pengantar tcp/ip dan routing

Magister Manajemen Sistem InformasiMagister Manajemen Sistem Informasi 11

PENGANTAR TCP/IP DAN PENGANTAR TCP/IP DAN ROUTINGROUTING

Dr. Tb. Maulana KusumaDr. Tb. Maulana [email protected]@staff.gunadarma.ac.id

http://staffsite.gunadarma.ac.id/mkusumahttp://staffsite.gunadarma.ac.id/mkusuma

Internet dan Jaringan KomputerInternet dan Jaringan Komputer

22Magister Manajemen Sistem InformasiMagister Manajemen Sistem Informasi

Internet ProtocolInternet Protocol(IP)(IP)


IP Addressing BasicsIP Addressing Basics

Symbolic namesSymbolic names are easier to remember a string, such are easier to remember a string, such as as www.course.comwww.course.com, than a , than a numeric addressnumeric address, such as , such as 199.95.728199.95.728—computers are the opposite—computers are the opposite

They deal with They deal with network addressesnetwork addresses in the form of bit in the form of bit patterns that translate into decimal numberspatterns that translate into decimal numbers

IP uses a three-part addressing scheme, as follows:IP uses a three-part addressing scheme, as follows:

SymbolicSymbolic

Logical numericLogical numeric

Physical numericPhysical numeric



In keeping with the layered nature of network models, it In keeping with the layered nature of network models, it makes sense to associate the MAC layer address with makes sense to associate the MAC layer address with the Data Link layer (or TCP/IP Network Access layer, if the Data Link layer (or TCP/IP Network Access layer, if you prefer to think in terms of that model), and to you prefer to think in terms of that model), and to associate IP addresses with the Network layer (or the associate IP addresses with the Network layer (or the TCP/IP Internet layer)TCP/IP Internet layer)

As data moves through intermediate hosts between the As data moves through intermediate hosts between the original sender and the ultimate receiver, it does so original sender and the ultimate receiver, it does so between pairs of machines, where each pair resides on between pairs of machines, where each pair resides on the same physical networkthe same physical network



At the Network layer, the original sender’s address is At the Network layer, the original sender’s address is represented in the IP source address field in the IP represented in the IP source address field in the IP packet header, and the ultimate recipient’s address is packet header, and the ultimate recipient’s address is represented in the IP destination address field in the represented in the IP destination address field in the same IP packet headersame IP packet header

The IP destination address value, in fact, is what drives The IP destination address value, in fact, is what drives the sometimes-long series of intermediate transfers, or the sometimes-long series of intermediate transfers, or hopshops, which occur as data makes its way across a , which occur as data makes its way across a network from sender to receivernetwork from sender to receiver


Anatomy of an IP AddressAnatomy of an IP Address

Numeric IP addresses use dotted decimal notation when Numeric IP addresses use dotted decimal notation when expressed in decimal numbers, and take the form expressed in decimal numbers, and take the form n.n.n.n., in which n.n.n.n., in which nn is guaranteed to be between zero is guaranteed to be between zero and 255 for each and every valueand 255 for each and every value

The numeric values in dotted decimal representations of The numeric values in dotted decimal representations of numeric IP addresses are usually decimal values, but numeric IP addresses are usually decimal values, but may occasionally appear in hexadecimal (base 16) or may occasionally appear in hexadecimal (base 16) or binary (base 2) notationbinary (base 2) notation


Anatomy of an IP AddressAnatomy of an IP Address

Duplication of numeric IP addresses is not allowed Duplication of numeric IP addresses is not allowed because that would lead to confusionbecause that would lead to confusionAlso, there is a notion of “neighborhood” when it comes Also, there is a notion of “neighborhood” when it comes to interpreting numeric IP addressesto interpreting numeric IP addressesProximity between two numeric IP addresses (especially Proximity between two numeric IP addresses (especially if the difference is only in the rightmost one or two if the difference is only in the rightmost one or two octets) can sometimes indicate that the machines to octets) can sometimes indicate that the machines to which those addresses correspond reside close enough which those addresses correspond reside close enough together to be on the same general network, if not on the together to be on the same general network, if not on the same physical cable segmentsame physical cable segment


IP Address ClassesIP Address Classes

Initially, these addresses were further subdivided into five Initially, these addresses were further subdivided into five classes, from Class A to Class Eclasses, from Class A to Class E

For the first three classes of addresses, divide the octets For the first three classes of addresses, divide the octets as follows to understand how they behave:as follows to understand how they behave:

Class AClass A nn h.h.hh.h.h

Class BClass B n.nn.n h.h h.h

Class CClass C n.n.nn.n.n h h

If more than one octet is part of the network or If more than one octet is part of the network or host portionhost portion of the address, then the bits are simply concentrated to of the address, then the bits are simply concentrated to determine the numeric addressdetermine the numeric address


IP Address ClassesIP Address Classes

The The network portionnetwork portion of that address is 10, whereas the of that address is 10, whereas the host portion is 12.120.2, treated as a three-octet numberhost portion is 12.120.2, treated as a three-octet number

Address Classes D and E are for special usesAddress Classes D and E are for special uses

Class D addresses are used for multicast Class D addresses are used for multicast communications, in which a single address may be communications, in which a single address may be associated with more than one network host machineassociated with more than one network host machine

This is useful only when information is broadcast to more This is useful only when information is broadcast to more than one recipient at a time so it should come as no than one recipient at a time so it should come as no surprise that video and teleconferencing applications, for surprise that video and teleconferencing applications, for example, use example, use multicast addressesmulticast addresses


