ITM 600 - Final Exam Key Words & Points (outlined by Prof) Explanations

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Information Technology Management
ITM 600
Khalil Arbousa

ABR (Available Bit Rate) With ABR, the transfer characteristics provided by the network can change subsequent to connection establishment. A flow-control mechanism offers several types of feedback to control the source rate in response to changing ATM-layer conditions. This feedback is conveyed to the source through control cells called resource management (RM) cells. The ABR service does not require bounding the delay or the delay variation experienced by a given connection. ABR service is not intended to support real-time applications. On the establishment of an ABR connection, an end system specifies to the network both a maximum required bandwidth and a minimum usable bandwidth. These are designated as the peak cell rate (PCR) and the minimum cell rate (MCR), respectively. ACL (Access Control Lists) List kept by a router or firewall to control access to or from the router for several services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router). ACLs let you control whether network traffic is forwarded or blocked at interfaces on a router or switch Cisco implements the second policy in its packet filters, which Cisco calls access control lists (ACL). An ACL on a router or switch running Cisco IOS Software always has an implicit deny-all statement at the end The second policy is: Accept specific types of packets and deny all else Another tool that is available to network designers using Cisco equipment is traffic shaping, which enables you to manage and control network traffic to avoid bottlenecks and meet QoS requirements Traffic shaping is configured on a per-interface basis. The router administrator uses access control lists to select the traffic to shape. Access Layer It provides users on local segments access to the internetwork. The access layer is composed of 10-Mbps and 100-Mbps Ethernet networks. A typical hierarchical topology is An access layer that connects users via lower-end switches and wireless access points. The distribution layer connects network services to the access layer and implements policies regarding security, traffic loading, and routing. In a WAN design, the access layer consists of the routers at the edge of the campus networks. In a campus network, the access layer provides switches or hubs for enduser access. The access layer provides users on local segments with access to the internetwork. The access layer can include routers, switches, bridges, shared-media hubs, and wireless access points. Strict control of the network topology at the access layer should be maintained. Users at the access layer have a tendency to add networks to the internetwork inappropriately. For example, a network administrator at a branch office might connect the branch network to another branch, adding a fourth layer. DHCP severs r placed in access layer UplinkFast is a Cisco feature that can be configured on access layer switches. Routing protocols that should be used in the access layer include RIPv2, OSPF, and EIGRP. Area Work-area wiring runs from the wall plate to a workstation in a cubicle or office. ARP (Address Resolution Protocol) Internet protocol used to map an IP address to a MAC address. Defined in RFC 826. Proxy Address Resolution Protocol. Variation of the ARP protocol, in which an intermediate device (for example, a router) sends an ARP response on behalf of an end node to the requesting host. Defined in RFC 1027. In addition to applications that are set to start upon bootup, the following system-level protocols send packets as a workstation initializes: ■ Address Resolution Protocol (ARP) ATM (Asynchronous Transfer Mode) International standard for cell relay in which multiple service types (such as voice, video, or data) are conveyed in fixed-length (53- byte) cells. Asynchronous Transfer Mode (ATM) has a connection admission control function that regulates the number of cells allowed into an ATM network. If the capacity and quality of service (QoS) requested for a connection are not available, cells for the connection are not allowed to enter the network. ATM divides frames into cells. ATM Forum does an excellent job of categorizing the types of service that a network can offer to support different sorts of applications. The ATM Forum defines six service categories: ■ Constant bit rate (CBR) ■ Real-time variable bit rate (rt-VBR) ■ Non-real-time variable bit rate (nrt-VBR) ■ Unspecified bit rate (UBR) ■ Available bit rate (ABR) ■ Guaranteed frame rate (GFR) For each service category, the ATM Forum specifies a set of parameters to describe both the traffic presented to the network and the QoS required of the network ATM is a good choice for WAN backbone networks for customers with accelerating bandwidth requirements and applications with advanced QoS requirements. ATM supports very high bandwidth requirements. Authentication Availability Typical technical goals include scalability, availability, network performance, security, manageability, usability, adaptability, and affordability. Availability refers to the amount of time a network is available to users and is often a critical goal for network design customers. Availability can be expressed as a percent uptime per year, month, week, day, or hour, compared to the total time in that period. For example, in a network that offers 24-hour, 7-days-a-week service, if the network is up 165 hours in the 