RE: HDLC [7:66324]
=?iso-8859-1?q?maine=20dude?= wrote: Hi, I have a couple of queries regarding HDLC and Frame Relay. I gather they're both forms of data encapsulation for data and basically this means putting the data in headers and trailers to identify to the next layer or computer how to deal with the data. Please advise whether this is correct. Both HDLC and Frame Relay have a header and trailer and yes, they do encapsulate network-layer data and above. But it's a bit of an exaggeration to say that they identify to the next layer or computer how to deal with the data. HDLC and Frame Relay are data-link layer protocols that provide Wide Area Networking (WAN) connectivity. Acting at the data-link layer, they are analagous to Ethernet or Token Ring in a LAN. You wouldn't say that Ethernet identifies to the next layer or computer how to deal with the data and you shouldn't say this about HDLC or Frame Relay either. They may identify what the next layer is, but not how to deal with the data. Think of the OSI model. Each layer calls on the layer below and depends on the service provided by the layer below, but not the other way around. Each layer passes the encapsulated data to the layer above without touching it or understanding what it does. Sorry if that's picky. The original HDLC packet format did not have a field to identify the payload, i.e. the type of network-layer data that is encapsulated. But modern derivitaves of HDLC, including Cisco HDLC and PPP do have such a field. The standard Frame Relay packet format doesn't have a field to identify the next layer either, but Cisco's Frame Relay format does. As mentioned, HDLC and Frame Relay are WAN protocols. The obvious difference from LANs is that they connect devices or sites across a relatively long distance. The other, and possibly more important, difference is that you need a service provider or telco to implement a WAN. With LANs, you own the whole thing. With WANs, you own the routers, but then you lease capacity from a service provider or telco and get an agreement that the provider will send your data across its internal network of switches that span the long distance. This brings with it an entire set of administrative, political, and monetary issues, and means from an implementation and troubleshooting point of view that you have to work with the provider's engineers and sales geeks. But it's worth it. There's no way you can set up your own link between San Francisco and Los Angeles, for example, without the help of a telco/service provider. Things like mountains, roads, earthquake faults, and pot farms would get in your way. Just kidding. :-) In the olden days, HDLC was sometimes used to connect computers, such as mainframes and terminal controllers. These days, in a Cisco-oriented environment, both HDLC and Frame Relay are used to connect routers. That's another difference from LANs. You wouldn't normally put HDLC or Frame Relay on an end computer, whereas an end computer does have an Ethernet NIC in it. HDLC and Frame Relay are built into the Cisco Internetwork Operating System (IOS) and use a serial interface for the hardware. Now, for the differences between HDLC and frame Relay. HDLC is used for a point-to-point link, as you mentioned. It's used on a leased line that you get from a telco. You could connect a router in Atlanta, for example, to the local telco and contract with them to get your data to a telco in New York, for example, where you connect another router to the telco there. The result is a permanent, real circuit (as opposed to virtual circuit) between Atlanta and New York that only you can use. What if you also have sites in Boston, Los Angeles, and Chicago, as well as Atlanta? Should you lease a point-to-point link to make every connection? The number of circuits would be n(n-1)/2 where n is the number of sites. That's expensive. And that's where Frame Relay comes in. Frame Relay allows you to have virtual circuits to many different sites. With Frame Relay, you can lease a single line into the service provider's Frame Relay cloud and then contract with them for virtual circuits to other sites. For example, if New York is your HQ, you could have just one line into the telco in New York, but a virtual circuit to every other site. The outlying sites communicate with each other through New York. Each of them also just has one link into their local telco. Your network traffic travels across the Frame Relay provider cloud, which is shared by all the provider's customers. Well, I'm running out of steam here and have to get to work. This is covered in many books and white papers, as you probably know. I'm not sure which book you are using. Cisco Academy maybe? But if you have some specific questions, let us know. I'm wondering too if you could try to get a tour of a company's network and get a better feel for this? Talk to some network engineers about their network designs and physical facilities, etc. This is something that
