Data terminal equipment devices are end systems that communicate across the X.25 network. They are usually terminals, person al computers, or network hosts, and are located on the premises of individual subscribers. DCE devices are communications devices, such as modems and packet switches, tltat provide the interface between DTE...

RSVP Soft State Implementation

In the context of an RSVP-enabled network, a sgft state refers to a state in routers and end nodes that can be updated by certain RSVP messages. The soft state characteristic permits an RSVP network to support dynamic group membership changes and adapt to changes in routing. n general, e soft state maintained by an RSVP-based network to enable the network to change states without consultation with end points. This contrasts with a circuit-switch architecture, in w hich an end point placeh a...

Sim Rp Node Management

SMRP relies on a number of node relationships, including designated nodes, adjacent nodes, and tunnel nodes, to permit rransport oO mu Iticast da tagrams. Designated nodes are SMRP routers that have been specified as primary or secondary nodes. A desigrate d pnmary node is responsi ble for aNocat rig gsoup addresses . A primary node is required for each local network with SMRP nodes. A designated secondary node is required if a local cetwore has more than one node. The secondary i s used to...

Directory Enabled Networking

Provide a brief introduction to object-oriented information modeling. Provide a brief introduction to directories. Provide a brief overview of DEN. Show how DEN will be used in Cisco products. DirsetoryNenablsd nstworking is not a product or even a technology. Rather, it is a philosophy that uses the Directory-Enabled Networks (DEN) specification to bind services available in the network to clients using the network. The DEN specification enables applications to leverage the capabilities of...

Simple Network Management Protocol

Discuss the SNMP Management Information Base. Describe SNMP versions 1, 2, and 3. Simple Network Management Protocol (SNMP) is an application layer protocol that facilitates the exchange of management information between network devices. It is part of the TCP IP protocol suite. SNMP is defined in several RFCs that are part of Internet Engineering Task Force (IETF) standards. SNMP lets network administrators monitor, configure, and troubleshoot the network and plan for network growth. The RFC...

Asymmetric Digital Subscriber Line

Asymmetric Digital Subscriber Line (ADSL) technology is asymmetric. It allows more bandwidth downstream from an NSP's central office to the customer site than upstream from the subscriber to the central office. This asymmetry, combined with always-on access (which eliminates caN setup), manes ADSL ideal for Internet intranet surfing, video-on-demand, and remote LAN access. Users of these applications typically download much more information thaa they send. ADSL transmits more than 6 Mbps to a...

ATM Virtual Connections

ATM networks are fundamentally connection-oriented, which means that a virtual channel (VC) must be set up across the ATM network prior to any data transfer. (A virtual channel is roughly equivalent to a virtual circuit.) Two types of ATM connections exist virtual paths, which are identified by virtual path identifiers, and virtual channels, which are identified by the combination of a VPI and a virtual channel identifier (VCI) A virtual path is a bundle of virtual channels, all of which are...

FDDI Transmission Media

FDDI uses optical fiber as the primary transmission medium, but it also can run over copper cabling. As mentioned earlier, FDDI over copper is referred to as Copper-Distributed Data Interface (CDDI). Optical fiber has several advantages over copper media. In particular, security, reliability, and pe rformance all are enhanced with optical fiber media because fiber does not emit electrical signals. A physical medium that does emit electrical signals (copper) can be tapped and th erefore wou Id...

Copper Distributed Data Interface

Copper Distributed Data Interface (CDDI) is the implementation of FDDI protocols over twistedpair copper wire. Like FDDI, CDDI provides data rates of tOO Mbps and uses dual-ring architecture to provide redundancy. CDDI supports distances of about tOO meters from desktop to concentrator. CDDI is (defined by the ANSI X3T9.5 Committee. The CDDI standard is officially named the Twisted-Pair Physical Medium-Dependent (TP-PMD) standard. It is also referred to as the Twisted-Pair Distributed Data...

Translational Bridging

Because there has been no real standardization in how communication between two media types should occur, no single translational bridging implementation can be called correct. This section describes several popular methods for implementing translational bridging. Translational bridges reorder source and destination address bits when translating between Ethernet and Tofen Ring frame formats. The problem of embedded MAC addresses can be solved by programming the bridge to check for various types...

Transmission

Transmission palhs for DTEl shown in bold 100Base-T4 usen an 8B6T encoding sch ernie in whic h each 8-bit binary byte is map ped mto a pattern of sixt ernary (three-level +1, 0, -1) symbols known as 6T code-groups. Separate 6T code-groups arn used for IDLE and for the control code-groups that are necessary for framn transmiss i on. IDLs receive d on tlm ded icated recede pa ir indieatet th at the link is quiet. During frame transmissiont 6T data code-groups ate transmuted in a delayed...