More About Class A AddressesMore About Class A Addresses

Expressed in binary form (ones and zeroes only), Class Expressed in binary form (ones and zeroes only), Class A addresses always take the form:A addresses always take the form:

0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb0bbbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb

The leading digit is always zero, and all other digits can The leading digit is always zero, and all other digits can be either ones or zeroesbe either ones or zeroes

On any IP network, addresses consisting of all zeroes On any IP network, addresses consisting of all zeroes and all ones are reserved for special uses, so of those and all ones are reserved for special uses, so of those 128 possible network addresses, only those from 128 possible network addresses, only those from 00000001 to 01111110 (or 1 to 126, in decimal terms) 00000001 to 01111110 (or 1 to 126, in decimal terms) are considered usableare considered usable


More About Class A AddressesMore About Class A Addresses

The address for network 10 is reserved for private network The address for network 10 is reserved for private network useuse

Also, by convention, the address 127.n.n.n is reserved for Also, by convention, the address 127.n.n.n is reserved for loopbackloopback testing (or checking the integrity and usability of a testing (or checking the integrity and usability of a TCP/IP protocol stack installed on any computerTCP/IP protocol stack installed on any computer


More About Class B AddressesMore About Class B Addresses

Class B addresses always take the form:Class B addresses always take the form:

10bbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb10bbbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb

The leading two digits are 10, and the remaining digits The leading two digits are 10, and the remaining digits can be either ones or zeroescan be either ones or zeroes

RFC 1918 stipulates that 16 Class B addresses, from RFC 1918 stipulates that 16 Class B addresses, from 172.16.0.0 to 172.32.255.255, are reserved for private 172.16.0.0 to 172.32.255.255, are reserved for private useuse

This means that the maximum number of This means that the maximum number of public IP public IP addressesaddresses for Class B is 16,382-16, or 16,366 for Class B is 16,382-16, or 16,366


Class B Address Facts and Class B Address Facts and FiguresFigures


More About Class C AddressesMore About Class C Addresses

Class C addresses always take the form:Class C addresses always take the form:110bbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb110bbbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb

The leading three digits are 110, and the remaining digits The leading three digits are 110, and the remaining digits can be either ones or zeroescan be either ones or zeroesNote that this scheme reduces the total number of Note that this scheme reduces the total number of networks possible by the most significant three bitsnetworks possible by the most significant three bits


More About More About Address Classes D and EAddress Classes D and E

Class D addresses always take the form:Class D addresses always take the form:

1110bbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb1110bbbb.bbbbbbbb.bbbbbbbb.bbbbbbbb

Class E addresses always take the form:Class E addresses always take the form:

11110bbb.bbbbbbbb.bbbbbbbb.bbbbbbbbb11110bbb.bbbbbbbb.bbbbbbbb.bbbbbbbbb

Class D is used for multicast addresses so that multiple Class D is used for multicast addresses so that multiple users can “share” a single IP address and receive the users can “share” a single IP address and receive the same broadcast across a network from a single same broadcast across a network from a single transmissiontransmission


The Vanishing IP Address The Vanishing IP Address SpaceSpace

IP addresses were assigned for public use, they were IP addresses were assigned for public use, they were assigned on a per-network basisassigned on a per-network basis

With the ever-increasing demand for public IP addresses With the ever-increasing demand for public IP addresses for Internet access, it should come as no surprise that, for Internet access, it should come as no surprise that, as early as the mid-1990s, experts began to predict that as early as the mid-1990s, experts began to predict that the Internet would “run out” of available IP addressesthe Internet would “run out” of available IP addresses


The Vanishing IP Address The Vanishing IP Address SpaceSpace

The causes for concern have abated somewhat, Here’s why:The causes for concern have abated somewhat, Here’s why: The technocrats at the IETF introduced a new way to The technocrats at the IETF introduced a new way to

carve up the IP address spacecarve up the IP address space——Classless Inter-Domain Classless Inter-Domain Routing (CIDR)Routing (CIDR)

A brisk trade in existing IP network addresses sprung up A brisk trade in existing IP network addresses sprung up during the same timeduring the same time

RFC 1918 reserves three ranges of IP addresses for RFC 1918 reserves three ranges of IP addresses for private useprivate use—a single Class A (10.0.0.0-10.255.255.255), —a single Class A (10.0.0.0-10.255.255.255), 16 Class Bs (172.16.0.0-172.31.255.255), AND 256 Class 16 Class Bs (172.16.0.0-172.31.255.255), AND 256 Class Cs (192.168.0.0-192.168.255.255). When used in tandem Cs (192.168.0.0-192.168.255.255). When used in tandem with a technology called with a technology called Network Address TranslationNetwork Address Translation (a.k.a (a.k.a NATNAT), private IP addresses can help lift the “cap” on ), private IP addresses can help lift the “cap” on public IP addressespublic IP addresses


IP Networks, Subnets, and IP Networks, Subnets, and MasksMasks

If two network interfaces are on the same physical If two network interfaces are on the same physical network, they can communicate directly with one another network, they can communicate directly with one another at the MAC layerat the MAC layer

In fact, each of the three primary IP address classesIn fact, each of the three primary IP address classes——namely A, B, and C—also has an associated default namely A, B, and C—also has an associated default subnet masksubnet mask


