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Published byLisbeth Pettersson Modified over 6 years ago
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Working at a Small-to-Medium Business or ISP – Chapter 7
ISP Services Working at a Small-to-Medium Business or ISP – Chapter 7
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Objectives Describe the network services provided by an ISP.
Describe the protocols that support the network services provided by an ISP. Describe the purpose, function, and hierarchical nature of the Domain Name System (DNS). Describe and enable common services and their protocols.
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Introducing ISP Services
Critical services for small-to-medium businesses: Web hosting Media streaming IP telephony File transfer
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Introducing ISP Services
Meeting customer requirements: Reliability Availability
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Protocols That Support ISP Services
The TCP/IP suite of protocols supports reliability
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Protocols That Support ISP Services
Transport needs determine the choice of Transport Layer Protocol
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Protocols That Support ISP Services
The TCP three-way handshake: Synchronization Synchronization acknowledgement Acknowledgement
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Protocols That Support ISP Services
How TCP supports reliability: Acknowledgement Retransmission Sequencing Flow control
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Protocols That Support ISP Services
UDP: not connection-oriented, simple protocol Used by online games, DHCP, DNS
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Protocols That Support ISP Services
TCP and UDP use ports to support multiple services
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Protocols That Support ISP Services
Socket: combination of Transport Layer port number and Network Layer IP address of host Socket pair: source and destination IPs and port numbers identify each conversation
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Domain Name System (DNS)
Networking naming systems translate human-readable names into machine-readable addresses srv2
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Domain Name System (DNS)
Advantages of DNS: Hierarchical structure Small, manageable zones Scalable
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Domain Name System (DNS)
Components of DNS: Resource records and domain namespace Domain name system servers Resolvers
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Domain Name System (DNS)
DNS name resolution: Dynamic updates Forward lookup zones Reverse lookup zones Primary zones Secondary zones
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Domain Name System (DNS)
Implementing DNS solutions: ISP DNS servers Local DNS servers
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Services and Protocols
ISPs provide many business-oriented services Secure versions of Application Layer protocols support customer security requirements
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Services and Protocols
HTTP is a request-response protocol HTTPS adds authentication and encryption
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Services and Protocols
FTP uses a protocol interpreter (PI) and data transfer process (DTP) Two connections: one to send commands, one for actual file data transfer
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Services and Protocols
SMTP: specific message format and processes running on both client and server POP3: mail is downloaded from server to client and then deleted IMAP4: keeps messages on server
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Summary TCP and UDP use port numbers to provide multiple services to hosts. DNS uses a hierarchical system of databases to resolve names and IP addresses of known hosts within networks and across the Internet. The most common services used on the Internet include FTP, FTPS, HTTP, HTTPS and SMTP. ISPs use high-performance servers to support these services.
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