Finals EXAM

Module 5 6 7

Network Layer

This layer is responsible for sending out packets between endpoints over multiple links. It’s also the lowest layer in the OSI Reference Model that deals with end-to-end transmission. Finally, this layer provides services to the transport layer.

Store and forward packet switching

The host sends a packet into the network; packets are then forwarded between routers

Connectionless service - datagrams

Packets are forwarded using a destination address inside, where different packets may take different paths

Connection-oriented virtual circuit

Packets are forwarded along a virtual circuit using a tag inside. A part of this is also already set up ahead of time

Forwarding

A routing algorithm process, where it processes arriving packets by looking up the appropriate outgoing link to use from the routing tables. In short, it is the sending of packets along a path the routing algorithm discovered.

Routing

The process in discovering network paths

Datagram

The term for packets, in analogy with telegrams and the network is called the ______ network.

Routing Algorithm

The algorithm that manages the tables and makes the routing decisions

Congestion Control

Congestion causes packet delay and loss that degrades performance.

Leaky bucket algorithm

No matter the rate of incoming packets, the outflow is always at a constant R or less

Token Bucket Algorithm

To send a packet, it must be able to retrieve tokens from the bucket. No more than a fixed amount of tokens can accumulate in the bucket.

MPLS (Multiprotocol Label Switching)

Used within ISP networks in the Internet, with IP packets wrapped in it’s header having a 20-bit connection identifier or label

Nonadaptive algorithm

This type of algorithm do not base their routing decisions on any measurements or estimates of the current topology and traffic.

Static Routing

Nonadaptive algorithms do not base their routing decisions on any measurements or estimates of the current topology and traffic. Instead, this procedure gives the choice of the route to use to get from I to J (for all I and J) is computed in advance, offline, and downloaded to the routers when the network is booted.

Adaptive algorithm

This type of algorithm change their routing decisions to reflect changes in the topology, and sometimes changes in the traffic as well.

DAG (Directed Acyclic Graph)

A permission where all of the possible paths can be chosen, the tree becomes a more general structure

NAT (Network address translation)

long-term solution is for the whole Internet to migrate to IPv6

ICMP (Internet Control Message Protocol)

connectionless network layer protocol used by devices like routers to diagnose communication issues. The operation of the Internet is monitored closely by the routers. When something unexpected occurs during packet processing at a router, it is reported via this.

ARP (Address Resolution Protocol)

Let’s nodes find target; maps dynamic IP addresses to fixed physical MAC addresses on a local area network (LAN).

DHCP (Dynamic Host Configuration Protocol)

A network protocol that automatically assigns IP addresses and configuration settings—such as subnet masks, default gateways, and DNS servers—to devices connecting to a network.

Flooding

When a routing algorithm is implemented, each router must make decisions based on local knowledge, not the complete picture of the network. This technique ensures that every incoming packet is sent out on every outgoing line except the one it arrived on.

Distance Vector Routing

This algorithm operates by having each router maintain a table (i.e., a vector) giving the best-known distance to each destination and which link to use to get there. It’s also referred to as Bellman-Ford

OSPF (Open Shortest Path first)

This is used to calculate the most efficient path for data packets within a single network or Autonomous System (AS).

BGP (Border Gateway Protocol)

Computes routes across interconnected, autonomous networks and to exchange routing and reachability information among different networks (Autonomous Systems)

Convergence

The settling of routes to best paths across the network

count to infinity problem

Gradually, all routers work their way up to infinity, but the number of exchanges required depends on the numerical value used for infinity. For this reason, it is wise to set infinity to the longest path plus 1.

Broadcasting

Sending a packet to all destinations simultaneously

Multidestination Routing

Where each packet contains either a list of destinations or a bit map indicating the desired destinations.

Transport Layer

Builds on the network layer to provide data transport from a process on a source machine to a process on a destination machine with a desired level of reliability that is independent of the physical networks currently in use.

Transport Protocol Data Unit (TPDU)

to enable end-to-end communication, handle flow control, ensure reliable delivery, and manage data sequencing between networked devices

Transport entity

The software and/or hardware within the transport layer that does the work

Internet Domain Sockets (AF_INET)

implemented via IP addresses and port numbers

Unix Domain Sockets (AF_UNIX)

implemented via filenames (think “named pipe”)

Stream (SOCK_STREAM)

A type of socket, uses TCP protocol. Connection-oriented service

Datagram (SOCK_DGRAM)

A type of socket, uses UDP protocol. Connectionless service

Raw (SOCK_RAW)

A type of socket used for testing

DNS (Domain Name System)

resolves high-level human-readable names for computers to low- level IP addresses

Name Servers

contain data for portions of the name space called zones (circled).

TCP (Transmission Control Protocol)

Connection-oriented. It establishes a reliable connection using a "three-way handshake" before sending data. It assigns sequence numbers, verifies delivery, and resends any lost packets.

UDP (User Datagram Protocol)

Connectionless. It simply sends "datagrams" (data packets) directly to the destination without establishing a connection or verifying that the recipient is ready. It does not check for lost packets or retransmit them.

SMTP (Simple Mail Transfer Protocol)

standard TCP/IP protocol used to send, relay, and transfer outgoing emails across the internet.

DCCP (Datagram Congestion Control Protocol)

A version of user datagram protocol with congestion control

SCTP (Stream Control Transmission Protocol)

A reliable transport-layer protocol that combines the error-free, connection-oriented features of TCP with the message-oriented speed of UDP.

URL (Uniform Resource Locator)

The specific character string used to identify and locate a unique resource on the internet or a computer network.

TSAP (Transfer Service Access Point)

A specific conceptual address or endpoint in the OSI networking model used to identify a specific application or service running on a device

NSAP (Network Service Access Points)

A conceptual location where the network layer delivers its services to the transport layer

CDN (Content Delivery Networks)

They scale Web servers by having clients get content from a nearby node (cache)

Peer to Peer Networks

Is an alternative CDN architecture with no dedicated infrastructure (i.e., servers); Clients serve content to each other as peers