Common Protocols and Interfaces - Part 2 Bridge Protocols IEEE 802.1 Spanning Tree Learning Bridge Protocol (STP) • IEEE Standard 802.1 is a bridging protocol • STP defines forwarding table operation for bridges that span multiple networks • It provides the function of frame (packet) forwarding table • It is dynamic and corrects forwarding problems such as forwarding loops or unavailable circuit paths. • Each data frame passing through a bridge is examined and forwarded on through a process called filtering
Common Protocols and Interfaces - Part 2 IEEE 802.1 Spanning Tree Learning Bridge Protocol (STP) (Continue…) • STP is a true bridging protocol and is inefficient and disadvantageous when used as a large networking protocol. • STP is better utilized when the network is made up of many point-to-point circuits. • STP elimination of loop paths ties up expensive leased-line resources. • Spanning tree table building after network failures takes considerable time and introduces long user delays.
Common Protocols and Interfaces - Part 2 IBM Source Routing Protocol (SRP) • The IBM SRP allows LAN workstations to specify their routing for each packet transmitted • Each packet transmitted by a workstation on the LAN to the bridge contains a complete set of routing information for the bridge to route upon • The information for source routing to perform its function is contained in the routing information field within the MAC sublayer frame • Refer to Figure 8.1 (p. 281) • IBM’s Token Ring implementation of source routing has a seven-hop count maximum
Common Protocols and Interfaces - Part 2 Source Route Transparent (SRT) Bridging • IEEE SRT marries the IEEE STP and the SRP into one bit-selective bridging protocol • Many bridges achieve forwarding rates of over 14,500 frames per second sustained over a long period of time using this technique. • SRP has more overhead than SRT, but the processing is reduced for each bridge it traverses • SRT can also allow SNA source routing into Ethernet TCP/IP networks and DECnet networks
Common Protocols and Interfaces - Part 2 Source Routing Extensions • Many vendors such as Bay Networks and Cisco Systems have implemented extensions to the SRB protocol. • These routers, while providing bridging capability, can transit bridged traffic across an entire WAN composed of multiple routers, and still the entire network will only count as a single hop (eliminating the seven-hop count restriction) • Routing tables are built dynamically through use of the source route explorer packets • This method improves reliability of transmission, eliminates the hop count restriction, and can decreases response time across the network.
Common Protocols and Interfaces - Part 2 Routing Protocols • Routers perform both routing and bridging functions. However, both methods require that the router performs address translation. • There are multiple routing protocols that build forwarding tables using different metrics • Routers use a series of algorithms to perform the task of routing, along with dynamic routing tables to manage this routing • Almost all routers support bridging protocols, as it is preferable to perform translation bridging with a router as opposed to encapsulation bridging with a bridge
Common Protocols and Interfaces - Part 2 Routing Protocols Defined • Routing, or gateway protocols, provide router-to-router communications between like routers using routing tables. • Communications can take place between autonomous systems and within autonomous systems EGP, IGRP, RIP, BGP, OSFP, IS-IS • Serial line protocols provide communications over serial or dial-up links between unlike routers HDLC, PPP, SLIP • Gateway protocols pass the routing table information and “keep alive” packets, and the serial line protocol passes the true user data
Common Protocols and Interfaces - Part 2 Routing Protocols Defined (Continue…) • Routers need to determine the best way to reach an address through a network of nodes. • Routing algorithms generally exchange information about a topology based upon in one or two generic methods • Distance vector:algorithms use neighbor nodes to periodically exchange vectors of the distance to every destination in the network • Link state: algorithms have each router learn the entire link state topology of the entire network. This is currently done by flooding only changes to the link state topology through the network
Common Protocols and Interfaces - Part 2 Routing Protocols Defined (Continue…) • The link state approach is more complex, but converges much more rapidly • Convergence is the rate at which a network goes from an unstable state to a stable state
