Networking: Routing and Forwarding

• A router's routing table tracks the routes for forwarding data to its destinations.
• The following routing algorithms can be used for network layer design: shortest path, distance vector, and link state.
• A static routing table has information entered manually.
• Hierarchy in routing tables reduces the size of the tables.
• The Internet is divided into autonomous systems for routing purposes.
• In distance vector routing, each node shares its routing table with immediate neighbors periodically and on changes.
• Link state routing utilizes the Dijkstra algorithm to build routing tables.
• A router connects two or more different networks.
• The network layer deals with packets of data.
• Error control is not a function of the network layer.
• In a virtual circuit network, each packet contains a short VC number.
• The network layer model with connectionless service is called a Datagram network.
• The primary function of the Network Layer is routing and forwarding.
• IPv4 size is 32 bits and IPv6 size is 128 bits.
• ICMP is a Network Layer protocol.
• Distance Vector Routing uses the Bellman-Ford algorithm.
• Slow convergence is a main disadvantage of Distance Vector Routing.
• The Time-To-Live (TTL) field in an IP packet prevents infinite loops.
• Providing error reporting and diagnostics is the primary purpose of the ICMP protocol.
• ICMP operates on the Network Layer of the OSI model.
• Both Ping and Traceroute rely on ICMP.
• IPsec primarily secures IP communications through authentication and encryption.
• IPsec operates at the Network Layer of the OSI model.
• Transport mode of IPsec encrypts only the payload of an IP packet.
• A key characteristic of a Datagram network is that each packet is routed independently.
• A key characteristic of a Virtual Circuit network is that a connection is established before data transmission.
• Distance Vector Routing involves each router knowing only its directly connected neighbors and sharing information periodically.
• RIP (Routing Information Protocol) exemplifies a Distance Vector Routing protocol.
• Link State Routing involves each router having a complete view of the network topology.
• OSPF (Open Shortest Path First) exemplifies a Link State Routing protocol.
• Link State Routing provides faster convergence and more accurate routing information compared to Distance Vector Routing.
• Dijkstra's Algorithm is used in Link State Routing to compute the shortest path.
• The primary function of a routing protocol is to determine the best path for data packets in a network.
• OSPF (Open Shortest Path First) exemplifies an Interior Gateway Protocol (IGP).
• BGP is used on the Internet for inter-domain routing.
• RIP (Routing Information Protocol) uses hop count as a metric to determine the best path.
• EIGRP is classified as a hybrid routing protocol.
• The maximum hop count allowed in RIP is 15.
• RIP sends periodic updates every 30 seconds.
• OSPF is a Link-State Protocol.
• BGP is a Path Vector Protocol.
• A primary function of BGP is to exchange routing information between autonomous systems.
• In BGP, AS stands for Autonomous System.
• External BGP (eBGP) exchanges routes between different autonomous systems.
• BGP uses the Path Vector Algorithm to determine the best path.
• An advantage of BGP is the ability to handle large-scale networks like the Internet.
• Cost is NOT a well-known BGP attribute.
• DHCP is responsible for dynamically assigning IP addresses.
• Broadcasting sends data to all nodes, while multicasting sends data to a specific group of nodes.
• A main disadvantage of the Flooding Routing Algorithm is high bandwidth consumption.
• Hierarchical routing features nodes grouped into clusters or regions.
• Hierarchical routing mainly improves scalability and efficiency.
• RIP refers to Routing Information Protocol.

Routing Protocols

• OSPF is developed considering IP Networks.
• BGP uses TCP as the protocol to transport.
• DHCP provides the IP address to the client.
• The header size of the ICMP message is 8 bytes.
• BGP routing protocol belongs to Exterior Gateway Protocols (EGP).
• Routing between one source and all hosts on a network is classified as broadcast routing.
• An Area Border Router (ABR) joins local areas to the backbone area in a hierarchical OSPF structure.
• EIGRP is a routing protocol that uses triggered updates and has no periodic updates.
• Traceroute is used to find the number of routers between a source and a destination.
• For purposes of routing, the Internet is divided into autonomous systems.
• Bandwidth is the primary metric used in OSPF.

Distance Vector Routing

• The number of routers in the network affects the convergence speed.
• Routing algorithms determine the best path for packets.

IGP

• Interior Gateway Protocols (IGPs) handle routing inside an autonomous system.
• All messages are authenticated as a security feature of OSPF.
• OSPF has a two-level hierarchy (local area and backbone).
• OSPF performs interior routing.
• Flooding forwards a packet to all outgoing links except the one it arrived on in a network.
• The main function of the network layer in the OSI model is packet forwarding and routing.

Distance Vector Routing Issue

• In Distance Vector Routing, loops in routing updates are the issue with the count-to-infinity problem.
• The main purpose of the Time-To-Live (TTL) field in an IPv4 header prevents packets from looping indefinitely.
• BGP is an Exterior Gateway Protocol (EGP).

