Network Layer 4 Port Assignment Conflict

This article is about software communication ports. For physical ports, see Computer port (hardware).

In computer networking, a port is an endpoint of communication in an operating system. While the term is also used for physical devices, in software it is a logical construct that identifies a specific process or a type of network service.

A port is always associated with an IP address of a host and the protocol type of the communication. It completes the destination or origination network address of a message. Ports are identified for each protocol and address combination by 16-bit unsigned numbers, commonly known as the port number.

Specific port numbers are commonly reserved to identify specific services. The lowest numbered 1024 port numbers are called the well-known port numbers, and identify the historically most commonly used services. In the client–server model of application architecture, the ports that network clients connect to for service initiation provide a multiplexing service, so that multiple simultaneous communication sessions may be initiated from these ports. After an initial service request connects to the well-known port number, the port is freed by switching the servicing of the request to a dedicated, connection-specific port number. The protocols that primarily use ports are the transport layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP).

Networking model[edit]

Transport layer protocols, such as the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP), transfer data using protocol data units (PDUs). For TCP, the PDU is a segment, and a datagram for UDP. Both protocols use a header field for recording the source and destination port number. A port number is a 16-bit unsigned integer, thus ranging from 0 to 65535. For TCP, port number 0 is reserved and cannot be used, while for UDP, the source port is optional and a value of zero means no port. A process associates its input or output channels via an Internet socket, which is a type of file descriptor, with a transport protocol, an IP address, and a port number. This is known as binding, and enables the process to send and receive data via the network. The operating system's networking software has the task of transmitting outgoing data from all application ports onto the network, and forwarding arriving network packets to processes by matching the packet's IP address and port number. For TCP, only one process may bind to a specific IP address and port combination. Common application failures, sometimes called port conflicts, occur when multiple programs attempt to use to the same port numbers on the same IP address with the same protocol.

Applications implementing common services often use specifically reserved well-known port numbers for receiving service requests from clients. This process is known as listening, and involves the receipt of a request on the well-known port and establishing a one-to-one server-client dialog, using the same local port number. Other clients may continue to connect to the listening port; this works because a TCP connection is identified by a tuple consisting of the local address, the local port, the remote address, and the remote port.[1] The well-known ports are defined by convention overseen by the Internet Assigned Numbers Authority (IANA). The core network services, such as the World-Wide Web, typically use well-known port numbers. In many operating systems special privileges are required for applications to bind to these ports, because these are often deemed critical to the operation of IP networks. Conversely, the client end of a connection typically uses a high port number allocated for short term use, therefore called an ephemeral port.

The port numbers are encoded in the transport protocol packet header, and they can be readily interpreted not only by the sending and receiving computers, but also by other components of the networking infrastructure. In particular, firewalls are commonly configured to differentiate between packets based on their source or destination port numbers. Port forwarding is an example application of this.

The practice of attempting to connect to a range of ports in sequence on a single computer is commonly known as port scanning. This is usually associated either with malicious cracking attempts or with network administrators looking for possible vulnerabilities to help prevent such attacks. Port connection attempts are frequently monitored and logged by computers. The technique of port knocking uses a series of port connections (knocks) from a client computer to enable a server connection.

Examples[edit]

An example for the use of ports is the Internet mail system. A server used for sending and receiving email generally needs two services. The first service is used to transport email to and from other servers. This is accomplished with the Simple Mail Transfer Protocol (SMTP). The SMTP service application usually listens on TCP port 25 for incoming requests. The second service is usually either the Post Office Protocol (POP) or the Internet Message Access Protocol (IMAP) which is used by e-mail client applications on users' personal computers to fetch email messages from the server. The POP service listens on TCP port number 110. Both services may be running on the same host computer, in which case the port number distinguishes the service that was requested by a remote computer, be it a user's computer or another mail server.

While the listening port number of a server is well defined (IANA calls these the well-known ports), the client's port number is often chosen from the dynamic port range (see below). In some applications, the clients and the server each use specific port numbers assigned by the IANA. A good example of this is DHCP in which the client always uses UDP port 68 and the server always uses UDP port 67.

Use in URLs[edit]

Port numbers are sometimes seen in web or other uniform resource locators (URLs). By default, HTTP uses port 80 and HTTPS uses port 443, but a URL like specifies that the web browser connects instead to port 8080 of the HTTP server.

Common port numbers[edit]

Main article: List of TCP and UDP port numbers

The Internet Assigned Numbers Authority (IANA) is responsible for the global coordination of the DNS Root, IP addressing, and other Internet protocol resources. This includes the registration of commonly used port numbers for well-known Internet services.

The port numbers are divided into three ranges: the well-known ports, the registered ports, and the dynamic or private ports.

The well-known ports (also known as system ports) are those from 0 through 1023. The requirements for new assignments in this range are stricter than for other registrations,[2] examples include:

The registered ports are those from 1024 through 49151. IANA maintains the official list of well-known and registered ranges.[3] The dynamic or private ports are those from 49152 through 65535. One common use for this range is for ephemeral ports.

History[edit]

The concept of port numbers was established by the early developers of the ARPANET in informal co-operation of software authors and system administrators.

The term port number was not yet used at this time. It was preceded by the use of the term socket number in the early development stages of the network. A socket number for a remote host was a 40-bit quantity.[4] The first 32 bits were similar to today's IPv4 address, but at the time the most-significant 8 bits were the host number. The least-significant portion of the socket number (bits 33 through 40) was an entity called Another Eightbit Number, abbreviated AEN.[5] Today, network socket refers to a related but distinct concept, namely the internal address of an endpoint (used within the node only).

