Access ID

You Access ID is the hardware address of your comlink, much like a MAC address. Other higher level addresses are assigned within the matrix grid your com is connected to (much like dynamic IP addresses). For all intensive purposes these other IDs are inconsequential. The Access ID uniquely identifies a comlink, but is can overridden by software (see spoofing).

Matrix Service Provider (MSP) accounts

For most users, when they connect to that dynamic, ever changing blob we call the matrix, their comlinks automatically log into one or more MSP accounts. This registers their MSP accounts to their current Access ID. This allows calls to be routed to their comlink. To put this in early 21st century terms, now your home phone, cell phone and work phone numbers now come one device that you can dynamically change out. These accounts also store contact lists, document files, whatever the end user desires.
In this way, your contact *numbers* are separate, but temporarily linked to, your Access ID.

Electronic communication: Written vs. Spoken

In the early 21st century, people selected between a variety of electronic formats to communicate. Voice, text & emails were the most common. As electronic communication continued to mature, so did voice recognition software allowing more common place live-time translation of communication. By 2070, translation of electronic communication is ubiquitous allowing a person to send as written and the recipient to receive as spoken or vice-versa without concern over the media; It just is.

Connectivity

Satellite Link: Requires both a satellite link and service account with a satellite provider.
LTG: Local telecommunications grid is a provider based connection using a service provider's cell tower that is in mutual signal range (all towers have a signal 6+). A direct connection is made to those towers. From there, the signal cascades from tower to tower until it finds a route to the other end.
NOTE: That route is not guaranteed to stay with the same provider or even to not enter the mesh network.
Wireless Mesh: Wireless mesh is when one com relays the matrix connection for another com, potentially infinitely extending the signal range.
NOTE: Even more so than provider based, this option is subject to interception and man-in-the-middle attacks.
PAN: A Personal Area Network range is determined by mutual signal range. This range negates man in the middle attacks but does not prevent interception or spoofing.
Slaving is actually a limited access PAN connection.
Optical Cable: This direct connect method is one of the most full-proof as long the node accessed is on the other end of the cable. This mode can also be used to access an internal network, a wired network or under the proper circumstances, to bypass anti-wireless defenses. example: connected to a drone that passes through a wall protected by wi-fi inhibiting wallpaper.
Skinlink: Much the same as an optical cable, but both nodes must be in contact of the bare skin of a single person/animal/creature.

Comlink Mode [sr4a, pg223]

The following are additional notes about the various modes, above & beyond the text or clarifying:
Active: Only active mode comlinks will communicate in a mesh network as unauthenticated connections are required for routing [Unwired, pg 54]. To get full access to AR, you also need to be in active mode. You can filter the details available for public viewing when in active mode, but the SIN loaded on the active com is not one of them. Spam filters can also be adjusted, but adjusting them too tightly restricts AR.
Passive: Passive allows you to see all AR, be restricts your access to interact with the AR until you authorize the generating node to interact with your com. For most users, passive mode requires too much continual tweaking and interaction to use.
Hidden: No interactive access to AR. Any presented AR can be seen, but not interacted with as your node (com) is not visible to the AR generating system. Additionally, a comlink in hidden mode cannot connect to the matrix as it does not respond to node detection requests. PAN-to-PAN and slave-node interactions are an exception as slaves are not hidden and p2p use a guaranteed transport protocol that assumes nodes are in mutual signal range until responses fail.
Due to the mesh-network nature of the Matrix, every wireless node can function as a router and will do so if not in passive or hidden mode - UnWired, pg54

Mode	Cable/ Skinlink	PAN?	LTG?	Mesh?	SIN Broadcast	AR Access
Active	Yes	Yes	Yes	Yes	Yes	Full
Passive	Yes	Yes	Yes	No	No	Restricted
Hidden	Yes	Yes	No	No	No	Non-interactive