1 14. internetworking. prof. sang-jo yoo 2 contents internetworking terms principles of...
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2Prof. Sang-Jo Yoo
ContentsContents
Internetworking Terms Principles of Internetworking Connectionless Internetworking The Internet Protocol Routing Protocols IPv6(IPNG)
3Prof. Sang-Jo Yoo
MIME
BGP FTP HTTP SMTP TELNET SNMP
UDP
ICMP OSPF
IP
TCP
Internetworking protocols in context within the TCP/IP protocol
BGP = border gateway protocolFTP = file transfer protocolHTTP=hypertext transfer protocolICMP=internet control message protocolIP = internet protocolOSPF= open shortest path first
MIME= Multi-purpose internet mail extensionSMTP = simple mail transfer protocolSNMP= simple network management protocolTCP = transmission control protocolUDP = user datagram protocol
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Internetworking termsInternetworking terms
Communication Network A facility that provides a data transfer service among devices
attached to the network. Internet
A collection of communication networks interconnected by bridges and/or routers.
Intranet Operates within the organization for internal purpose.
End system A device used to connect one of networks.
Intermediate System A device used to connect two networks.
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Internetworking termsInternetworking terms
Intermediate System Layer 1 : Repeaters copy individual bits between cable segments
Layer 2 : Bridges store and forward data link frames between LANs
Layer 3 : Multi-protocol Routers forward packets between dissimilar networks
Layer 4 : Transport Gateways connect byte streams in the transport layer
Above Layer 4 : application Gateways allow internetworking above layer 4
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Principles of InternetworkingPrinciples of Internetworking Requirements of internetwork service: provide
a link between networks. At minimum, a physical and link control connection is needed
the routing and delivery of data between processes on different networks
an accounting service internetworking facility must accommodate a number of
differences among networks different addressing schemes different maximum packet size different network-access mechanism different timeouts Error recovery/status reporting/ routing tech./user access control connection, connectionless
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Architectural approaches two dimensions for describing the internetworking function
the mode of operation(connection-mode or connectionless) the protocol architecture
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Internetwork architectures
Sharing protocol of the end systems
a) Connection modeNetwork layer(N)
b) Connectionless modeInternet Protocol(I)
c) Bridgedata link layer(M)
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Connection OrientedConnection Oriented
Assume that each network is connection oriented IS connect two or more networks
IS appear as DTE to each network Logical connection set up between DTEs
Concatenation of logical connections across networks
Individual network virtual circuits joined by IS
May require enhancement of local network services 802, FDDI are datagram services
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Connection Oriented IS FunctionsConnection Oriented IS Functions
Relaying Routing
e.g. X.75 used to interconnect X.25 packet switched networks
Connection oriented not often used (IP dominant)
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Connectionless OperationConnectionless Operation
Corresponds to datagram mechanism in packet switched network
Each NPDU treated separately Network layer protocol common to all DTEs and routers
Known generically as the internet protocol
Internet Protocol One such internet protocol developed for ARPANET RFC 791 Lower layer protocol needed to access particular network
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Connectionless InternetworkingConnectionless Internetworking
Advantages Flexibility Robust No unnecessary overhead
Unreliable Not guaranteed delivery Not guaranteed order of delivery
Packets can take different routes
Reliability is responsibility of next layer up (e.g. TCP)
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Design Issues of IP-controlled Design Issues of IP-controlled InternetInternet
Routing Datagram lifetime Fragmentation and re-assembly Error control Flow control
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RoutingRouting
End systems and routers maintain routing tables Indicate next router to which datagram should be sent Static
May contain alternative routes
Dynamic Flexible response to congestion and errors
Source routing Source specifies route as sequential list of routers to be followed Security Priority
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Datagram LifetimeDatagram Lifetime
Datagrams could loop indefinitely Consumes resources Transport protocol may need upper bound on datagram life
Datagram marked with lifetime Time To Live field in IP Once lifetime expires, datagram discarded (not forwarded) Hop count
Decrement time to live on passing through a each router
Time count Need to know how long since last router
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Fragmentation and Fragmentation and Re-assemblyRe-assembly
Different packet sizes When to re-assemble
At destination Results in packets getting smaller as data traverses internet
Intermediate re-assembly Need large buffers at routers Buffer space will be used up storing partial datagrams. All fragments must go through same router
Inhibits dynamic routing
IP re-assembles at destination only
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Error ControlError Control
Not guaranteed delivery Router should attempt to inform source if packet discarded
Because of time to live expiring Congestion FCS errors
Source may modify transmission strategy May inform high layer protocol
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Flow ControlFlow Control
Allows routers and/or stations to limit rate of incoming data
Limited in connectionless systems Send flow control packets
Requesting reduced flow
e.g. ICMP
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The Internet ProtocolThe Internet Protocol
Internet Protocol (IP) Isolates the transport and application protocols from the messy
details of each network.
