NT1210 Introduction to Networking - YPW · NT1210 Introduction to Networking ... protocols. Analyze network ... most used today happen to be standards. Networking Standards Compared

NT1210 Introduction to Networking

Unit 3:Chapter 3, TCP/IP Networks

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ObjectivesObjectivesCompare and contrast the OSI and TCP/IP models and their applications to actual networks.

Explain the functionality and use of typical network protocolsprotocols.

Analyze network components and their primary functions in a typical data network from both logical andfunctions in a typical data network from both logical and physical perspectives.

Differentiate among major types of LAN and WAN g j ytechnologies and specifications and determine how each is used in a data network.

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ObjectivesObjectives

Differentiate between proprietary and nonproprietary protocols.

Explain the use of IP addressing in data networks.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Product Standards and Rules

T i i C t l P t l (TCP) / I t t P t lTransmission Control Protocol (TCP) / Internet Protocol (IP).

Requests for Comment (RFC): Documents created byRequests for Comment (RFC): Documents created by network stakeholders to comment and improve ideas for standards.

Define how products work.

Used by network designers.

Open source.

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Defining the Rules for a TCP/IP Network

H d d ft k t th t t blHardware and software work together to create usable network.

Protocols (network software): Hypertext TransferProtocols (network software): Hypertext Transfer Protocol (HTTP), Simple Mail Transfer Protocol (SMTP), Post Office Protocol (POP), etc.

Used on networked devices (hardware): Phones, game systems, televisions, tablets, computers, software, networking devices cables etcnetworking devices, cables, etc.

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TCP/IP id tifi b th t ff d h it k t thTCP/IP identifies both stuff and how it works together:Defines protocols.

D fi t f L l A N t k (LAN ) d WidDefines concepts of Local Area Networks (LANs) and Wide Area Networks (WANs).

Defines concept of links and nodes the functions of each.

Definition of TCP/IP network: Network built using TCP/IP standards and rules.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Standards

R d d t il f tl h t t h l i d dRecord details of exactly what new technologies do and how they do it.

Help everyone agree to how something works so that itHelp everyone agree to how something works so that it works well within network.

Important feature: Documentation of ideas that matter toImportant feature: Documentation of ideas that matter to anyone creating networking products or designing networks.

Example: Brief history of Web browsers and servers as envisioned by Web creator Tim Berners-Lee. http://bit ly/vd0pWEhttp://bit.ly/vd0pWE

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: HTTP Example

HTTP b lif id d d t il f h it t kHTTP began life as idea and details of how it was to work had to be determined:

What byte values does browser use to send HTTP GET?What byte values does browser use to send HTTP GET?

What byte value does server use to send HTTP REPLY?

Is // required before name of server in web address?

How does server tell browser when it can’t find requested object?

How does server tell browser where object’s bytes begin and end?

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Hardware

St d d l t b th h d d ftStandards apply to both hardware and software.

Example: NICs connectors.Without standards, not all cables would fit NIC’s port (proprietary configurations).

Fixes size and shape standards for connectors and otherFixes size and shape standards for connectors and other networking gear set.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Hardware

E l Thi bl h RJExample: This cable has an RJ-45 connector. (RJ-45 is the name of the standard for the connector)connector).

The NIC has an RJ-45 port of the same sizethe same size.

The RJ-45 has 8 pins and looks much like the RJ-11 which is commonly know as a “Phone Connector,” but is half the size of the RJ-45.

Figure 3-1Example of Physical Standard: RJ-45 Connector (on Cable) and Socket (on NIC)10

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Types of Standards, Part 1

N ti l St d d d b ti l tNational: Standard approved by a national government which then appoints an organization to oversee it.

Example: Electrical power outlets’ size, shape, electrical current, p p , p , ,voltage.

International: Standard approved by a group of nations that typically relates to functions that benefit fromthat typically relates to functions that benefit from consistency among the participating nations.Vendor (proprietary): Standard approved by a single vendor which allows the vendor to keep control yet allows other vendors to use them so they are interoperableinteroperable.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Types of Standards, Part 2

V d G St d d d b fVendor Group: Standard approved by a group of vendors (vendor consortium, vendor alliance, vendor forum).)

Wants their standards to become national/international standards. Can move quicker than national/international standards groupsCan move quicker than national/international standards groups.Works to get compatible products to market quicker, while working with formal standards groups.

