20
votes
Worst-case efficiency of PPP escaping mechanism
You might care to read RFC 1547 "Requirements for an Internet Standard Point-to-Point Protocol" which explains how the PPP was chosen. The thing I'd suggest you are missing is that ...
- 16.4k
18
votes
Why does PPP need an underlying protocol?
Why does PPP need a wrapping protocol?
PPP is not a layer-1 protocol, so it needs a layer-1 protocol to carry it. Protocols like ethernet are both layer-1 and layer-2 protocols, so PPP can use ...
- 101k
12
votes
Why does PPP need an underlying protocol?
PPP is designed to ride on top of a byte-oriented, point-to-point physical-layer protocol like a simple modem-style serial link.
Ethernet is no simple serial protocol but it requires frame-level ...
- 88.1k
10
votes
Why PPTP, L2TP, PPPOE are in OSI Layer2?
PPTP, PPPoE, and L2TP all provide OSI Layer 2 services. That is, the user of these protocols (usually, a network layer protocol suite) thinks it's running over a "normal" link layer. ...
- 330
6
votes
Accepted
Why does PPP need an underlying protocol?
( As others have already said, PPPoE is literally PPP over Ethernet. And similarly PPPoA is PPP over ATM. )
Ethernet and ATM are oddities in the networking world as they define both a layer-1 and ...
- 32.6k
6
votes
Accepted
What is PPP and why does it not have a MAC address?
The Point-to-Point Protocol (PPP) is a data link layer protocol that's designed to run on top of a simple serial link as physical layer. Its main functionality is defined in RFC 1661.
Since there are ...
- 88.1k
5
votes
What is a "rotary dialer" in the context of dialup connections?
In the 1990s in a British regional ISP, we had a choice from the telephone company of getting two settings for multiple lines:
In the ordinary hunt group, the next incoming call would arrive on the ...
- 16.4k
5
votes
What is a "rotary dialer" in the context of dialup connections?
From the HOWTO you linked:
rotary dial in set of telephone lines
When I wore a younger man's clothes, back in the late 1990ies, I ran a bunch of Shiva LAN Rovers (in their IBM guise labelled as ...
- 8,876
4
votes
How is the length of a PPP frame known?
Sure, there is a 2-byte checksum followed by a magic byte, but that is hardly collision-proof.
Occurrences of the magic byte are escaped. There are two types of escaping used, called "character ...
- 142
4
votes
Accepted
How do protocols like PPTP, L2TP work below IP level
In real life, you can't stick to the OSI model entirely. It's helpful and necessary as a guide on how to structure the components in a complex network but you can't always say that's layer x.
...
- 88.1k
4
votes
Accepted
Why are the Address and Control fields constant in PPP protocol?
The address and control fields were designed with future changes in mind, and other values "may be defined at a later time, or by prior agreement."
(RFC 1662 "PPP in HDLC-like Framing&...
- 16.4k
4
votes
Accepted
How exactly does CHAP authentication work?
CHAP is defined in RFC 1994.
You concatenate the identifier, the password (secret), and the challenge, in ASCII, in that order. The response is hashMD5(identifier.secret.challenge), sent in binary (16 ...
- 88.1k
4
votes
Accepted
Address Field In PPP Protocol
As you have guessed the PPP address field was defined by RFC 1662 and has no function. It must be all ones according to the RFC or it should be silently discarded.
Address Field
The ...
- 30k
3
votes
Accepted
Is PPP a useful choice for fiber connections?
PPP is a protocol for transporting higher-layer protocols (like IP) over a simple serial interface. Since you'd already be running Ethernet, PPP doesn't work and is of no use anyway. You could use ...
- 88.1k
3
votes
Assigning static IP addresses to dialin PPP users on Cisco IOS
Actually this is relatively easy. Yes, you need AAA, but you don't need an external server.
aaa authentication ppp default local
aaa authorization network default local
aaa attribute list Static-1.2....
3
votes
PPP, Ethernet and PPPoE differences
The main point of using PPPoE is to have an authenticated session, a concept Ethernet by itself doesn't have. That allows an ISP to concentrate packets from many users in their backhaul network and ...
- 88.1k
3
votes
Accepted
IPv6 in PPP - should be an Interface Identifier negotiated FOR both ends of a link? Clarification of RFC 5072 needed
...upon completion of the negotiation, different interface-identifier
values are to be selected for the ends of the PPP link.
In other words, by the time the negotiation is done, the two ends of ...
- 2,426
3
votes
Accepted
Why is L2TP based on PPP and not PPPoE?
PPP is independent of the underlying transport, PPPoE requires to be run on Ethernet (or a like tunnel). But of course, you can also run L2TP with PPPoE (RFC 3817).
- 88.1k
3
votes
Accepted
How is the length of a PPP frame known?
The PPP header starts with a 16-bit protocol id. You need to look at that first in order to know how to interpret the rest.
If the protocol id is LCP/IPCP/IPv6CP then the header structure typically ...
- 200
3
votes
Accepted
PPP, VPN, Tunneling and OSI model
Your question is really too broad, and home networking and consumer-grade devices are explicitly off-topic here, but I will try to give you some general answers.
PPP is a layer-2 protocol, the same ...
- 101k
3
votes
Accepted
What is SLIP good for?
SLIP was an early protocol (mid-1980s) for running IPv4 over a serial line. It was very cumbersome due to both sides requiring identical configuration and compatible SLIP versions.
It was succeeded by ...
- 88.1k
3
votes
Accepted
How PPPoE uses addressing to know destination Mac address?
You're getting too hung up on the ethernet side of the equation. Yes, ethernet is a multi-point medium. PPPoE does not use it that way. The PPPoE discovery/setup process creates a single, one-to-one ...
- 32.6k
2
votes
Accepted
PPP sessions on packet return?
Yes - the BRAS is both stripping the PPP[oE] frame (...and some L2/L3 underlay information, depending on the design in use) off of frames coming from the subscriber device and is adding both the PPP[...
- 6,152
2
votes
Accepted
Configuring PPPoE client through OMCI on Huawei ma5608T
I work for Huawei and I have configured PPPoE, both client and server, recently for an AR200 router, to be honest with you, I don't know how much of a difference exist between my equipment and yours.
...
2
votes
Accepted
PPP, Ethernet and PPPoE differences
1) Can I use PPP to connect to my router from PC? If no, then why?
That depends. If you have network interfaces in your PC and router that support PPP, then yes.
2) Why I need PPPoE? Where it is ...
- 101k
2
votes
Assigning static IP addresses to dialin PPP users on Cisco IOS
No. The only way to set the address per user is with AAA (radius/tacacs) There used to be ways to pin an address per line, but it's never been possible by user. – Ricky Beam
I believe Ricky Beam's ...
- 181
2
votes
Accepted
can two devices communicate without physical layer?
can 2 device communicate with each other without data going to physical layer?
No. The physical layer is the one actually doing the bit lifting. Without physically transporting the data to another ...
- 88.1k
2
votes
What is the addressing problem of SLIP?
SLIP simply provided no means to negotiate connection parameters like addressing. (I'm using past tense because I cannot imagine that anyone is still using this laborious, even archaic protocol.)
So, ...
- 88.1k
Only top scored, non community-wiki answers of a minimum length are eligible