Semester 3 Chapter 1:

OSI Model

Identify and describe the functions of each of the seven layers of the OSI reference model.

Application:

This layer provides services to application processes, such as E-mail, file transfer and terminal emulation, that are outside the OSI reference model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronises cooperating applications, and establishes agreement on provedures for error recovery and control of data integrity.

Presentation:

This layer ensures that information sent by the application layer of one system will be readable by the application layer of another. The presentation layer is also concerned with the data structures used by programs amd therefore negotiates data transfer syntax for the application layer.

Session:

The session layer establishes, manages and terminates sessions between applications and manages data exchange between presentation layer entities.

Transport:

This layer is responsible for reliable network communication between end nodes. The transport layer provides mechanisms for establishment, maintenance and termination of virtual circuits, transport fault detection and recovery, and information flow control.

Network:

The network layer provides connectivity and path selection between two end systems. The network layer is the layer at which routing occurs.

Data Link:

Provides transit of data across a physical link. The data link layer is concerned with physical addressing, network topology, line discipline, error notification, oredered delivery of frames and flow control. The IEEE divides the layer into two sub layers: the MAC sublayer and the LLC sublayer.

Physical:

The physical layer defines the electrical, mechanical, procedural, and functional specifications for the physical links between systems.

Define and explain the 5 conversion steps of data encapsulation.

1: Build the data: As a user sends for example, an email message, its alphanumeric characters are converted to data that can travel across the internetwork.

2: Package the data for end to end transport: The data is packaged for internetwork transport. By using segments, the transport function ensures that the message hosts at both ends of the email system can reliably communicate.

3: Add the network address to the header: The data is put into a packet or a datagram that contains a network header with source and destination logical IP addresses. These network addresses help network devices send the packets across the network along a dyna,ically chosen path.

4: Add the local (MAC) address to the data link header: Each network device must put the packet into a frame. The frame includes a header with the physical address of the next directly connected device in the path.

5: Convert to bits for transmission: The frame must be converted into a pattern of 1s and 0s (bits) for transmission on the medium (usually a wire). A clocking function enables the devices to distinguish these bits as they travel across the medium. The medium on the physical internetwork can vary along the path used.

Identify at least 3 reasons why the industry uses a layered model.

-           It breaks the network into smaller, simpler parts that are easier to develop

-           It facilitates standardisation of network components to allow multiple vendor development and support.

-                     It allows different types of network hardware and software to communicate with each other.

-                     Prevents changes in one layer from affecting the other layers, so that they can develop more quickly.

Addressing

Define and describe the function of a MAC address.

A standardised data link layer address that is required for every device that connects to a LAN. Other devices in the network use these addresses to locate specific devices in the network and to create and update routing tables and data structures. MAC addresses are six bytes long and are controlled by the IEEE.

A MAC address is a 48-bit address expressed as 12 hexadecimal digits. The first six hexadecimal digits of a MAC address contain a manufacturer identification, also known as an Organisationally Unique Identifier. The last six hexadecimal digits are administered by each vendor and often represent the interface serial number.

Describe data link addresses and network addresses, and identify the key differences between them.

Data link addresses are addresses that reside at the data link layer of the OSI model. Data link addresses are MAC addresses. MAC addresses are flat addresses, that is, they have no hierarchy, unlike network addresses. Network addresses are made up of two main parts; a network portion and a host portion. The network portion identifies the network that the host resides on. Routers use network layer addresses to make path determination decisions for network layer packets. Routers also use the data link layer address to send the packet to its intended destination host. As a packet trvels across a network, the IP address of the destination never changes but the data link address changes so that the packet can be switched to the next hop.

Describe and create the different classes of IP addresses [and subnetting].

Class A addresses use the first 8 bits of the IP address to identify the network which the host belongs to. A class A IP address is in the range 0.0.0.0 to 127.255.255.255, although the 127.0.0.0 address range is reserved for special purposes. The subnet mask of 255.0.0.0 will also identify a class A network. Also, the first bit in a class A address is always 0.

Class B IP addresses have the first two bits of their addresses set to 10. This puts class B IP in the range 128.0.0.0 to 191.255.255.255. Class B networks always use the first 16 bits of the IP address to identify the network. Class B networks always have the subnet mask 255.255.0.0.

Class C networks are identified by having the first three bits of their IP addresses set to 110. The range for class C IP addresses is 192.0.0.0 to 223.255.255.255.

Subnetting involves borrowing contiguous bits from the host range in an IP address. To subnet you must borrow at least two bits and leave two bits. You cannot have all 0s or 1s for a subnet ID. Therefore the number of usable subnets is always 2 less than the total. To work out how many subnets you have created you should multiply 2 to the power of the number of bits you have borrowed. EG. 2^2 = 4, 2^3 = 8, 2^4 = 16. For every contiguous bit you borrow from a host range, you double the amount of subnets possible.

Identify the functions of the TCP/IP Transport Layer Protocols.

The TCP/IP Transport layer provides two protocols, Transmission Control Protocol and User Datagram Protocol.

TCP is a connection oriented reliable protocol that provides flow control by providing sliding windows and offers reliability by providing sequence numbers and acknowledgements. TCP resends anything that is not acknowledged and supplies a virtual circuit between end user applications. The advantage of TCP is that it provides guaranteed delivery of segments.

UDP is a connectionless unreliable protocol that is responsible for transmitting messages but provides no software checking for segment delivery. The advantage of UDP is speed. Because UDP provides no acknowledgements, less traffic is sent across the network, making transfer faster.