De Facto: Standard that exists because it is what isDe Facto: Standard that exists because it is what is currently in use, usually not written down.

Example: MS-Word has become de facto standard of most offices.

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Not all protocols and hardware specs are standardized;Not all protocols and hardware specs are standardized; however, most used today happen to be standards.

Figure 3-2Networking Standards Compared to Protocols and Hardware Specs13

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: TCP/IP Model

D fi l t f t d d i l t d t th tDefines large set of standards implemented together to create safe and useful network.Model name has many variations but all refer to sameModel name has many variations but all refer to same idea.

TCP/IP network architecture, TCP/IP networking model, TCP/IP networking blueprintnetworking blueprint.

Organizes standards into layers so…Humans can understand what networks do.Easier to divide work among different products.Devices can be interoperable.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: TCP/IP Model

C l d i fCommonly-used version of TCP/IP model has five layers.

Original TCP/IP model had fourOriginal TCP/IP model had four layers:

Bottom two layers of model ycombined into Network Interface layer (or Network Access layer).

Figure 3-3TCP/IP Model15

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: TCP/IP ModelIncludes standards created for TCP/IP as well as someIncludes standards created for TCP/IP, as well as some created by other standards groups.Each standards-setting group follows some kind of process:g g p p

Repeated experimentationDocumentationReviewReviewComments, etc.

Example: Internet Engineering Task Force (IETF) acts as primary standards group for TCP/IP model, so model includes standards created by both IETF and other standards groups.standards groups.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Organizations Useful to TCP/IP

Figure 3-4Sources of Standards in the TCP/IP Model17

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IETF (www.ietf.org)

W k t d d tti f TCP/IPWorks as standard-setting group for TCP/IP.Decides:

What needs to be updatedWhat needs to be updatedWhat new standards need to be added

Organized around working groups made up of volunteers who work on new standards (create “internet drafts”).

Experiments, changes details, improves how new technology works, then shares changes.Submits findings into standards process.Document created by group can become informational or experimental RFC if draft not submitted.p

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: IETF Working Groups Process

Figure 3-5Standard and Non-Standard TCP/IP RFCs19

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: IEEE (www.ieee.org)

I tit t f El t i l d El t i E i (IEEE)Institute of Electrical and Electronics Engineers (IEEE).Plays huge role in networking and for TCP/IP in general.World’s largest professional organizationWorld s largest professional organization.IEEE standards for TCP/IP define LANs (including Ethernet, most commonly used wired and wireless LAN technology).y gy)Not agency of any particular government or agency.US government appoints ANSI to manage US standards

i d t iacross industries.ANSI certifies standards by certifying other standards groups.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: ITU

International Telecommunications UnionInternational Telecommunications Union.International standards body that focuses on standards for telecom and WAN networking technologies.g g

Example: ITU standards define country codes for international phone calls.

Enables worldwide digital voice communications byEnables worldwide digital voice communications by standardizing voice codecs.TCP/IP model uses ITU standards for same reasons it uses IEEE standards.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Vendor Consortia & Other Groups

Vendor Group/Consortium: Vendors team up to get quickVendor Group/Consortium: Vendors team up to get quick and broad acceptance in marketplace.Group agrees on standardized version of new technology BEFORE formal standards group sets standards.

Example: Wi-Fi Alliance (www.wi-fi.org) helped get new wireless technology to market quicker than formal IEEE standards process gy q pwould have.Tested products to certify (confirm) they worked together.Created pre-standard rules.Created pre standard rules.Allowed vendors to brand products as “Wi-Fi certified”.Worked with IEEE to help overall standards process.

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Overall process: No matter whether a person with good ideas worksOverall process: No matter whether a person with good ideas works through the Wi-fi Alliance or IEEE, when those two groups cooperate, products get to market sooner, and the standards happen.

Figure 3-6Vendor Groups Impact on Speed to Market23

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: LAN/WAN Standards

Figure 3-7TCP/IP Using Other Standards for LAN and WAN24

Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: Standards

While a single standard typically focuses on one protocol or hardware spec, the TCP/IP model collects all the standards needed to do everything required to make a complete modern network into one handymodern network into one handy model.

Each device in the network andEach device in the network and each component follows a subset of the TCP/IP standards, depending on its role.