On March 26, 1972, Vint Cerf and Jon Postel called for documenting the then-current usages and establishing a socket number catalog in RFC 322. Network administrators were asked to submit a note or place a phone call, "describing the function and socket numbers of network service programs at each HOST".[6]

This catalog was subsequently published as RFC 433 in December 1972 and included a list of hosts and their port numbers and the corresponding function used at each host in the network. This first registry function served primarily as documentation of usage and indicated that port number usage was conflicting between some hosts for "useful public services".[5]

The document promised a resolution of the conflicts based on a standard that Postel had published in May 1972 in RFC 349, in which he first proposed official assignments of port numbers to network services and suggested a dedicated administrative function, which he called a czar, to maintain a registry.[7]

The 256 values of the AEN were divided into the following ranges:

  • 0 through 63: network-wide standard functions
  • 64 through 127: host-specific functions
  • 128 through 239: reserved for future use
  • 240 through 255: any experimental function

The Telnet service received the first official assignment of the value 1. In detail, the first set of assignments was:[7]

1 Telnet 3 File transfer 5 Remote job entry 7 Echo 9 Discard

In the early ARPANET, the AEN was also called a socket name,[8] and was used with the Initial Connection Protocol (ICP), a component of the Network Control Program (NCP).[9][10] NCP was the forerunner of the modern Internet protocols. Today the terminology service name is still closely connected with port numbers, the former being text strings used in some network functions to represent a numerical port number.

See also[edit]

References[edit]

  1. ^Postel, John. "RFC 793". Retrieved 29 June 2012. 
  2. ^Michelle Cotton; Lars Eggert et al. (August 2011). Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry. IETF. doi:10.17487/RFC6335. BCP 165. RFC 6335. https://tools.ietf.org/html/rfc6335. Retrieved April 2014. 
  3. ^"Port Numbers". Internet Assigned Numbers Authority (IANA). 
  4. ^RFC 36, Protocol Notes, S. Crocker (16 March 1970)
  5. ^ abRFC 433, Socket number list, J. Postel, N. Neigus (22 December 1972)
  6. ^RFC 322, Well Known Socket Numbers, V. Cerf, J. Postel (26 March 1972)
  7. ^ abRFC 349, Proposed Standard Socket Numbers J. Postel (30 May 1972)
  8. ^RFC 197, Initial Connection Protocol--Reviewed, A. Shoshani, E. Harslem (14 July 1971)
  9. ^NIC 7104, ARPANET Protocol Handbook
  10. ^Postel, Jon; Feinler, E. (1978). ARPANET Protocol Handbook. Menlo Park, CA: Network Information Center. 
On This Page

Introduction
Term Usage
Microsoft Server Product Ports
Ports and Protocols
For More Information
Related Topics

Introduction

This document discusses the network ports and protocols that are used by server products and their subcomponents in the Microsoft Windows Server System.

The Windows Server System includes a comprehensive and integrated infrastructure that is designed to meet the requirements of developers and information technology (IT) professionals. This system is designed to run programs that information workers can use to obtain, analyze, and share information quickly and easily. These Microsoft server products use a variety of network ports and protocols to communicate with client and server systems. While dedicated firewalls, host-based firewalls, and Internet Protocol Security (IPSec) filters can be used to help secure your network, if these technologies are configured to block ports and protocols that are used by the Windows Server System, a server may not be able to respond to legitimate client requests. If a server is unable to respond to legitimate client requests, it may not function properly or at all.

Top Of Page

Term Usage

The following list provides an overview of the information contained in this document:

  • The "Microsoft Server Product Ports" section of this document contains a brief description of each service, displays the logical name of that service, and indicates the ports and protocols required by each service for correct operation. Use this section to help identify the ports and protocols that a particular service uses.

  • The "Ports and Protocols Table" section of this document includes a table that summarizes the information from the "System Services Ports" section. The table is sorted by port number instead of by the service name. Use this section to quickly determine which services listen on a particular port.

This document uses certain terms in specific ways. To help avoid confusion, make sure that you understand how this document uses these terms. The following list describes these terms:

  • System services: The Windows Server System includes many products, such as the Microsoft Windows Server 2003 family, Microsoft Exchange 2000 Server, and Microsoft SQL Server 2000. Each of these products includes many components; system services is one of those components. System services that are required by a computer are either started automatically by the operating system during startup or are started as required during typical operations. For example, some system services that are available on computers running Windows Server 2003, Enterprise Edition, include the Server service, the Print Spooler service, and the World Wide Web Publishing Service. Each system service has a friendly service name and a service name. The friendly service name is the name that appears in graphical management tools, such as the Services Microsoft Management Console (MMC) snap-in. The service name is the name that is used with command-line tools and with many scripting languages. Each system service may provide one or more network services.

  • Application protocol: In the context of this document, an application protocol is a high-level network protocol that uses one or more TCP/IP protocols and ports. Examples of application protocols include HTTP, server message blocks (SMBs), and Simple Mail Transfer Protocol (SMTP).

  • Protocol: Operating at a lower level than the application protocols, TCP/IP protocols are standard formats for communicating between devices on a network.

    The TCP/IP suite of protocols includes TCP, User Datagram Protocol (UDP), and Internet Control Message Protocol (ICMP).

