Test 3

21-18

Network consisting of 3 IP networks (for IP addresses starting with 223, first 24 bits are network address)

Does a router need to use the same technology to connect 2 networks in the same general category?

No. For example, a router can connect an Ethernet to a Wi-Fi network

WAN Default Routes

Default routes are used in large tables where many nodes may go to a specific route. There can be only one default route.

Why does IPv4 need to improve?

It has been a huge success of Internet; but: Needs more IP addresses Needs QoS for applications (various application)

What is a hardware address?

The hardware address (also known as the Ethernet, physical, or MAC address) is a 12 byte hexadecimal number that is unique to the Ethernet card on your machine It will often be displayed in one of the following formats: • 08:00:2B:BC:31:DC The first 24 bits (three bytes) identify the manufacturer, and the remaining bits uniquely identify the type of device and provide a specific serial number for the unit.

WAN Forwarding Table

The table generally has 2 columns, One column contains the destination nodes and the other column contains the link (edge) the packet must be forwarded to to reach the destination node in the fastest manner from the current node the packet is in. f.table→

What does a Port Based VLAN do?

Traffic isolation Dynamic membership Forwarding between VLANs → done via routing

What's a network ?

(from IP address perspective) Device interfaces with same network part of IP address. Can physically reach each other without intervening router

What are the primary attributes that designers have to chose when trying to change the IP?

* Addresses * Packet formats * Delivery techniques independent of the details of the underlying hardware

What 4 things does IPv4 define to accommodate heterogeneous hardware?

A network-independent addressing scheme. Datagram format. Encapsulations. Fragmentation strategy.

What 2 main principles are needed to achieve a seamless communication system?

Protocol software must hide the details of physical networks It should offer the illusion of a single, large network

IPv4 has been successful. It has made it possible for the Internet to (3 things):

To handle heterogeneous networks. Dramatic changes in hardware technology. Cope with increases in scale Internet protocols provide a set of abstractions

A router can connect these 3 things:

two LANs a LAN and a WAN or two WANs

LAN Connection Devices

Application - Gateway............. Transport Network Data Link Physical

STP

Spanning Tree Protocol

WAN

Wide Area Network

An IP address scheme, guarantees what 2 properties?

* Each computer is assigned a unique address (i.e., a single address is never assigned to more than one computer). * Network number (prefix) assignments must be coordinated globally. _____Suffixes are assigned locally without global coordination.

An IP address suffix:

* Identifies a specific computer (host/node) on the network. * Each computer on a given network is assigned a unique suffix.

An IP address prefix:

* Identifies the physical network to which the host is attached. *Each network in the Internet is assigned a unique network number.

LAN Bridges

- Connects 2 LAN segments... - A bridge listens in promiscuous mode on each segment. - Receives intact frame from a segment, forwards to other segment. - 2 LAN segments connected by a bridge, behave like a single LAN. A computer on either segment, can send a frame to a computer on either segment. -Uses destination MAC address in the frame, to filter the forward address. - If supported, a broadcast is delivered to all connected computers.

Link State Routing is...?

- uses shortest path first routing. - Uses Dijkstra's to find the shortest path. - Broadcasts out to all switches on network. - Good for small network = total complexity O(n^2).

Physically a router is ?

--- An independent hardware system dedicated to the task of interconnecting networks --- Contains a processor and memory as well as a separate I/O interface for each network to which it connects

When designing a network technology, what 3 main factors determine what can be achieved at a given cost.

-Capacity -Maximum delay -Distance

Layer 2 switch

-Sometimes called a Layer 2 switch -an electronic device that resembles a hub -a switch provides multiple ports (like a hub) that each attach to a single comp. -a switch allows computers to send frames to one another.

How a switch is different from a hub, repeaters, and bridge?

-a hub is an analog device that forwards signals among computers -a switch is a digital device that forwards packets. -Switch is overall better! Using a switched LAN gives you parallelism. Since switches use a fabric/intelligent interface to provide parallel internal paths, a switch with N ports can transfer up to N/2 packets simultaneously.

The goal of a WAN is to ?

