Cisco Press CCDA Study Guide

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.RSVP is used to specify the QoS by both hosts and routers.Hosts use RSVP to request a QoS level from the network on behalf of an application datastream.Routers use RSVP to deliver QoS requests to other routers along the path(s) of the datastream.In doing so, RSVP maintains the router and host state to provide the requested service.To initiate an RSVP multicast session, a receiver first joins the multicast group specified by anIP destination address by using the Internet Group Membership Protocol (IGMP).In the caseof a unicast session, unicast routing serves the function that IGMP, coupled with Protocol-Independent Multicast (PIM), serves in the multicast case.After the receiver joins a group, apotential sender starts sending RSVP path messages to the IP destination address.The receiverapplication receives a path message and starts sending appropriate reservation request messagesspecifying the desired flow descriptors using RSVP.After the sender application receives areservation request message, the sender starts sending data packets.NetWare Protocol SuiteNetWare is a network operating system (NOS) that provides transparent remote file access andnumerous other distributed network services, including printer sharing and support for variousapplications, such as electronic mail transfer and database access.NetWare specifies the upperfive layers of the OSI reference model and, as such, runs on virtually any media-access protocol(layer 2).Additionally, NetWare runs on virtually any kind of computer system, from PCs tomainframes.Introduced in the early 1980s, NetWare was developed by Novell, Inc.It wasderived from Xerox Network Systems (XNS), which was created by Xerox Corporation in thelate 1970s, and is based on a client-server architecture.Clients (sometimes called workstations)request services, such as file and printer access, from servers.Internetwork Packet Exchange (IPX) is the original NetWare network layer (Layer 3) protocolused to route packets through an internetwork.IPX is a connectionless datagram-based networkprotocol and, as such, is similar to the Internet Protocol found in TCP/IP networks.The Sequenced Packet Exchange (SPX) protocol is the most common NetWare transportprotocol at Layer 4 of the OSI model.SPX resides on top of IPX in the NetWare Protocol Suite.SPX is a reliable, connection-oriented protocol that supplements the datagram service providedby the IPX protocol.SPX was derived from the Xerox Networking Systems (XNS) SequencedPacket Protocol (SPP).NetWare supports a wide variety of upper-layer protocols, including the following:" NetWare shell Runs on clients and intercepts application input/output (I/O) calls todetermine whether they require network access for completion.Client applications areunaware of any network access required for completion of application calls." NetWare Remote Procedure Call (NetWare RPC) Another more generalredirection mechanism similar in concept to the NetWare shell supported by Novell.CH01.book Page 531 Friday, January 7, 2000 5:35 PMRouting 531" NetWare Core Protocol (NCP) A series of server routines designed to satisfyapplication requests coming from, for example, the NetWare shell.The services providedby NCP include file access, printer access, name management, accounting, security, andfile synchronization." Network Basic Input/Output System (NetBIOS) A session layer interfacespecification from IBM and Microsoft.NetWare s NetBIOS emulation software allowsprograms written to the industry-standard NetBIOS interface to run within NetWaresystem.NetWare application layer services include:" NetWare message-handling service (NetWare MHS) A message-deliverysystem that provides electronic mail transport." Btrieve Novell s implementation of the binary tree (btree) database-accessmechanism." NetWare loadable modules (NLMs) Add-on modules that attach into a NetWaresystem.NLMs currently available from Novell and third parties include alternate protocolstacks, communication services, and database services." IBM Logical Unit (LU) 6.2 network-addressable units (NAUs) Supportto allow peer-to-peer connectivity and information exchange across IBM networks.NetWare packets are encapsulated within LU 6.2 packets for transit across an IBMnetwork.IPX AddressingAs with other network addresses, Novell IPX network addresses must be unique.Theseaddresses are represented in hexadecimal format and consist of two parts: a network numberand a node number.The IPX network number, which is assigned by the network administrator,is 32 bits long.The node number, which usually is the Media Access Control (MAC) addressfor one of the system s network interface cards (NICs), is 48 bits long.NetWare Routing and Service Advertisement ProtocolsIPX uses the following protocols for routing and service advertisement:" IPX Routing Information Protocol (RIP) A distance vector routing protocolthat sends routing updates every 60 seconds.To make best-path routing decisions, IPXRIP uses a tick as the metric, which in principle is the delay expected when using aparticular length.One tick is 1/18th of a second.In the case of two paths with an equaltick count, IPX RIP uses the hop count as a tie breaker.CH01.book Page 532 Friday, January 7, 2000 5:35 PM532 Appendix C: Internetworking Technology Review" Service Advertisement Protocol (SAP) An IPX protocol through whichnetwork resources, such as file servers and print servers, advertise their addresses and theservices they provide.Advertisements are sent via SAP every 60 seconds.Services areidentified by a hexadecimal number, which is called a SAP identifier (for example, 4 = fileserver and 7 = print server).SAP is pervasive in current networks based on NetWare 3.11and earlier but is utilized less frequently in NetWare 4 [ Pobierz całość w formacie PDF ]

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