Figure 3-8Conceptual View of TCP/IP Model

p g

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Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: History of Networking Models

Fi t i l t hit k t i 1950 dFirst commercial computers hit market in 1950s and became more common in larger companies by 1960s.

Personal computers hit market in late 1970s andPersonal computers hit market in late 1970s and became common in 1980s.

Networks didn’t exist yet.Networks didn t exist yet.

Eventually computer vendors saw need to create network between computers.

Individual vendors created their own proprietary networking products and networking models.

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Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: History of Networking ModelsTypical enterprise network from the 1980s used 3 differentTypical enterprise network from the 1980s—used 3 different models to operate:

IBM networking model.DEC networking model.Other vendor that could connect them together.

Figure 3-9Typical Mix of Corporate Networks over Three Decades27

Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: History of Networking ModelsWh t h d i t i l t i t k f th 1980 i t thWhat happened in typical enterprise networks from the 1980s into the early 21st century? Enter TCP/IP…

Figure 3-10Typical Migration of Enterprise Networks from Vendor Models to TCP/IP28

Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: OSI Model

O S t I t ti (OSI)Open Systems Interconnection (OSI) model.

ISO began work on OSI model followingISO began work on OSI model following timeline that was close to TCP/IP’s:

Started in 1970s.

Progressed on individual standards in 1980s.

Allowed standards-based vendor products to start appearing by early 1990s.

Figure 3-11The OSI Model29

Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: OSI ModelThe biggest differences between the TCP/IP and OSI models exist at the top.

The TCP/IP model defines many functions as part of the application layer while the OSIapplication layer, while the OSI model split those functions into multiple layers.

Figure 3-12Mapping the Layers of the TCP/IP and OSI Models30

Comparing TCP/IP to Other NetworkingComparing TCP/IP to Other Networking Models: OSI Model

Figure 3-13Three Example Standards, and the Phrases to Use31

Understanding How a TCP/IP NetworkUnderstanding How a TCP/IP Network Works: LANs vs. WANs

When defining LANs and WANs, always consider the Data Link and Physical layers as local versus remote—or owned versus leased.

Figure 3-14The Terms LAN and WAN in the TCP/IP Model32

Understanding How a TCP/IP Network

B th th d d i t th l f h t th

Understanding How a TCP/IP Network Works: LAN Physical LinksBoth the sender and receiver must agree on the rules of how to use the electrical circuit. The sending NIC sends the bits over the loop to create the electrical signal. Signal varies over time to encode different bits. The receiving NIC must know what rules the sender uses so it canThe receiving NIC must know what rules the sender uses so it can interpret the circuit changes into the correct 0s and 1s (bits).

Figure 3-15NICs on Both Ends of a Cable Creating a Loop33

Understanding How a TCP/IP Network

E Eth t LAN d i t t th LAN i bl Th

Understanding How a TCP/IP Network Works: LAN SwitchesEvery Ethernet LAN device connects to the LAN using a cable. The cable installers run a cable from each device to a central place on that floor, usually to a switch that sits in a locked room called a wiring room By connecting all the cables to the switch all are connect to theroom. By connecting all the cables to the switch, all are connect to the LAN—and each other.

Figure 3-16Using a LAN Switch to Physically Connect Devices to a LAN34

BreakBreak

Take 15

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Data Link LayerTh Eth t D t Li k l / t d d d fi th l ( t l ) th tThe Ethernet Data Link layer/standards define the rules (protocols) that tells the devices how and when to use the Ethernet Physical layer.

Figure 3-17Using an Address to Send Data to the Right LAN Device36

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Data Communication over Layers 1 & 21 The server sends the data over the physical link but only after the1. The server sends the data over the physical link, but only after the

sever adds the destination MAC (physical) address of 1111.1111.1111 to the data.

2 The switch sees the destination address and switches the data to2. The switch sees the destination address and switches the data to PC1—and PC1 only.

3. The data arrives at PC1, and PC1 knows the data is meant for it because of the MAC addressbecause of the MAC address.

Figure 3-17Using an Address to Send Data to the Right LAN Device37

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Data Link Layer

M t l h d d/ t il t tMany protocols use headers and/or trailers to store bytes of info that control data flow through network.

Data Link protocols typically add both header andData Link protocols typically add both header and trailer.