  • Port: This is the network port that the system service listens on for incoming network traffic.

This document does not specify which services rely on other services for network communication. For example, many services rely on the remote procedure call (RPC) or DCOM features in Microsoft Windows to assign them dynamic TCP ports. The Remote Procedure Call service coordinates requests by other system services that use RPC or DCOM to communicate with client computers. Many other services rely on network basic input/output system (NetBIOS) or SMB, protocols that are actually provided by the Server service. Others rely on HTTP or HTTPS. These protocols are provided by Internet Information Services (IIS). A full discussion of the architecture of the Windows operating systems is beyond the scope of this document. However, detailed documentation on this subject is available on Microsoft TechNet and on the Microsoft Developer Network (MSDN). While many services may rely on a particular TCP or UDP port, only a single service or process can be actively listening on that port at any one time.

When you use RPC with TCP/IP or with UDP/IP as the transport, inbound ports are frequently dynamically assigned to system services as required; TCP/IP and UDP/IP ports that are higher than port 1024 are used. These are frequently informally referred to as "random RPC ports." In these cases, RPC clients rely on the RPC endpoint mapper to tell them which dynamic ports were assigned to the server. For some RPC-based services, you can configure a port instead of letting RPC assign one dynamically. You can also restrict the range of ports that RPC dynamically assigns to a small range, regardless of the service. For more information, see "Related Topics" later in this document.

This document includes information about the system services roles and the server roles for the Microsoft products that are listed in the "For More Information" section of this document. Although this information may also apply to Microsoft Windows XP and Microsoft Windows 2000 Professional, this document is intended to focus on server-class operating systems. Therefore, this document describes the ports that a service listens on instead of the ports that client programs use to connect to a remote system.

Top Of Page

Microsoft Server Product Ports

This section provides a description of each system service, includes the logical name that corresponds to the system service, and displays the ports and the protocols required by each service.

Application Layer Gateway (ALG) Service

This subcomponent of the Internet Connection Sharing (ICS)/Internet Connection Firewall (ICF) service provides support for plug-ins that allow network protocols to pass through the firewall and work behind ICS. Application Layer Gateway plug-ins have the power to open ports and change data (such as ports and IP addresses) embedded in packets. File Transfer Protocol (FTP) is the only network protocol with a plug-in that is released with Windows Server 2003, Standard Edition, and Windows Server 2003, Enterprise Edition.

The ALG FTP plug-in is designed to support active FTP sessions through the network address translation (NAT) engine used by these components. The ALG FTP plug-in does this by redirecting all traffic passing through the NAT destined for port 21 to a private listening port in the 3000-5000 range on the loopback adapter. The ALG FTP plug-in then monitors and updates FTP control channel traffic so that the FTP plug-in can plumb port mappings through the NAT for the FTP data channels. The FTP plug-in will also update ports in the FTP control channel stream.

System Service Name ALG

Application protocol

Protocol

Port

FTP control

TCP

21

ASP.NET State Service

The ASP.NET State service provides support for ASP.NET out-of-process session states. The ASP.NET State service stores session data out-of-process. The service communicates with ASP.NET running on a Web server using sockets.

System Service Name aspnet_state

Application protocol

Protocol

Port

ASP.Net Session State

TCP

42424

Certificate Services

Certificate Services is part of the core operating system that enables a business to act as its own certification authority (CA). In this way, the business can issue and manage digital certificates for applications and protocols such as Secure/Multipurpose Internet Mail Extensions (S/MIME), Secure Sockets Layer (SSL), Encrypting File System (EFS), IPSec, and smart card log on. Certificate Services relies on RPC and DCOM to communicate with clients using random TCP ports greater than 1024.

System Service Name CertSvc

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Cluster Service

The Cluster service controls server cluster operations and manages the cluster database. A cluster is a collection of independent computers that is as easy to use as a single computer. Managers, programmers, and users see the cluster as a single system. The software distributes data among the nodes of the cluster. If a node fails, other nodes provide the services and data formerly provided by the missing node. When a node is added or repaired, the cluster software migrates some data to that node.

System Service Name ClusSvc

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Cluster Services

UDP

3343

Computer Browser

The Computer Browser system service maintains an up-to-date list of computers on your network and supplies the list to programs that request it. The Computer Browser service is used by Windows-based computers enabled to view network domains and resources. Computers designated as browsers maintain browse lists, which contain all shared resources used on the network. Earlier versions of Windows applications, such as My Network Places, the NET VIEW command, and Microsoft Windows NT Explorer, all require browsing capability. For example, opening My Network Places on a computer running Windows XP displays a list of domains and computers, which is accomplished by the computer obtaining a copy of the browse list from a computer designated as a browser.

System Service Name Browser

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

NetBIOS Name Resolution

UDP

137

NetBIOS Session Service

TCP

139

DHCP Server

Using the Dynamic Host Configuration Protocol (DHCP), the DHCP Server service automatically allocates IP addresses and enables advanced configuration of network settings, such as Domain Name System (DNS) servers and Windows Internet Name Service (WINS) servers to DHCP clients. The network administrator establishes one or more DHCP servers that maintain TCP/IP configuration information and provide it to clients.