IP Subnets and Supernets IP Subnets and Supernets

A subnet mask is a special bit pattern that “blocks off” A subnet mask is a special bit pattern that “blocks off” the network portion of an IP address with an all-ones the network portion of an IP address with an all-ones patternpattern

The reason why concepts like subnets and supernets The reason why concepts like subnets and supernets are important for TCP/IP networks is because each of are important for TCP/IP networks is because each of these ideas refers to a single “local neighborhood” on these ideas refers to a single “local neighborhood” on such a network, seen from a routing perspectivesuch a network, seen from a routing perspective



Thus, a subnet mask that is larger than the default mask Thus, a subnet mask that is larger than the default mask for the address in use divides a single network IP for the address in use divides a single network IP address into multiple subnetworksaddress into multiple subnetworks

The The network prefixnetwork prefix identifies the number of bits in the IP identifies the number of bits in the IP address, counting from the left that represents the actual address, counting from the left that represents the actual network address itself, and the additional two bits of network address itself, and the additional two bits of subnetting represent the bits that were borrowed from subnetting represent the bits that were borrowed from the host portion of that IP address to extend the network the host portion of that IP address to extend the network portionportion



The entire network address, including the network prefix The entire network address, including the network prefix

and the subnetting bits, is called the and the subnetting bits, is called the extended network extended network

prefixprefix

This activity of stealing bits from the host portion of This activity of stealing bits from the host portion of

further subdivide the network portion of an address is further subdivide the network portion of an address is

called subnetting a network address, or called subnetting a network address, or subnettingsubnetting



When a computer on one subnet wishes to communicate When a computer on one subnet wishes to communicate with a computer on another subnet, traffic must be with a computer on another subnet, traffic must be forwarded from the sender to a nearby IP gateway to forwarded from the sender to a nearby IP gateway to send the message on its way from one subnet to anothersend the message on its way from one subnet to another

SupernettingSupernetting takes the opposite approach: by combining takes the opposite approach: by combining contiguous network addresses, it steals bits from the contiguous network addresses, it steals bits from the network portion and uses them to create a single, larger network portion and uses them to create a single, larger contiguous address space for host addressescontiguous address space for host addresses


Calculating Subnet MasksCalculating Subnet Masks

The simplest form of subnet masking uses a technique The simplest form of subnet masking uses a technique called called constant-length subnet masking (CLSM)constant-length subnet masking (CLSM),, in which in which each subnet includes the same number of stations and each subnet includes the same number of stations and represents a simple division of the address space made represents a simple division of the address space made available by subnetting into multiple equal segmentsavailable by subnetting into multiple equal segments

Another form of subnet masking uses a technique called Another form of subnet masking uses a technique called variable-length subnet masking (VLSM)variable-length subnet masking (VLSM) and permits a and permits a single address to be subdivided into multiple subnets, in single address to be subdivided into multiple subnets, in which subnets need not all be the same sizewhich subnets need not all be the same size


Calculating SupernetsCalculating Supernets

Supernets “steal” bits from the network portion of an IP Supernets “steal” bits from the network portion of an IP address to “lend” those bits to the host partaddress to “lend” those bits to the host part

As part of how they work, supernets permit multiple IP As part of how they work, supernets permit multiple IP network addresses to be combined and make them network addresses to be combined and make them function together as if they represent a single logical function together as if they represent a single logical networknetwork


Classless Inter-Domain Routing Classless Inter-Domain Routing (CIDR)(CIDR)

CIDR gets its name from the notion that it ignores the CIDR gets its name from the notion that it ignores the

traditional A, B, and C class designations for IP traditional A, B, and C class designations for IP

addresses, and can therefore set the network-host ID addresses, and can therefore set the network-host ID

boundary wherever it wants to, in a way that simplifies boundary wherever it wants to, in a way that simplifies

routing across the resulting IP address spacesrouting across the resulting IP address spaces


Classless Inter-Domain Routing Classless Inter-Domain Routing (CIDR)(CIDR)

Creating a CIDR address is subject to the following Creating a CIDR address is subject to the following limitations:limitations: All the addresses in the CIDR address must be All the addresses in the CIDR address must be

contiguouscontiguous When address aggregation occurs, CIDR address When address aggregation occurs, CIDR address

blocks work best when they come in sets that are blocks work best when they come in sets that are greater than one, and equal to some lower-order bit greater than one, and equal to some lower-order bit pattern that corresponds to all onespattern that corresponds to all ones

CIDR addresses are commonly applied to Class C CIDR addresses are commonly applied to Class C addressesaddresses

To use a CIDR address on any network, all routers in To use a CIDR address on any network, all routers in the routing domain must “understand” CIDR notationthe routing domain must “understand” CIDR notation


CIDR NotationCIDR Notation

CIDR notation of an IP address: CIDR notation of an IP address:

192.0.2.0/18192.0.2.0/18

"18" is the prefix length. It states that the first 18 bits are the "18" is the prefix length. It states that the first 18 bits are the network prefix of the address (and 14 bits are available for network prefix of the address (and 14 bits are available for specific host addresses) specific host addresses)

CIDR notation can replace the use of subnetmasks (but is more CIDR notation can replace the use of subnetmasks (but is more general)general)

IP address 128.143.137.144 and subnetmask 255.255.255.0 IP address 128.143.137.144 and subnetmask 255.255.255.0 becomes 128.143.137.144/24becomes 128.143.137.144/24