Figure 3-18Data Link Header and Trailer, Like a Couple of Sticky Notes38

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: WANs

WAN h i l li k t d b i id ( llWAN physical links created by service provider (usually Telco) used by customer company in its corporate network.

Example: FredExample: Fred buys house three miles from Barney’s house. Instead of building private road pbetween their houses, Barney and Fred use public road already builtand Fred use public road already built.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: WANs

WAN t li k b t it f t t kWANs create link between sites of corporate network when company could not physically cable between sites itself.Example: Company has two sites 3 miles apart; although Ethernet LAN standards allow for 3-mile-long cables to connect LAN s itches at both sites compan can’tconnect LAN switches at both sites, company can’t legally lay cable over other people’s land between sites.

Solution: Contract with 3rd party company that has right to run cables near existing roads.Links are leased (rented) from 3rd party company by customers.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: WAN Examples

T l h h li i t t hTelco has phone line into most houses.Electric company has power lines into most buildings.Cable TV company has cable lines into most buildingsCable TV company has cable lines into most buildings.Government lets utility companies y pdig up road to install cables or hang cables fromhang cables from poles above ground.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Leased Lines

C t i l t f bl di tl b t t tCreates equivalent of cable directly between two remote sites.Enterprises lease lines to connect remote sitesEnterprises lease lines to connect remote sites.Leased lines create 2-way path to transmit data at pre-determined speed (for pre-determined price!).

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Enterprises use Layer 3 devices called routers to connect to the WAN leased line at each site.

The Telco connects the ends of the leased line directly into the enterprise’sThe Telco connects the ends of the leased line directly into the enterprise’s routers in their WAN interfaces (ports) on each end of the link.

Figure 3-21Physical Cabling of a Leased Line, from Each Customer Site to Central Office (CO)43


Two leased lines:Two leased lines: One connecting Miami to Atlanta.One connectingOne connecting Miami to Boston.

The length of the leasedThe length of the leased line could literally run across the street in a city or thousands of c ty o t ousa ds omiles across a country.

(WAN lines that look like lightning bolts represent leased lines.)

Figure 3-22Leased Line, Cabling View, with Routers Connecting LAN and WAN44

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Data Link Protocols for Leased Lines

High level Data Link Control (HDLC standardized byHigh-level Data Link Control (HDLC—standardized by ISO). Point-to-Point Protocol (PPP—defined by TCP/IP in RFC ( y1661).Both define address in header to identify devices on h i l li kphysical link

When router sends data over leased line, data can only go to router on other end of link.to oute o ot e e d oEvery Data Link protocol focuses on particular Physical layer technology.Routers typically sit at border between different data links.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Data Link Protocol Encapsulation

R t t i ff ld D t Li k h d l d d dRouters strip off old Data Link headers no longer needed and replace them with new Data Link headers needed for next leg (hop) of the data’s journey to its destination.

Figure 3-23Encapsulation and De-encapsulation46

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Encapsulation Example

1. Sending device adds Ethernet Data Link header/trailer to data before1. Sending device adds Ethernet Data Link header/trailer to data before sending across LAN.

2, 3. Border router removes Ethernet header/trailer and adds new WAN one (e.g., PPP) then sends data over WAN link.one (e.g., PPP) then sends data over WAN link.

4, 5. Destination border router discards PPP header/PPP header/trailer and adds new Ethernet header/trailer for destination device and sends data over LAN.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Header/Trailer Encapsulation ExampleSi il t t t k h t k l t iSimilar to steps you take when you take a long trip:

1.Start by taking subway train to airport.

2 Take plane to2.Take plane to another city.

3.Rent car at destination.

4.Drive car to final destination.

None of above vehicles accomplished entire trip from start to finish;None of above vehicles accomplished entire trip from start to finish; takes planes, trains, and automobiles!

Figure 3-24Routers Separate a Network into Separate Data Links48

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP Addressing

Identifies device in TCP/IP network.Identifies device in TCP/IP network.Every device must have unique IP address.IP address has 32 bits written in dotted decimal notation (DDN) of four sets of eight bits each with dot (period) between each number.Networking devices see decimal numbers as binary

Binary IP Address Equivalent DecimalIP Address

00000001 00001000 00010000 00100000 1 8 16 32

Networking devices see decimal numbers as binary.