IOS

Log into a router using both user and priviledged modes.

Router con0 is now available

Press Return to get started

User access verification

Password:

Router>

Router>enable

Password:

Router#

Use the context-sensitive help facility

Typing a question mark (?) at the user mode prompt (Router>) or privileged prompt (Router#) will display a list of context sensitive, commonly used commands

Use the command history and editing features.

Ctrl-P or Up arrow key: Recalls last (previous) command

Ctrl-N or Down arrow key: Recalls most recent command

Show History: Shows command buffer

Ctrl-A: Moves to the beginning of the command line

Ctrl-E: Moves to the end of the command line

Esc-B: Moves back one word

Ctrl-F: Moves forward one character

Ctrl-B: Moves back one character

Esc-F: Moves forward one word

Examine router elements (RAM, ROM, CDP, show)

RAM: Stores routing tables, the ARP cache, the fast-switching cache, packet bufferring and packet hold queues. RAM also provides running memory for the routers configuration file while the router is powered on.

ROM: Contains power-on diagnostics, a boot-strap program, and operating system software. Software upgrades in ROM require replacing pluggable chips on the motherboard.

CDP: The Cisco discovery protocol provides a single proprietary command that enables network administrators to access a summary of what the configurations look like on other directly connected routers

Show: show <command> helps you obtain vital information that you need when monitoring and troubleshooting router operations.

Manage configuration files from the priviledged exec mode.

configure terminal: Configures the router manually from the console terminal

configure memory: Loads configuration information from non-volatile random access memory.

copy tftp running-config: Loads configuration information from a network tftp server

show running-config: Displays the current configuration in RAM

copy running-config startup-config: Stores the current configuration in RAM into NVRAM

copy running-config tftp: Stores the current configuration in RAM on a network tftp server

show startup-config: Displays the saved configuration, which is the contents of NVRAM

erase startup-config: Erases the contents of NVRAM

Control router passwords, identification, and banner.

Router Passwords:

enable password <password>

enable secret <password>

Identification:

hostname <Router Name>

Banner:

banner motd# <Type your message here>

Identify the main Cisco IOS commands for router startup.

Router#            show running-config

Router#            show startup-config

Router#            copy running-config startup-config

Router#            reload

Enter an initial configuration using the setup command.

Router# setup

Enter Hostname:

Enter Enable Secret:

Enter Enable Password:

Enter Virtual Terminal Password:

Configure IP? [Yes]

Configure Interface Serial0: Yes

Configure Interface Serial1: Yes

Configure Interface Ethernet 0: Yes

Configure Interface Ethernet 1: Yes

Copy and manipulate configuration files.

configure terminal: Configures the router manually from the console terminal

configure memory: Loads configuration information from non-volatile random access memory.

copy tftp running-config: Loads configuration information from a network tftp server

show running-config: Displays the current configuration in RAM

copy running-config startup-config: Stores the current configuration in RAM into NVRAM

copy running-config tftp: Stores the current configuration in RAM on a network tftp server

show startup-config: Displays the saved configuration, which is the contents of NVRAM

erase startup-config: Erases the contents of NVRAM

List the commands to load Cisco IOS software from: flash memory, a TFTP server, or ROM.

Router (config)# boot system flash IOS_filename

Router (config)# boot system tftp IOS_filename tftp_address

Router (config)# boot system rom

Prepare to backup, upgrade, and load a backup Cisco IOS software image.

show flash

copy flash tftp

copy tftp flash

Prepare the initial configuration of your router and enable IP.

Router>ena

Password:

Router#configure terminal

Router(config)#hostname <name>

Hostname(config)interface e0

Hostname(config-if)ip address <address> <subnet mask>

Hostname(config-if)no shut

Add the RIP routing protocol to your configuration.

Hostname(config-if)router rip

Hostname(config-router)network xxx.xxx.xxx.xxx

Configure IP Addresses.

Hostname(config)interface e0

Hostname(config-if)ip address <address> <subnet mask>

Hostname(config-if)no shut

Verify IP Addresses.

ping <ipaddress>

show interface e0/1/2/3 s0/1/2/3

show ip interface

Explain the services of separate and integrated multiprotocol routing.

Routers are capable of concurrently supporting multiple independant routing protocols and maintaining routing tables for several routed protocols.

List problems that each routing type encounters when dealing with topology changes and describe techniques to reduce the number of these problems.

Static Routing:

Static routing is where the network administrator has to input route changes directly into the routing table whenever there is a change to the networks topology. One way to solve the problem of constantly having to manually update routing tables is to employ a dynamic routing protocol. Dynamic routing protocols automatically adjust routing tables whenever there is a change to the topology by passing periodic or event triggered updates to neighbouring routers. These neighbouring routers then update their routing tables and recalculate the best routes to known networks.

Dynamic Routing:

Dynamic Routing protocols encounter the problem of routing loops. Routing loops occur when routers suffer from slow convergence due to differing line speeds and latency. Because routers do not have a consistent view of the network, routing updates can activate routes that a previous router has stated is unreachable. This can cause a count to infinity where the routers' metric counts to infinity as the packets loop around and around. The distance vector protocol answer to the count to infinity problem is to define a maximum. Distance vector protocols have a maximum hop count. When the packet has the maximum hop count value, the router discards the packet.

Another answer to the problem of routing loops is the Split Horizon. Split Horizon stops a router that received an update sending the same information out of the the same interface.