RE: HDLC, line protocols, and keepalives. [7:62928]
As usual, you were absolutely correct Pricilla! The part which I didn't mention (because, for some reason, I figured that it was unimportant) was that this is an HDLC circuit going to my provider for a VPN circuit. They have a Nortel Shasta 5000 (essentially an IP multi-service edge router) and the tech confirmed that they do not have keepalives set on it. Thank you very much for your expertise! Geoff Mossburg -Original Message- From: Priscilla Oppenheimer [mailto:[EMAIL PROTECTED]] Sent: Wednesday, February 12, 2003 11:02 PM To: [EMAIL PROTECTED] Subject: RE: HDLC, line protocols, and keepalives. [7:62928] It sure sounds like your service provider isn't using keepalives, i.e. has no keepalive configured on their serial interface. Both ends have to either be using keepalives or not, with the same timer. You would think that they would checked that, but the symptoms point to that being the problem. Let us know if that's not the case, though. In fact, let us know if you find out that it is the case! Thanks. Priscilla Mossburg, Geoff (MAN-Corporate) wrote: All, I'm having a problem that I don't understand and I was hoping someone out there might be able to give me some insight. I have a 2503 with an HDLC connection on Serial0 going out to my service provider. The running-config is very basic (sanitized, of course): version 11.2 ! ip subnet-zero ! interface Serial0 ip address x.x.x.18 255.255.255.252 keepalive 9 no fair-queue ! interface Serial1 shutdown ! interface BRI0 no ip address shutdown ! router eigrp 100 network 10.0.0.0 ! no ip classless ! bridge 11 protocol ieee end The problem I am having is that the line protocol is bouncing, but neither my provider nor I can find a problem. I have swapped all the cables AND the router, but the problem persists. I noticed that the line protocol goes down for 9 seconds, then is up for 18 seconds, then the cycle repeats. For SG, I lowered the keepalives to 2 seconds; sure enough, the line protocol dropped for 2 seconds, then was up for 4. By removing keepalives altogether, the circuit stays up! What is going on here? Am I missing something painfully obvious? Thanks! Geoff Mossburg Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=62988t=62928 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HDLC, line protocols, and keepalives. [7:62928]
It sure sounds like your service provider isn't using keepalives, i.e. has no keepalive configured on their serial interface. Both ends have to either be using keepalives or not, with the same timer. You would think that they would checked that, but the symptoms point to that being the problem. Let us know if that's not the case, though. In fact, let us know if you find out that it is the case! Thanks. Priscilla Mossburg, Geoff (MAN-Corporate) wrote: All, I'm having a problem that I don't understand and I was hoping someone out there might be able to give me some insight. I have a 2503 with an HDLC connection on Serial0 going out to my service provider. The running-config is very basic (sanitized, of course): version 11.2 ! ip subnet-zero ! interface Serial0 ip address x.x.x.18 255.255.255.252 keepalive 9 no fair-queue ! interface Serial1 shutdown ! interface BRI0 no ip address shutdown ! router eigrp 100 network 10.0.0.0 ! no ip classless ! bridge 11 protocol ieee end The problem I am having is that the line protocol is bouncing, but neither my provider nor I can find a problem. I have swapped all the cables AND the router, but the problem persists. I noticed that the line protocol goes down for 9 seconds, then is up for 18 seconds, then the cycle repeats. For SG, I lowered the keepalives to 2 seconds; sure enough, the line protocol dropped for 2 seconds, then was up for 4. By removing keepalives altogether, the circuit stays up! What is going on here? Am I missing something painfully obvious? Thanks! Geoff Mossburg Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=62935t=62928 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC STAC Compression [7:56073]