CIDR notation allows to drop traling zeros of network addresses:CIDR notation allows to drop traling zeros of network addresses:

192.0.2.0/18192.0.2.0/18 can be written ascan be written as 192.0.2/18192.0.2/18


CIDR address blocksCIDR address blocksCIDR notation can nicely express blocks of addressesCIDR notation can nicely express blocks of addressesBlocks are used when allocating IP addresses for a company and for routing tables Blocks are used when allocating IP addresses for a company and for routing tables (route aggregation)(route aggregation)

CIDR Block Prefix # of Host AddressesCIDR Block Prefix # of Host Addresses /27/27 3232 /26/26 6464 /25/25 128128 /24/24 256256 /23/23 512512 /22/22 1,0241,024 /21/21 2,0482,048 /20/20 4,0964,096 /19/19 8,1928,192 /18/18 16,38416,384 /17/17 32,76832,768 /16/16 65,53665,536 /15/15 131,072131,072 /14/14 262,144262,144 /13/13 524,288524,288


Public Versus Private IP Public Versus Private IP AddressesAddresses

The private IP address ranges may be expressed in The private IP address ranges may be expressed in the form of IP network addresses, as shown in Table the form of IP network addresses, as shown in Table 2-42-4

Private IP addresses have one other noteworthy Private IP addresses have one other noteworthy limitationlimitation


Public Versus Private IP Public Versus Private IP AddressesAddresses

Some IP services require what’s called a secure Some IP services require what’s called a secure end-to-end-to-end connectionend connection—IP traffic must be able to move in —IP traffic must be able to move in encrypted form between the sender and receiver without encrypted form between the sender and receiver without intermediate translationintermediate translation

Most organizations need public IP addresses only for Most organizations need public IP addresses only for two classes of equipment:two classes of equipment: Devices that permit organizations to attach networks Devices that permit organizations to attach networks

to the Internetto the Internet Servers that are designed to be accessible to the Servers that are designed to be accessible to the

InternetInternet


Managing Access Managing Access to IP Address Informationto IP Address Information

Although use of private IP addresses mandates NAT or Although use of private IP addresses mandates NAT or a similar address substitutions or masquerade capability, a similar address substitutions or masquerade capability, some organizations elect to use address substitutions or some organizations elect to use address substitutions or masquerade even when they use perfectly valid public IP masquerade even when they use perfectly valid public IP addresses on their internal networksaddresses on their internal networks

Proxy servers can provide what is sometimes called Proxy servers can provide what is sometimes called reverse proxyingreverse proxying

This permits the proxy server to front for servers inside This permits the proxy server to front for servers inside the boundary by advertising only the proxy server’s the boundary by advertising only the proxy server’s address to the outside world, and then forwarding only address to the outside world, and then forwarding only legitimate requests for service to internal servers for legitimate requests for service to internal servers for further processingfurther processing


Obtaining Public IP AddressesObtaining Public IP Addresses

Unless you work for an organization that has Unless you work for an organization that has possessed its own public IP addresses since the possessed its own public IP addresses since the 1980s (or acquired such addresses through merger 1980s (or acquired such addresses through merger or acquisition), it’s highly likely that whatever public IP or acquisition), it’s highly likely that whatever public IP addresses your organization uses were issued by the addresses your organization uses were issued by the very same ISP who provides your organization with very same ISP who provides your organization with Internet accessInternet access

Because all devices accessible to the Internet must Because all devices accessible to the Internet must have public IP addresses, changing providers often have public IP addresses, changing providers often means going through a tedious exercise called means going through a tedious exercise called IP IP renumberingrenumbering


IP Addressing SchemesIP Addressing Schemes

To the uninitiated, it may appear that all these IP To the uninitiated, it may appear that all these IP addresses are randomly assigned, or perhaps generated addresses are randomly assigned, or perhaps generated automatically by some computer somewhereautomatically by some computer somewhere

A great deal of thought has gone into the strategy for A great deal of thought has gone into the strategy for allocating IP addresses around the worldallocating IP addresses around the world


The Network SpaceThe Network Space

There are a number of critical factors that typically There are a number of critical factors that typically constrain IP addressing schemes, and we look at these constrain IP addressing schemes, and we look at these in two groupsin two groups

The first group of constraints determines the number and The first group of constraints determines the number and size of networkssize of networks

These are:These are: Number of physical locationsNumber of physical locations Number of network devices at each locationNumber of network devices at each location Amount of broadcast traffic at each locationAmount of broadcast traffic at each location Availability of IP addressesAvailability of IP addresses Delay caused by routing from one network to anotherDelay caused by routing from one network to another


IPv6 - IP Version 6IPv6 - IP Version 6

IP Version 6IP Version 6 Is the successor to the currently used IPv4 Is the successor to the currently used IPv4 Specification completed in 1994Specification completed in 1994 Makes improvements to IPv4 (no revolutionary changes)Makes improvements to IPv4 (no revolutionary changes)

One (not the only !) feature of IPv6 is a significant increase in One (not the only !) feature of IPv6 is a significant increase in of the IP address to of the IP address to 128 bits (16 bytes)128 bits (16 bytes)

IPv6 will solve – for the foreseeable future – the IPv6 will solve – for the foreseeable future – the problems with IP addressingproblems with IP addressing

10102424 addresses per square inch on the surface of the addresses per square inch on the surface of the Earth.Earth.


