Firstly, don't tell me this is the wrong forum, because the ss7 tag doesn't exist on network engineering, and this isn't a security question; also, you'll find questions like this on SO.
This answer claims that E1 with CAS has 31 bearer channels, and CCS, 30B+D, which means he is implying that CAS refers to only in-band signalling, i.e. robbed bit signalling.
This contradicts that and claims that CAS refers to in-band (31B) and out-of-band (TS16 signalling, 30B+D). It also refers to out-of-band CAS as 'Channel Associated'.
This suggests there are three CCS variants, one being Channel Associated.
Common Channel Signalling (CCS)
Is there a difference between out-of-band 'Channel Associated' CAS and 'Channel Associated' CCS or is it the same thing? Perhaps 'Channel Associated' CCS refers to a separate lone E1 carrying signalling links separate from the voice E1 bundle (31D and 31B); then again, the image for it depicts only a single circuit for the signalling, which would be 30+D, which is out-of-band CAS...
To make matters worse, this shows CCS to be what the previous source classed as Quasi-Associated CCS and draws the dichotomy with CAS, ignoring the existence of the apparent 'Channel Associated CCS', suggesting that CCS is exclusively Quasi-Associated and refers to the existence of separate STPs, whereas CAS refers to a lack of separate STPs.
Can someone clear up this ambiguous terminology and arrive at proper distinctions? It seems nobody knows, as the sources use conflicting classifications.
There are only 2: CCS and CAS. CCS refers to Common Channel Signaling, meaning that the link with signaling (protocol independent) may or may not be in the E1. CAS refers to Channel Associated Signaling, were the channel with the signaling IS in the E1.
E1 CAS refers to the E1 with a fixed TS for signaling, like MFC:R2 which uses time slot 16 for line signals (4 bits Tx, 4 bits for Rx, mostly only used only 2 bits called A and B). Usually some people may refer to this as 30B+D, but it's not correct due that term is tied to ISDN PRI, where 30 TS for Bearer plus 1 TS Data. Normally the switch will reject the creation of a PRI on top of a CAS interface, because the D channel on EuroISDN PRI is 16, as well as MFC:R2, hence ISDN PRI is only CCS. However, you can create SS7 CICs in the same E1 created as CAS (also normally use TS 16 to control echo cancellers or DCME's for international long distance over TDM) very well documented in the old Siemens EWSD switch.
E1 CCS refers to the interface with 31 TS available to be used for CCS circuits, but mostly for SS7 links and CICs (or even B channels). You can create the SS7 link in any channel you want (in TDM switches you need to create a semi-permanent connection to reach a link processor), as well as the CICs.
What you are referring as Associated and Quasi-associated is the way as you connect the SS7 link with the network, but nothing to do with the physical interface definition. When a SS7 link is connected in associated mode, means that you know the SPC (Signaling Point Code) from the switch adjacent, and only that SPC. All the signaling is between those switches and nothing else (usually only ISUP). Quasi-associated means that your link is connected to STP (Signaling Transfer Point), who serves as signaling router to reach other SPCs in the network. So you can have some CICs between switch A and B, but the signaling link is not connected directly in the same way as the CICs, instead you send the messages from the switch A to the STP to reach the switch B, but also you can send any message to any node in the network (if is allowed), as well as dialogs for transaction with DB (TCAP) or Mobile (MAP). Funny note, there were some old implementations of EuroISDN PRI were you can manage several PRI E1 with just one link in the same way as SS7 does, but I've seen very few of those cases. This is also well known in the EWSD as PA Slave (Primary Access Slave).
Hope this helps.