Which Network Package Support Hdlc?

The supported protocol standards in HDLC analyzer are LAPF, LAPD, LAPD+IP, LAPX+IP, X. 25, Cisco HDLC Protocols.

Supported Protocols.

Supported Protocols Specification Used
SNMP RFC 1157,1155,1902,3416,2863,2578,3418,2011,2012 etc
LAPB, X.25 ITU-T Recommendation X.25
Cisco HDLC
ARP RFC 826

What is HDLc in networking?

HDLC is a data link protocol used on synchronous serial data links. HDLC cannot support multiple protocols on a single link because it lacks a mechanism to indicate which protocol it is carrying. The Cisco version of HDLC uses a proprietary field that acts as a protocol field.

What is HDLC frame format?

HDLC is a group of data link (Layer 2) protocols used to transmit synchronous data packets between point-to-point nodes. Data is organized into addressable frames. This format has been used for other multipoint-to-multipoint protocols, and inspired the HDLC-like framing protocol described in RFC 1662.

Can HDLC support multiple protocols on a single link?

HDLC cannot support multiple protocols on a single link because it lacks a mechanism to indicate which protocol it is carrying. The Cisco version of HDLC uses a proprietary field that acts as a protocol field.

What is HDLC in networking?

HDLC (High-level Data Link Control) is a group of protocols or rules for transmitting data between network points (sometimes called nodes). In more technical terms, HDLC is a bit-oriented, synchronous data link layer protocol created by the International Organization for Standardization (ISO).

Is HDLC a WAN connection type?

HDLC stands for High-Level Data Link Control protocol. Like the two other WAN protocols mentioned in this article, HDLC is a Layer 2 protocol (see OSI Model for more information on Layers). HDLC is a simple protocol used to connect point to point serial devices.

Where is HDLC protocol used?

HDLC is commonly used in leased-line connections in which the WAN link’s endpoints are terminated with CSU/DSUs (Channel Service Unit/Data Service Units) connected to Cisco routers running Internetwork Operating System (IOS). Routers and access servers from other vendors often use PPP instead of HDLC.

How does Cisco implement HDLC?

Cisco HDLC frames uses an alternative framing structure to the standard ISO HDLC. To support multiple protocols encapsulation, cHDLC frames contain a field for identifying the network protocol.

What is HDLC frame packet?

High-level Data Link Control (HDLC) is a group of communication protocols of the data link layer for transmitting data between network points or nodes. Since it is a data link protocol, data is organized into frames. A frame is transmitted via the network to the destination that verifies its successful arrival.

Is HDLC used today?

HDLC can be used for point-to-multipoint connections via the original master-slave modes Normal Response Mode (NRM) and Asynchronous Response Mode (ARM), but they are now rarely used; it is now used almost exclusively to connect one device to another, using Asynchronous Balanced Mode (ABM).

Which encapsulation is used in connecting Cisco devices?

The default encapsulation type for synchronous serial interfaces on a Cisco device is HDLC. If the default configuration has been changed, you can still modify the encapsulation type of a serial interface with encapsulation hdlc interface configuration command.

What are the LAN protocols?

Some of the most common LAN protocols are ‘Ethernet,’ ‘Token Ring’ and ‘Fiber Distributed Data Interface,’ or ‘FDDI.’ ‘Ethernet’ is by far the most common type of LAN protocol. It is found in homes and offices throughout the world and is recognizable by its common ‘CAT5’ copper cable medium.

Is DSL a WAN?

No, a DSL port connects to a Cable Internet connection. a WAN port is an Ethernet networking port.

Is HDLC Cisco proprietary?

Yes – the Cisco version of HDLC is indeed cisco proprietary and won’t run with any other vendors. There are other vendors out there that actually supports HDLC, but you won’t be able to run them towards a Cisco-device.

What are the three frame types supported by HDLC describe each?

These three different classes of frames used in HDLC are given below.

  • I-frame : I-frame stands for Information frames. This frame is generally used for transporting user data from network layer.
  • S-frame : S-frame stands for Supervisory frames.
  • U-frame : U-frame stands for Unnumbered frames.
  • Why is HDLC used in WAN?