IPv6 HeaderIPv6 Header

version(4 bits)

Traffic Class(8 bits)

Flow Label(24 bits)

Payload Length (16 bits)Next Header

(8 bits)Hop Limits (8 bits)

Source IP address (128 bits)

32 bits

Destination IP address (128 bits)


IPv6 vs. IPv4: Address IPv6 vs. IPv4: Address ComparisonComparison

IPv4IPv4 has a maximum of has a maximum of

223232 4 billion addresses 4 billion addresses

IPv6IPv6 has a maximum of has a maximum of

22128128 = (2 = (23232))4 4 4 billion 4 billion xx 4 billion 4 billion xx 4 billion x 4 billion 4 billion x 4 billion addresses addresses


Notation of IPv6 addressesNotation of IPv6 addresses

Convention:Convention: The 128-bit IPv6 address is written as The 128-bit IPv6 address is written as eight 16-bit integerseight 16-bit integers (using hexadecimal digits for each integer)(using hexadecimal digits for each integer)

CEDF:BP76:3245:4464:FACE:2E50:3025:DF12CEDF:BP76:3245:4464:FACE:2E50:3025:DF12

Short notation:Short notation:

Abbreviations of leading zeroes:Abbreviations of leading zeroes:

CEDF:BP76:0000:0000:009E:0000:3025:DF12 CEDF:BP76:0000:0000:009E:0000:3025:DF12

CEDF:BP76:0:0:9ECEDF:BP76:0:0:9E :0:3025:DF12:0:3025:DF12

““:0000:0000:0000” can be written as “::”:0000:0000:0000” can be written as “::”

CEDF:BP76:0:0:FACE:0:3025:DF12 CEDF:BP76:0:0:FACE:0:3025:DF12 CEDF:BP76::FACE:0:3025:DF12CEDF:BP76::FACE:0:3025:DF12

IPv6 addresses derived from IPv4 addresses have 96 leading zero bits. IPv6 addresses derived from IPv4 addresses have 96 leading zero bits. Convention allows to use IPv4 notation for the last 32 bits.Convention allows to use IPv4 notation for the last 32 bits.

::80:8F:89:90 ::80:8F:89:90 ::128.143.137.144 ::128.143.137.144


IPv6 Provider-Based AddressesIPv6 Provider-Based Addresses

The first IPv6 addresses will be allocated to a provider-based planThe first IPv6 addresses will be allocated to a provider-based plan

Type:Type: Set to “010” for provider-based addressesSet to “010” for provider-based addressesRegistry:Registry: identifies the agency that registered the address identifies the agency that registered the address

The following fields have a variable length (recommeded length in “()”)The following fields have a variable length (recommeded length in “()”)Provider:Provider: ID of Internet access provider ID of Internet access provider (16 bits)(16 bits)Subscriber:Subscriber: ID of the organization at provider ID of the organization at provider (24 bits)(24 bits)Subnetwork:Subnetwork: ID of subnet within organization ID of subnet within organization (32 bits)(32 bits)Interface:Interface: identifies an interface at a node identifies an interface at a node (48 bits)(48 bits)

Registry ID

Registry ID

Provider ID

Provider ID010010 Subscriber

ID Subscriber

IDInterface

IDInterface

IDSubnetwork

IDSubnetwork

ID


Transmission Control ProtocolTransmission Control Protocol(TCP)(TCP)


Connectionless protocolsConnectionless protocols provide the simplest kind of provide the simplest kind of transport services because they simply package transport services because they simply package messages, taken as is from the TCP/IP Application layer, messages, taken as is from the TCP/IP Application layer, into datagramsinto datagrams

A datagram slaps a header onto the higher-layer data A datagram slaps a header onto the higher-layer data and passes it to the IP layer, where that datagram is and passes it to the IP layer, where that datagram is fitted with an IP header and packetized, after which it fitted with an IP header and packetized, after which it may be transmitted across the networkmay be transmitted across the network

Understanding Connectionless Understanding Connectionless Transport ProtocolsTransport Protocols


Understanding Connectionless Understanding Connectionless Transport ProtocolsTransport Protocols

This method is called This method is called best-effort deliverybest-effort delivery

UDP runs up to 40% faster than TCP, under some UDP runs up to 40% faster than TCP, under some conditions, because it does next to nothingconditions, because it does next to nothing

It’s also typical for connectionless protocols to handle the It’s also typical for connectionless protocols to handle the following kinds of tasks:following kinds of tasks:

Message checksumMessage checksum

Higher-layer protocol identificationHigher-layer protocol identification


User Datagram Protocol (UDP)User Datagram Protocol (UDP)

It’s appropriate to provide the following detailed It’s appropriate to provide the following detailed description for UDP:description for UDP: No reliability mechanismsNo reliability mechanisms No delivery guaranteesNo delivery guarantees No connection handlingNo connection handling Identifies Application layer protocol conveyedIdentifies Application layer protocol conveyed Checksum for entire message carried in UDP headerChecksum for entire message carried in UDP header No buffering servicesNo buffering services No segmentationNo segmentation


UDP Header Fields and UDP Header Fields and FunctionsFunctions

UDP is defined in RFC 768UDP is defined in RFC 768

When the Protocol field of an IP header contains the value 17 (0x11), the UDP header When the Protocol field of an IP header contains the value 17 (0x11), the UDP header follows the IP headerfollows the IP header