...allow as many computers as possible to send packets simultaneously

Most WANs separate a packet switch into two parts:

1) A layer 2 switch that connects local computers 2) A router that connects to other sites.

How many networks are here?

6 Networks 223.1.1.... 223.1.9.... 223.1.7.... 223.1.8.... 223.1.2.... 223.1.3.... Three Routers Interconnecting six subnets.

What is an adaptive bridge?

A bridge must know which computers are attached to which segments. Adaptive bridges will learn the locations of computers automatically, using Source Addresses.

What is IPv4 Dotted Decimal Notation?

A notation more convenient for humans to understand is used. Notation that has been accepted is: -----express each 8-bit section of a 32-bit number as a decimal value. -----use periods to separate the sections.

What is a LAN Repeater?

A repeater is an analog device used to propagate LAN signals over long distances. A repeater does not understand packets or signal coding, it merely amplifies the signal received.

What are the 5 IP classes?

A, B, C, D, E A, B, C have: ---net-id ---host-id D, E are: ---not divided.

All host computers must use a uniform _________________ scheme?

Addressing

What is a Virtual Local Area Network switch?

Allows a manager to configure a single switch to emulate multiple, independent switches. Makes it appear there are multiple switches.

What is a Repeater?

Analog device used to propagate LAN signals over long distances Amplifies the signal received Does not understand packets or signal coding Over Physical layer (level 1)

Routing Table (Forwarding Table)

Central ------SDN

21-13

Class A - Class B - Military??? Class C - Class D - Class E

21-20

Class A - Military Class B - Educaiton We have so many people, with so many devices in all classes. The classes are complaining that we need to have more addresses, but we cant.

What is the most common IP class for large Organizations?

Class B Example: 130.5.5.25 10000010.00000101.00000101.00011001 o Network Address_____16bits _____130.5 o Host Address_____16bits _____5.25

What is unique to a MAC Based VLAN ?

Configured by network manager

DVR

Distance Vector Routing

DST

Distributed Spanning Tree

WAN Dynamic Routing

Dynamic routing is technique used for dealing with failures in a network. Since two nodes may disconnect due to a failure → the routing tables must constantly be updated.

What is WAN hierarchical addressing?

Example: like a home address; street address → city → state Hierarchical addressing divides each address into 2 parts, switch, and computer on site. In practice (IPv4), instead of a identifying a site, each packet switch is assigned a unique number. First part identifies a packet switch. Second part identifies a specific computer. Address [2,6] = packet switch 2, comp on port 6

LAN Distance Limitation

Fundamental part of LAN designs. Factors: - Capacity - Maximum Delay - Distance

Why is IPv4 difficult to change?

IP is difficult to change because: IP lies at heart of the Internet protocol IPv4 has a proven track record

What does a distributed spanning tree do?

It prevents a cycle from causing an endless loop in bridging. Views bridges as nodes on a graph, and imposes a tree on that graph so that we cannot get stuck in an endless cycle.

LSR

Link State Routing

LAN

Local Area Network

What are 2 VLAN disadvantages?

Managerial overhead VLANs limit - up to 4096 different VLANs

Could IP be redesigned to use hardware addresses instead of the 32-bit addresses it currently uses?

NO, we can't redesign the IP to use hardware addresses instead of the 32-bit addresses. The MAC address is static, in regards to the manufacturer, and thedevice ID which cannot change; and if said device is moved either within, or outside of its current location, the IP address that is defining the current location, will change. As stated, the hardware address is definite, and would not be able to be altered for its new location (network, etc.) which allows it to be routed through the network. If we had a larger IP then we could be allowed to alter our network routing address, and maintain the definitive hardware destination address, but with that 32bit, we would not be able to allow for the necessary path.

How does a subnet work?

Once a packet has arrived at an organization's gateway or connection point with its unique network number, it can be routed within the organization's internal gateways using the subnet number. The router knows which bits to look at (and which not to look at) by looking at a subnet mask, which is a screen of numbers that tells you which numbers to look at underneath. Example: 130.5.5.25 o Network Address - 130.5 o Subnet Address - . 5 o Host Address - . 25

What are 4 VLAN Benefits?