00000001 00001000 00010000 00100000 1.8.16.3201010101 10101010 00001111 11110000 85.170.15.24000001010 00000101 00011010 00010101 10.5.26.2101111110 10000001 01010101 11111000 126 129 85 24801111110 10000001 01010101 11111000 126.129.85.24800100001 01000001 10000001 00010001 33.65.129.17

Table 3-1Example IP Addresses, Binary and DDN Formats49

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP AddressingE h PC ith ti i t th TCP/IP t k hEach PC with a connection into the TCP/IP network has a unique IP address.

Figure 3-25IP Addresses in a Network Diagram50

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP AddressingR t l bi l ith th IP t l i th t th t (f d)Routers play a big role with the IP protocol in that they route (forward) data based on the destination IP address. To do that, a router must connect using multiple interfaces to multiple data links.

Example: Each router has 2 interfaces: One for WAN link and one for LAN.

Figure 3-26Routers: Multiple Interfaces, Multiple IP Addresses51

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP Addressing Grouping

T k IP ti k dd d i lTo make IP routing work, addresses grouped using rules.IP groups addresses in different ways: Classful networksand subnettingand subnetting .Rules give network engineers flexibility in how they assign addresses, but still allow IP routinggto work efficiently.

Figure 3-27Five Classful IP Networks52

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP Addressing Grouping

IP Cl f l N t kIP Classful Networks

Class IP Range Designed for

A 1.0.0.0 – 126.255.255.255 Large enterprises, government agencies, etc.

B 128 0 0 0 191 255 255 255 Medium-sized businesses, B 128.0.0.0 – 191.255.255.255 organizations, etc.

C 192.0.0.0 – 223.255.255.255 For small entities and home networks

D 224.0.0.0 – 239.255.255.255 MulticastE 240.0.0.0 – 255.255.255.255 Experimental, research

Five Classful IP Networks53

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP Addressing Update—IPv6

IP version 4 addresses no longer issued out (all used).Based on 32-bit addresses 192.168.3.5, dotted decimal.

IP version 6 is new IP addressing schemeIP version 6 is new IP addressing scheme.Based on 128-bit address.

Expressed in 8 sets of 4 hexadecimal numbers, for example: p p2001:0db8:85a3:0000:0000:8a2e:0370:7334.Creates billions and billions of IP addresses: 2128, or approximately 3.4×1038 (a number with 37 zeros).pp y ( )

For all practical purposes, eliminates classful networks and need for subnetting.World IPv6 Launch took place on 6 June 2012.

Five Classful IP Networks54

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network:IP Routing

IP ti d fi tl h t f d d t iIP routing defines exactly how routers forward data in network.

Each router connects to multiple physical links so hasEach router connects to multiple physical links so has multiple physical interfaces (ports).

Router has rules that tell it how to make routingRouter has rules that tell it how to make routing decisions.

IP routing relies on two ideas: Sender addresses data.

Routers forward data based on destination IP address.

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Moving data on network relies on routers to forward data to correct destination host.Routers talk to each other (using protocols) to learnRouters talk to each other (using protocols) to learn about IP addresses in network.Routers keep routing information in their RAM in IP routing tables.

Figure 3-29Routing Tables on R1 and R2, for Network 12.0.0.056


PC11 d IP 4 k t t PC21 b ddi IP h d th t i l dPC11 sends an IPv4 packet to PC21 by adding an IP header that includes its address and the destination’s IPv4 address to the data (payload).

Figure 3-28Web Client Host PC11 Puts 12.1.1.21 into the IP Header Destination IP Address Field57


1. PC11 sends data with destination IPv4 address 12.1.1.21 (PC21) to R1.2. R1 compares destination

IP address listed in header with its routing table. R1 finds matching table entry that tells R1 to send data14.1.1.2 (R2)(R2).

3. R21sends packet to router R2.

4, 5. R2’s routing table says that network IPv4 12.0.0.0 is local so R2 forwards data over LAN directly to PC21.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Forwarding Packets

IP t d dd IP h d t l dIP creates and adds IP header to payload.Sending host adds IP header (Network Layer address) and Data Link layer header/trailer before sending dataand Data Link layer header/trailer before sending data onto network.IP header follows Data Link header in frame.