UDP Port Numbers and UDP Port Numbers and ProcessesProcesses


Understanding Understanding Connection-Oriented ProtocolsConnection-Oriented ProtocolsConnection-oriented protocols create a Connection-oriented protocols create a logical logical connectionconnection directly between two peers on an directly between two peers on an internetworkinternetwork

Connection-oriented protocols track the transfer of data, Connection-oriented protocols track the transfer of data, and ensure it arrives successfully through and ensure it arrives successfully through acknowledgementsacknowledgements and and sequence number trackingsequence number tracking

An acknowledgement is a An acknowledgement is a positive responsepositive response, indicating a , indicating a set of data arrivedset of data arrived


Understanding Understanding Connection-Oriented ProtocolsConnection-Oriented ProtocolsConnection-oriented peers use sequence number Connection-oriented peers use sequence number tracking to identify the amount of data transferred, and tracking to identify the amount of data transferred, and any any out-of-order packetsout-of-order packetsConnection-oriented protocols have a Connection-oriented protocols have a timeout timeout mechanismmechanism that indicates when a host waited too long that indicates when a host waited too long for a communication, and such communication should be for a communication, and such communication should be assumed lostassumed lostConnection-oriented protocols also have a Connection-oriented protocols also have a retry retry mechanismmechanism that enables them to recover lost data by that enables them to recover lost data by retransmitting it a specified number of timesretransmitting it a specified number of times


Transmission Control Protocol Transmission Control Protocol (TCP)(TCP)

TCP offers connection-oriented services with TCP offers connection-oriented services with sequencing, sequencing, error recoveryerror recovery, and a , and a sliding windowsliding window mechanismmechanism

Because of TCP’s Because of TCP’s end-to-end reliabilityend-to-end reliability and flexibility, and flexibility, TCP is the preferred transport method for applications TCP is the preferred transport method for applications that transfer large quantities of data and require reliable that transfer large quantities of data and require reliable delivery servicesdelivery services

TCP hosts create a TCP hosts create a virtual connectionvirtual connection with each other with each other using a handshake processusing a handshake process


Transmission Control Protocol Transmission Control Protocol (TCP)(TCP)

TCP transfers data as a continuous stream of bytes, with TCP transfers data as a continuous stream of bytes, with no knowledge of the underlying no knowledge of the underlying messagesmessages or message or message boundaries that might be contained in that boundaries that might be contained in that byte streambyte stream


TCP Startup Connection TCP Startup Connection Process (TCP Handshake)Process (TCP Handshake)

TCP offers a connection-oriented transport that begins TCP offers a connection-oriented transport that begins with a handshake between two hostswith a handshake between two hosts

One host initiates the handshake to another host to: One host initiates the handshake to another host to:

(a)(a) Ensure the destination host is availableEnsure the destination host is available

(b)(b) Ensure the destination host is listening on the Ensure the destination host is listening on the destination port numberdestination port number

(c)(c) Inform the destination host of the initiator’s sequence Inform the destination host of the initiator’s sequence number so the two sides can track data as it is number so the two sides can track data as it is transferredtransferred


TCP Handshake Is TCP Handshake Is a Three-Packet Processa Three-Packet Process


TCP Connection TerminationTCP Connection Termination

The TCP The TCP

connection connection

termination termination

process process

requires requires

four four

packetspackets


TCP Sequence and TCP Sequence and Acknowledgement ProcessAcknowledgement Process

The sequence and acknowledgement process The sequence and acknowledgement process guarantees that packets are ordered properly and guarantees that packets are ordered properly and protects against missing segmentsprotects against missing segments

During the handshake process, each side of the During the handshake process, each side of the connection selects its own starting sequence numberconnection selects its own starting sequence number

During the TCP startup and During the TCP startup and teardown sequencesteardown sequences, the , the Sequence Number and Acknowledgement Number fields Sequence Number and Acknowledgement Number fields increment by one, even though no valid data is sent or increment by one, even though no valid data is sent or receivedreceived


TCP Congestion ControlTCP Congestion Control

CongestionCongestion is the overloading of the network or a is the overloading of the network or a receiverreceiver

Overloading a receiver occurs when the number of data Overloading a receiver occurs when the number of data bytes is greater than the bytes is greater than the advertised windowadvertised window

The The current windowcurrent window is always the lesser of what the is always the lesser of what the network and receiver can handlenetwork and receiver can handle

When TCP data is received, it is placed in this When TCP data is received, it is placed in this TCP TCP buffer areabuffer area



TCP has four defined congestion control mechanisms to ensure the TCP has four defined congestion control mechanisms to ensure the most efficient use of most efficient use of bandwidthbandwidth, and quick error and congestion , and quick error and congestion recoveryrecovery

TCP supports TCP supports windowingwindowing—the process of sending numerous data —the process of sending numerous data packets in sequence without waiting for an intervening packets in sequence without waiting for an intervening acknowledgementacknowledgement

The four mechanisms, defined in detail in RFC 2581, are:The four mechanisms, defined in detail in RFC 2581, are:

Slow startSlow start

Congestion AvoidanceCongestion Avoidance

Fast RetransmitFast Retransmit

Fast RecoveryFast Recovery


Network Window and Receiver Window Determine Network Window and Receiver Window Determine the Current Congestion Window Sizethe Current Congestion Window Size



Slow StartSlow StartWhen a TCP host starts up, the size of the congestion When a TCP host starts up, the size of the congestion window is not knownwindow is not knownThe initial value of the window being used is twice the The initial value of the window being used is twice the sender’s MSS settingsender’s MSS setting