    HDLC is a simple protocol used to connect point to point serial devices. For example, you have point to point leased line connecting two locations, in two different cities. HDLC would be the protocol with the least amount of configuration required to connect these two locations.

    Which field was added by Cisco to the HDLC frame?

    Cisco’s HDLC has both the Control field and a proprietary field that identifies the layer 3 protocol.

    What are the two types of encapsulation methods on a serial link?

    One of the options to encapsulate traffic across the serial connection is HDLC (High-Level Data Link Control). Although supporting point-to-point and multipoint configurations, HDLC and its Cisco implementation is the default encapsulation for serial lines and only point-to-point connections are allowed.

    What is HDLc in networking?

    HDLC is a data link protocol used on synchronous serial data links. HDLC cannot support multiple protocols on a single link because it lacks a mechanism to indicate which protocol it is carrying. The Cisco version of HDLC uses a proprietary field that acts as a protocol field.

    What is HDLC frame format?

    HDLC is a group of data link (Layer 2) protocols used to transmit synchronous data packets between point-to-point nodes. Data is organized into addressable frames. This format has been used for other multipoint-to-multipoint protocols, and inspired the HDLC-like framing protocol described in RFC 1662.

    Can HDLC support multiple protocols on a single link?

    HDLC cannot support multiple protocols on a single link because it lacks a mechanism to indicate which protocol it is carrying. The Cisco version of HDLC uses a proprietary field that acts as a protocol field.

    CCNA Certification: Configuring HDLC and PPP Encapsulation.doc

    In preparation of your CCNA exam, we want to make sure we cover the various concepts that we could see on your Cisco CCNA exam.So to assist you, below we will discuss one of the more difficult CCNA concepts; Configuring HDLC and PPP Encapsulation.doc.As you progress through your CCNA exam studies, I am sure with repetition you will find this topic becomes easier.So even though it may be a difficult concept and confusing at first, keep at it as no one said getting your Cisco certification would be easy! Configuring HDLC and PPP Encapsulation
     
    HDLC is a data link protocol used on synchronous serial data links. HDLC cannot support multiple protocols on a single link because it lacks a mechanism to indicate which protocol it is carrying.
    The Cisco version of HDLC uses a proprietary field that acts as a protocol field. This field makes it possible for a single serial link to accommodate multiple network-layer protocols. Cisco’s HDLC is a point-to-point protocol that can be used on leased lines between two Cisco devices. PPP should be used when communicating with non-Cisco devices.To change the encapsulation back to HDLC from some other protocol, use the following command from interface configuration mode: Router(config-if) encapsulation hdlc
     
    PPP Encapsulation
    PPP uses a Network Control Protocol (NCP) component to encapsulate multiple protocols and uses Link Control Protocol (LCP) to set up and negotiate control options on the data link.
     
    PPP Configuration Options
    Cisco routers using PPP encapsulation include the LCP options shown in the following table.
    1. The Password Authentication Protocol (PAP) and the Challenge Handshake Authentication Protocol (CHAP) are two authentication protocols to choose from.
    2. The use of compression settings on PPP connections increases the effective throughput.
    3. The quality and magic number options, which are used for error detection, help to ensure a dependable and loopfree data link.
    4. Cisco IOS Release 11.1 and later versions include support for multilink. It increases throughput while simultaneously decreasing latency between peer routers.
    5. PPP callback is supported in Cisco IOS Release 11.1 and later. It provides a higher level of security. In response to receiving the initial DDR call, the router requests that it be called back and then terminates the call.
     
    Establishing a PPP Session
    The three phases of PPP session establishment are link establishment, authentication, and network protocol.
    1. In order to configure and test the data link, each PPP device transmits LCP packets to the other devices in the PPP network. The negotiation of options such as the maximum receive unit, compression, and connection authentication occurs here. When there are no figures available, default values are assumed.
    2. Optional authentication—After the link has been created, the peer can be verified by entering his or her credentials.
    3. Network layer protocol (NCP) packets are used to choose and configure network layer protocols at the network layer level of abstraction. After they have been setup, the network layer protocols can begin transmitting datagrams over the network.
     
