February 3, 2022 Club Meeting
Thursday, February 3, 2022 at 7:00 PM Via Zoom. Login sent via email or upon request.
Program: Power over Ethernet (PoE), Tom McDermott, N5EG
The February meeting will be a presentation on Power over Ethernet (PoE), how it works, and the different versions available.
PoE is seeing increasing usage beyond just powering VoIP telephones. For example, many wireless data radios use PoE to avoid the need for feedlines and their associated loss (especially important as microwave frequencies). The AREDN network radios generally use PoE to power the outside unit.
The presentation will discuss how PoE works, some safety mechanisms built in, and midspan and endspan power injection.
Announced in the February 2022 issue of The Repeater.
Meeting Notes
From the March 2022 issue of The Repeater.
RVARC meeting minutes 2022-02-03
7:00 pm meeting began,11 attendees on Zoom
No treasurer’s report this month.
Not much action at Winter Field Day: Allan, K7GT, had no contacts, Luke, KJ7BKH, got one contact.
Scott, NA7OM: No possibility for Hyatt Lake for Field Day 2022. Meanwhile, he is going to the Philippines this Summer, hopefully with his DU License, if it can be obtained.
7:20 pm Presentation on Power over Ethernet by Tom, N5EG
Tom’s slide deck is available at: k7mfr.org/files/Power-over-Ethernet.pdf
The presentation went over common applications, history, the 3 types of POE, the injection modes, power capacities & negotiation, pinouts and wiring, and links to available standards documents. Very good information there for modern networking.
7:54 pm End presentation
Discussion:
The POE++ standardization took a long time to complete due to difficulty achieving consensus, but it should have a long lifetime thereafter.
Spanning Tree Protocol (STP and RSTP) will break topological loops in Ethernet local area switched networks so that infinite feedback loops don’t occur. [Ed Note: Ethernet floods a network when it doesn’t know where to send a packet, as opposed to IPv4 which drops the packet.]
Ethernet switches build tables of MAC-source-address to physical-switch-port correspondences. They don’t switch on IP address. [Ed Note: all end computers need to keep track of devices on the local subnet using the Address Resolution Protocol (ARP). The gateway address is used to route packets not destined for the local subnet].
The 48-bit Ethernet MAC addresses are not globally unique anymore.
Carrier-grade NAT on IPV4 (NAT 444), like in Starlink, breaks inbound routing because ports now map to different customers, rather than just services. CGNAT allows one IPv4 address to be shared by up to 128 different unrelated customers. It’s a very painful band-aid to work around Ipv4 address exhaustion. It breaks a lot of stuff.
4in6 allows edge IPV4 addresses to be routed over IPV6 backbones. IPV6, proposed in the 1990’s, still hasn’t become heavily used at the home equipment level.
100/1000 CAT5e/CAT6 Ethernet cables can be as long as 100 meters between switches.
Border Gateway Protocol (BGP), is used by Internet Service Providers (ISP’s) to advertise network reachability to others (competitors sometimes) without having to disclose their interior network topology. The whole ISP network is seen as one Autonomous System (AS).
An anecdotal story was that a recent BGP error took out Facebook’s path to its DNS server, thereby preventing all tech access to it, its servers, and locking out many from its offices via the card access door locks. BGP can be a very complicated protocol indeed.
Luke, KJ7BKH:March 12-13 there will be the QSO Today convention online. ( see www.qsotodayhamexpo.com) He will give a DMR presentation there, for those interested in that mode.
8:34 pm End meeting
John Armstrong, KF7UMK, secretary