System Service Name DHCPServer

Application protocol

Protocol

Port

DHCP Server

UDP

67

MADCAP

UDP

2535

Distributed File System

The Distributed File System (DFS) service manages logical volumes distributed across a local or wide area network (LAN or WAN) and is required for the Microsoft Active Directory SYSVOL share. DFS is a distributed service that integrates disparate file shares into a single logical namespace.

System Service Name Dfs

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

NetBIOS Session Service

TCP

139

LDAP Server

TCP

389

LDAP Server

UDP

389

SMB

TCP

445

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

NetBIOS Datagram Service

UDP

138

Distributed Link Tracking Server

The Distributed Link Tracking Server system service stores information so that files moved between volumes can be tracked to each volume in the domain. The Distributed Link Tracking Server service runs on each domain controller in a domain. This service enables the Distributed Link Tracking Server Client service to track linked documents that have been moved to a location in another NTFS file system volume in the same domain.

System Service Name TrkSvr

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Distributed Transaction Coordinator

The Distributed Transaction Coordinator (DTC) system service is responsible for coordinating transactions that are distributed across multiple computer systems and resource managers, such as databases, message queues, file systems, or other transaction-protected resource managers. The DTC system service is necessary if transactional components will be configured through COM+. It is also required for transactional queues in Message Queuing (MSMQ) and SQL Server operations that span multiple systems.

System Service Name MSDTC

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

DNS Server

The DNS Server system service enables DNS name resolution by answering queries and update requests for DNS names. The presence of DNS servers is crucial for locating devices and services identified using DNS names and domain controllers in the Active Directory directory service.

System Service Name DNS

Application protocol

Protocol

Port

DNS

UDP

53

DNS

TCP

53

Event Log

This system service logs event messages issued by programs and the Windows operating system. Event Log reports contain information that can be useful in diagnosing problems. Reports are viewed in Event Viewer. The Event Log service writes events sent by applications, services, and the operating system to log files. The events contain diagnostic information in addition to errors specific to the source application, service, or component. The logs can be viewed programmatically through the Event Log application programming interfaces (APIs) or through the Event Viewer in an MMC (Microsoft Management Console) snap-in.

System Service Name Eventlog

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Exchange Server

Microsoft Exchange Server includes several system services. When a MAPI client such as Microsoft Outlook connects to an Exchange server, the client first connects to the RPC endpoint mapper (the RPC Locator Service) on TCP port 135. The RPC endpoint mapper tells the client which ports to use to connect to the Exchange Server service, which are dynamically assigned. Exchange Server 5.5 uses two ports, one each for the information store and the directory. Microsoft Exchange 2000 Server and Exchange Server 2003 use three ports, one for the information store and two for the system attendant, respectively. Alternatively, Microsoft Outlook 2003 can use RPC over HTTP to connect to servers running Exchange Server 2003. Exchange can also provide support for other protocols, such as SMTP, POP3, and IMAP.

Application protocol

Protocol

Port

IMAP

TCP

143

IMAP over SSL

TCP

993

POP3

TCP

110

POP3 over SSL

TCP

995

Randomly allocated high TCP ports

TCP

RANDOM

RPC

TCP

135

RPC over HTTP

TCP

593

SMTP

TCP

25

SMTP

UDP

25

Fax Service

The Fax service, a Telephony Application Programming Interface (TAPI)-compliant system service, provides fax capabilities from your computer. The Fax service allows users to send and receive faxes from their desktop applications using either a local fax device or a shared network fax device.

System Service Name Fax

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

NetBIOS Session Service

TCP

139

SMB

TCP

445

File Replication

The File Replication system service allows files to be automatically copied and maintained simultaneously on multiple servers. File Replication service (FRS) is the automatic file replication service in Windows 2000 and the Microsoft Windows Server 2003 family. Its function is to replicate the Sysvol on all domain controllers. In addition, FRS can be configured to replicate files among alternate targets associated with the fault-tolerant DFS.

System Service Name NtFrs

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

File Server for Macintosh

The File Server for Macintosh system service enables Macintosh computer users to store and access files on a computer running Windows Server 2003. If this service is turned off or blocked, Macintosh clients cannot access or store files on your computer.

System Service Name MacFile

Application protocol

Protocol

Port

File Server for Macintosh

TCP

548

FTP Publishing Service

The File Transfer Protocol (FTP) Publishing service provides FTP connectivity. The FTP control port is 21 by default, but you can configure this system service through the Internet Information Services (IIS) Manager (a snap-in). The default data port (used for active mode FTP) is automatically set to one less than the control port, so if you configure the control port to 4131, the default data port will be 4130. Most FTP clients use passive mode, which means that the client initially connects to the FTP server through the control port; the FTP server assigns a high TCP port between 1025 and 5000; and the client opens a second connection to the FTP server for transferring data. The range of high ports can be configured through the IIS metabase.

System Service Name MSFtpsvc

Application protocol

Protocol

Port

FTP control

TCP

21

FTP default data

TCP

20

Randomly allocated high TCP ports

TCP

RANDOM

HTTP SSL

The HTTP SSL system service enables IIS to perform SSL functions. SSL is an open standard for establishing a secure communications channel to prevent the interception of critical information, such as credit card numbers. Primarily, this service enables secure electronic financial transactions on the Web, although it is designed to work on other Internet services as well. You can configure the ports for this service through IIS Manager.