Hierarchical Routing Objective

• The primary goal of hierarchical routing is to simplify routing tables and improve scalability.
• In OSPF, area border routers (ABRs) connect different OSPF areas.
• Flooding is used to broadcast packets but it creates loops.
• Intradomain Routing is routing inside an autonomous system.
• A 4-byte IP address consists of network address and host address.
• Each packet in a virtual circuit network contains a short VC number.
• Datagram networks utilize IP Addresses.
• A statement that is NOT true about Virtual Circuit networks is that each packet carries full destination information.
• The function of a routing protocol is to determine the best path for data packets in a network.
• RIP sends periodic updates every 30 seconds.
• A Link-State Advertisement (LSA) is used in OSPF to exchange link-state information between routers.
• Backbone Area (Area 0) is a valid OSPF area type.

Routing Disadvantage

• Dependence on cluster heads, which may cause failures is a disadvantage of hierarchical routing.
• The Bellman-Ford algorithm is used by Distance Vector Routing.
• Default Routing forwards packets when the destination network is unknown by routers.
• Managing multicast group memberships is the primary purpose of IGMP.
• IGMP operates at the Network Layer of the OSI model.
• IGMP is mainly used with multicast IP traffic.
• Sending unicast packets is NOT a function of IGMP.
• A Router connects multiple networks together.

Primary Router Function

• Preventing switching loops is NOT a main function.
• An IPv4 address contains 4 octets.
• More address space is a primary advantage of IPv6 over IPv4.
• An IPv6 address is represented in hexadecimal notation.
• The primary goal of the shortest path routing algorithms finds the path with the minimum cost or distance.
• The Bellman-Ford algorithm can handle negative weight edges, while Dijkstra's algorithm cannot.
• In a Distance Vector Routing algorithm, each router maintains a table containing routes to all known destinations.
• Commonly, the Bellman-Ford Algorithm is used in Distance Vector Routing.
• Routers exchange routing information periodically, even if no changes occur, in Distance Vector Routing.
• A packet in flooding is forwarded to neighbors until both the time-to-live (TTL) field expires and the packet reaches the destination.
• The primary reason for redundant transmissions in flooding is that every node forwards a received packet to all its neighbors.
• Reduced energy consumption is NOT an advantage of flooding routing in WSNs.
• The flooding algorithm is best suited for highly dynamic networks with frequent topology changes.

Path Vector Routing

• Path vector routing is mainly used in inter-domain routing (e.g., between Autonomous Systems).
• Border Gateway Protocol (BGP) is based on the path vector routing algorithm.
• A path vector routing protocol maintains a complete path (list of AS numbers) to the destination for each route.
• The Routing Information Protocol (RIP) works based on 3 types of timers.
• The routing-update timer controls the advertising of regular update messages in RIP.
• In RIP routing protocol, the route is removed from the table after 180 Sec.
• BGP is primarily used between Autonomous Systems (ASs).

Autonomous Systems

• The Autonomous System (AS) is a collection of Routers under a single administrative domain.
• Route Request is NOT a BGP message type.
• The primary purpose of DHCP is to assign IP addresses dynamically to devices on a network.
• A MAC address is NOT a typical piece of information provided by DHCP.
• Link State routing algorithm uses link cost information.
• The primary purpose of a subnet mask divides an IP network into smaller networks.
• The DHCP Acknowledge message finalizes the DHCP IP address allocation process.
• OSPF advertisements are distributed inside an Autonomous System.

Primary Distance Vector

• The main reason distance vector routing is not used for inter-domain routing is that it does not scale well due to slow convergence and looping issues.
• Frequency of routing updates can impact the performance of distance vector routing.
• Interior Gateway Protocols (IGPs) handle routing inside autonomous systems.
• Routes change slowly over time; it is Static routing.
• The protocol that is divided the routers into regions is Hierarchal algorithms.
• In a single inter Autonomous System, each AS can learn which router can reach to another Autonomous System.
• Periodic timer is use to controls the advertising of regular update messages.
• In Rip protocol, if there is a problem on a internet and no update is received within the allotted 180s, the route is considered expired.
• The reason for authenticating all OSPF messages is to prevent malicious intrusion and unauthorized access.
• The primary functionality of backbone routers in OSPF, so they run OSPF routing, but only runs within the backbone area.
• Link state Update is one of the OSPF message type that are used to provide the senders cost to its neighbor.
• Link state ack is one of the OSPF message type that are used to announces which update the sender has.
• The primary function of eBGP is that obtain subnet reach ability information from neighboring Autonomous Systems.
• The primary function of iBGP is that propagate reach ability information to all AS-internal routers.
• The BGP message used to advertises new path is UPDATE.
• ICMP message consist of The type, code, and the first 8 bytes of the IP datagram causing the error, when reporting an error.
• Fragmentation occurs in the network layer due to different MTU sizes in networks.
• Identification, Flags, and Fragment Offset is the IPv4 header field used to manage fragmentation.
• In RIP Expiration Timer set the max hop to 16.
• The protocol responsible for reassembling fragmented packets at the destination is IP.
• Greater security is NOT a disadvantage of fragmentation.
• If a fragmented packet is lost during transmission, the entire original packet is retransmitted.
• In IPv6, only the source node can fragment packets.