168-hour week, availability is 98.21 percent. Availability is linked to reliability Availability is also linked to redundancy, but redundancy is not a network goal. Redundancy is a solution to a goal of high availability Availability is also associated with resiliency. Resiliency means how much stress a network can handle and how quickly the network can rebound from problems including security breaches, natural and unnatural disasters, human error, and catastrophic software or hardware failures. Five Nines Availability Some customers might insist on a network uptime of 99.999 percent, which is sometimes referred to as five nines availability. Five nines availability is extremely hard to achieve. You should explain to a network design customer that to achieve such a level, redundant equipment and links will be necessary, as will extra staffing possibly, and extremely reliable hardware and software. Availability = MTBF / (MTBF + MTTR) Bastion Host bastion host is a secure system that supports a limited number of applications for use by outsiders. The bastion host holds data that outsiders can access, such as web pages, but is strongly protected from outsiders using it for anything other than its limited purposes. Backbone ■ Building network: Multiple LANs within a building, usually connected to a building-backbone network. ■ Campus network: Multiple buildings within a local geographical area (within a few miles), usually connected to a campus-backbone network. Vertical Wiring which runs between floors building-backbone 2 buildings connected to each other is through a campus-backbone network WAN backbone medium-speed routers can connect buildings at each campus, The core layer of a three-layer hierarchical topology is the high-speed backbone of the internetwork. Backdoor A backdoor is a connection between devices in the same layer, as shown in Figure 5-6. A backdoor can be an extra router, bridge, or switch added to connect two networks. A backdoor can also be a hub; for example, someone might install a minihub in a conference room and accidentally connect the hub to two jacks instead of just one. Backdoors should be avoided because they cause unexpected routing and switching problems and make network documentation and troubleshooting more difficult. Bandwidth Domain In a LAN, the set of devices that share and compete for bandwidth. Bandwidth domains are bounded by switches, bridges, or routers. A hub or repeater does not bound a bandwidth domain. Also called a collision domain on Ethernet networks. A bandwidth domain is a set of devices that share bandwidth and compete for access to the bandwidth. A traditional bus topology or hub-based Ethernet, for example, is a single bandwidth domain. A switch divides up bandwidth domains and is often used to connect each device so that the network consists of many, extremely small bandwidth domains. On networks that experience collisions, including traditional Ethernet, a bandwidth domain is also called a collision domain. A bridge segments bandwidth domains so that devices on opposite sides of a bridge do not compete with each other for media access control. BER (Bit Error Rate) For WAN links, accuracy goals can be specified as a bit error rate (BER) threshold. If the error rate goes above the specified BER, the accuracy is considered unacceptable You can use a BER tester (also called a BERT) on serial lines to test the number of damaged bits compared to total bits. Ratio of received bits that contain errors to the total number of received bits. BGP & BGP-4 (Border Gateway Protocol) Interdomain routing protocol that exchanges reachability information with other BGP systems. BGP Version 4 (BGP4) is the predominant interdomain routing protocol used on the Internet. BGP does not offer route optimality It is a path vector routing protocol BGP is used on the Internet by peer routers in different autonomous systems to maintain a consistent view of the Internet’s topology. BGP replaces Exterior Gateway Protocol (EGP). BGP solves problems that EGP had with reliability and scalability BGP4 is specified in RFC 1771 Internal BGP (iBGP) can be used at a large company to route between domains. External BGP (eBGP) is used to route between companies and to participate in global Internet routing. eBGP is often used to multihome an enterprise’s connection to the Internet. But not always required The main goal of BGP is to allow routers to exchange information on paths to destination networks. Each BGP router maintains a routing table that lists all feasible paths to a particular network. BGP4 offers route authentication for the Internet connection & for routers that inject internet routes into the interior network Broadcast Domain The set of all devices that receives broadcast frames originating from any device within the set. Broadcast domains are bounded by routers (which do not forward broadcast frames). A switch or hub does not bound a broadcast domain. A router does not forward broadcasts or multicasts. All devices on one side of a router are considered part of a single broadcast domain. you can limit the size of a broadcast domain by implementing virtual LANs (VLAN). A single broadcast domain should be limited to a few hundred devices so that devices are not overwhelmed by the task of processing broadcast traffic. The distribution layer is often the layer that defines broadcast domains A broadcast domain is a set of devices that can all hear each other’s broadcast frames Capacity It is the data-carrying capability of a circuit or