Figure 3-30Encapsulation on the Sending Host: Frame and Packet59

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Forwarding Packets

F E l t d d t th t i l d D t Li kFrame: Encapsulated data that includes Data Link header and trailer—plus everything in between (including IP header).)Packet: What sits between Data Link header and trailer.Router discards Data Link header and trailer when it receives frame, leaving IP packet.Router then encapsulates packet into new Data Link header and trailer (with next hop Data Link address)header and trailer (with next hop Data Link address) when it forwards IP packet.Encapsulation/de-encapsulation process continues until IP packet delivered to destination.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Routing IP Packets

Figure 3-31Routers: Remove Packet from Frame, Send Packet inside a New Frame61

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Routing IP Packets1 Sending host sends Ethernet frame to router1. Sending host sends Ethernet frame to router.2. Router:

a. Removes IP packet from inside frame and discards old Data Link h d /t ilheader/trailer.

b. Decides where to route IP packet (to next router across WAN link).c. Encapsulates packet in new PPP frame and sends across link.

3. PPP frame holds original IP packet as it crosses WAN link to destination router.

4 Destination router repeats same three steps as sending4. Destination router repeats same three steps as sending router.

5. Ethernet frame (with original IP packet) crosses LAN and i t d ti ti d iarrives at destination device.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Transport ProtocolsT t l t l id th ti t t kTransport layer protocols provide the connection to network

applications (apps).

Figure 3-32Widening Scope of Higher TCP/IP Layers63

Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: Transport Protocols TCP and UDP

T t l t d d ti tiTransport layer connects source and destination applications.

Port number: Used by transport protocol to identifyPort number: Used by transport protocol to identify each destination app.

Transmission Control Protocol (TCP) – Connection-Transmission Control Protocol (TCP) Connectionoriented.

User Datagram Protocol (UDP) – Connectionless.

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Defining the Rules for a TCP/IP Network:Defining the Rules for a TCP/IP Network: TCP/IP Roles Summary, Part 1

TCP/IP t k d li bit f d i t thTCP/IP network delivers bits from one device to another and from one application to another.

Applications run on various devicesApplications run on various devices.

Application vendors use protocols that let apps communicate through network.communicate through network.

Application layer protocols rely on Transport layer protocols to connect sending app to destination app.

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E h li ti ’ it h t TCP UDPEach application’s writer chooses to use TCP, UDP, or some other less common Transport protocol.TCP and UDP use port numbers (specified in header)TCP and UDP use port numbers (specified in header) that identify destination app.Transport layer protocols rely on IP to deliver packets from sending host to destination host.Sending host adds IP header which includes destination IP addressIP address.Each router reacts to destination IP address to make routing choice.

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IP d fi d t il t k t k i tiIP defines details to make network communication possible, including logical IP addressing and routing.IP relies on Data Link and Physical layers to deliverIP relies on Data Link and Physical layers to deliver frames across LANs and WANs.Data Link layer defines how to best use physical link, and adds Data Link headers/trailers that contain delivery information (MAC addresses).Physical layer defines how to encode bits over cable orPhysical layer defines how to encode bits over cable or wirelessly.

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Host orLayer Name Key Functions

Host or Network Device Focus

PhysicalPhysical parts that communicate, and energy over those parts (electricity light radio)

Network Cables, radio over those parts (electricity, light, radio).

Data LinkRules about when to use physical links; Addressing specific to the physical links.

Network LAN Switch

Internetwork (Network)

Logical addressing (addressing independent of the physical links); routing.

Network Router

TCommunications functions useful to apps,

HAny endpoint

Transportpp ,

but likely useful to many apps. Host

y pdevice

ApplicationCommunication functions specific to a particular app

Host Any endpoint device

Table 3-2TCP/IP Model Summary68

particular app. device

S mmar This chapterSummary: This chapter…Distinguished between the key terms related to networking standards, including standard, protocol, and model.Listed the layers of the TCP/IP model and explainedListed the layers of the TCP/IP model and explained the purpose of the TCP/IP model.Named standards organizations on which the TCP/IP model relies.Briefly compared the history of the OSI and TCP/IP models and classified the layers of each in comparisonmodels and classified the layers of each in comparison to each other.

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Summary: This chapter…Summarized the key functions of Ethernet LANsSummarized the key functions of Ethernet LANs.Summarized the key functions of leased line WANs.Explained how IP addressing and IP routing work p g gtogether.Defined how different headers help move data through a net orka network.Listed two Transport layer protocols: TCP and UDP.

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Questions? Comments?

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