I have applied that command on Cisco Router in a live network. It increases bandwidth that 64k to 128 Kbps. I have tested it works by ping response times and file transfer. It really works... Tim Champion wrote: Is anyone out there using STAC compression on HDLC links in a live network? If so what is the maximum speed link you would apply it to and has it brought significant benefits. Many thanks in advance Tim Champion -- Metin YILDIZLI SEKOM Iletisim Sistemleri Fulya Mahallesi Akincibayiri Sokak No:10/1 Mecidiyekvy /ISTANBUL Tel: (90) 212 2889352 Fax: (90) 212 2674961 Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=56075t=56073 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HDLC STAC Compression [7:56073]
What router models did you enable it on, and what sort of traffic goes over the link? -Original Message- From: Metin YILDIZLI [mailto:metin;sekom.com.tr] Sent: 22 October 2002 12:06 To: [EMAIL PROTECTED] Subject: Re: HDLC STAC Compression [7:56073] I have applied that command on Cisco Router in a live network. It increases bandwidth that 64k to 128 Kbps. I have tested it works by ping response times and file transfer. It really works... Tim Champion wrote: Is anyone out there using STAC compression on HDLC links in a live network? If so what is the maximum speed link you would apply it to and has it brought significant benefits. Many thanks in advance Tim Champion -- Metin YILDIZLI SEKOM Iletisim Sistemleri Fulya Mahallesi Akincibayiri Sokak No:10/1 Mecidiyekvy /ISTANBUL Tel: (90) 212 2889352 Fax: (90) 212 2674961 = This email has been content filtered and subject to spam filtering. If you consider this email is unsolicited please forward the email to [EMAIL PROTECTED] and request that the sender's domain be blocked from sending any further emails. = Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=56079t=56073 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC and Routing protocols [7:5739]
Are you treating them as NBMA ??? - Original Message - From: Rizzo Damian To: Sent: Thursday, May 24, 2001 10:49 AM Subject: HDLC and Routing protocols [7:5739] Anyone know why I would have problems with apparently ANY routing protocol over an HDLC point-to-point Link? Works fine with static routes, but when I try to implement any routing protocol (RIP, EIGRP, OSPF, etc..) they don't seem to work (no routes discovered). Am I missing something? Thanks! -Rizzo FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=5743t=5739 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HDLC and Routing protocols [7:5739]
Not to be rude or anything, but did you turn on IP routing? Darel R Graham -Original Message- From: Rizzo Damian [mailto:[EMAIL PROTECTED]] Sent: Thursday, May 24, 2001 10:49 AM To: [EMAIL PROTECTED] Subject: HDLC and Routing protocols [7:5739] Anyone know why I would have problems with apparently ANY routing protocol over an HDLC point-to-point Link? Works fine with static routes, but when I try to implement any routing protocol (RIP, EIGRP, OSPF, etc..) they don't seem to work (no routes discovered). Am I missing something? Thanks! -Rizzo FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Message Posted at: http://www.groupstudy.com/form/read.php?f=7i=5747t=5739 -- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
"Howard C. Berkowitz" wrote: I wasn't aware of that! Thanks. But isn't loop detection also a PPP option? Yes, it's described as part of RFC1661, but it might be a catch-22. The magic number field used for this is optional and must be negotiated. Cisco routers do attempt magic number negotiation and do detect looped paths, and let me check current doc... DO maintain a line protocol up status as long as "down-when-looped" has NOT been configured. So you're quite right -- for Cisco to Cisco, PPP and HDLC will both treat this the same way. OTOH, if the encapsulation were frame-relay or some other, then a loop causes a line protocol down state (e.g., LMI or ILMI polling fails). With Cisco to non-Cisco, particularly Ascend Pipelines, I have seen the magic number negotiation fail, and the Cisco reported a loop condition because the Ascend was echoing back the packet with the Cisco's magic number. But that was a while back. So thanks, Howard, for responding! - Marty At 10:16 PM 2/19/2001 -0500, Marty Adkins wrote: "Howard C. Berkowitz" wrote: HDLC really doesn't offer any advantages over PPP, so it really reflects someone who doesn't want to do minimum reconfiguration of their Ciscos to worry about using PPP for multivendor compatibility. Well, one small advantage is that Cisco's proprietary HDLC keepalive will report a loop condition on the layer 1. And it will also, by default, treat a looped interface as "line protocol up", which is great for testing, using just the router. Marty Adkins Email: [EMAIL PROTECTED] Mentor Technologies Phone: 240-568-6526 133 National Business Pkwy WWW: http://www.mentortech.com Annapolis Junction, MD 20701Cisco CCIE #1289 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