Holddown timers are also used to prevent routing loops. Holddown is when a router will reject routing updates with a poorer metric than it originally received from a neighbour router that indicates the network is down. If the router receives an update from that same router it will mark the route as accessible. If the router receives an update from another router with a poorer metric for the same route, it rejects the update for the holddown period.

A poison reverse update is designed to prevent larger routing loops. A poison reverse updates explicitly indicate that a network or subnet is unreachable, rather than implying that a netwrok is unreachable by excluding it in updates.
Chapter 2:

LAN Switching

Describe the advantages of LAN segmentation.

The primary reason to segment LANs is to isolate traffic between segments and to achieve more bandwidth per user by creating smaller collision domains. Each segment is its own collision domain. Without LAN segmentation, LANs larger than a small workgroup would quickly become clogged with traffic and collisions and would deliver severely reduced bandwidth.

Describe LAN segmentation using bridges.

Bridges learn a network's segmentation by building address tables that contain the physical address of each networkdevice, as well as the port to use to reach the device. Ethernet bridges are transparent to the other devices on the network

Describe LAN segmentation using routers.

A router operates at the network layer and bases all of its forwarding decisions on the layer 3 protocol address. It accomplishes this by examining the destination address on the data packet and then looking in its routing table for forwarding intstructions.

Describe LAN segmentation using switches.

A LAN switch is a high-speed multi-port bridge that has one port for each node or segment of the LAN. A switch segments a LAN into microsegments, thereby creating collision-free domains from one formerly larger collision domain. Switches make frame forwarding decisions by building a table of the MAC addresses of the hosts attached to each port.

Describe the benefits of network segmentation with bridges.

Ethernet LANs that use a bridge for segmenting the LAN provide more bandwidth per user because there are fewer users on the segments than when compared to the entire LAN. The bridge only allows those frames that have destinations outside the segment to pass through.

Describe the benefits of network segmentation with routers.

Routers create the highest level of segmentation because of their capability to make exact determinations of where to send the data packet.

Describe the benefits of network segmentation with switches.

In switched ethernet, each node is directly connected to one of its ports or a segment that is connected to one of the switch's ports. This creates a 10/100 Mbps connection between each node and each segment on the switch. A computer directly connected to an ethernet switch is its own collision domain and accesses the full 10/100 Mbps.

Name and describe two switching methods.

Store And Forward: The entire frame is received before any forwarding takes place. The destination and/or the source address are read and filters are applied before the frame is forwarded.

Cut-Through: The switch reads the destination address before receiving the entire frame. The frame is then forwarded before the entire frame arrives.

Fast-forward switching: This method of switching offers the lowest level of latency by immediately forwarding a packet after receiving the destination address. Because fast-forward switching does not check for errors, there may be times when frames are relayed with errors. Although this occurs infrequently and the destination network adapter discards the faulty frame upon receipt.

Fragment-free switching: Fragment-free switching filters out collision fragments, which are the majority of packet errors, before forwarding begins. Fragment-free switching waits until the received packet has been determined not to be a collision fragment before forwarding the packet

Distinguish between cut-through and store-and-forward switching.

Cut-through - The switch reads the destination address before receiving the entire frame. The frame is then forwarded before the entire frame arrives. This mode decreases the latency of the transmission and has poor LAN Switching error detection.

Fast-forward switching - This method of switching offers the lowest level of latency by immediately forwarding a packet after receiving the destination address. Because fast-forward switching does not check for errors, there may be times when frames are relayed with errors.

Fragment-free switching - Fragment-free switching filters out collision fragments, which are the majority of packet errors, before forwarding begins. Fragment-free switching waits until the received packet has been determined not to be a collision fragment before forwarding the packet

Define and describe the function of a MAC Address.

Previously answered above

Ethernet

Describe network congestion problem in Ethernet networks.

Todays networks are experiencing an increase in the transmission of large graphics files , images, full-motion video, and multimedia applications, as well as an increase in the number of users in the network. All these factors place an even greater strain on bandwidth. As more people utilize a network to share large files, access file servers, and connect to the internet, network congestion occurs. This can result in slower response times, longer file transfers, and network users becoming less productive due to network delays.

Describe full- and half-duplex Ethernet operation.

Ethernet is a half-duplex design. Each ehternet host checks the network to see whether data is being transmitted before it transmits additional data. If the network is already in use, the transmission is delayed. Despite transmission deferral, two or more ehternet hosts can transmit at the same time, which results in a collision. When a collision occurs, the hosts that first detects the collision will send a jam signal. Upon hearing the jam signal, each host will wait a random period of time before attempting to retransmit. this process takes up all of the available bandwidth, resulting in a total loss of transmission until the random period of time expires.

Full-duplex ethernet allows the transmission of a packet and the reception of a different packet at the same time. This simultaneous transmission and reception requires the use of two pairs of wires in the cable and a switched connection between each node. This connection is considered point to point and is collision free. To transmit and receive simultaneously, a dedicated port is required for each node.

Describe the features and benefits of Fast Ethernet.

Fast ethernet offers a speed increase 10 times that of the 10BaseT ethernet specification while preserving such qualities as frame format, MAC mechanisms, and MTU. Such similarities allow the use of existing 10BaseT applications and network management tools on Fast Ethernet networks.

Describe the guidelines and distance limitations of Fast Ethernet.

Fast Ethernet can carry 100 Mbps, using baseband signalling, with a maximum unrepeated distance of 100 metres using Cat-5 UTP. Uses the standard ethernet broadcast-oriented logical bus topology. Based on extension to the 802.3 specification.