Common Protocols and Interfaces - Part 2 Distance Vector Routing Protocols • It is used by the Internet’s Routing Information Protocol (RIP). • A key advantage of the distance vector is its simplicity • A key disadvantage is that the topology information message grows larger with the network and the time for it to propagate through the network increases as the network grows • IP RIP automatically summarizes at the edges of a class (A,B,C) network • OSFP can be configured to summarize on more arbitrary area boundaries • IPX RIP doesn’t do any summarization at all • Refer to Figure 8.2 (p. 284)
Common Protocols and Interfaces - Part 2 Distance Vector Routing Protocols (Continue…) • RIP • Operates in a connectionless mode at the application layer, interfacing with transport layer protocols through UDP • Its decision for routing is based upon hop count only (no length of the hop) • This can cause problems when a higher-bandwidth path is available and desirable for transport • Refer to Figure 8.3 (p. 285) • RIP has a hop-count restriction of 16 hops, and is prone to routing loops if misconfigured
Common Protocols and Interfaces - Part 2 Distance Vector Routing Protocols (Continue…) • IGRP • Superior than RIP because it understands bandwidth limitations between hops, as well as time delays • It is tunable to make it faster if desired • It doubles the transmit time of information between nodes, amplifying the opportunity for a convergence problem • EGP and BGP • Exterior routing protocols used between separately administered networks • ISPs use BGP to share routing information between their networks
Common Protocols and Interfaces - Part 2 Link State Routing Protocols • The link state advertisement method was designed to address the scalability issues of the distance vector method. • Routing tables are exchanged with neighbors, but every device on the network must be at least one other device’s neighbor • Link state updates are sent using 64-byte packets (depending on the specific protocol) in a multicast mode, and require acknowledgments • This protocol will also notify users if their address is unreachable • This method is more memory intensive for the router, and requires large amounts of buffers and memory space
Common Protocols and Interfaces - Part 2 Link State Routing Protocols (Continue..) • There are three major implementations of link state routing protocols on the market: • Open Shortest Path First (OSPF): • Based upon shortest path, bandwidth available, cost in dollars, congestion, interface costs, and time delay • All costs for links are designated on the outbound router port • Supports point-to-point, broadcast, and NonBroadcast MultiAccess (NBMA). • OSFP is only useful with TCP/IP networks
Common Protocols and Interfaces - Part 2 Link State Routing Protocols (Continue..) • Intermediate System to Intermediate System (IS-IS) • Used to route between network nodes • An extension of IS-IS (Dual IS-IS) can support both OSI and TCP/IP networks simultaneously • However, OSPF provides a wider range of interface costs than IS-IS • Novell’s NLSP • Proprietary Novell protocol • Refer to Table 8.1 (p. 297)
Common Protocols and Interfaces - Part 2 Network and Transport Layer Protocols- The Internet Protocol Suite (TCP/IP) Structure of TCP/IP • TCP provides a reliable, sequenced delivery fo data to applications. • UDP only provides an unacknowledged datagram capability • TCP also provides adaptive flow control, segmentation, and reassembly, and prioritized data flows. • Refer to Figure 8.4 (p. 289) • A number of applications interface to TCP and UDP: FTP, TELNET, SNMP, TFTP, RPC, NFS
Common Protocols and Interfaces - Part 2 IP Packet Formats • Refer to Figure 8.5 (p. 290) Internet Protocol (IP) Addressing • Uses 32-bit IP addresses as a global addressing scheme • IP addresses are grouped into classes A, B, C • Refer to Figure 8.6 (p. 291) • Internet addresses are assigned and managed by Internet Assigned Numbers Authority (IANA) • IP works with TCP for end-to-end reliable transmission of data across the network • TCP will control the amount of unacknowledged data in transit by reducing either the window size or the segment size
Common Protocols and Interfaces - Part 2 TCP/IP Functions • IP provides a connectionless datagram delivery service to the transport layer • TCP provides an end-to-end reliable delivery, error control, retransmission, or flow control • Refer to Figure 8.7 (p. 292) • IP provides the means for devices to discover the topology of the network, as well as to detect changes of state in nodes, links, and hosts • Refer to Figure 8.8 (p 294)
Common Protocols and Interfaces - Part 2 Traffic and Congestion Control Aspects of TCP/IP • TCP flow control uses a sliding window flow-control protocol, like X.25 • However, the window is of a variable size, instead of the fixed window size used by X.25 • Refer to Figure 8.9 (p. 294) Service Aspects of TCP/IP • TCP/IP implementations typically constitute a router, TCP/IP workstation and server software, and network management. • Operation of IP over a number of network, data link, and physical layer services is defined.