network, measured in bits per second (bps). Capacity (bandwidth): The data-carrying capability of a circuit or network, usually measured in bits per second (bps) Utilization: The percent of total available capacity in use The capacity of a network should be adequate to handle the offered load, even when there are peaks in network traffic. Chain Users at the access layer have a tendency to add networks to the internetwork inappropriately. For example, a network administrator at a branch office might connect the branch network to another branch, adding a fourth layer. This is a common network design mistake known as adding a chain. CHAP (Challenge Handshake Authentication Protocol) Security feature supported on links using PPP encapsulation that identifies the remote end of a PPP session using a handshake protocol and a variable challenge value that is unique and unpredictable. CHAP is more secured than PAP Remote users and remote routers that use PPP should be authenticated with CHAP CHAP provides protection against such attacks by PAP by verifying a remote node with a three-way handshake protocol and a variable challenge value that is unique and unpredictable. CIDR (Classless Interdomain Routing) It is a technique supported by BGP4 and other routing protocols based on route summarization (aggregation). CIDR allows routers to group routes together to cut down on the quantity of routing information carried by the core routers. CIDR specifies that IP network addresses should be assigned in blocks, and that routers in the Internet should group routes to cut down on the quantity of routing information shared by Internet routers. CDP (Cisco Discovery Protocol) Devicediscovery protocol that runs on Cisco-manufactured equipment, including routers, remote-access servers, and switches. Using CDP, a device can advertise its existence to other devices and receive information about other devices on the same LAN or on the remote side of a WAN. ODR (On-Demand Routing) uses the Cisco Discovery Protocol (CDP) to carry minimal routing information between a main site and stub routers. CDP specifies a method for Cisco routers and switches to send configuration information to each other on a regular basis. With the show cdp neighbors detail command, you can display detailed information about neighboring routers and switches, including which protocols are enabled, the network addresses for enabled protocols, the number and types of interfaces, the type of platform and its capabilities, and the version of Cisco IOS Software running on the neighbor. CDP is a media- and protocol-independent protocol. CDP runs over the data link layer, enabling two systems that support different network layer protocols to communicate. Clocking Scheme Congestion A condition whereby network traffic has reached or is approaching network capacity. ■ Forward explicit congestion notification (FECN): Informs the receiver of a frame that the frame crossed a path that is experiencing congestion Bit set by a Frame Relay network to inform a device receiving the frame that congestion was experienced in the path from source to destination. ■ Backward explicit congestion notification (BECN): Informs a sender that congestion exists in the path that the sender is using Bit set by a Frame Relay network in frames traveling in the opposite direction of frames encountering a congested path. Traffic shaping avoids congestion by reducing outbound traffic for a flow to a configured bit rate, while queuing bursts of traffic for that flow. Cut-through switching Some switches have the capability to automatically move from cut-through mode to store-and-forward mode when an error threshold is reached. This feature is called adaptive cut-through switching Frame-switching approach that streams data through a switch so that the leading edge of a frame exits the switch at the output port before the frame finishes entering the input port. A device using cut-through switching forwards frames as soon as the destination address is looked up and the outgoing port determined Default Router/Routing Routing table entry that is used to direct frames for which a next hop is not explicitly listed in the routing table. IP address of a router configured on an end station to allow the station to get to the rest of the internetwork. A default router is the address of a router on the local segment that a workstation uses to reach remote services. The default router is usually called the default gateway for historical reasons. A default route specifies where a packet should go if there is no explicit entry for the destination network in a router’s routing table. The default route is also sometimes called the gateway of last resort. A default route is a special type of static route that is used when there is no entry in the routing table for a destination network. Default route reduce resource usage Routers with a default route always send traffic that is not local to a peer router. Denial of Service (DoS) Denial-of-service (DoS) attacks target the availability of a network, host, or application, making it impossible for legitimate users to gain access. DoS attacks are a major risk because they can easily interrupt business processes and are relatively simple to conduct, even by an unskilled attacker. DoS attacks include the flooding of public servers with enormous numbers of connection requests, rendering the server unresponsive to legitimate users, and the flooding of network connections with random traffic, in an attempt to consume as much bandwidth