System Service Name HTTPFilter

Application protocol

Protocol

Port

HTTPS

TCP

443

Internet Authentication Service

The Internet Authentication Service (IAS) performs centralized authentication, authorization, auditing, and accounting of users connecting to a network - either LAN or remote - using VPN equipment, Remote Access Equipment (RAS), or 802.1X Wireless and Ethernet/Switch Access Points. IAS implements the Internet Engineering Task Force (IETF) standard RADIUS protocol, which enables heterogeneous network access equipment.

System Service Name IAS

Application protocol

Protocol

Port

Legacy RADIUS

UDP

1645

Legacy RADIUS

UDP

1646

RADIUS Accounting

UDP

1813

RADIUS Authentication

UDP

1812

ICF/ICS

This system service provides NAT, addressing and name resolution services for all computers on your home or small-office network. When ICS is enabled, your computer becomes an "Internet gateway" on the network, enabling other client computers to share one connection to the Internet; such as a dial-up or broadband connection. This service provides basic DHCP and DNS services, but will work with the full-featured Windows DHCP or DNS services.

When ICF/ICS is acting as a gateway for the rest of the computers on your network, it provides DHCP and DNS services to the private network on the internal network interface. It does not provide these services on the externally-facing interface.

System Service Name SharedAccess

Application protocol

Protocol

Port

DHCP Server

UDP

67

DNS

UDP

53

DNS

TCP

53

Kerberos Key Distribution Center

The Kerberos Key Distribution Center (KDC) system service enables users to log on to the network using the Kerberos version 5 authentication protocol. As in other implementations of the Kerberos protocol, the KDC is a single process that provides two services: the Authentication Service, which issues ticket-granting tickets, and the Ticket-Granting Service, which issues tickets for connections to computers in its own domain.

System Service Name Kdc

Application protocol

Protocol

Port

Kerberos

TCP

88

Kerberos

UDP

88

License Logging Service

License Logging Service (LLS) is a tool that was originally designed to help customers manage licenses for Microsoft server products that are licensed in the Server Client Access License (CAL) model. LLS was introduced with Windows NT Server 3.51. By default, LLS is disabled in Windows Server 2003. Because of original design constraints and evolving license terms and conditions, LLS cannot provide an accurate view of the total number of CALs that are purchased as compared to the total number of CALs that are used on a single server or across the enterprise. The CALs that are reported by LLS may conflict with the interpretation of the End User License Agreement (EULA) and with Product Usage Rights (PUR). LLS will not be included in future versions of the Windows operating system. (Only users of Small Business Server should enable this service on their servers.)

System Service Name LicenseService

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

NetBIOS Session Service

TCP

139

SMB

TCP

445

Local Security Authority

The Local Security Authority (LSASS) service provides core operating system security mechanisms. It uses random TCP ports assigned through the RPC service for domain controller replication.

Although LSASS can use all of the following protocols, it may only use a subset of them. For example, if you are configuring a VPN gateway that lies behind a filtering router, you might use L2TP with IPSec. If so, then you must allow IPSec ESP (IP protocol 50), NAT-T (TCP on port 4500), and IPSec ISAKMP (TCP on port 500) through the router. Although IPSec ESP is required for L2TP, it is actually monitored by the Routing and Remote Access service.

System Service Name LSASS

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Global Catalog Server

TCP

3269

Global Catalog Server

TCP

3268

LDAP Server

TCP

389

LDAP Server

UDP

389

LDAP SSL

UDP

636

LDAP SSL

TCP

636

IPSec ISAKMP

UDP

500

NAT-T

UDP

4500

Message Queuing

The Message Queuing system service is a messaging infrastructure and development tool for creating distributed messaging applications for Windows. Such applications can communicate across heterogeneous networks and send messages between computers that may be temporarily unable to connect to each other. Message Queuing provides guaranteed message delivery, efficient routing, security, support for sending messages within transactions, and priority-based messaging.

System Service Name msmq

Application protocol

Protocol

Port

MSMQ

UDP

1801

MSMQ

TCP

1801

MSMQ-DCs

TCP

2101

MSMQ-Mgmt

TCP

2107

MSMQ-Ping

UDP

3527

MSMQ-RPC

TCP

2105

MSMQ-RPC

TCP

2103

RPC

TCP

135

Messenger

The Messenger system service sends messages to or receives messages from users and computers, administrators, and the Alerter service. This service is not related to Microsoft Windows Messenger or MSN Messenger. When this service is disabled, the NET SEND and NET NAME shell commands will no longer function. Messenger notifications sent to computers or users currently logged on the network will not be received.

System Service Name Messenger

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

Microsoft Exchange MTA Stacks

In Exchange 2000 Server and Exchange Server 2003, Message Transfer Agent (MTA Stacks) is frequently used to provide backward-compatible message transfer services between Exchange 2000 Server-based servers and Exchange Server 5.5-based servers in a mixed-mode environment.

Application protocol

Protocol

Port

X.400

TCP

102

Microsoft Operations Manager 2000

Microsoft Operations Manager 2000 (MOM) delivers enterprise-class operations management by providing comprehensive event management, proactive monitoring and alerting, reporting, and trend analysis. After installing Service Pack 1, MOM will stop using the clear-text communications channel, and all traffic between the MOM agent and the MOM server will be encrypted over TCP port 1270. The MOM Administrator console uses DCOM to connect to the server. This means that administrators managing the MOM server over the network must have access to random high TCP ports, too.

