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Address Used to Identify a Process on a Host: Physical vs Port vs Logical

Address Used to Identify a Process on a Host: Physical vs Port vs Logical

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Nov 4, 2026

To identify a specific process (application) running on a host over a network, networking uses the host’s IP address together with a transport-layer port number. The port number identifies which process on that host should receive the incoming data, after the IP address has identified the host. This is why “port address” is the correct choice in questions like: “The address which is used to identify a process on a host is (i) physical (ii) port (iii) logical (iv) specific.”2

Port number and IP address work together: IP targets the host; the port targets the process. In contrast, physical address is used for link-layer delivery, not for selecting an application process.

Mermaid view of the “host vs process” split:

Footnotes

  1. Port Number (TCP/UDP) — Internet Engineering Task Force / IANA overview - Explains ports as identifiers for services/application endpoints on TCP/UDP. ↩

  2. TCP: How it works (ports demultiplexing) — RFC 9293 (TCP specification) - TCP uses port numbers to identify endpoints; includes concepts of local/remote ports. ↩

  3. MAC address — Wikipedia - Defines MAC addresses as link-layer identifiers for network interfaces. ↩

Understanding IP Addresses and Ports (Host vs Process)

Key idea (exam-target)

If the question specifically says “identify a process on a host”, the intended answer is almost always: (ii) port address—because ports are designed to demultiplex traffic to the correct application process on a given host.2

Demultiplexing is exactly the role of the port number in TCP/UDP stacks.2

Correct option: (ii) port address

Footnotes

  1. Port Number (TCP/UDP) — Internet Engineering Task Force / IANA overview - Explains ports as identifiers for services/application endpoints on TCP/UDP. ↩ ↩2

  2. TCP: How it works (ports demultiplexing) — RFC 9293 (TCP specification) - TCP uses port numbers to identify endpoints; includes concepts of local/remote ports. ↩ ↩2

How to spot the right option quickly

If an option mentions “process,” think transport-layer demultiplexing → ports (TCP/UDP). If it mentions “device/network interface,” think IP/MAC → not “process.”

Don’t confuse port vs physical vs logical

MAC/physical addresses are link-layer identifiers for frames; logical addresses (in OS memory) are for memory management, not network process addressing. Process-on-host in networking corresponds to port.

How networking delivers data to the correct process on a host

  1. 1
    Step 1

    Routers use the packet’s IP address to deliver it to the correct host.

  2. 2
    Step 2

    Once the host receives the packet, the transport layer (TCP/UDP) examines the included port number.

  3. 3
    Step 3

    The transport layer uses the port to demultiplexing and pass the payload to the correct application/process.

  4. 4
    Step 4

    The receiving process reads the payload from its socket/endpoint associated with that port.

Comparing the options

OptionWhat it typically refers to in computer networking/OSCan it identify a process on a host?
(i) physical addressMAC address (link layer)No—MAC identifies a network interface on a link, not an application process.
(ii) port addressTCP/UDP port number (transport layer)Yes—ports identify the application/process on a host.2
(iii) logical addressOften OS logical/memory address or sometimes an abstract identifierUsually no for network process addressing; OS logical addresses are memory-related, not transport demux.
(iv) specific addressToo vague; not a standard networking term for “process identification”Not the intended correct answer in standard networking MCQs

Footnotes

  1. MAC address — Wikipedia - Defines MAC addresses as link-layer identifiers for network interfaces. ↩

  2. Port Number (TCP/UDP) — Internet Engineering Task Force / IANA overview - Explains ports as identifiers for services/application endpoints on TCP/UDP. ↩

  3. TCP: How it works (ports demultiplexing) — RFC 9293 (TCP specification) - TCP uses port numbers to identify endpoints; includes concepts of local/remote ports. ↩

  4. Logical address (memory management) — Wikipedia - Defines logical addresses in the OS memory management context, not network process addressing. ↩

Addressing layers for process delivery

Physical (MAC) delivery

Link layer

Frames are delivered to the correct interface on the local link using MAC addresses."

Footnotes

  1. MAC address — Wikipedia - Defines MAC addresses as link-layer identifiers for network interfaces. ↩

Host delivery

Network layer

Routers deliver packets to the correct host using IP addresses."

Footnotes

  1. TCP: How it works (ports demultiplexing) — RFC 9293 (TCP specification) - TCP uses port numbers to identify endpoints; includes concepts of local/remote ports. ↩

Process delivery

Transport layer

Ports (TCP/UDP) identify the process/application on that host.2"

Footnotes

  1. Port Number (TCP/UDP) — Internet Engineering Task Force / IANA overview - Explains ports as identifiers for services/application endpoints on TCP/UDP. ↩

  2. TCP: How it works (ports demultiplexing) — RFC 9293 (TCP specification) - TCP uses port numbers to identify endpoints; includes concepts of local/remote ports. ↩

Common confusions (FAQ)

Knowledge Check

Question 1 of 3
Q1Single choice

The address which is used to identify a process on a host is

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