"Howard C. Berkowitz" wrote: HDLC really doesn't offer any advantages over PPP, so it really reflects someone who doesn't want to do minimum reconfiguration of their Ciscos to worry about using PPP for multivendor compatibility. Well, one small advantage is that Cisco's proprietary HDLC keepalive will report a loop condition on the layer 1. And it will also, by default, treat a looped interface as "line protocol up", which is great for testing, using just the router. Marty Adkins Email: [EMAIL PROTECTED] Mentor Technologies Phone: 240-568-6526 133 National Business Pkwy WWW: http://www.mentortech.com Annapolis Junction, MD 20701Cisco CCIE #1289 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
I wasn't aware of that! Thanks. But isn't loop detection also a PPP option? At 10:16 PM 2/19/2001 -0500, Marty Adkins wrote: "Howard C. Berkowitz" wrote: HDLC really doesn't offer any advantages over PPP, so it really reflects someone who doesn't want to do minimum reconfiguration of their Ciscos to worry about using PPP for multivendor compatibility. Well, one small advantage is that Cisco's proprietary HDLC keepalive will report a loop condition on the layer 1. And it will also, by default, treat a looped interface as "line protocol up", which is great for testing, using just the router. Marty Adkins Email: [EMAIL PROTECTED] Mentor Technologies Phone: 240-568-6526 133 National Business Pkwy WWW: http://www.mentortech.com Annapolis Junction, MD 20701Cisco CCIE #1289 _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
PPP uses magic numbers to detect loops. You'll see warnings about receiving your magic #, etc if it detects a loop. The magic number is a optional feature though and every vendor doesn't use it or have it enabled by default. If using BayRS's 'Wellfleet Standard' which is their implementation of HDLC - IP will come up if the circuit/line is looped somewhere. Setting it to HDLC on Cisco or Bay is a good test for pointing problem to carrier when they've tested the line and swear its ok and tests clean. It's also a good way to make sure the cables between the router interface and the CSU/DSU config are good. To prove it's not your equipment you unplug the circuit from the CSU/DSU and IP will go down if your local equipment is functioning/configured fine. Also, HDLC is less picky then PPP usually. Changing the encaps to HDLC may be useful in troubleshooting either a PPP configuration problem or line/circuit issue. If IP comes up and you can ping other end then you have connectivity to the other site - but how good? :) Time to look at the interface stats to see what errors your getting. --- "Howard C. Berkowitz" [EMAIL PROTECTED] wrote: I wasn't aware of that! Thanks. But isn't loop detection also a PPP option? At 10:16 PM 2/19/2001 -0500, Marty Adkins wrote: "Howard C. Berkowitz" wrote: HDLC really doesn't offer any advantages over PPP, so it really reflects someone who doesn't want to do minimum reconfiguration of their Ciscos to worry about using PPP for multivendor compatibility. Well, one small advantage is that Cisco's proprietary HDLC keepalive will report a loop condition on the layer 1. And it will also, by default, treat a looped interface as "line protocol up", which is great for testing, using just the router. __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail - only $35 a year! http://personal.mail.yahoo.com/ _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
On Fri, 9 Feb 2001, Jeremy Dumoit wrote: Getting some good info here.. So cisco has their own implementation of HDLC.. is it compatible with other non-cisco devices (nothing particular in mind here)? What does the control field of a cisco HDLC frame look like? Thanks!!! Several non-cisco manufacturers have reverse engineered the cisco proprietary HDLC and have it working fine..imagestream and redback come to mind... Brian Jeremy _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] --- I'm buying used CISCO gear!! email me for a quote Brian Feeny e:[EMAIL PROTECTED] CCNP+Voice/ATM/Security p:318.222.2638x109 CCDPf:318.221.6612 Network Administrator ShreveNet Inc. (ASN 11881) _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