Congestion AvoidanceCongestion AvoidanceOnce the window size has increased using the Once the window size has increased using the Slow Slow Start algorithmStart algorithm, if an error occurs (a timeout), the window , if an error occurs (a timeout), the window size is divided in halfsize is divided in halfNext, the Next, the Congestion Avoidance algorithmCongestion Avoidance algorithm is used to is used to increase the window size in a linear mannerincrease the window size in a linear manner



Fast Retransmit / Fast RecoveryFast Retransmit / Fast Recovery

When an out-of-order data segment is received, the When an out-of-order data segment is received, the receiver should immediately send receiver should immediately send duplicate ACKsduplicate ACKs

The Fast Recovery process dictates that when a host The Fast Recovery process dictates that when a host receives three duplicate ACKs, it must immediately start receives three duplicate ACKs, it must immediately start retransmitting the retransmitting the lost segmentslost segments, without waiting for the , without waiting for the retransmission timer to expireretransmission timer to expire


TCP Header Fields and TCP Header Fields and FunctionsFunctions

You should recognize some characteristics of the TCP header, You should recognize some characteristics of the TCP header, such as the Source and Destination Port Number fieldssuch as the Source and Destination Port Number fields

The definitions for the The definitions for the Source Port Number FieldSource Port Number Field and and Destination Port Number FieldDestination Port Number Field are the same as those for the are the same as those for the UDP fieldsUDP fields


Common and Appropriate Uses Common and Appropriate Uses for TCP and UDPfor TCP and UDP

Given that TCP is robust and reliable, and UDP is not, Given that TCP is robust and reliable, and UDP is not, why would any Application layer protocol or service why would any Application layer protocol or service choose UDP for transport when TCP is readily available?choose UDP for transport when TCP is readily available?

The short answer to that question is overheadThe short answer to that question is overhead

For some lightweight services, such as messenger For some lightweight services, such as messenger service, TCP is overkill, and UDP is used insteadservice, TCP is overkill, and UDP is used instead


Common and Appropriate Uses Common and Appropriate Uses for TCP and UDPfor TCP and UDP

For applications, such as RIP, that rely on regular For applications, such as RIP, that rely on regular updates of routing tables, and track timeout values as updates of routing tables, and track timeout values as part of ordinary behavior, the extra reliability of TCP isn’t part of ordinary behavior, the extra reliability of TCP isn’t necessary, and UDP is used insteadnecessary, and UDP is used instead

TCP was designed in an era when 300-bps TCP was designed in an era when 300-bps communications was considered fast, and when noisy communications was considered fast, and when noisy lines or intermittent communications problems made lines or intermittent communications problems made long-haul, reliable transmission of data inherently risky long-haul, reliable transmission of data inherently risky without access to a robust, reliable transport servicewithout access to a robust, reliable transport service

TCP is a more important transport than UDP, and is still TCP is a more important transport than UDP, and is still used for the majority of TCP/IP Application layer used for the majority of TCP/IP Application layer protocols and servicesprotocols and services


RoutingRouting


Understanding Routing Understanding Routing

We start our discussion by explaining the routing tableWe start our discussion by explaining the routing table

This table is a database that lives in the memory of the This table is a database that lives in the memory of the routerrouter

Entries in this database are known as “routes” and Entries in this database are known as “routes” and consist of a network address, a “next hop” (routing consist of a network address, a “next hop” (routing jargon for the IP address of the next router in the path to jargon for the IP address of the next router in the path to the destination), various metrics, and vendor-specific the destination), various metrics, and vendor-specific informationinformation


Understanding RoutingUnderstanding Routing

A routing table is a compilation of all the networks that A routing table is a compilation of all the networks that the router can reachthe router can reach

The routing table is used as follows: When a packet is The routing table is used as follows: When a packet is received on a network interface, the first thing the router received on a network interface, the first thing the router must do is find out where the packet wants to go, so the must do is find out where the packet wants to go, so the router reads the first field in the IP header, which is the router reads the first field in the IP header, which is the Destination Address, and then looks in the Network field Destination Address, and then looks in the Network field of its routing table for a matchof its routing table for a match



A route entry can be placed in a routing table in three A route entry can be placed in a routing table in three basic waysbasic waysThe first way is through direct connectionThe first way is through direct connectionThe second is that it can be manually configuredThe second is that it can be manually configuredThe third way that an entry can be placed in a routing The third way that an entry can be placed in a routing table is dynamically, by using a table is dynamically, by using a routing protocolrouting protocolRouters use routing protocols to share information about Routers use routing protocols to share information about the various networks on an internetworkthe various networks on an internetwork



Thus, you simply configure the protocol on each router, Thus, you simply configure the protocol on each router, and the routers will convey and the routers will convey Network Layer Reachability Network Layer Reachability Information (NLRI)Information (NLRI) to each other to each other

Routed protocols are Layer 3 protocols that are used to Routed protocols are Layer 3 protocols that are used to get packets through an internetworkget packets through an internetwork

There are two primary ways to group routing protocolsThere are two primary ways to group routing protocols

The first is by the method they use to communicateThe first is by the method they use to communicate



The two primary “flavors” employed by routing protocols The two primary “flavors” employed by routing protocols are are distance vectordistance vector and and link-statelink-state