System Service Name one point

Application protocol

Protocol

Port

MOM-Clear

TCP

51515

MOM-Encrypted

TCP

1270

Microsoft POP3 Service

The Microsoft POP3 Service provides e-mail transfer and retrieval services. Administrators can use this service to store and manage e-mail accounts on the mail server. When you install Microsoft POP3 Service on the mail server, users can connect to the mail server and retrieve e-mail using an e-mail client that supports the POP3 protocol, such as Microsoft Outlook.

System Service Name POP3SVC

Application protocol

Protocol

Port

POP3

TCP

110

Microsoft SQL Server

Microsoft SQL Server 2000 provides a powerful and comprehensive data management platform. The ports used by each instance of SQL Server can be configured through the Server Network Utility.

System Service Name SQLSERVR

Application protocol

Protocol

Port

SQL over TCP

TCP

1433

SQL Probe

UDP

1434

MSSQL$UDDI

This system service installs during the installation of the Universal Description, Discovery, and Integration (UDDI) feature of the Windows Server 2003 family of operating systems, which provides UDDI capabilities within an enterprise. The SQL Server database engine is the core component of this feature.

System Service Name SQLSERVR

Application protocol

Protocol

Port

SQL over TCP

TCP

1433

SQL Probe

UDP

1434

Net Logon

The Net Logon system service maintains a secure channel between your computer and the domain controller to authenticate users and services. It passes the user's credentials through a secure channel to a domain controller and returns the domain security identifiers and user rights for the user. This is commonly referred to as pass-through authentication. Net Logon starts automatically when the computer is a member of a domain. In the Windows 2000 Server and Windows 2003 Server families, the Net Logon service publishes service resource records in the DNS. Net Logon service is enabled only on computers that belong to a domain. When it is running, it relies on the Server and Local Security Authority services to listen for incoming requests. On domain member computers, it uses RPC over named pipes; on domain controllers, it uses RPC over named pipes, RPC over TCP/IP, mailslots, and LDAP.

System Service Name Netlogon

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

NetBIOS Name Resolution

UDP

137

NetBIOS Session Service

TCP

139

SMB

TCP

445

NetMeeting Remote Desktop Sharing

The NetMeeting Remote Desktop Sharing system service allows authorized users to remotely access your Windows desktop from another personal computer over a corporate intranet by using Microsoft NetMeeting. You must explicitly enable this service in NetMeeting. You also can disable or shut down through an icon in the Windows notification area.

System Service Name mnmsrvc

Application protocol

Protocol

Port

Terminal Services

TCP

3389

Network News Transfer Protocol

The Network News Transfer Protocol (NNTP) system service allows computers running Windows Server 2003 to act as news servers. Clients can use a news client such as the Microsoft Outlook Express messaging client to retrieve newsgroups from the server and read headers or bodies of the articles in each newsgroup.

System Service Name NntpSvc

Application protocol

Protocol

Port

NNTP

TCP

119

NNTP over SSL

TCP

563

Performance Logs and Alerts

The Performance Logs and Alerts system service collects performance data from local or remote computers based on preconfigured schedule parameters, then writes the data to a log or triggers an alert. The Performance Logs and Alerts service starts and stops each named performance data collection based on the information contained in the named log collection setting. This service runs only if at least one performance data collection is scheduled.

System Service Name SysmonLog

Application protocol

Protocol

Port

NetBIOS Session Service

TCP

139

Print Spooler

The Print Spooler system service manages all local and network print queues and controls all print jobs. The print spooler is the center of the Windows printing subsystem and controls all printing jobs. It manages the print queues on the system and communicates with printer drivers and input/output (I/O) components, for example, the USB port and the TCP/IP protocol suite.

System Service Name Spooler

Application protocol

Protocol

Port

NetBIOS Session Service

TCP

139

SMB

TCP

445

Remote Installation

The Remote Installation system service provides the ability to install Windows 2000, Windows XP, and Windows Server 2003 on Pre Execution Environment (PXE) remote boot-enabled client computers. The Boot Information Negotiation Layer (BINL) service, the primary component of Remote Installation Services (RIS), answers PXE client requests, checks Active Directory for client validation, and passes client information to and from the server. The BINL service is installed when you either add the RIS component from Add/Remove Windows Components, or select it when initially installing the operating system.

System Service Name BINLSVC

Application protocol

Protocol

Port

BINL

UDP

4011

Remote Procedure Call

The Microsoft Remote Procedure Call (RPC) system service is a secure inter-process communication (IPC) mechanism that enables data exchange and invocation of functionality residing in a different process. The different process can be on the same computer, on the LAN, or across the globe through a WAN or VPN connection. RPC service serves as the RPC endpoint mapper and Component Object Model (COM) Service Control Manager (SCM). Many services depend on the RPC service to start successfully.

System Service Name RpcSs

Application protocol

Protocol

Port

RPC

TCP

135

RPC over HTTP

TCP

593

Remote Procedure Call Locator

The Remote Procedure Call Locator system service enables RPC clients using the RpcNs family of application programming interfaces (APIs) to locate RPC servers and manages the RPC name service database. This service is turned off by default.

System Service Name RpcLocator

Application protocol

Protocol

Port

NetBIOS Session Service

TCP

139

SMB

TCP

445

Remote Storage Notification

The Remote Storage Notification system service notifies users when they read from or write to files that are available only from a secondary storage media. If this service is stopped, notification does not occur.

System Service Name Remote_Storage_User_Link

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Remote Storage Server

The Remote Storage Server system service stores infrequently used files in a secondary storage medium. Stopping this service prevents users from moving or retrieving files from the secondary storage media.