    PPP Authentication Protocols
    PPP Authentication Protocol is a simple two-way handshake that’s used to establish a remote node’s identity. It takes place after the PPP link is established. The remote node repeatedly sends its username and password to the router until authentication is acknowledged or the connection is terminated. CHAP is a three-way handshake that takes place at link startup and periodically throughout the session to verify the remote node’s identity. After the PPP link is established, the local router sends a challenge message to the remote node. The remote node responds with a calculated value (typically, an MD5 function is used). The local router checks the response against its own calculated value. If the values match, the authentication is acknowledged. Otherwise, the connection is terminated immediately.
     
    How Secure Is PAP/CHAP?
    With PAP, passwords are sent across the link without encryption or protection against trial-and-error attacks. This level of security is usually sufficient for token-type passwords that change with each authentication. CHAP uses unpredictable challenge values, which limit exposure to attacks. Local router or authentication servers (TACACS) control the challenges’ frequency and timing.
     
    PPP Encapsulation and Authentication Overview
    You must do the following before enabling PAP or CHAP:
    1. Link establishment—Each PPP device sends LCP packets to setup and test the data link established by the other PPP devices. Options such as the maximum receive unit, compression, and connection authentication are all negotiated in this section of the contract.. When there are no figures available, default values are taken.
    2. Optional authentication—After the link has been established, the peer can be verified by entering his or her password.
    3. Network layer protocol (NCP) packets are used to choose and configure network layer protocols at the network layer level of the protocol stack. After they have been setup, the network layer protocols can begin transmitting datagrams across the channel.
    Here’s a CHAP configuration example:
    RouterA>enable
    RouterA config term
    RouterA(config) hostname CiscoKits
    RouterA(config) username cisco password ccna
    RouterA(config) interface serial 0
    RouterA(config-if) encapsulation ppp
    RouterA(config-if) ppp authentication chap
    RouterA(config-if) exit
    RouterA(config) exit
    RouterA show interface s0
     
    The password must be the same for both routers using CHAP.To encrypt passwords, enter the service password-encryption command while in global configuration mode.
     
    Configuring HDLC and PPP Encapsulation Summary
    1. Link establishment—Each PPP device sends LCP packets to configure and test the data link established by the other PPP device. Options like as the maximum receive unit, compression, and connection authentication are all negotiated in this section of the protocol.. When no figures are supplied, default values are assumed.
    2. Authentication (optional)—After the link has been established, it is possible to authenticate the peer.
    3. Network layer protocol (NCP) packets are used to choose and configure network layer protocols at the network layer layer level. The network layer protocols can begin transmitting datagrams across the connection after they have been setup.
     
    Continue on to the Implementing Subnet Planning Article
     

    Overview

    • The HDLC protocol is a data link layer protocol that operates at the data link layer. A data frame is encoded with information using the HDLC protocol, which allows for data flow control and error correction. Each flag is made up of eight bits – one for each color (01111110). A Frame Check Sequence (FCS) is utilized at the conclusion of each frame to ensure that the data is not corrupted in any way. A cyclic redundancy check (CRC), also known as a forward error correction (FEC), is computed by using the polynomial x16 + x12 + x5 + 1 (FCS 16 bits) or x0+x1+x2+x4+x5+x7+x8+x10+x11+ x12 + x16 + x22+ x23+ x26+x32 (FCS 32 bits) (FCS 32 bits). Only flags are present during idle times in the data channel. The HDLC protocol analyzer from GL has the capacity of capturing and analyzing HDLC data over a full duplex T1 or E1 line in real time. The data channel may make use of the whole T1 or E1 line or only a portion of the line. T1 or E1 lines may have numerous data channels, which might complicate things further. After configuring the HDLC data channel settings and initiating the decoding process, the main screen displays the HDLC frames that have been received in hex format, as seen below. The flags are removed, and all other data, including the CRC bytes, is shown. HDLC analyzers from the following manufacturers are supported by GL Communications: Prerequisites: GL’s field-proven E1 or T1 internal cards or USB Laptop E1 or T1 external units, as well as the required licenses and Windows XP (or higher) operating system
    • Remote/Offline HDLC Analyzer (Prerequisites: Hardware Dongle and Windows XP (or higher) operating system)
    • Real-time HDLC Analyzer (Prerequisites: GL’s field-proven E1 or T1 internal cards or USB Laptop E1 or T
    • In addition, the HDLC applications listed below are supported, which aid in the transmission and capture of pre-defined HDLC frames even more effectively: A number of tools are available, including HDLC Playback, HDLC Impairment Utility, HDLC Tx RxTest Application, and automated HDLC testing using a client-server architecture.