Chapter 3:

VLANs

Describe the operation of the Spanning Tree Protocol and its benefits.

The Spanning-Tree Algorithm, implemented by the Spanning-Tree Protocol, prevents loops by calculating a stable spanning-tree network topology. When creating fault-tolerant networks, a loop-free path must exist between all Ethernet nodes in the network. The Spanning-Tree Algorithm is used to calculate a loop-free path. Spanning-tree frames, called bridge protocol data units (BPDUs), are sent and received by all switches in the network at regular intervals and are used to determine the spanning-tree topology.

A switch uses Spanning-Tree Protocol on all Ethernet and Fast Ethernet based VLANs. Spanning-Tree Protocol detects and breaks loops by placing some connections in a standby mode, which are activated in the event of an active connection failure. A separate instance of Spanning-Tree Protocol runs within each configured VLAN, ensuring Ethernet topologies that conform to industry standards throughout the network.

Describe the operation of virtual LANs.

A VLAN is a logical grouping of devices or users that can be grouped by function, department, or application, regardless of their physical segment location. VLAN configuration is done at the switch via software.

Describe the benefits of virtual LANs.

Switches have many benefits. A LAN switch allows many users to communicate in parallel through the use of virtual circuits and dedicated network segments in a collision free environment. This maximizes the bandwidth available on the shared medium.

Moving to a switched LAN environment is very cost-effective because you can reuse existing hardware and cabling.

The power of the switch combined with the software to configure LANs give network administrators great flexibility in managing the network.

VLANs can effectively extend the firewall from the router to the switch.

Broadcast traffic within one VLAN is not transmitted outside the VLAN. Conversely, adjacent ports do not receive any of the broadcast traffic generated from other VLANs. This type of configuration substantially reduces the overall broadcast traffic, frees bandwidth for real user traffic, and lowers the overall vulnerability of the network to broadcast storms.

Flow Control:

Define flow control and describe the three basic methods used in networking.

A technique for ensuring that a transmitting entity does not overwhelm a receiving entity with data When the buffers on the receiving device are full, a message is sent to the sending device to suspend the transmission until the data in the buffers has been processed.

Windowing: The number of data packets a the sender is allowed to have outstanding without having received an acknowledgment is known as windowing

Acknowledgment: Positive acknowledgment with retransmission is one technique that guarantees reliable delivery of data. Positive acknowledgment requires a recipient to communicate with the source, sending back an acknowledgment message when it receives data.

Three-Way Handshake: TCP hosts establish a connection-oriented session with one another using a three-way handshake. A three-way handshake synchronises a connection at both ends before data is transferred.  The exchange of introductory sequence numbers during the connection sequence is important because it ensures that any data that is lost due to transmission problems can be recovered.

Chapter 5:

OSI Model

Describe the three major portions of an IP address.

The 3 major portions of an IP address are:

1.      Network: A logically grouped segment of computers within a common network

2.      Subnet: Subdivisions of a major network. Made by borrowing bits from the host range.

3.      Host: The computer, server or other device that is attached to a network segment

Describe the functions of the TCP/IP network-layer protocols and how they are used for path determination.

Connectionless network processes are often referred to as being packet switched. In these processes, as the packets pass from source to destination they can switch to different paths, as well as, possibly arrive out of order. IP is a connectionless system; it treats each packet independently.

In connection-oriented systems, a connection is established between the sender and the recipient before any data is transferred. Connection-oriented network processes establish a connection with the recipient first and then begin the data transfer. All packets travel sequentially across the same virtual or physical circuit.

Routing Protocols:

Add the IGRP routing protocol to your configuration.

router igrp <AS Number>

network <directly connected networks>

Describe the function of a router in delivering data packets between different networks.

Router packet delivery process: After examining a packet's destination protocol address, the router determines that it either knows or does not know how to forward the packet to the next hop. If the router does not know how to forward the packet and there is no default route, it typically drops the packet. If the router knows how to forward the packet, it changes the destination physical address to that of the next hop and transmits the packet.

Describe the function and limitations of static route entries in a Router.

Before routing begins, the network administrator establishes static routing table mappings. These mappings do not change unless the network administrator changes them.

Describe the functions and advantages of dynamic routing protocols.

They adjust to changing network circumstances. They do this by analyzing incoming routing update messages.

Describe the difference between routed and routing protocols.

Routed protocols: Protocol that can be routed by a router. A router must be able to interpret the logical internetwork as specified by that routed protocol.

Routing protocols: Process of finding a path to a destination host. Routing is very complex in large networks because of the many potential intermediate destinations a packet might traverse before reaching its destination host.

Describe the function of a routing table in the router.

Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes.

Describe what a routing metric is and what the various components mean.

Routing metrics are used to help router to help determine the path to choose for the packet to travel:

Hope count: The number of routers a packet must go through to reach a destination

Load: The amount of network activity on a network resource such as a router or a link

Reliability: The error rate of each network link

Bandwidth: The data capacity of a link

Delay: The length of time required to move a packet from source to destination

Cost: The generic term based on bandwidth, dollar expense, or other measurement or metric, that is used to represent the desirability of a path.

Describe the difference between distance vector and link state routing protocols.

Distance Vector routing protocol: Based on the number of hops in a route to find a shortest-path spanning tree. Distance vector routing algorithms call for each router to send its entire routing table in each update.

Link State routing protocols: When each router broadcasts or multicasts information regarding the cost of reaching each of its neighbors to all nodes in the internetwork.