Common Protocols and Interfaces - Part 2 IP Next Generation (IPng)-IPv6 • Expands the address size from 32 to 128 bits • Simple dynamic auto-configuration capability • Easier multicast routing with addition of “scope” field • Anycast feature-send packet to anycast address and it is delivered to one of the nodes which allows nodal routing control • Capability to define quality of service to a traffic flow added • Reduction of overhead-some header fields are optional • More flexible protocol design for future enhancements • Authentication, data integrity, and confidentiality options • Easy transition and interoperability with IPv4 • Support for all IPv4 routing algorithms (e.g., OSPF, RIP, etc)
Common Protocols and Interfaces - Part 2 Legacy SNA • SNA still maintains the predominant corporate mainframe architecture, accounting for over 50 percent of world-wide data communications networks. • Traditional SNA architecture is master-slave and thus hierarchical in nature. • SNA is now moving toward a more distributed, peer-to-peer architecture called Advanced Peer-to-Peer Networking (APPN) Building Blocks of Traditional SNA • Host Processor: is also called a Central Processing Unit (CPU). Devices include the IBM 3090, 4381, and 9370
Common Protocols and Interfaces - Part 2 • Cluster Controller or Terminal Controllers: control a cluster of 8 to 32 typically coax-attached terminals and printers. • Refer to Figure 8.11 (p. 298) • Refer to Figure 8.12 (p. 298) • Establishment Controller Units: or ECUs are a form of cluster controllers that can act as a gateway for mainframe connectivity to a Token Ring or Ethernet LAN for VTAM access. • Refer to Figure 8.13 (p. 299)
Common Protocols and Interfaces - Part 2 Communications Controllers (CCs) or Front-End Processors (FEPs): provide access for connecting cluster controllers to a mainframe through a Network Control Protocol (NCP). • FEPs perform front-end processing for the host, route data within the SAN protocol stack between CCs, and can act as concentrators to multiple controllers, terminals, and other communication devices. • Refer to Figure 8.14 (p. 300) • Refer to Figure 8.14 (p. 301) • Refer to Figure 8.15 (p. 301)
Common Protocols and Interfaces - Part 2 • Interconnect Controllers: such as the IBM 3172 provide direct connection for a mainframe to an Ethernet, Token Ring, or FDDI LAN user access to VTAM • Refer to Figure 8.17 (p. 302) • IBM Minicomputers: such as the AS400 and System/36 form the cornerstone of most APPN networks. • Communications Access Methods: include both ACF/VTAM and ACF/TCAM • Operating Systems (OS) include MVS/XA, MVS/ESA, DOS/VSE, and OS/2 • Host Applications: include CICS,IMS/DC, and TSO
Common Protocols and Interfaces - Part 2 Network Addressable Units - PUs, LUs, and Domains • Synchronization of communications, resource management, and control of the network are managed by Network Addressable Units (NAUs) • LU (logical unit) - are “sessions” between end-user access ports on the network • PU (physical unit) - manages the LU • SSCP (systems services control point) - defines a single point for domain control • A network device PU, LU, SSCP is combined to form the network addressable unit (NAU), which forms the network address for a given device.