    HDLC Analyzer Main Features

    • Displays the Summary, Detail, Hex dump, Statistics, and Call Detail Views
    • the contents of this view may be copied to the clipboard
    • this view also displays the Hex dump View.
    • In the Summary View, you can see information about the timeslots, sub channels, frames, and devices as well as LAPD and LAPF specific information as well as IP information such as source/destination IP addresses, TCP source ports, and TCP destination ports.
    • X.25, Cisco HDLC protocols are supported for decoding as well as LAPF, LAPD+IP, LAPX+IP, and LAPD+IP+IP.
    • The Detail View displays decodes of user-selected frames from the Summary View
    • the Summary View provides decodes of all frames.
    • This view, which provides statistics for the whole collected data set, includes frame count, byte count, frames/sec, bytes/sec, and other metrics.
    • Viewing the frame information in HEX and ASCII forms is possible using Hex dump View. It is also possible to copy the contents of this view to the clipboard.
    • Filtering and searching capabilities are supported based on C/R, SAPI, TEI, CTL, P/F, N(S), N(R), and FUNC
    • and
    • Any protocol field may be included in the summary view, filtering, and search tools, giving users greater freedom in monitoring the protocol fields that are important to them.
    • It is possible to export information from the Summary View details to a comma-delimited file for further import into a database or spreadsheet.
    • Exporting comprehensive decode information to an ASCII file is a feature available.
    • The status bar displays information such as the running % usage, the number of frames taken, CRC errors, and frame faults, among other things.
    • Option to construct several aggregate column groups and prioritize the groupings according to the requirements in order to present the summary results as effectively as possible
    • Enables users to construct search/filter criteria automatically based on the selections made on the current screen
    • With the help of GL’s Network Surveillance System, remote monitoring is possible.

    Additional features supported by Real-time/Remote HDLC Analyzer:

    • You can capture streams on the designated time slots (contiguous or non-contiguous), sub-channels, or the whole bandwidth allocated to the capture. Frames may also be stored in one, n x 64 kbps, or n x 56 kbps data channels
    • however, this is not the case.
    • Other variants supported by the program include inverted or non-inverted data, byte reversal or non-reversal, and byte reversal or non-reversal.
    • The real-time capture filter can be used to filter frames based on the duration of each frame.
    • With several GUI instances, it is possible to decode multiple streams of HDLC communication on various T1/E1 channels at the same time.
    • The decoding of frames with FCS of 16 bits and 32 bits, as well as none, may be accomplished.
    • By utilizing the HDLC Transmit/Receive/Playback program, it is possible to later use the captured frames for traffic simulation.
    • A single T1/E1 server can be accessible by several distant clients at the same time, and the T1/E1 server remains fully functioning while being accessed as a server. This allows users to do T1/E1 operations locally on the server while a client is visiting the same server in real time (only for Remote Analyzers)
    • and

    Additional features supported by Offline HDLC Analyzer:

    • You can capture streams on the designated time slots (contiguous or non-contiguous), sub-channels, or the whole bandwidth allocated to the stream. It is also possible for frames to be carried in one or more data channels, each of which can be either one or two 64 kbps or 56 kbps.
    • The program also accommodates other variants such as inverted or non-inverted data, as well as byte reversal or non-reversal
    • and so on.
    • Frame length can be filtered out using the real-time capture filter, which can be configured.
    • With distinct GUI instances, it is possible to decode several streams of HDLC communication on various T1/E1 channels at the same time.
    • The decoding of frames with FCS of 16 bits and 32 bits, as well as none, may be achieved.
    • Using the HDLC Transmit/Receive/Playback program, captured frames can be utilized for traffic simulation in the future.
    • If a single T1/E1 server is being used to serve several distant clients at the same time, the T1/E1 server continues to work normally. This allows users to do T1/E1 operations locally on the server while a client is visiting the same server in real time (only for Remote Analyzers).