System Service Name Remote_Storage_Server

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Routing and Remote Access

The Routing and Remote Access (RRAS) system service provides multiprotocol LAN-to-LAN, LAN-to-WAN, VPN, and NAT routing services. In addition, the RRAS service also provides dial-up and VPN remote access services.

Although RRAS can use all of the following protocols, typically it will only use a subset of them. For example, if you are configuring a VPN gateway that lies behind a filtering router, you will probably only use one technology. If you use L2TP with IPSec, then you must allow IPSec ESP (IP protocol 50), NAT-T (TCP on port 4500), and IPSec ISAKMP (TCP on port 500) through the router. Although NAT-T and IPSec ISAKMP are required for L2TP, these ports are actually monitored by the Local Security Authority. For more information, see "Related Topics" later in this document.

System Service Name RemoteAccess

Application protocol

Protocol

Port

GRE (IP protocol 47)

GRE

n/a

IPSec AH (IP protocol 51)

AH

n/a

IPSec ESP (IP protocol 50)

ESP

n/a

L2TP

UDP

1701

PPTP

TCP

1723

Server

The Server system service provides RPC support, and file, print, and named pipe sharing over the network. The Server service allows the sharing of local resources, such as disks and printers, so that other users on the network can access them. It also allows named pipe communication between applications running on other computers and your computer, which is used for RPC. Named pipe communication is memory reserved for the output of one process to be used as input for another process. The input-accepting process does not have to be local to the computer.

System Service Namelanmanserver

Application protocol

Protocol

Port

NetBIOS Datagram Service

UDP

138

NetBIOS Name Resolution

UDP

137

NetBIOS Session Service

TCP

139

SMB

TCP

445

SharePoint Portal Server

The SharePoint Portal Server system service enables enterprises to develop an intelligent portal that seamlessly connects users, teams, and knowledge so that people can take advantage of relevant information across business processes to help them work more efficiently. Microsoft Office SharePoint Portal Server 2003 provides an enterprise business solution that integrates information from various systems into one solution through single sign-on and enterprise application integration capabilities, with flexible deployment options and management tools.

Application protocol

Protocol

Port

HTTP

TCP

80

HTTPS

TCP

443

Simple Mail Transfer Protocol

The Simple Mail Transfer Protocol (SMTP) system service is an e-mail submission and relay agent. It can accept and queue e-mail for remote destinations and retry at specified intervals. Windows domain controllers use the SMTP service for intersite e-mail-based replication. The Collaboration Data Objects (CDO) for the Windows Server 2003 COM component can use the SMTP service to submit and queue outbound e-mail.

System Service Name SMTPSVC

Application protocol

Protocol

Port

SMTP

TCP

25

SMTP

UDP

25

Simple TCP/IP Services

Simple TCP/IP Services implements support for the following protocols:

  • Echo, port 7, RFC 862

  • Discard, port 9, RFC 863

  • Character Generator, port 9, RFC 864

  • Daytime, port 3, RFC 867

  • Quote of the Day, port 17, RFC 865

System Service Name SimpTcp

Application protocol

Protocol

Port

Chargen

TCP

19

Chargen

UDP

19

Daytime

TCP

13

Daytime

UDP

13

Discard

TCP

9

Discard

UDP

9

Echo

UDP

7

Echo

TCP

7

Quotd

UDP

17

Quotd

TCP

17

SMS Remote Control Agent

Systems Management Server (SMS) 2003 provides a comprehensive solution for change and configuration management for the Microsoft platform, enabling organizations to provide relevant software and updates to users quickly and cost-effectively.

Application protocol

Protocol

Port

SMS Remote Chat

UPD

2703

SMS Remote Chat

TCP

2703

SMS Remote Control (control)

UDP

2701

SMS Remote Control (control)

TCP

2701

SMS Remote Control (data)

TCP

2702

SMS Remote Control (data)

UDP

2702

SMS Remote File Transfer

UDP

2704

SMS Remote File Transfer

TCP

2704

SNMP Service

The SNMP Service system service allows incoming Simple Network Management Protocol (SNMP) requests to be serviced by the local computer. The SNMP service includes agents that monitor activity in network devices and report to the network console workstation. SNMP service provides a method of managing network hosts, such as workstation or server computers, routers, bridges, and hubs from a centrally-located computer running network management software. SNMP performs management services by using a distributed architecture of management systems and agents.

System Service Name SNMP

Application protocol

Protocol

Port

SNMP

UDP

161

SNMP Trap Service

The SNMP Trap Service receives trap messages generated by local or remote SNMP agents and forwards the messages to SNMP management programs running on your computer. The SNMP Trap Service, when configured for an agent, generates trap messages if any specific events occur. These messages are sent to a trap destination. For example, an agent can be configured to initiate an authentication trap if an unrecognized management system sends a request for information. Trap destinations consist of the computer name, or the IP address, or IPX address of the management system. The trap destination must be a network-enabled host that is running SNMP management software.

System Service Name SNMPTRAP

Application protocol

Protocol

Port

SNMP Traps Outbound

UDP

162

SQL Analysis Server

The SQL Analysis Server system service is a component of SQL Server 2000. It can be used to create and manage OLAP cubes and data mining models. The analysis server may access local or remote data sources for the purposes of creating and storing cubes or data mining models.