The routing protocols used inside a routing domain are The routing protocols used inside a routing domain are called called Interior Gateway Protocols (IGPs)Interior Gateway Protocols (IGPs), and the routing , and the routing protocols used to connect these routing domains are protocols used to connect these routing domains are known as known as Exterior Gateway Protocols (EGPs)Exterior Gateway Protocols (EGPs)


Distance Vector Routing Distance Vector Routing ProtocolsProtocols

There are several There are several distance vector routing protocolsdistance vector routing protocols in in use todayuse today

The most popular by a wide margin is The most popular by a wide margin is Routing Routing Information Protocol (RIP)Information Protocol (RIP), followed by a Cisco , followed by a Cisco proprietary protocol called proprietary protocol called Interior Gateway Routing Interior Gateway Routing Protocol (IGRP)Protocol (IGRP)

These protocols have several things in common that These protocols have several things in common that distinguish them from link-state protocolsdistinguish them from link-state protocols


Distance Vector Routing Distance Vector Routing ProtocolsProtocols

The second major distinction is that they “route by The second major distinction is that they “route by rumor”rumor”


Link-State Routing ProtocolsLink-State Routing Protocols

Link-state routing protocolsLink-state routing protocols differ from distance vector differ from distance vector routing protocols in two primary waysrouting protocols in two primary ways

The first is that they do not router by rumorThe first is that they do not router by rumor

The second major difference is that they do not The second major difference is that they do not periodically broadcast their entire tablesperiodically broadcast their entire tables


Link-State Routing ProtocolsLink-State Routing Protocols

In this configuration, Routers A, B, and C send Hello packets In this configuration, Routers A, B, and C send Hello packets to Network 1to Network 1As they hear each other’s Hello packets, each router builds an As they hear each other’s Hello packets, each router builds an adjacencies databaseadjacencies database


Areas, Autonomous Areas, Autonomous Systems, and Border RoutersSystems, and Border RoutersExtremely large networks can be broken down into Extremely large networks can be broken down into regions called regions called Autonomous Systems (ASs)Autonomous Systems (ASs)

These Autonomous Systems are under the same These Autonomous Systems are under the same administrative controladministrative control

The routers that connect Autonomous Systems are The routers that connect Autonomous Systems are called called Autonomous System Border Routers (ASBRs)Autonomous System Border Routers (ASBRs)


An Exterior Gateway Protocol Is Used An Exterior Gateway Protocol Is Used to Connect Two Autonomous Systemsto Connect Two Autonomous Systems


Interior Gateway Protocols Interior Gateway Protocols (IGPs)(IGPs)

Interior Gateway Protocols are used to exchange routing Interior Gateway Protocols are used to exchange routing information within an ASinformation within an AS

These protocols are also referred to as These protocols are also referred to as intra-domain intra-domain routing protocolsrouting protocols

The most commonly used IGPs are Routing Information The most commonly used IGPs are Routing Information Protocol (RIP) (versions 1 and 2) and Open Shortest Protocol (RIP) (versions 1 and 2) and Open Shortest Path First (OSPF)Path First (OSPF)


Enhanced Interior Gateway Enhanced Interior Gateway Routing Protocol (EIGRP)Routing Protocol (EIGRP)

IGRP was developed in the 1980s by Cisco Systems in IGRP was developed in the 1980s by Cisco Systems in

an effort to provide a more efficient interior gateway an effort to provide a more efficient interior gateway

protocolprotocol

IGRP was updated in the early 1990sIGRP was updated in the early 1990s—the updated —the updated

version is called version is called Enhanced Interior Gateway Routing Enhanced Interior Gateway Routing

Protocol (EIGRP)Protocol (EIGRP)


Exterior Gateway Protocols Exterior Gateway Protocols (EGPs)(EGPs)

Exterior Gateway Protocols are used to exchange Exterior Gateway Protocols are used to exchange routing information between Autonomous Systemsrouting information between Autonomous Systems

These protocols are also referred to as These protocols are also referred to as inter-domain inter-domain routing protocolsrouting protocols

Interestingly, the name Exterior Gateway Protocol was Interestingly, the name Exterior Gateway Protocol was assigned to the first implementation of this type of assigned to the first implementation of this type of routingrouting


Border Gateway Protocol (BGP)Border Gateway Protocol (BGP)

BGP is a distance vector protocol and is the replacement BGP is a distance vector protocol and is the replacement for EGPfor EGP

The current version of BGP is version 4, which is defined The current version of BGP is version 4, which is defined in RFC 1771in RFC 1771

BGP offers three types of routing operations:BGP offers three types of routing operations:

Inter-autonomous system routingInter-autonomous system routing

Intra-autonomous system routingIntra-autonomous system routing

Pass-through autonomous system routingPass-through autonomous system routing


Typical BGP DesignTypical BGP Design


Border Gateway Protocol (BGP)Border Gateway Protocol (BGP)

Figure 10-15 illustrates how BGP is used for Figure 10-15 illustrates how BGP is used for inter-inter-autonomous system routingautonomous system routing

When BGP is configured for When BGP is configured for intra-autonomous system intra-autonomous system routingrouting, the BGP routers are located within the same AS, the BGP routers are located within the same AS

Pass-through autonomous system routingPass-through autonomous system routing enables BGP enables BGP peer routers to exchange routing information across an peer routers to exchange routing information across an AS that does not support BGPAS that does not support BGP

pengantar tcp/ip dan routing

Documents

ip addressnumeric ip

network addresses

ip destination address

numeric ip addressesproximity

network layer

ip source address field

classes of addresses

mac layer address