Priscilla Oppenheimer wrote: > MADMAN wrote: > >>Stuart Pittwood wrote: >> >>>It has been mooted to me that we might get better performance >> >>from our >> >>>1Mb line by using HDLC rather than PPP. >>> >>> >>> >>>Is this correct? >> >> HDLC is more efficient so I guess yes. > > > In what way is HDLC more efficient than PPP?
Since there is a little less overhead it is more efficient but not to the extent that one should be concerned. > > >>If I recall >>correctly, >>(someone will let me know if not;) PPP rides on top of HDLC. You definately know more details than I but I did a quick search and the second item on this URL mentions the PPP/HDLC relationship so I somewhat in the ballpark no? ;) http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/ppp.htm Dave > > > I would be glad to correct you. :-) > > HDLC is really more of an architecture than a specific protocol and there > are many derivatives of it. PPP is just one of them, as is Cisco's HDLC. > Other derivitaves include LAPB, LAPD, and LLC2. > > The standard PPP and Cisco HDLC are so similar in frame format you can > barely tell them apart. > > Cisco HDLC encapsulation has: > > one-byte address field, which is set to 0x0F for most frames > one-byte control byte that is always set to 0x00 > two-byte protocol type field > > > Guess what PPP has? Essentially the exact same thing: > > one-byte flag field set to 0x7F > one-byte address field, set to 0x11 > one-byte control field set to 0xC0 > one or two-byte protocol field > > > Both HDLC and PPP also have a control protocol for keeping the link up. HDLC > has SLARP. It sends keepalives. PPP has the Link Control Protocol. It brings > the link up and send echos and echo replies. > > Cisco HDLC can also use SLARP to assign an IP address to the other end. > > PPP has the Network Control Protocols in many different varieties. The IP > variety can assign IP addresses. > > PPP also supports authentication, which Cisco HDLC doesn't. > > _______________________________ > > Priscilla Oppenheimer > www.troubleshootingnetworks.com > www.priscilla.com > > > > >>> >>> >>>If so is it just a case of changing the Encapsulation PPP to >>>Encapsulation HDLC on both ends of the link? >> >> Assuming you have a Cisco on both ends, yes. >> >> >>> >>> >>>Are there any implications I should be aware of? >> >> One big advantage of PPP in the ability to authenticate. >>Though 1M >>seems odd I assume it's a dedicated link and authentication is >>not an issue. >> >> Dave >> >> >>> >>> >>>Thanks >>> >>> >>> >>>_________________________ >>> >>>Stuart Pittwood, MCSE >>> >>>IT Technician >>> >>>Amery-Parkes Solicitors >> >>-- >>David Madland >>CCIE# 2016 >>Sr. Network Engineer >>Qwest Communications >>612-664-3367 >> >>"You don't make the poor richer by making the rich poorer." >>--Winston >>Churchill -- David Madland CCIE# 2016 Sr. Network Engineer Qwest Communications 612-664-3367 "You don't make the poor richer by making the rich poorer." --Winston Churchill Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=64485&t=64362 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