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IP services the interface with a higher layer(e.g. TCP) Send primitive - used to request transmission of a data unit Deliver primitive - used to notify a user of the arrival of a data unit
Send ( Source Address Destination Address Protocol Type of service indicators Identifier Don’t-fragment identifier Time to live Data length Option data Data )
Deliver ( Source Address Destination Address Protocol Type of service indicators
Data length Option data Data )
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Type of service indicator requests particular QoS and guides routing decision
precedence - a measure of datagram’s relative importance (8 levels) reliability (normal or high) delay throughput
the options parameter security source routing route recording stream identification timestamping
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IP Protocol
IP header
IHL : internet header length in 32-bit words, minimum is 5,(20 octets)Flag(3 bits) : More bit, Don’t fragment bit and last 1 bit is reservedProtocol : indicates the next higher level protocol at the destinationpadding(variable) : used to ensure that the datagram header is a multiple of 32 bits
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IP address 32 bit (network id + host id)
Special IP address0.0.0.0 this host255.255.255.255 broadcast on LAN127.x.x.x Loopback
1.0.0.0 to 127.255.255.255
128.0.0.0 to 191.255.255.255
192.0.0.0 to 223.255.255.255
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Technically, TCP/IP addresses identify interfaces, not system. In most cases, hosts have but a single interface. Routers usually support multiple interfaces
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Type of addresses Unicast addresses: refer to a single interface; network takes
responsibility for delivering the message to that interface. Multicast addresses: identify sets of interfaces.
This function lets a system generate a message once and delivered to many different recipients.
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Anycast addresses: refers to one of a set of interfaces New feature with IPv6. Includes many interfaces from different systems The network considers its work complete when it delivers the
message to any of the appropriate interfaces.
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Subnets and Subnet MasksSubnets and Subnet Masks
Allow arbitrary complexity of internetworked LANs within organization
Insulate overall internet from growth of network numbers and routing complexity
Each LAN assigned subnet number Host portion of address partitioned into subnet number and
host number Local routers route within subnetted network Subnet mask indicates which bits are subnet number and
which are host number
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Subnet mask of R1 and R211111111.11111111.11111111.11100000255.255.255.224Terminal B IPx.x.x.00111001 (192.228.17.57)After maskingSubnet : 1Host 25
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The Internet Control Message Protocol(ICMP) ICMP provides feedback about problems in communication
environment. ICMP is a user of IP ( not reliable) ICMP message
Destination unreachable Time exceeded Parameter problem - syntactic or semantic error in an IP Source quench - flow control (rate control) Redirect - redirect routing Echo/echo-reply - testing that communication is possible Timestamp /Timestamp reply - sampling the delay characteristics of
the internet Address mark / Address mark reply
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IPv6(IPNG)IPv6(IPNG)
History IPv4 : the present IP
32-bit address system cannot accommodate the rapidly increasing IP address demands
IPv5 : experimental real-time Stream Protocol, a connection-oriented internet level protocol
IPv6 : IPNG (IETF: internet engineering task force) Call for Proposal June, 1992 (RFC 1550) “The Recommendation for the IP Next Generation Protocol”,
Jan,1995 (RFC 1883 ~ RFC 1887)
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IPv6 Enhancements over IPv4 Expanded address space
128-bit address
Improved Option Mechanism simplify the protocol, to allow routers to process packets faster
Increased Address Flexibility anycast , multicast
Support for Resource allocation pay more attention to type of service, particularly for real-time data
Security Capabilities authentication, privacy
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IPv6 Structure
define special options that require hop-by-hop processing
extended routing, similar source routing
packet integrity and authentication
privacy
IPv6 packet with all extension header