Common Protocols and Interfaces - Part 2 Network Addressable Units - PUs, LUs, and Domains (Continue…) • Each device in the network is labeled a node • An area controlled by one host is called the domain • The primary communications protocol is SDLC • Refer to Figure 8.18 (p. 304) SNA Legacy Software Communications • Virtual Telecommunications Access Method (VTAM) is the software that resides in the host computer and communicates with the “dumb” terminals attached to the 3174 • The FEP runs a software called Network Control Program (NCP)
Common Protocols and Interfaces - Part 2 IBM SNA/SDLC Migration to LAN/WAN Internetworking • One of the advantages of placing SNA traffic over a WAN is that broadcast packets and unnecessary polling overhead can be eliminated, similar to a more dynamic method of filtering • There are many methods of tying SNA networks into the non-SNA WAN environment
Common Protocols and Interfaces - Part 2 SNA over X.25 - NPSI • IBM offers software and hardware called the Network Control Protocol (NCP) Packet Switching Interface (NPSI) as one option for encapsulating SDLC traffic for transport across the WAN • NPSI encapsulates SNA traffic into X.25 packets • Refer to Figure 8.19 (p. 305) QLLC Conversion - SNA over X.25 • The requirement for NPSI can be eliminated by attaching a Token Ring interface to the 3475, and translating from MAC to QLLC protocol • Refer to Figure 8.20 (p. 305)
Common Protocols and Interfaces - Part 2 PAD/FRAD SDLC/Bisync/Async Consolidation/Encapsulation • Automatic teller machines (ATMs) use the bisync protocol to communicate their transactions back to the controller. • Low-speed SNA traffic using Async (polled and nonpolled), Bisync, and SDLC can be aggregated into a single device and the protocol encapsulated into a single protocol for access to the WAN. • Refer to Figure 8.21 (p. 307)
Common Protocols and Interfaces - Part 2 Traditional Source Route Bridging (SRB) and Remote SRB (RSRB) • SNA traffic can be bridged between Toekn Ring LANs and across the WAN • Replacing point-to-point SDLC links with a Token Ring connection eliminates polling across the entire WAN • Refer to Figure 8.22 (p. 308) • While SRB offers a simplistic approach, it has many problems associated with it
Common Protocols and Interfaces - Part 2 SDLC to LLC2 Protocol Conversion • To methods to consolidate IBM 3x74 devices into a single FEP • SDLC to LLC2 protocol conversion • Serial tunneling solution • In SDLC to LLC2 conversion, remote 3x74 devices can connect via SDLC to a TCP/IP router. The router will then convert the SDLC traffic into Token Ring format LLC2 • LLC2 encapsulation is performed at logical link layer 2 • Refer to Figure 8.23 (p. 309) • An external device other than the WAN router is sometimes used to convert the SNA SDLC to LLC2
Common Protocols and Interfaces - Part 2 SNA SDLC Serial tunneling (Synchronous Pass-Through over IP) • One method of routing point-to-point 3270 traffic from an IBM 3174 cluster controller is through SDLC serial tunneling, also called synchronous pass-through • The router encapsulates the SDLC traffic into an IP packet and routes it through the network • Synchronous or transparent pass-through, or tunneling, provides point-to-point mapping with IP encapsulation of the SNA SDLC traffic • Refer to Figure 8.24 (p. 310)
Common Protocols and Interfaces - Part 2 Remote SDLC/3270 polling with retransmission • Eliminates polling overhead with a technique called spoofing or local acknowknowledge • The access device passes only blocks containing SNA data over the dedicated SNA line. Polling is done locally with both primary and secondary modules performing the polling functions. • Refer to Figure 8.25 (p. 311) • Two variations • encapsulation (or packetization) of SNA traffic or emulation • routing of PU2s and PU4s in native mode
Common Protocols and Interfaces - Part 2 Remote SNA switching with host pass-through • This replaces the primary and secondary polling nodes with primary and secondary SNA nodes in the router • This provides dynamic path routing rather than the SNA-specified routing, and eliminates the need to establish SNA cross-domain host sessions • Refer to Figure 8.26 (p. 311) SNA Routing • Method 1: APPN Type 4 routing establishes an optimum path between routers for host communications through router emulation of SNA type 4 routing • Method 2: SNA cross domain type 5/4 host/FEP routing
Common Protocols and Interfaces - Part 2 RFC 1434, DLSw (RFC 1795), DLSw+, and RSRB • DSLw was developed to allow basic transport of SDLC traffic routed within TCP/IP • DLSw+ was designed to fix the scalability problems of DLSw by counting the entire TCP/IP network as a single “hop”, regardless of how many devices the network uses. • Refer to Figure 8.28 (p. 313)
Common Protocols and Interfaces - Part 2 RFC 1490 - SNA and Multiprotocol Traffic Encapsulation across FR Networks • TCP/IP encapsulation over FR • offers the ability to perform routing and nondisruptive rerouting of SNA traffic • Refer to Figure 8.29 (p. 315) • Remote bridging over FR • Routers located at every site perform a triple encapsulation of the SNA data within LLC, MAC, and then FR frames • Refer to Figure 8.30 (p. 315) • Native LLC2 over FR • Use of native LLC2 over FR for direct FEP connection • Refer to Figure 8.31 (p. 315)
Common Protocols and Interfaces - Part 2 Advanced Program-to-Program Communication (APPC) • provides peer-to-peer intelligent sessions between peripheral PU2.1 nodes • This constitutes an LU6.2 device-to-LU6.2 device session without involving the host using VTAM and the front-end processor using NCP • APPC supports both dynamic and automatic routing between LU6.2 devices, but it does not support multiple protocols nor mainframe to terminal traffic • The main limitations to APPC are the huge amount of memory (up to 500K) required to run a workstation and the lack of software support.