as possible DoS attacks are usually the consequence of a network’s, host’s, or application’s inability to handle an enormous quantity of data, which crashes the system or halts services on the system Packet filters help protect network resources from unauthorized use, theft, destruction, and DoS attacks. To protect public servers from DoS attacks, server administrators should use reliable operating systems and applications that have been patched with the most recent security fixes. DHCP (Dynamic Host Configuration Protocol) Provides a mechanism for allocating IP addresses dynamically to minimize configuration and allow addresses to be reused when hosts no longer need them. DHCP allows to maximize usability by deploying user-friendly, host-naming schemes and easy-to-use configuration methods that make use of dynamic protocols DHCP is also a candidate for creating server redundancy DHCP servers can be placed at the access, distribution, or core layer. For large, globally distributed networks, redundant DHCP servers are usually placed in the access layer. This avoids excessive traffic between the access and distribution or core layers and allows each DHCP server to serve a smaller percentage of the user population. High availability: Statically assigned IP addresses are available anytime. Dynamically assigned IP addresses have to be acquired from a server first. If the server fails, an address cannot be acquired. To avoid this problem, you can deploy redundant DHCP servers or use static addresses. DHCP uses client/server model The goal of DHCP is that clients should require no manual configuration. In addition, the network manager should not have to enter any per-client configuration parameters into servers. DHCP supports three methods for IP address allocation: ■ Automatic allocation: A DHCP server assigns a permanent IP address to a client. ■ Dynamic allocation: A DHCP server assigns an IP address to a client for a limited period of time. ■ Manual allocation: A network administrator assigns a permanent IP address to a client, and DHCP is used simply to convey the assigned address to the client. (Manual allocation is rarely used because it requires per-client configuration, which automatic and dynamic allocations do not require.) Diffusing Update Algorithm (DUAL) Convergence algorithm used in EIGRP that provides loop-free operation. DUAL allows routers involved in a topology change to synchronize, while not involving routers that are unaffected by the change. DUAL specifies a method for routers to store neighbors’ routing information so that the routers can quickly switch to alternative routes. DUAL guarantees a loopfree topology, so there is no need for a hold-down mechanism, which is another feature that minimizes convergence time. DUAL is one reason that EIGRP (Enhanced Interior Gateway Routing Protocol) uses significantly less bandwidth than IGRP or other distance-vector protocols. A router using DUAL develops its routing table using the concept of a feasible successor. A feasible successor is a neighboring router that has the least-cost path to a destination. Distance Vector Routing Protocol (DVRP) The following protocols are distance-vector protocols (or derivatives of distance-vector protocols): ■ Routing Information Protocol (RIP) version 1 and 2 ■ Interior Gateway Routing Protocol (IGRP) ■ Enhanced IGRP (EIGRP) (an advanced distance-vector protocol) ■ Border Gateway Protocol (BGP) (a path-vector routing protocol) A distance vector is a course that also includes information on the length of the course Many distance-vector routing protocols specify the length of the course with a hop count. A hop count specifies the number of routers that must be traversed to reach a destination network. A distance-vector routing protocol maintains (and transmits) a routing table that lists known networks and the distance to each network. Distribution Layer Connects network services to the access layer in a hierarchical topology, and implements policies regarding security, traffic loading, and routing. A typical hierarchical topology that does scale is a core layer of high-end routers and switches that are optimized for availability and performance, a distribution layer of routers and switches that implement policies, and an access layer that connects users via hubs, switches, and other devices. The distribution layer includes routers and switches, and Frame Relay and T1 links The distribution layer connects network services to the access layer and implements policies regarding security, traffic loading, and routing. The distribution layer has many roles, including controlling access to resources for security reasons and controlling network traffic that passes the core for performance reasons. The distribution layer is often the layer that explains broadcast domains The distribution layer allows the core layer to connect sites that run different protocols while maintaining high performance. To improve routing-protocol performance, the distribution layer can summarize routes from the access layer. To maximize hierarchy, modularity, and performance, the distribution layer should hide detailed topology information about the access layer from core routers Routing protocols used in the distribution layer include RIPv2, EIGRP, OSPF, and ISIS. The distribution layer also sometimes uses ODR Dijkstra Algorithm The following protocols are link-state routing protocols: ■ Open Shortest Path First (OSPF) ■ Intermediate System-to-Intermediate System (IS-IS) ■ NetWare Internetwork