Skip to main content

RSTP Optimization - Eliminating Listening and Learning

Why Legacy STP's Listening and Learning States Were Essential for Half-Duplex Networks and How RSTP Optimizes for Modern Ethernet

The listening and learning states in legacy STP (802.1D) were largely a product of network design at the time, which included many half-duplex connections and shared network segments (e.g., hubs and collision domains). These states were necessary to ensure stability and prevent loops in such environments.

Here's why these states were important:

  1. Half-Duplex Networks and Collision Domains:

    • In half-duplex environments (e.g., when hubs were common), collisions could occur because multiple devices shared the same medium. This meant that careful management of forwarding decisions was crucial to avoid packet loss and network loops.
    • The listening and learning states gave STP time to make sure there were no loops or improper configurations in the network, allowing BPDUs to propagate across the network and determine the best path for forwarding.

  2. Listening State:

    • During the listening phase, a port listened for BPDUs to ensure no loop-causing devices were present. This was essential when network segments were shared, as one device’s action could affect the entire segment.
    • It also allowed STP to establish the proper topology before allowing data traffic.

  3. Learning State:

    • In the learning state, the switch began to populate its MAC address table but still didn't forward traffic. This was another safeguard in collision-prone, shared networks, allowing the switch to understand the network's MAC addresses before forwarding packets.

Because of these factors, fixed timers were used to ensure that enough time was given for the network to stabilize before allowing data traffic. The transitions between these states (listening, learning, and then forwarding) helped to avoid forwarding loops and collisions in such shared network environments.

Why RSTP Optimizes This:

With modern full-duplex links and point-to-point connections (where collisions no longer occur), RSTP eliminates much of the need for such long waiting periods. RSTP transitions faster, leveraging direct handshakes between switches rather than relying on timers, allowing for much quicker convergence.

So, while the listening and learning states in legacy STP were crucial for stability in older half-duplex networks, they are less relevant in today’s full-duplex, point-to-point Ethernet environments, which RSTP optimizes for.

Labels:

Comments

Post a Comment

Popular posts from this blog

How to import Putty Saved Connections to mRemoteNG

Just started using mRemoteNG and its being very cool to connect to different remote connection with different protocols e.g Window Remote Desktop, VNC to Linux, SSH, HTTP connection etc. from a single application. As new user I configured some remote desktop connection which was quite easy to figure out. But when I wanted to add SSH connections, it came in my mind to import all of the saved connections in the putty. But I couldn't figure it out how can it be done, though it was quite easy and here are the steps. Open your mRemoteNG Create a folder if you want segregation of multiple networks Create a new connection Enter the IP address of remote server under connection in Config pane Under the config pane, select protocol " SSH version 2 ".  Once you select protocol to SSH version 2 you are given option to import putty sessions, as shown in the snap below. In the above snap, I have imported CSR-AWS session from my saved sessions in Putty.
1 comment
Read more

Understanding PKI The Complete Process Explained

The Complete Public Key Infrastructure (PKI) Process: From Key Generation to Certificate Verification Public Key Infrastructure (PKI) is the backbone of secure communication on the internet. It ensures that sensitive data exchanged between clients and servers remains private and authentic. This blog post will guide you through the entire PKI process, from generating keys to verifying certificates and ensuring they haven't been revoked. 1. Key Pair Generation The first step in PKI is generating a public-private key pair using an asymmetric cryptographic algorithm, such as RSA or ECDSA: The private key is securely stored on the server and never shared. The public key is included in the certificate and shared with the Certificate Authority (CA) during the certificate request process. This key pair enables encryption and decryption, which are essential for secure communication. 2. Creating a Certificate Signing Request (CSR) The server creates a Certificate Signing Request (CSR) to...
Post a Comment
Read more

AS Path Prepending: Controlling Inbound Traffic in BGP

AS Path Prepending is a BGP feature used to make a specific path appear less preferred by artificially lengthening the AS path. This is done by adding your AS number multiple times to the AS path. It is a common method to influence inbound traffic from external networks. Longer AS Path = Less preferred route . Example Scenario : You have two ISPs: ISP1 (through CE1) and ISP2 (through CE2). You want inbound traffic from the internet to prefer ISP1 over ISP2. Network Topology : CE1 (connected to ISP1): 10.0.1.1/30 CE2 (connected to ISP2): 10.0.2.1/30 iBGP Router (Internal) connected to both CE1 (10.0.1.2/30) and CE2 (10.0.2.2/30). Configuration on CE2 (AS Path Prepending to Make ISP2 Less Preferred) : Create a route map to prepend your AS path multiple times for CE2: route-map PREPEND_AS permit 10 set as-path prepend 65001 65001 65001 Apply this route map to the neighbor in the BGP configuration for CE2: router bgp 65001 neighbor 10.0.2.1 remote-as 65002 neighbor 10.0.2.1 ro...
Post a Comment
Read more