Application protocol

Protocol

Port

SQL Analysis Services

TCP

2725

SQL Server: Downlevel OLAP Client Support

This system service is used by SQL Server 2000 when the SQL Analysis Server service must support connections from downlevel (OLAP Services 7.0) clients.

Default Ports for OLAP Services Used by SQL Server 7.0

Application protocol

Protocol

Port

OLAP Services 7.0

TCP

2393

OLAP Services 7.0

TCP

2394

SSDP Discovery Service

The SSDP Discovery service implements the Simple Service Discovery Protocol (SSDP) as a Windows service. The SSDP Discovery service manages receipt of device presence announcements, updating its cache and passing these notifications along to clients with outstanding search requests. The SSDP Discovery service also accepts registration of event callbacks from clients, turns these into subscription requests, and monitors for event notifications, passing them along to the registered callbacks. This system service also provides hosted devices with periodic announcements.

Currently, the SSDP event notification service uses TCP port 5000. In Windows XP Service Pack 2, it relies on TCP port 2869.

System Service Name SSDPRSRV

Application protocol

Protocol

Port

SSDP

UDP

1900

SSDP event notification

TCP

2869

SSDP legacy event notification

TCP

5000

Systems Management Server

Systems Management Server (SMS) 2003 provides a comprehensive solution for change and configuration management for the Microsoft platform, enabling organizations to provide relevant software and updates to users quickly and cost-effectively.

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

NetBIOS Datagram Service

UDP

138

NetBIOS Name Resolution

UDP

137

NetBIOS Session Service

TCP

139

TCP/IP Print Server

The TCP/IP Print Server system service enables TCP/IP-based printing using the Line Printer Daemon protocol. The Line Printer Daemon Service (LPDSVC) on the server receives documents from native Line Printer Remote (LPR) utilities running on UNIX computers.

System Service Name LPDSVC

Application protocol

Protocol

Port

LPD

TCP

515

Telnet

The Telnet system service for Windows provides ASCII terminal sessions to Telnet clients. Telnet Server supports two types of authentication and supports four types of terminals: American National Standards Institute (ANSI), VT-100, VT-52, and VTNT.

System Service Name TlntSvr

Application protocol

Protocol

Port

Telnet

TCP

23

Terminal Services

Terminal Services provides a multisession environment that allows client devices to access a virtual Windows desktop session and Windows-based programs running on the server. Terminal Services allows multiple users to be connected interactively to a computer.

System Service Name TermService

Application protocol

Protocol

Port

Terminal Services

TCP

3389

Terminal Services Licensing

The Terminal Services Licensing system service installs a license server and provides registered client licenses when connecting to a Terminal Server. The Terminal Services Licensing service is a low-impact service that stores the client licenses that have been issued for a Terminal Server, and then tracks the licenses that have been issued to client computers or terminals.

System Service NameTermServLicensing

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Terminal Services Session Directory

The Terminal Services Session Directory system service allows clusters of load-balanced Terminal Servers to route a user's connection request to the server where the user already has a session running. Users will be routed to the first-available Terminal Server, regardless of whether they've got a running session elsewhere in the cluster. Load Balancing pools the processing resources of several servers using the TCP/IP networking protocol. You can use this service with a cluster of terminal servers to scale the performance of a single terminal server by distributing sessions across multiple servers. Session Directory keeps track of disconnected sessions on the cluster, and ensures that users are reconnected to those sessions.

System Service Name Tssdis

Application protocol

Protocol

Port

RPC

TCP

135

Randomly allocated high TCP ports

TCP

RANDOM

Trivial FTP Daemon Service

The Trivial FTP (TFTP) Daemon system service does not require a user name or password and is an integral part of the Remote Installation Services (RIS). The Trivial FTP Daemon service implements support for the TFTP protocol defined by the following RFCs:

  • RFC 350 - TFTP

  • RFC 2347 - Option extension

  • RFC 2348 - Block size option

  • RFC 2349 - Timeout interval, and transfer size options

Trivial File Transfer Protocol is designed to support diskless boot environments. TFTP Daemons listen on UDP port 69, but respond from a randomly allocated high port. Therefore, enabling this port will allow the TFTP service to receive incoming TFTP requests, but will not allow the selected server to respond to those requests. Allowing the selected server to respond to inbound TFTP requests cannot be accomplished unless the TFTP server is configured to respond from port 69.

System Service Name tftpd

Application protocol

Protocol

Port

TFTP

UDP

69

Universal Plug and Play Device Host

The UPnP Host discovery system service implements all of the components required for device registration, control, and responding to events for hosted devices. The information registered pertaining to a device (description, lifetimes, containers) are optionally persisted to disk and announced on the network after registration or on system restart. The service also includes the Web server, which serves the device, as well as service descriptions and a presentation page.

System Service Name UPNPHost

Application protocol

Protocol

Port

UPNP

TCP

2869

Windows Internet Name Service

The Windows Internet Name Service (WINS) enables NetBIOS name resolution. The presence of WINS servers is crucial for locating network resources that can be identified using NetBIOS names. WINS servers are required unless all domains have been upgraded to Active Directory, and all computers on the network are running Windows 2000 Server or later. WINS servers communicate with network clients using NetBIOS Name Resolution. WINS Replication is required between WINS servers only.

System Service Name WINS

Application protocol

Protocol

Port

NetBIOS Name Resolution

UDP

137

WINS Replication

TCP

42

WINS Replication

UDP

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