Performance Managing Cost and Time Reduction Creating Virtual Work Group Enhancing Security Limit

3 Types of VLAN switches?

Port-based VLANS MAC-based VLANs Protocol-based VLANS

An IP address is divided into these 2 parts?

Prefix Suffix

What is Spanning Tree Protocol?

Root bridge election ---Bridges multicast a packet w/ bridge ID → smallest ID chosen Shortest path computation ---Each bridge computes shortest path to root bridge Forwarding ---Interface that connects to the shortest path is enabled An interface that doesn't lie on the shortest path is blocked

The basic component used to connect heterogeneous networks is a?

Router

What is WAN Next-Hop Forwarding?

Routing term that refers to the next closest router a packet can go through. A packet switch doesn't need to know how to reach all computers, Switch only needs to know link to use to reach a given switch. Forwarding table (routing table): Lists all possible packet switches and gives a next hop for each Source Independence - Next-hop forwarding doesn't depend on the packet's original source and allows forwarding to be compact and efficient ---1 - Only 1 table is required ---2 - Only destination needs to be extracted from packet

SDN

Software Defined Network

What does IPv4 support?

Support heterogeneous networks, dramatic changes in H/W technology, and extreme increases in scale.

What is the main difference between the internet, and a physical network?

That the Internet is an abstraction imagined by its designers and created entirely by protocol software.

For WAN To achieve simultaneous transmission, packet switches perform store and forward processing...

The store operation occurs when a packet arrives. I/O hardware in the switch places a copy of the packet in memory The forward operation occurs once a packet has arrived and is waiting in memory. The processor Examine → Routing → Forwarding

How to create a forwarding table?

There are different forwarding table schemes depending on: - Dynamic routes - Default routes - LSR and DVR and next-hop A forwarding table data table stored in a router, lists the routes to network destinations. Sometimes distances are associated w/ these routes on the table. Basic approaches to create F.Table - Static routing ----- + Simplicity and low overhead but - inflexible - Dynamic routing -----Most WANs use dynamic routing. Forwarding table must guarantee: 1) Universal Communication: The table in each switch must contain a valid next-hop route for each possible destination address) 2) Optimal Routes: the next-hop value for a given destination must point to the shortest path to the destination.

What is a fiber modem?

Transceiver device that converts optical Ethernet signal to other protocol signal. Does 2 main things: -Accept packets over the Ethernet interface and send them over the optical fiber -Accept packets that arrive over the optical fiber send them over the Ethernet interface.

What is a Trunk Port?

Trunk port: carries frames between VLANS defined over multiple switches.

VLAN

Virtual Local Area Network (switch)

Wide Area Network Architecture

WAN Arch. does not need to be symmetric. WAN has more scalability (vs a LAN) WAN provides sufficient capacity to permit all computers to communicate. Satellite bridge that connects pcs and printers is just an extended LAN. Traditional WAN Arch. Packet switch Is a special-purpose hardware device is placed at each site P.S. provides 1) local connections for computers at the site 2) connections for data circuits that lead to other sites A packet switch is a small computer system Since advent of LAN (more modern)

IP Class C

o 192.168.0.0 --> 192.168.255.255 (2^8) - 2 o Subnet mask: 255.255.255.0 o Net-id . Net-id . Net-id . host-id o 192 - 223 networks (first octet)

IP Class A

o 10.0.0.0 --> 10.255.255.255 (2^24) - 2 o Subnet mask: 255.0.0.0 o Net-id . host-id . host-id . host-id o 1 - 126 networks (first octet = 126) 127.0.0.0 --> 127.255.255.255 are reserved for loopback and diagnostic functions.

IP Class B

o 172.16.0.0 --> 172.31.255.255 (2^16) - 2 o Subnet mask: 255.255.0.0 o Net-id . Net-id . host-id . host-id o 128 - 191 networks (first octet)

Suppose you are an ISP with a / 24 address block. Explain whether you accommodate a request from a customer who needs addresses for 255 computers.

• ISP with a / 24 address block • 32-24 = 8 • 2^8 = 256 • First spot - all 0's = network ID/address • Last spot - all 1's = broadcast address. • 256 - network ID - broadcast address = 254 usable address.