Describe what convergence is in a network.

The speed and ability of a group of internetworking devices running a specific routing protocol to agree on the topology of an internetwork after a change in that topology

Describe what an autonomous network is and what general type of protocol is used to communicate between autonomous networks.

Autonomous networks are Networks under a common administration sharing a common routing strategy. Areas subdivide autonomous systems. An autonomous system must be assigned a unique 16-bit number by the IANA.

Interior Gateway protocols are: Used to exchange routing information within an autonomous system.

Exterior Gateway protocols are: Internet protocol for exchanging routing information between autonomous systems. EGP is an obsolete protocol that has been replaced by BGP.

Chapter 6:

General

Describe what an access control list is.

An access control list is a list of instructions you apply to a router's interface. These lists tell the router what kinds of packets to accept and what kinds of packets to deny.

Describe the function of Access control lists on routers.

The function of Access control lists on routers is allows or deny certain packets to go through the router.

Describe the reasons access control list are used.

Four reasons for using access control lists are:

1.      Limit network traffic and increase network performance

2.      Provide traffic flow control

3.      Provide a basic level of security for network access

4.      Decide which types of traffic are forwarded or blocked at the router interfaces

Describe how segmentation with routers and access control lists are related.

With segmentation, you use a router to create two or more different networks. Each network is attached to a router interface. By using access control lists you can control what traffic gets to enter or exit an interface and where that traffic can be routed.

Configure Standard and extended access lists to filter IP traffic.

Standard access lists: Block all traffic from a network, allow all traffic from a specific network, or deny protocol suites. Standard ACLs check the source address of packets that could be routed.

Eg.  access list 1 deny 192.168.220.0 0.0.0.255

Extended access lists are: most often to test conditions because they provide a greater range of control than standard ACLs. You would use an extended ACL when you want to allow Web traffic but deny File Transfer Protocol (FTP) or telnet from non-company networks. Extended ACLs check for both source and destination packet addresses.

Eg. access list 100 deny tcp 192.168.220.0 0.0.0.255 192.168.250.0 0.0.0.255

Monitor and verify selected access list operations on the router.

N/A

OSI Model

Define the layers of the OSI model where standard access control lists function, and what fields in the data packet header they are concerned with.

Standard access control lists can filter traffic at the network layer. ACLs filter routed packets. The fields in the data packet ACLs are concerned with are: Frame Headers, Packet Header and Segment Header

Define the layers of the OSI model where extended access control lists function, and what fields in the data packet header they are concerned with.

Extended access control lists are used to filter traffic at the network layer of the OSI model. They can also be used to filter traffic transport layer protocols. The fields in the data packet ACLs are concerned with are: Frame Headers, Packet Header and Segment Header

Chapter 7:

General

Describe connectionless data packet delivery over a network.

Connectionless network processes are often referred to as being packet switched. In these processes, as the packets pass from source to destination they can switch to different paths, as well as, possibly arrive out of order. IP is a connectionless system; it treats each packet independently.

Novell IPX Protocol

Describe the format for IPX addressing and how unique networks are identified.

IPX addresses have the following format:

A two-part address-the network number and the node number.  The node number is usually the Media Access Control (MAC) address for a network interface in the end node. Novell IPX supports multiple logical networks on an individual interface; each network requires a single encapsulation type. The network administrator is responsible for assigning network numbers to router interfaces and nodes.

Describe the function of the Service Advertisement Protocol (SAP) within IPX.

Netware’s SAP allows network resources, including file and print servers, to advertise their network addresses and the services they provide. Each service is identified by a number, called a SAP identifier. SAP updates are sent every 60 seconds.

Describe the three major types of SAP advertisements.

The three major types of SAP advertisements are:

4: Netware File Server

7: Print Server

24: Remote bridge Server (Router)

Describe the concept of client /server in a Novell network.

NetWare clients automatically discover available network services because Novell servers and routers announce their services by using SAP broadcasts.

Describe the function and process of Get Nearest Server (GNS) in a Novell network.

One type of SAP advertisement is GNS, which enables a client to quickly locate the nearest server for login. The NetWare client/server interaction begins when the client powers up and runs its client startup programs. These programs use the clients adapter on the LAN and initiate the connection sequence for the Netware command shell to use. The connection sequence is a broadcast that comes from a client using SAP. The nearest NetWare file server responds with another SAP.; the protocol type is GNS. From that point on the client can log into the target server, make a connection, set the packet size, and proceed to use server resources.

Monitor Novell IPX operation on the router.

N/A

List the required IPX address and encapsulation type.

N/A

Enable the Novell IPX protocol and configure interfaces.

N/A

Configure IPX access lists and SAP filters to control basic Novell traffic.

N/A

Routing

Describe the concept of multi-protocol routing.

Multi-protocol routing is where a router delivers packets from several routed protocols, such as TCP/IP & IPX over the same data links.

Describe what function of the router will control the flow of SAP advertisements across the network.

Routers do not forward SAP broadcasts. Instead each router builds its own SAP table and forwards the SAP table to other routers. By default this occurs every 60 seconds, but the router can use access control lists to control the SAPs accepted or forwarded.

Semester 4

Chapter 2:

WANs

Differentiate between the following WAN services: Frame Relay, ISDN/LAPD, HDLC, and PPP.

Frame relay is a statistical multiplexed service which uses layer 2 identifiers and permanent virtual circuits. Information contained in frames shares bandwidth with other WAN Frame Relay service providers.