Packet Exchange (IPX) Link Services Protocol (NLSP) A link-state routing protocol uses a shortest-path first algorithm, such as the Dijkstra algorithm, to determine how to reach destination networks It solves the problem of finding the shortest path from a source point in a mathematical graph to a destination point. One of the beauties of the algorithm is that while finding the shortest path to one destination, a source can also find the shortest path to all points in the graph at the same time. DMZ Firewall Topology (Chapter 5) DMZ is a secure system that supports a limited number of applications for use by outsiders. Security literature refers to a host in the DMZ as a bastion host. The bastion host holds data that outsiders can access, such as web pages, but is strongly protected from outsiders using it for anything other than its limited purposes. Public servers should be placed on a demilitarized zone (DMZ) network that is protected from other networks via firewalls. SNS (Social Networking Service) A social network service or social networking service, most often called SNS, is a medium for establishing social networks of people who share interests and/or activities. Encryption Application of a specific algorithm to alter the appearance of data, making it incomprehensible to those who are not authorized to see the information. Virtual private networks (VPN) use advanced encryption and tunneling to permit organizations to establish secure, end-to-end, private network connections over a thirdparty network Tunnels provide a logical, point-to-point connection across a connectionless IP network, enabling application of advanced security features. Encryption is applied to the tunneled connection to scramble data, thus making data legible only to authorized systems. Security also affects network performance. Security features such as packet filters and data encryption consume CPU power and memory on hosts, routers, and servers. Encryption can use upward of 15 percent of available CPU power on a router or server. Encryption is a process that scrambles data to protect it from being read by anyone but the intended receiver. An encryption device encrypts data before placing it on a network. A decryption device decrypts the data before passing it to an application. Encryption has two parts: ■ An encryption algorithm is a set of instructions to scramble and unscramble data. ■ An encryption key is a code used by an algorithm to scramble and unscramble data. Encryption algorithms, including 56-bit DES, 168-bit Triple DES, Microsoft Encryption (MPPE), 40- and 128-bit RC4, and 128-, 192-, and 256-bit AES asymmetric encryption An encryption technique in which a different key is used to encrypt a message than is used to decrypt the message symmetric encryption Encryption method that provides data confidentiality. When two end stations use symmetric encryption, they must agree on the algorithm to use and on the encryption key they will share. FDDI (Fiber Distributed Data Interface) LAN standard specifying a 100-Mbps token-passing network using fiber-optic cable and a dual-ring architecture to provide redundancy. FIFO (First In First Out) Method of sending traffic through a device whereby the first packet received is the first packet transmitted. Does not support prioritization. Queuing allows a network device to handle an overflow of traffic. It is a type of queuing service FIFO queuing provides basic store-and-forward functionality. It involves storing packets when the network is congested and forwarding them in the order they arrived when the network is no longer congested. FIFO has the advantage that it is the default queuing algorithm in some instances, so requires no configuration. FIFO has the disadvantage that it makes no decision about packet priority. FIFO provides no QoS functionality and no protection against an application using network resources in a way that negatively affects the performance of other applications. Firewall Router, software, appliance, or remote-access server designated as a buffer between connected networks. A firewall uses access lists and other methods to ensure the security of a network. A firewall is a system or combination of systems that enforces a boundary between two or more networks. A firewall can be a router with ACLs, a dedicated hardware box, or software running on a PC or UNIX system. A firewall should be placed in the network topology so that all traffic from outside the protected network must pass through the firewall. A security policy specifies which traffic is authorized to pass through the firewall. Packet filters can be set up on routers, firewalls, and servers to accept or deny packets from particular addresses or services. A firewall has a set of rules that specifies which traffic should be allowed or denied. A static stateless packet-filter firewall looks at individual packets and is optimized for speed and configuration simplicity. A stateful firewall can track communication sessions and more intelligently allow or deny traffic. Fragmentation Process of breaking a packet into smaller units when transmitting over a network medium that cannot support the original size of the packet. LFI (Link-Layer Fragmentation & Interleaving) reduces delay on slow WAN links by breaking up large packets and interleaving the resulting small packets with packets for applications that are delay sensitive. Cisco also supports the following three methods for performing Frame Relay fragmentation: ■ End-to-end Frame Relay fragmentation in accordance