On Fri, 9 Feb 2001, Jeremy Dumoit wrote: Getting some good info here.. So cisco has their own implementation of HDLC.. is it compatible with other non-cisco devices (nothing particular in mind here)? What does the control field of a cisco HDLC frame look like? Thanks!!! Several non-cisco manufacturers have reverse engineered the cisco proprietary HDLC and have it working fine..imagestream and redback come to mind... Brian There's nothing terribly secret about Cisco's HDLC, and, as far as I know, it's not one of their patented technologies. HDLC really doesn't offer any advantages over PPP, so it really reflects someone who doesn't want to do minimum reconfiguration of their Ciscos to worry about using PPP for multivendor compatibility. Neither PPP nor HDLC is really optimal for very high bandwidth, such as SONET. There are some protocols such as SRP being proposed for running IP over optical. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HDLC
Thats right, cisco hdlc is not compatible with other vendors implemenation of hdlc. An HDLC frame format is shown below: 111 2 variable 2 1 +++++---++-- --+ |flag|addr|ctrl|protocol|data | FCS |flag| |0x7E||0x00|| | |0x7E| +++++---++-- --+ flag = start/end of frame = 0x7E (Other special characters: Idle = 0xFF, Abort = 0x7F) address = this is really a frame type field 0x0F = Unicast Frame 0x80 = Broadcast Frame 0x40 = Padded Frame 0x20 = Compressed Frame Protocol = the Ethernet type of the encapsulated data: 0x0800 = IP 0x6003 = DECnet ... 0x6558 = Bridged Frame 0x8035 = Keepalive Frame 0x80C4 = CDP The bits in the frame (not counting the flag bytes) are 0 bit stuffed to insure that there is never more then 5 1 bits in a row on the wire. Therefore 0xFF, 0xFE, 0xFC, 0x7E, 0x7F, 0x3F bytes could never be in the data portion of the frame - so they are free to be used for start/end framing and other special functions on the wire. /Stuart. -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Jeremy Dumoit Sent: Friday, February 09, 2001 1:45 PM To: [EMAIL PROTECTED] Subject: HDLC Getting some good info here.. So cisco has their own implementation of HDLC.. is it compatible with other non-cisco devices (nothing particular in mind here)? What does the control field of a cisco HDLC frame look like? Thanks!!! Jeremy _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC
Getting some good info here.. So cisco has their own implementation of HDLC.. is it compatible with other non-cisco devices (nothing particular in mind here)? What does the control field of a cisco HDLC frame look like? Thanks!!! Jeremy It's a little unfair to deprecate an "implementation" of HDLC. HDLC, as the standard is written, is much more an architecture for data link protocols than a protocol to be implemented and have multivendor compatibility. LAP, LAP-B, LAP-D, and LAP-F are all HDLC subsets that I would expect to be interoperable. Cisco, Codex/Motorola, Ascom/Timeplex, etc., would have made me much happier if they simply had said they had proprietary link protocols with HDLC-style framing. Remember that PPP wasn't around at the time these protocols were deployed. X.25 LAP (perhaps not LAP-B) was, but, again, link-level retransmission is not necessarily desirable. _ FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
RE: HDLC, SDLC...
I can explain the first three protocols namely hdlc, sdlc, lapb First of all they are all WAN protocols, which is layer 2 protocol for communicating across a WAN link, which protocol to use depends on two factors the WAN technology that you use and the communicating equipment HDLC stands for High-level Data link Control which is the default encapsulation type on point-to-point , dedicated links. It is used typically when communicating bet two CISCO devices. It is a bit oriented synchronous data link layer protocol.HDLC specifies a data encapsulation method on synchronous serial links using frame characters and checksums. If communicating with a non-Cisco device , synchronous PPP is a more viable option SDLC stands for Serial Data Link Control use mainly for SNA networks and lapb Link Access Procedure, Balanced is for X.25 links Jason -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of perez claude-vincent Sent: Wednesday, September 06, 2000 1:46 PM To: [EMAIL PROTECTED] Subject: HDLC, SDLC... Dear all, I am a little bit confused about the difference of framing between hdlc, sdlc, lapb, lapd, llc2. Can someone help me? Thank you, cvp. __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC, SDLC...