ISDN / LAPD: A set of digital services that transmits voice and data over existing phone lines. LAPD is an ISDN data-link layer protocol for the D channel.

HDLC: A bit oriented synchronous data link layer encapsulation protocol developed by ISO. Is very streamlined and has no windowing or flow control.

PPP: PPP is an encapsulation method used over synchronous and asynchronous data lines. PPP offers control of data link setup, dynamic assignment of IP addresses, network protocol multiplexing, link configuration and link quality testing, error detection, and negotiation options for network layer address and data compression negotiations.

Chapter 3:

General

Describe the three major characteristics of a Wide Area Network

A WAN is a data communication network that operates beyond a LANs geographic scope.

You must subscribe to a WAN service provider.

A WAN uses data-links such as ISDN and Frame relay to connect locations of an organisation together, to locations of other organisations and to external services such as databases.

Describe what a Regional Bell Operation Company (RBOC) is and what is its function

A Regional Bell Operating Company is an organisation that provides wide area network services through frame realy, dedicated links and ISDN.  The RBOC is the carrier service that nterconnects geographically separate locations of networks.

OSI Model

Describe which two layers of the OSI model WANs typically address

WANs function at the lowest three layers of the OSI model. The physical, data link and network layers.

Describe what a WAN data link protocol is and what is its function

A data link protocol describes how data is carried over a single link between systems. The data link layer defines how data is encapsulated.

Describe the purpose of DTE and DCE devices and what layer of the OSI model do they apply to

DTE devices are usually routers and connect a Local Area Network to a WAN service provider. The DCE is usually the device that connects the router to the service provider to connect to data links. DTEs typically operate at layer three, the network layer, while DCE’s operate at layer 1.

List four common data link layer WAN protocols

Point-to-point protocol (PPP)

HDLC

Cisco/IETF

ISDN

WAN

Describe what a Point of Presence (POP) and Central Office (CO) are and what is their function

The point of presence is where telephone and data services are provided into a building.

The Central Office is the local telephone company office where all local loops for a service provider connect. It is where circuit switching of subscriber lines occurs

Describe how Time Division Multiplexing (TDM) works and what WAN technology uses it

Time Division Multiplexing is where traffic from many sources is multiplexed onto a single medium. TDM multiplexes traffic into fixed time slots.

Describe what Customer Premise equipment is.

Customer Premises Equipment is where the customers devices are physically located. Includes devices owned by the customer and equipment leased from a service provider.

Describe the data encapsulation process across a WAN link

The WAN data link layer defines how data is encapsulated for transmission to remote sites. WAN data link protocols describe how frames are carried between end systems on a single data path. All serial line encapsulations have the following frame format which has the following fields:

Flag: Indicates the beginning and end of a frame

Address: A 1 or 2 byte field to address the end station in multidrop environments

Control: Indicates whether the frame is an information, a supervisory, or an unnumbered type frame.

Data: The encapsulated data

FCS: the frame check sequence

Flag: the trailing flag identifier

Describe connection oriented and connectionless services across a WAN

Connection oriented services include services such as ISDN and dedicated lines. Connection oriented services establish a dedicated physical circuit between end points.  Connectionless services are services such as frame relay and SMDS. These services establish a connection to a service provider when needed and then terminate the connection when idle.

Describe how WAN signalling standards effect the throughput of WAN services

Throughput of WAN services is only limited by the service you are connected to. WAN signalling standards address speeds in the range of 64 Kbps to 22488.32 Mbps. If throughput is starting to diminish, the service provider should be contacted in order to provision a faster link, either by upgrading to a higher CIR, or, changing the connection type, ie from ISDN to T1.

Describe what a dedicated leased line is and how it is used

A dedicated leased line provides a full time service over point-to-point serial links. Dedicated leased lines are usually used for backbone or core connectivity between major sites. A dedicated synchronous router port is required for each line as well as a CSU/DSU to connect to the service provider. Dedicated lines are ideal for high-volume environments with a steady flow of traffic.

Describe what packet switched connections are and what WAN services use this technology

Packet switching is a WAN switching method in which network devices share a permanent virtual circuit, which is like a point-to-point link that transports packets from a source to a destination. X.25, frame relay, and SMDS are all packet switched WAN technologies.

Describe what a hierarchical WAN design model is and what are the major benefits

In a hierarchical structure, the network is organised in layers, each of which has one or more specific functions.

The major benefits are: Scalability, Ease Of Implementation, Ease Of Troubleshooting, Predictability, Protocol Support, Manageability.

Describe the functions of each layer in a three layer hierarchical WAN model

The core layer provides fast wide-area connections between geographically remote sites, tying a number of campus networks together in a corporate or enterprise WAN. Core links are usually point-to-point and there are no hosts in this layer.

The distribution layer gives network services to multiple LANs within a WAN environment. This layer is where the WAN backbone network is found. This layer is implemented on large sites and is used to interconnect buildings.

The access layer is usually a LAN or group of LANs, typically ethernet or token ring, that provides front line access to network services. The access layer is where almost all hosts are attached to the network, including servers of all kinds and user workstations.

Describe why server placement and associated traffic patterns are important to understand when designing a WAN

Servers should be placed at the highest level router to which sites need to connect to in order to limit the number of routers crossed and traffic generated in a WAN. If a server is placed at a lower layer router, and users from other networks need to use it, then the traffic will have to be routed through more routers than is necessary. Servers should be placed at the apex router of networks that need to connect to it.

Chapter 4:

OSI Model

Describe the OSI model layer(s) at which the Point-to-Point Protocol (PPP) operates and its function at those layers.