Common Protocols and Interfaces - Part 2 Advanced Peer-to-Peer Networking (APPN) • It allows routing LAN traffic independent of a front-end processor or a mainframe between workstations or peer devices called End Nodes (ENs). • ENs are typically LU workstations running APPN software • The routing devices between ENs, such as FRADs and routers, are called Network Nodes (NNs). • Refer to Figure 8.32 (p. 318) • APPN moves users away from FEPs and mainframes and toward routers • Unfortunately, the entire network-routed topology is stored at each node, and error check and recovery with retransmission of lost packets is performed at each node in the network
Common Protocols and Interfaces - Part 2 Channel Extension - Cisco’s Channel Interface Processor (CIP) • Cisco has available a method of providing a VTAM-to-TCP/IP gateway that uses the direct interface from the host to the router via the older bus-and-tag interface or the newer 17 Mbps ESCON channel interface • Since TCP/IP and VTAM run in the mainframe, no 3172 and no NCP are required. • Refer to Figure 8.33 (p. 319)
Common Protocols and Interfaces - Part 2 NETBIOS/NETBEUI • NETBIOS is predominantly used as the PC LAN program networks and transport protocol in Token Ring implementations. • The IBM NETBIOS Extended User Interface (NETBEUI) allows NETBIOS to be transparently passed over the 802.2 LLC protocol and interface accessing the token ring adapter at the MAC layer SNA-to-OSI Gateway • Implementing a full SNA-to-OSI gateway is an expensive alternative
Cisco IP Routing
Objectives • Understand the IP routing process • Create and verify static routing • Create and verify default routing • Resolve network loops in distance-vector routing • Configure and verify RIP routing • Configure and verify IGRP routing
Routing • Definition • What must routers know?
Router>en Router#config t Router(config)#hostname 2621A 2621A(config)#interface fa0/0 2621A(config-if)#ip address 172.16.10.1 255.255.255.0 2621A(config-if)#no shut 2621A Configuration
Router>en Router#config t Router(config)#hostname 2501A 2501A(config)#int e0 2501A(config-if)#ip address 172.16.10.2 255.255.255.0 2501A(config-if)#no shut 2501A(config-if)#s0 2501A(config-if)#ip address 172.16.20.1 255.255.255.0 2501A(config-if)#no shut 2501A Configuration
Router>en Router#config t Router(config)#hostname 2501B 2501B(config)#int e0 2501B(config-if)#ip address 172.16.30.1 255.255.255.0 2501B(config-if)#no shut 2501B(config-if)#s0 2501B(config-if)#ip address 172.16.20.2 255.255.255.0 2501B(config-if)#clock rate 64000 2501B(config-if)#no shut 2501B(config-if)#int s1 2501B(config-if)#ip address 172.16.40.1 255.255.255.0 2501B(config-if)#clock rate 64000 2501B(config-if)#no shut 2501B Configuration