Network Glossary

Efforts to become a Network expert

1. STP (Spanning Tree Protocol)

• A protocol to prevent looping that occurs in Switches or Bridges

• In Switch or Bridge configurations, if there are two or more paths from source to destination, only one path is kept and the rest are disconnected; when a problem occurs with the active path, the disconnected paths are brought back one by one

2. Spine-leaf architecture

• Composed of 2 switching layers: spine and leaf

  • The leaf layer aggregates traffic from servers

  • Consists of access switches that connect directly to the spine or network core

  • Spine switches connect all leaf switches

  • Leaf switches are mounted in racks and are responsible for server communication within that rack

• Proposed to support recent traffic trends of increasing server-to-server communication

3. ToR (Top of Rack)

• A switch placed at the top of a server rack where servers are installed

• A switch deployed to handle traffic for the servers installed in that rack

4. packet

• A portmanteau of package and bucket; a bundled unit of data cut for easy transmission through a communication network

  • Represents the size of data to be transmitted at once

• A packet consists of a header, data, and trailer

  • The header contains the recipient's internet address and sequence information

  • The trailer contains error information

• Generally, the data unit at Layers 34 is defined as a packet, and the data unit at Layers 12 is called a frame

5. NIC (Network Interface Card)

• A card or interface that connects a PC or server to the network

• Terms used to refer to NIC include (quite diverse..):

  • Network Interface Controller

  • Network Card

  • LAN Card

    • In the past, Ethernet was only used in LANs (Local Area Networks), so the Network Interface Card came to be called a LAN Card!

  • Physical Network Interface

    • Emphasizes the meaning of a physical intermediary point connecting the inside and outside of a computer

    • Using this term can cause NIC to be mistaken as a Layer 1 (Physical Layer) component, but NIC is a Layer 2 (Data Link Layer) component!

  • Ethernet Card

    • Since most networks are made of Ethernet, NICs connecting to Ethernet are used for general network connections, hence the name Ethernet Card

  • Network Adaptor

6. Sequence Number

• When splitting packets at Layer 4, the sending order noted in the packet header is the Sequence Number

• Also called seq or sequence number

7. ACK (Acknowledgement) Number

• When splitting packets at Layer 4, the receiving order noted in the packet header is the ACK Number

• Also called ack number or acknowledgement number

8. MSS (Maximum Segment Size)

• When an application creates and sends data, the data flow layer properly splits the data to match network conditions and delivers it to the other party

  • The value that reverse-calculates from the size the network can accommodate to induce data to be split into appropriate sizes when it comes down to Layer 4 is called MSS (Maximum Segment Size)

• MSS is the maximum data value that can be held at Layer 4

9. MTU (Maximum Transmission Unit)

• The size of data that can be sent at once in a network is called MTU (Maximum Transmission Unit)

  • The typical size that regular Ethernet can accommodate is 1,500 bytes

• MTU is the maximum data value that can be held at Layer 2

  • At Layer 2, the size of data excluding Layer 2 header sizes is called the MTU size

• Since the standard header sizes of Layer 3's IP header and Layer 4's TCP header are each 20 bytes, regular Ethernet uses an MSS value of 1,460 bytes

  MTU (1,500 bytes) = IP header (20 bytes) + TCP header (20 bytes) + MSS (1,460 bytes)

10. PDU (Protocol Data Unit)

• The part combining header and data at each layer is called PDU

• The name for PDU differs by Layer

  • Layer 1 (Physical Layer): Bits

  • Layer 2 (Data Link Layer): Frame

  • Layer 3 (Network Layer): Packet

  • Layer 4 (Transport Layer): Segment

  • Layer 5 (Session Layer): Data

  • Layer 6 (Presentation Layer): Data

  • Layer 7 (Application Layer): Data

11. BPDU (Bridge Protocol Data Unit)

• Frame data for information exchange between Switches (Bridges)

  • Becomes the data for STP (Spanning Tree Protocol) to prevent network loops that can occur within a network

• Provides the information needed for STP to construct a loop free leaf topology

• When a Switch (Bridge) boots, it sends BPDU out of each port every 2 seconds, exchanging STP information with each other

  • In other words, Bridges exchange BPDU with each other to determine who is the root bridge, which port is the root port, and which port will be the designated port

12. SSL (Secure Socket Layer)

• A cryptographic protocol designed to provide communication security for Networks

• Applied to communications using TCP/IP networks such as the Internet

• Ensures security and integrity between Transport Layer (L4) endpoints during communication

• Protocols such as HTTP, FTP, TELNET are combined with security protocols like SSL to create HTTPS, SFTP, SSH and similar protocols

13. TLS (Transport Layer Security)

• An upgraded version of SSL

• HTTP using encrypted connections via TLS is called HTTPS (secure)

  • Uses port 443 instead of the default port 80

• TLS and HTTPS

• TLS

  • A protocol for various types of secure communication

  • Covers not only HTTP but also protocols like FTP and SMTP

• HTTPS

  • A protocol for secured HTTP communication by layering the HTTP protocol on top of TLS

  • Refers only to the combination of TLS and HTTP protocols

14. SSID (Service Set Identifier)

• An identifier under the IEEE 802.11 wireless networking standard that indicates the service set (Network) to connect to

  • Displayed when using the Internet through a WiFi module

  • Acts as an ID that distinguishes one wireless LAN from another

• Designed with unique names to distinguish among WiFi networks in a given area

• Creation rules

  • Maximum 32 characters (32 bytes)

  • Case-sensitive

  • Some special characters can be used

    • ?, ", $, [, , ], and +.

  • The following characters cannot appear at the beginning

    • !, #, and ;