PPP operates at the lower three layers of the OSI model.

Network Layer: PPP uses Network Control Protocol to allow the simultaneous use of multiple network layer protocols.

At the Data Link Layer PPP uses HDLC to encapsulate datagrams over serial links. PPP also uses the Link control Protocol for establishing, maintaining and testing the data-link connection.

At the physical layer, PPP can use synchronous and asynchronous physical media.

Describe what major types of WAN links are supported by PPP.

PPP supports synchronous and asynchronous physical media for WAN links.

Describe what the function of the Network Control Protocol (NCP) is within PPP.

PPP supports or encapsulates several network layer protocols such as IP, and IPX.

Describe what the function of the Link Control Protocol (LCP) is within PPP.

The Link Control Protocol is for establishing, configuring, and testing the data-link connection. If the link quality is sufficient, network layer protocols will be brought up.

Describe the functions of PAP and CHAP in a PPP implementation.

PAP and CHAP are authentication methods used by PPP. The authentication options require that the calling side of the link enter authentication information to help ensure that the user has the network administrators permission to make the call.

PAP is not a strong authentication protocol. Passwords are sent across the link in clear text, and there is no protection from playback or repeated trial-and-error attacks.

CHAP is used to periodically verify the identity of the remote node using a three-way-handshake. CHAP does not allow a caller to attempt an authentication without a challenge.

Identify PPP operations to encapsulate WAN data on Cisco Routers

PPP LCP Configuration Options

Chapter 5:

General

Describe the user requirement for implementing ISDN to a site

ISDN allows digital signals to be transmitted over existing telephone wiring. ISDN is generally viewed as an alternative to leased lines, which can be used for telecommuting and networking small or remote offices into LAN’s. Telephone companies developed ISDN as part of an effort to standardize subscriber services.

Describe at what layer of a hierarchical WAN model an ISDN link should be installed

The ISDN link will be installed in the distribution layer of a hierarchical WAN model, because it is the backup link from the gateway router to the ISP.

Define what three layers of the OSI model ISDN standards address.

Physical: The ISDN Basic Rate Interface physical layer specification is defined in ITU-T I4.30. The Primary Rate Interface specification is defined in ITU-T I.431

Data Link: The ISDN data-link layer specification is based on LAPD and is formally specified in ITU-T Q.920 and ITU-T Q.921

Network: The ISDN network layer is defined in ITU-T Q.930

ISDN

Describe the 3 data channels used in ISDN BRI and describe their functions

A BRI service provides two B channels and one D channel. The BRI B-channel service operates at 64Kbps and carries data, while the BRI D-channel service operates at 16Kbps and carries signaling information to set up and control calls. The D-channel signaling protocol spans the OSI reference model’s Physical, Data Link, and Network layers. The D channel can also be used for other functions like an alarm system for a building, or anything that doesn’t need much bandwidth. D channels work with LAPD at the Data Link layer. When configuring ISDN BRI, you will need to obtain a Service Profile Identifier (SPID), and you should have one SPID for each B channel. SPID’s can be thought of as the telephone number of each B channel. The ISDN device gives the SPID to the ISDN switch, which then allows the device to access the network for service. Without a SPID, many ISDN switches don’t allow an ISDN device to place a call on the network.

Describe what ISDN protocols that start with "Q" address

Q covers how switching and signaling operates. The term signaling in this context means the process of call setup used. Q.921 describe the data-link processes of link access procedure on the D channel, which functions like the layer 2 processes in OSI reference model. Q.931 specifies OSI reference model layer 3 functions.

Describe what ISDN protocols that start with "I" address

I deal with concepts, terminology and general. The I.100 serial includes general concepts of ISDN and structure of other I-serials recommendations. The I.200 serial deals with service aspects of ISDN. The I.300 serial describes network aspects. The I.400 serial describe how the Unique Identifying Number (UIN) is provided.

Describe what ISDN protocols that start with "E" address

E is the recommended telephone network standard for ISDN.

Describe the five major devices in a ISDN implementation

The five major devices in an ISDN include terminals, terminal adapters (TAs), network-termination (NT) devices, line-termination equipment, and exchange-termination equipment.

The difference between TE1 and TA is subtle but significant. If you buy an ISDN card for your computer you have turned your computer into a TE1. However, if you buy an ISDN device that lets you plug your computer’s Ethernet into an ISDN conversion box, then you're computer is a TE2, and the conversion box is a TA.

Describe the four major reference points in an ISDN implementation

Reference points are a series of specifications that define the connections between the equipment used in the ISDN network. ISDN has four reference points that define logical interfaces, these are:

Describe the function of Point to Point Protocol in an ISDN Implementation

PPP is typically used with ISDN to provide data encapsulation, link integrity, and authentication.

Describe why it is important to know the ISDN switch type when configuring an ISDN connection

ISDN service providers use a variety of switch types for their ISDN services. Services offered by carriers vary considerably from area to area. Just like modems, each switch type operates slightly differently and has a specific set of call setup requirements. As a result, before you can connect a router to an ISDN service, you must be aware of the switch types used at the Central Office (CO). You specify this information during router configuration so the router can place ISDN network-level calls and send data.

Describe the function of SPID numbers and why it is important when configuring and ISDN connection

SPID’s can be thought of as the telephone number of each B channel. The ISDN device gives the SPID to the ISDN switch, which then allows the device to access the network for service. Without a SPID, many ISDN switches don’t allow an ISDN device to place a call on the network.