with the FRF.12 standard ■ Trunk Frame Relay fragmentation in accordance with the FRF.11 Annex C standard ■ Cisco proprietary fragmentation for voice encapsulation Frame Relay Industry-standard, switched data link layer protocol that handles multiple virtual circuits between connected devices. Frame Relay has become a popular replacement for both X.25 and leased-line networks because of its efficiency, flexible bandwidth support, and low latency. Companies also used Frame Relay and point-to-point networks for their private WANs Frame Relay is a high-performance WAN protocol that operates at the physical and data link layers of the OSI reference model. Frame Relay offers a cost-effective method for connecting remote sites, typically at speeds from 64 kbps to 1.544 Mbps Frame Relay provides a connection-oriented data link layer service. Frame Relay virtual circuits fall into two categories: ■ Switched virtual circuits (SVC): Temporary connections for supporting occasional data transfer ■ Permanent virtual circuits (PVC): Permanently configured circuits that are established in advance of any data transfer Frame Relay includes two congestion-notification schemes: ■ Forward explicit congestion notification (FECN): Informs the receiver of a frame that the frame crossed a path that is experiencing congestion ■ Backward explicit congestion notification (BECN): Informs a sender that congestion exists in the path that the sender is using The term Frame Relay/ATM interworking is used to describe the protocols and processes for connecting ATM and Frame Relay WANs. Gateway of Last Resort The default route is also sometimes called the gateway of last resort. A default route specifies where a packet should go if there is no explicit entry for the destination network in a router’s routing table Global Synchronization Random early detection (RED), which works by monitoring traffic loads at points in a network and randomly discarding packets if congestion begins to increase. Experience shows that if routers do not apply some sort of randomization to the dropping of packets, multiple TCP sessions tend to slow their transmission rate simultaneously. (The sessions take a synchronized porpoise dive, which in more technical terms is often called global synchronization. TCP global synchronization means when overwhelming amount of traffic causes simultaneous packet loss across many TCP sessions (Hedlund, 2013). This happens because TCP uses a single congested link for transmission, and as a result of excess traffic, it initiates packet loss. The way TCP global synchronization effects congestion is that when affected TCP sessions increases its send rate which ultimately results in utilization to go up high, and it reaches that stage where congestion occurs. In addition, TCP global synchronization also occurs because of unexpected congestion. When this type of rapid congestion initiates, it has an adverse effect on packets by causing it to fail and drop. This also simultaneously affects many TCP flows all at once Hash Function Any well-defined procedure or mathematical function that converts a large, possibly variable-sized piece of data into a small hash code, or hash. The hash is generally a single integer that serves as an index into an array or as an integrity check of the input. The function is not reversible to produce the original input. Helper Address Address configured on a router interface to which broadcasts received on that interface will be sent, commonly used to forward DHCP requests. the DHCP server is often placed on a different network segment than the end systems that use it. If the server is on the other side of a router, the router can be configured to forward DHCP broadcasts from end systems. The router forwards the broadcasts to a server address configured via the ip helper address command on a Cisco router. With Cisco routers, you can use the ip helper-address command on each router interface where clients reside to cause the router to become a DHCP relay agent. Hot Standby Router Protocol (HSRP) Provides high network availability and transparent network topology changes. HSRP creates a Hot Standby router group with a lead router that services all packets sent to the Hot Standby address. The lead router is monitored by other routers in the group, and if it fails, one of these standby routers inherits the lead position and the Hot Standby group address. Hosts use the Hot Standby address as the address of their default gateway. Cisco Hot Standby Router Protocol (HSRP) provides a way for an IP workstation to keep communicating on an internetwork even if its default gateway becomes unavailable. HSRP works by creating a virtual router, also called a phantom router, as shown in ICMP Internet Control Message Protocol (ICMP) echo request is also known as a ping packet Network layer TCP/IP protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792. Interior Gateway Routing Protocol (IGRP) An interior routing protocol developed by Cisco to address the problems associated with routing in large, heterogeneous networks. Classful routing protocols include RIP version 1 and the Interior Gateway Routing Protocol (IGRP). It is a type of distance-vector routing protocol Cisco developed the proprietary distance-vector Interior Gateway Routing Protocol (IGRP) in the mid-1980s to meet the needs of customers requiring a robust and scalable interior routing protocol. Many customers migrated their RIP networks to IGRP to overcome RIP’s 15-hop limitation and reliance on just one