The document discusses services provided by internet service providers (ISPs) including email, web hosting, media streaming, IP telephony, and file transfer. It describes how protocols like TCP/IP, UDP, and DNS support these services and ensure reliability and availability for customers. Key protocols and services covered include HTTP, HTTPS, FTP, SMTP, POP3, IMAP, and DNS for translating names to IP addresses in a hierarchical system.

1. ISP Services
Working at a Small-to-Medium Business or ISP –
Chapter 7
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2. 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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3. Introducing ISP Services
Critical services for small-to-medium businesses:
 Email
 Web hosting
 Media streaming
 IP telephony
 File transfer
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4. Introducing ISP Services
Meeting customer requirements:
 Reliability
 Availability
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5. Protocols That Support ISP Services
 The TCP/IP suite of protocols supports
reliability
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6. Protocols That Support ISP Services
 Transport needs determine the choice of
Transport Layer Protocol
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7. Protocols That Support ISP Services
The TCP three-way handshake:
 Synchronization
 Synchronization acknowledgement
 Acknowledgement
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8. Protocols That Support ISP Services
How TCP supports reliability:
 Acknowledgement
 Retransmission
 Sequencing
 Flow control
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9. Protocols That Support ISP Services
 UDP: not connection-oriented, simple protocol
 Used by online games, DHCP, DNS
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10. Protocols That Support ISP Services
 TCP and UDP use ports to support multiple
services
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11. 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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12. Domain Name System (DNS)
 Networking naming systems translate human-
readable names into machine-readable
addresses
srv2
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13. Domain Name System (DNS)
Advantages of DNS:
 Hierarchical structure
 Small, manageable zones
 Scalable
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14. Domain Name System (DNS)
Components of DNS:
 Resource records and domain namespace
 Domain name system servers
 Resolvers
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15. Domain Name System (DNS)
DNS name resolution:
 Dynamic updates
 Forward lookup zones
 Reverse lookup zones
 Primary zones
 Secondary zones
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16. Domain Name System (DNS)
Implementing DNS solutions:
 ISP DNS servers
 Local DNS servers
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17. Services and Protocols
 ISPs provide many business-oriented services
 Secure versions of Application Layer protocols
support customer security requirements
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18. Services and Protocols
 HTTP is a request-response protocol
 HTTPS adds authentication and encryption
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19. 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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20. 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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21. 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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