They are all based on the original work done by IBM for SDLC. SDLC uses a complicated master-slave scheme that is not used in the other protocols. However, the fields in all of the frames of the protocols mentioned were basically derived from a special case of the SDLC protocol. Regards, MLC perez claude-vincent [EMAIL PROTECTED] wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Dear all, I am a little bit confused about the difference of framing between hdlc, sdlc, lapb, lapd, llc2. Can someone help me? Thank you, cvp. __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC, SDLC...
These are all Layer 2 protocols. This site has some very good explanations of the differences. http://www.sangoma.com/tutorial.htm LLC2 = IEEE 802.2 Logical Link Control Type 2. Used by SNA and NetBIOS on a LAN. Frame Format: http://www.protocols.com/pbook/lan.htm#LLC LAPD = Access protocol on ISDN D channel. Ensures error free transmission. Frame Format: http://www.protocols.com/pbook/isdn.htm#LAPD HDLC = Sets the framing structure for synchronous communications and is responsible for the error-free movement of data between network nodes. There are two different implementations of HDLC, HDLC NRM (also known as SDLC) and HDLC LAPB. NRM is MAster/slave. LAPB is peer-to-peer. Frame Format: http://www.protocols.com/pbook/x25.htm#HDLC LAPB = CCITT adaptation of HDLC. Used to carry X.25 commands and control frames. Supports full-duplex operations and is peer-to-peer (neither end plays the role of master on a permanent basis). Frame Format: http://www.protocols.com/pbook/x25.htm#LAPB SDLC = Developed by IBM. Performes the layer 2 functions of the SNA hierarchy. SDLC is virtually identical to HDLC Normal Response Mode and was developed to replace the Bisynchronous protocol for WAN connections between IBM equipment. Primarily half-duplex but is capable of supporting full-duplex. Not a peer-to-peer protocol like HDLC/LAPB, X.25, and Frame-Relay. Frame Format: http://www.protocols.com/pbook/sna.htm#SDLC Nope this helps, Karen E Young Network Engineer ELF Technologies, Inc [EMAIL PROTECTED] perez claude-vincent To: [EMAIL PROTECTED] claude_vincent@cc: yahoo.com Subject: HDLC, SDLC... Sent by: nobody@groupstud y.com 09/05/2000 10:46 PM Please respond to perez claude-vincent Dear all, I am a little bit confused about the difference of framing between hdlc, sdlc, lapb, lapd, llc2. Can someone help me? Thank you, cvp. __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
Re: HDLC, SDLC...
Another thing to keep in mind is that Cisco does not use a standard HDLC header. That's why PPP is recommended for interoperability with non-Cisco devices. Cisco doesn't take advantage of any of the reliability features of standard HDLC, and Cisco added a field to the header to identify the next layer up, such as IP, DDP, DECnet, etc. Cisco's HDLC has been discussed many times on this list, so check the archives for more details. Priscilla At 05:34 AM 9/6/00, michael champion wrote: They are all based on the original work done by IBM for SDLC. SDLC uses a complicated master-slave scheme that is not used in the other protocols. However, the fields in all of the frames of the protocols mentioned were basically derived from a special case of the SDLC protocol. Regards, MLC perez claude-vincent [EMAIL PROTECTED] wrote in message [EMAIL PROTECTED]">news:[EMAIL PROTECTED]... Dear all, I am a little bit confused about the difference of framing between hdlc, sdlc, lapb, lapd, llc2. Can someone help me? Thank you, cvp. __ Do You Yahoo!? Yahoo! Mail - Free email you can access from anywhere! http://mail.yahoo.com/ ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED] Priscilla Oppenheimer http://www.priscilla.com ___ UPDATED Posting Guidelines: http://www.groupstudy.com/list/guide.html FAQ, list archives, and subscription info: http://www.groupstudy.com Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