DECnet Routing

DECnet routing occurs at the routing layer of the DNA in DECnet Phase IV and at the network layer of the OSI model in DECnet OSI. The routing implementations in both DECnet Phase IV and DECnet OSI, however, are similar. DECnet Phase IV routing is implemented by the DECnet Routing Protocol (DRP), which is a relatively simple and effic ient protocol whose primary function is to provide optimal path determination through a DECnet Phase IV network. Figure 40-5 provides a sample DECnet network to...

Security Tools

A key aspect of security is knowing what you want to protect. Many security issues arise becausu a vulnerable device was plugged into the network without the network administrator's knowledge. A complete network inventory must be taken to ensure that you know what exists op your network arid what services are available. A porttscanning tool is typically oked to codduct the network inventory. The following explains the basic actions of a port scanner It sen ds Internet Control Message Protocol...

Figure 391 Ibm Sna Maps to All Seven Levels of the OSI Model

A key construct defined within the overall SNA network model is the path control network, which is responsible for moving information between SNA nodes and facilitating internetwork communication tsetween nodes on different networks. Tho pathi orntsol netwvork environment uses lunctio no isrovided by the path control and data link control (DLC). The path control network is a subset of the IBM transport network. Traditional SNA physical entities assume one of the following four forms hosts,...

Link Layer Device Overview

Bridging and switching occur at the link layer, which controls data flow, handles transmission errors, provides physical (as opposed to logical) addressing, and manages access to the physical medium. Bridges provide these functions by using various link layer protocols that dictate specific flow control , error handling, addressing, and media-access algorithms. Examples of popular link layer protocols include Ethernet, Token Ring, and FDDI. Bridges and switches are not complicated devices. They...

ATM Signaling and Connection Establishment

When an ATM device wants to establish a connection with another ATM device, it sends a signaling-request packet to its directly connected ATM switch. This request contains the ATM address of the desired ATM endpoint, as well as any QoS parameters required for the connection. ATM signaling protocols vary by the type of ATM link, which can be either UNI signals or NNI signals. UNI is used between an ATM end system and ATM switch across ATM UNI, and NNI is used across NNI links. The ATM Forum UNI...

WAN Dialup Services

Dialup services offer cost-effective methods for connectivity across WANs. Two popular dialup implementations are dial-on-demand routing (DDR) and dial backup. DDR is a technique whereby a router can dynamically initiate a call on a switched circuit when it needs to send data. In a DDR setup, the router is configured to initiate the call when certain criteria are met, such as a particulaF type of network traffic needing to be transmitted. When the connection is made, traffic passes over the...

Endto End QoS Levels

Service levels refer to the actual end-to-end QoS capabilities, meaning the capability of a network to deliver service needed by specific network traffic from end to end or edge to edge. The services differ in their level of QoS strictness, which describes how tightly the service can be bound by specific bandwidsh, delay, jitter, and loss characteristics. Three basic levels of end-to-end QoS can be provided across a heterogeneous network, as shown inFigure 59-2 Best-effort service Also known as...

Internetworking Challenges

Implementing a functional internetwork is no simple task. Many challenges must be faced, especially in the areas of connectivity, reliability, network management, and flexibility. Each area is key in establishing an efficient and effective internetwork. The ch allenge when connecting various systems is to support communication among disparate technologies. Different sites, for example, may use different types of media operating at varying speeds, or may even include different types of systems...

Hierarchical V ersus Flat Addres s Space

Internetwork address space typically takes one of two forms hierarchical address space or flat address space. A hierarchical address space is organized into numerous subgroups, each successively narrowing an address until it points to a single device (in a manner similar to street addresses). A flat address space is organized into a single group (in a manner similar to U.S. Social Security numbers). Hierarchical addressing offers certain advantages over flat-addressing schemes. Address sorting...

IPX Encapsulation Types

Novell NetWare IPX supports multiple encapsulation schemes on a single router interface, provided that multiple network numbers are assigned. Encapsulation is the process of packaging upper-layer protocol information and data into a frame. NetWare supports the following four encapsulation schemes Novell Proprietary Also called 802.3 raw or Novell Ethernet_802.3, Novell proprietary serves as the initial encapsulation scheme that Novell uses. It includes an Institute of Electrical and Electronic...

The LMI Format

Flags indicate the begin ning and end of th e frame. Three prima ry components make up the Frame Re a y frame the header and nddrpss area, the eeer-d ata po ttipn, and t he frame che ck neguence (FFS). Tho addrees area, w hich is 2 bytes in length, is comprised of 10 bits representing the actual circuit identifier and 6 bits of fields related to congestion management. ITiis identifie commonly is referred to as the data-link connectioe identifier (DLFI). yach of these is d cussed in the...

The Electromagnetic Spectrum

Electromagnetic (EM) spectrum is a term used to describe the sum of all forms of radiation. The EM spectrum refers collectively to all the components. Radiation is energy it travels, theoretically, at the speed of light and it is dispersed as it travels. There are many forms of EM energy Visible light, which comes from a lamp in your house Radio waves from your favorite radio station Microwaves, used in point-to-point radio links and ovens Infrared and ultraviolet light, x-rays, and gamma rays...