State a relevant use and context for ISDN networking

Remote access involves connecting users located at remote locations through dial-up connections. The remote location can be a telecommuter’s home or a small remote office. The dial-up connection can be made via an analog connection using basic telephone service or via ISDN.

Identify ISDN protocols, function groups, reference points, and channels

The BRI local loop is terminated at the customer premises in an NT1. The interface of the local loop at the NT1 is called the U reference point. On the customer premise side of the NT1 is the S/T reference point. ISDN LAN routers provide routing between ISDN BRI and the LAN by using dial-on-demand routing (DDR). DDR automatically establishes and releases circuit-switched calls, providing transparent connectivity to remote sites based on networking traffic. DDR automatically establishes and releases circuit-switched calls, providing transparent connectivity to remote sites based on networking traffic. DDR also controls establishment and release of secondary B channels based on load thresholds. Multi-link PPP is used to provide bandwidth aggregation when using multiple B channels. Some ISDN applications may require the SOHO user to take direct control over ISDN calls. Reference points are a series of specifications that define the connections between the equipment used in the ISDN network. ISDN has four reference points that define logical interfaces, these are:

Describe Cisco's implementation of ISDN BRI

Two common types of ISDN CPE are available for BRI services: LAN routers and PC TA's. PC TA’s connect to PC workstations either by the PC bus or externally through the communications ports and can be used similarly to analog modems.

PC TA's can provide a single PC user with direct control over ISDN session initiation and release, similar to using an analog modem. Cisco 200 Series PC cards can provide ISDN services to a PC.

General

Describe at what layer of a hierarchical WAN model an Frame Relay link should be installed

The Frame Relay link will be installed in the distribution layer of a hierarchical WAN model, this is because it is the main link between all our routers.

OSI Model

Describe what layers of the OSI model Frame Relay standards address and their functions at these layers.

Frame Relay is a Data-link layer protocol; its function is to provide encapsulation and security to data being transmitted over the network.

Frame Relay

Describe DLCIs and their functions in a Frame Relay implementation.

A DLCI is a number that identifies the logical circuit  between the source and destination device. The Frame Relay maps the DLCIs between each pair of routers to create a permanent virtual circuit.

Describe LMIs and their function in a Frame Relay implementation.

A signalling standard between the customers premises equipment device and the Frame Relay switch that is responsible for managing the connection and maintaining status between the devices.

Describe a 'Permanent Virtual Circuit'.

A Permanent virtual circuit (PVC) is a virtual circuit that is permanently established.

Describe connection-oriented network service and connectionless network service, and identify the key differences between them

Frame Relay is a connection-orientated service. A connection-orientated service is always connected throughout the whole network, whereas a connectionless service is only connected when it needs to be.

Describe 'Committed Information Rate' (CIR) and its function.

The Committed Information Rate (CIR) is the rate at which a Frame Relay network agrees to transfer data under normal conditions.

Describe 'Forward Explicit Congestion Notification' (FECN) and its function.

Forward Explicit Congestion Notification (FECN) is when a Frame Relay switch recognizes congestion in the network; it then sends an FECN packet to the destination device indicating that congestion has occurred and congestion avoidance measures should be implemented.

Describe 'Backward Explicit Congestion Notification' (BECN) and its function

Backward Explicit Congestion Notification (BECN) is when a Frame Relay switch recognizes congestion in the network; it then sends a BECN packet to the source router instructing the router to reduce the rate at which it is sending packets.

Describe 'Discard Eligibility' (DE) and its function.

Discard Eligibility (DE) is when the router detects network congestion. The DE bit is set on the traffic that was received after the CIR was met. The Frame Relay switch will drop packets with the DE bit set first.

Recognize key Frame Relay terms and features

Access Rate: The clock speed of the connection to the frame relay cloud.

Data-Link Connection Identifier: A DLCI is a number that identifies the logical circuit between the source and destination device.

Local Management Interface: A signalling standard between the cutomer premises equipment device and the Frame Relay switch that is responsible for managing the connection and maintaining status between the devices

Committed Information Rate: The CIR is the guaranteed rate, in bits per second, that the service provider commits to providing.

Committed Burst: The maximum number of bits that the switch agrees to transfer during a time interval.

Excess Burst: The maximum number of uncommitted bits that the Frame Relay switch attempts to transfer beyond the CIR.

Forward Explicit Congestion Notification: When a frame relayswitch recognises congestion in the network, it sends a FECN paket to the destination device, indicating that congestion has occurred.

Backward Explicit Congestion Notification: When a Frame Relay recognises congestion in the network, it sends a BECN packet to the source router instructing the router to reduce the rate at which it is sending packets.

Discard Eligibility Indicator: A set bit that indicates the frame may be discarded in preference to other frames if congestion occurs.

List commands to configure Frame Relay LMIs, maps, and subinterfaces

The command for Frame relay LMI’s is:

Router(config-if)#frame-relay lmi-type LMI type to be used

The command for Frame relay maps is:

Router#show frame-relay map

Subinterface configuration commands:

Interface serial number.subinterface number [multipoint | point-to-point]

Ip address <ip address> <subnet mask>

Encapsulation frame-relay [cisco | ietf]

Bandwidth <kilobits>

No shutdown

List commands to monitor Frame Relay operation in the router

The following commands help monitor operation of Frame Relay and associated protocols:

Router(config-t)#int interface or sub-interface number
Router# show interfaces serial

Router#show frame-relay pvc
Router#show frame-relay map
Router#show frame-relay lmi