Port List

20/TCP FTP - data 23/TCP,UDP Telnet protocol—unencrypted text communications 25/TCP,UDP

Simple Mail Transfer Protocol (SMTP)—used for e-mail routing between mail servers

42/TCP,UDP WINS Bootstrap Protocol (BOOTP) Client; also used by Dynamic Host Configuration Protocol 68/UDP (DHCP) 88/TCP Kerberos—authentication system 69/UDP Trivial File Transfer Protocol (TFTP) 137/TCP,UDP NetBIOS NetBIOS Name Service 138/TCP,UDP NetBIOS NetBIOS Datagram Service 139/TCP,UDP NetBIOS NetBIOS Session Service 143/TCP,U Internet Message Access Protocol (IMAP)—used for retrieving, organizing, and DP synchronizing e-mail messages 179/TCP BGP (Border Gateway Protocol) 161/TCP,UDP Simple Network Management Protocol (SNMP) 389/TCP,UDP Lightweight Directory Access Protocol (LDAP) 369/TCP,UDP Rpc2portmap 119/TCP Network News Transfer Protocol (NNTP)—used for retrieving newsgroup messages 118/TCP,UDP SQL (Structured Query Language) Services 445/TCP Microsoft-DS Active Directory, Windows shares 530/TCP,UDP RPC 636/TCP,UDP Lightweight Directory Access Protocol over TLS/SSL (LDAPS 1080/TCP SOCKS proxy 1723/TCP,UDP Microsoft Point-to-Point Tunneling Protocol (PPTP) 2967/TCP Symantec AntiVirus Corporate Edition

The OSI Reference Model and TCP/IP

=================================================================================================== | No. | ISO Layer Name | TCP/IP Layers | Responsibility | =================================================================================================== | | | | | | | | | Applications running on a PC or other | | 7 | Application | | device. Applications like telnet, FTP, | | | | | and HTTP operate at this layer. | | | | | | |----------------------| There is no clear |-----------------------------------------| | | | distinction | | | | | between these | Provides an abstraction for data | | 6 | Presentation | layers in the | representation differences between | | | | TCP/IP protocol. | applications. | | | | | | |----------------------| |-----------------------------------------| | | | | | | | | | Offers an optional bidirectional or | | 5 | Session | | full-duplex service if not provided | | | | | by the transport layer. | | | | | | |----------------------|--------------------------------|-----------------------------------------| | | | | | | 4 | Transport | TCP, UDP, and ICMP(1) | Provides end-to-end management. For | | | | | example, TCP provides flow control, | | | | | acknowledgement, sequencing, and error | | | | | correction; TCP also provides | | | | | connection-oriented "reliable" | | | | | communications. UDP provides | | | | (1): ICMP could very well be | connectionless communication, a very | | | | positioned at layer 3 | thin layer on top of IP. However, it | | | | but it is positioned at | provides "unreliable" communication, | | | | layer 4 because ICMP | that is, the data may get to its | | | | must be first placed | destination, or it may not. | | | | within an IP packet | | | | | of which IP is a layer 3 | TCP also provides a concept of | | | | protocol. | of session management at this layer. | | | | | | |----------------------|--------------------------------|-----------------------------------------| | | | | | | | | | Is responsible for the routing of | | 3 | Network | IP, ARP, and RARP. | packets (which encapsulates frames) | | | | | across the network. | | | | | | |----------------------|--------------------------------|-----------------------------------------| | | | | | | 2 | Data Link | The data link | Regulates access to the network. | | | | | Provides point-to-point frame | | | | (Ethernet, ATM+IP, FDDI, | formation and management for various | | | | & Token Ring all span | protocols. All frames contain | | | | the data link and physical | source addresses and a destination | | | | layers) | addresses. | | | | | | |----------------------|--------------------------------|-----------------------------------------| | | | | | | | | | Controls the physical attachment | | 1 | Physical | Physical, as mentioned | to the network, including wiring | |

SESSION LAYER The Session layer is responsible for dialog control between devices. It establishes, maintains, and terminates session between applications, as well as data transfer control between processes and management. It organizes communication between two presentation layer systems with three modes: simplex, half-duplex, and fullduplex. It splits a session into three phases: connection establishment, data tranfer, and connection release, which enables coordination of the requests and responses that result from the communication of different hosts. E.g. NFS, RPC, SQL, X Windows. TRANSPORT LAYER The Host-to-Host Transport layer merges network layer connections and provides a reliable packet delivery mechanism. Services segment, reassemble, and merge data from upper-layer apps, provide end-to-end data transport, and establish a logical connection between the sending and receiving host. This layer is responsible for reliable communication between end nodes as well as the maintenance and termination of virtual circuits. The transport layer also provides mechanisms for sequencing, multiplexing upper-layer apps, and session establishment. It provides transparent data transfer and fault recovery and ensures data integrity via flow control. • • • •

The recipient sends an acknowledgment to the sender when it receives the segments Any unacknowledged segments are retransmitted Segments are sequenced into their proper order upon arrival A manageable data flow is maintained to avoid congestion and data loss.