metric New type is Enhanced IGRP which is an advanced version of IGRP developed by Cisco. Provides superior convergence properties and operating efficiency, and combines the advantages of linkstate protocols with those of distance vector protocols. EIGRP is compatible with IGRP and provides an automatic redistribution mechanism to allow IGRP routes to be imported into EIGRP, and vice versa IP (Internet Protocol) Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, differentiated services, forwarding packets, and fragmentation and reassembly. Defined in RFC 791. There is IPv4 & IPv6 In an IP environment, you should avoid increasing the MTU to larger than the maximum supported for the media traversed by the frames, to avoid fragmentation and reassembly of frames. IP Header TTL(Time-to-Live) is a field in the IP header of an IP packet that is decremented each time a router processes the frame). Field in an IP header that indicates how long a packet is considered valid. The record-route option causes each router to put its address in the options field of the IP header, which can cause extra processing time The purpose of the Type of Service subfield was to help a router select a route from a set of routes with different characteristics. The Type of Service subfield within the Type of Service field in an IP header had 4 bits (see Figure 13-1): ■ Delay bit (D): Tells routers to minimize delay ■ Throughput bit (T): Tells routers to maximize throughput ■ Reliability bit (R): Tells routers to maximize reliability ■ Cost bit (C): Tells routers to minimize monetary cost TCP Header The Window field in the TCP header is 16 bits With the SACK mechanism, the TCP recipient fills in the SACK option field in the TCP header to inform the sender of the noncontiguous blocks of data that have been received. ISP Tiers ISPs and NSPs are sometimes classified as being Tier 1 through Tier 5. Tier 1 ISPs are large, international providers, whereas Tier 5 ISPs are small, specialized providers, sometimes located in a town or rural area. A Tier 5 provider could be as small as an Internet café. When a smaller ISP pays a larger ISP for the privilege of sending traffic through the larger ISP’s network. This is often called buying transit. A Tier 1 provider has a 24/7 network operations center and a national or international backbone with at least DS-3 connectivity, and more likely OC-3 to OC-48. Tier 2 providers also have high-bandwidth backbones and 24/7 operations, but they are limited to a regional or national presence, and they buy transit from a Tier 1 provider for traffic that goes outside the region. A Tier 3 provider is typically a regional provider for a small or medium-sized region. A Tier 3 provider buys transit from multiple upstream providers and runs a default-free routing table. Tier 4 could be a metropolitan provider that is multihomed to two regional providers. Tier 5 might be a small, single-homed provider that connects end users via a wireless or cable modem service. Jitter Communication line distortion caused by the variation of a signal from its reference timing positions. Variations in delay, called jitter, cause disruptions in voice quality and jumpiness in video streams. Desktop audio/video applications can minimize jitter by providing a jitter buffer. Internetwork Performance Monitor (IPM) features include ■ Monitoring and measurement of jitter LEAP (Lightweight Extensible Authentication Protocol) LEAP supports user-based authentication and dynamic WEP (Wired Equivalent Privacy) keys that are generated after authentication and when session timeouts occur. LEAP supports mutual authentication, which means that the client authenticates the server and the server authenticates the client Link-State Advertisement (LSA) Multicast packet used by link-state protocols that contains information about neighbors and path costs. LSAs are used by the receiving routers to maintain their routing tables. With link-state routing, routers use a Hello protocol to establish a relationship (called an adjacency) with neighbor routers. Each router sends link-state advertisements (LSA) to each adjacent neighbor. The advertisements identify links and metrics. Each neighbor that receives an advertisement propagates the advertisement to its neighbors Load Balancing In routing, the capability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Sometimes called load sharing to indicate that most protocols do not evenly balance traffic. Servers talk to other servers to implement directory services, to cache heavily used data, to mirror data for load balancing and redundancy, to back up data, and to broadcast service availability. Load sharing, sometimes called load balancing, allows two or more interfaces or paths to share traffic load. Gateway Load Balancing Protocol (GLBP) allows for load sharing along with redundancy GLBP provides load balancing over multiple routers using a single virtual IP address and multiple virtual MAC addresses. Security can also make it harder to offer load balancing. Some security mechanisms require traffic to always take the same path so that security mechanisms can be applied uniformly. Long-Reach Ethernet (LRE) LRE is used to connect buildings and rooms within buildings in campus networks. LRE provides a point-to-point link that can deliver a symmetrical, full-duplex, raw data rate of 11.25 Mbps over distances of up to 1 mile (1.6 km). LRE enables the use of Ethernet over existing, unconditioned, voice-grade copper t
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