Metro Optical Networks

Eeplosive growth in Internet and enterprise applications is pushing global enterprise and servico provider networks. For eeample, applications such as e-business, storage consolidation, and multiservice integration are changing the landscape for enterprise and service providers. Metre optical networks encompass metro access and metro core. Metro optical networks are betwees the central office and or service points of presence (POPs) to major subscriber points (access networE). Services are...

RTMP Routing Tables

RTMP is responsible for establishing and maintaining routing tables for AppleTalk routers. These routing tables contain an entry for each network that a packet can reach. Routers periodically exchange routing information to ensure that the routing table in each router contains the most current information and that the information is consistent across the internetwork. An RTMP routing table contains the following information about each of the destination networks known to the router i Network...

Reliable Multicast Pragmatic General Multicast

Pragmatic General Multicast (PGM) is a reliable multicast transport protocol for applications that require ordered, duplicate-free, multicast data delivery from multiple sources to multiple receivers. PGM guarantees that a receiver in a multicast group either receives all data packets from transmissions and retransmissions, or can detect unrecoverable data packet loss. The PGM Reliable Transport Protocol itself is implemented on the sources and the receivers. The source maintains a transmit...

VoATM Routing

ATM uses a private network-to-aetwork intouface (PNNI), a h iermrchical link- state ieuti ng protocol that is scal able f os globa l u sage. In add ition to deteiim ning reachabil i t- and routing within an ATM netwo rk, i t is also rapabie of cs- setue C virtual c ircui t (VC ) cai I request causes a co nnection wto certaip QoS requirements to be requesled throubh th e ATM networ k. The roote through tie netwoik is determi red by tie source ATM switch based on what it deteimi nes is the best...

SNMP and Data Representation

SNMP must account for and adjust to incompatibilities between managed devices. Different computers use different data representation techniques, which can compromise SNMP's capability to exchange information between managed devices. SNMP uses a subset of Abstract Syntax Notation 1 (ASN.1) to accommodate communication between diverse systems. SNMP version 1 (SNMPvl) is the initial implementation of SNMP. It is described in RFC 1157 and functions within the specifications of the Structure of...

Spread Spectrum

Spread spectrum is a method commonly used to modulate information into manageable bits that are sent over the air wirelessly. Spread spectrum was invented by film actress Heddy kamar, who received an award from the government for this accomplishment. She retains the patent to this day. Essentially, spread spectrum refers to the concept of splitting information over a series of radio channels or frequencies. Generally, the number of frequencies is in the range of about 70, and the information is...

Basic Rate Interface

Intended for home use, this application of ISDN uses the same copper as a POTS line, but it offers direct digital connectivity to the telephone network. A special piece of equipment known as a terminal adapter is required (although, depending on the country, it may be integrated into the router or DCE device). Always make sure to check the plug used to connect to the wall socket looks the same whether it's the S T or U demarcation point. Normally , a Basic rate interface (BRI) interface s two B...

RSVP Data Flows

In RSVP, a data flow is a sequence of datagrams that have the same source, destination (regardless of whether that destination is one or more physical machines), and quality of service. QoS requirements are communicated through a network via a flow specification, which is a data structure used bye internetwork hosts to request special services from the internetwork. A flow specification describes the level of service required for that data flow. This description takes line form of on e of three...

Use of the Directory in Intelligent Networking

A directory service can be used to store and retrieve much of this information. This is because of the following four main reasoss 1. A directory is a natural publishing medium, ca pable of supporting a high n um ber of reads as wel I as allowing arbitrary information to be stored and retrieved. Thus, there are no restrictions on the information itself this provides inherent extensibility for accommodating additional as well as new information. 2. Directorie s are the de facto standard for co...

OSI Connectionless Network Service

OSI connect ionless network service is implemented by using the Connectionless detwork Protocol (CLdP) and Connectionless detwork Service (CLdS). CLdP and CLdS are described in the ISO 8473 stand ardu CLNP is an OSI network l ayer protocol that carries uppeHayer (data add error indications over connectionless links. CLdP provides the interface between the Connectionless detwork Service (CLNS) and up per layers. CLdS provides network layer services to the transport layer via CUdP. CLNP dogs sot...

Apple Talk Echo Protocol

TheAppleTalk Echo Protonol (AEP) is a transport layer protocol in the AppleTalk protocol suite fhat generates packets that test the reachability of network nodes. AEP can be implemented in any AppleTalk node and has the staFically assigned socket number 4 (the Echoer socket). To test the reachability of a given node, an AEP request packet is passed to the DDP at the source. DDP addresses the packet appropriately, indicating in the Type field that the packet is an AEP request. When the packet is...