    Supported Protocols

    In the following section, you will find a description of the protocols that the GL HDLC analyzer supports: The following protocol standards are supported by the HDLC analyzer: LAPF, LAPD, LAPD+IP, LAPX+IP, X.25, Cisco HDLC Protocols, and more.

    Supported Protocols Specification Used
    LAPD CCITT Q.920/921
    LAPF ITU-T Q.922
    IP RFC 791
    TCP RFC 793
    UDP RFC 768
    ICMP RFC 792
    STUN RFC 3489
    DNS RFC 1035
    DHCP RFC 1533, 2131
    HTTP RFC 2616
    FTP RFC 959
    SNMP RFC 1157,1155,1902,3416,2863,2578,3418,2011,2012 etc
    LAPB, X.25 ITU-T Recommendation X.25
    Cisco HDLC
    ARP RFC 826

    Summary, Detail and Hex dump Views

    A description of the protocols supported by GL’s HDLC analyzer can be found below. The HDLC analyzer supports the following protocol standards: LAPF, LAPD, LAPD+IP, LAPX+IP, X.25, and Cisco HDLC Protocols.

    Real-time/Remote and Offline Analysis

    Users may capture and analyze multiple HDLC links using real-time or remote analyzers, and they can record all or filtered data into a trace file for further analysis.In addition to being utilized for offline analysis, the recorded trace file may also be exported as a comma-delimited or ASCII file.The user must select the following parameters for doing real-time capturing: time slot(s), bit inversion, octet bit reversion, user/network side, FCS, and data transfer rate.The HDLC File Playback option allows a recorded trace file to be broadcast back on T1/E1 utilizing the HDLC File Playback option.Users can evaluate data acquired by fractional DS0 and DS1 links, respectively, using the sub channel and N x 56 hyper channel technologies.

    Filtering and Search

    Using the current screen option, the user may define search and filter criteria that are automatically generated from the traffic being recorded or filtered into a trace file.The HDLC analyzer’s filter and search tools add a strong dimension to its capabilities, allowing it to isolate needed frames from the collected frames in real-time, remotely, or off-line situations.Users can define custom frame lengths to filter frames during real-time capture by entering arbitrary values in the frame length field.After the capture has been completed, the frames can be filtered according to the following criteria: CTL, C/R, Modifier Function, N(R), N(S), P, P/F, SAPI, Supervisory function, and TEI.Similar to this, the search feature allows the user to look for a certain frame based on a set of specified search parameters.

    Aggregate Column Group

    Column Group for Aggregate Summary Information The aggregate column groups function of the protocol analyzer is a new feature that has been included.In addition, the user may construct several aggregate column groups and prioritize the groups according to the requirements in order to present the summary results in the most efficient manner.In the Summary View, the Aggregate Column Group is displayed.The most recent results are listed in the table below.The root aggregate group0 summary columns are presented first, followed by Group1 and Group2 in the order of the priority assigned to each group.

    Statistics View

    An essential aspect of the HDLC analyzer is the availability of statistics, which can be retrieved for all frames in both real-time and offline modes. The performance and trend of the HDLC network may be studied using several statistics derived from the protocol fields and other factors.

    Enhanced Trace Saving Options

    It is possible for users to control the captured trace files by storing the trace using a variety of standards, such as trace files with user-defined prefixes, trace files with date-time prefixes, and a slider control to show the total number of files, file size, frame count, and time limit.A trace file may be created using this functionality, and the recorded frames can be stored into it depending on the filtering criteria established using the display filter function.

    Save/Load All Configuration Settings

    The Protocol Configuration window serves as a centralized interface for all of the critical settings that must be made in the analyzer to function properly.The choices available include protocol selection, starting parameters, stream/interface selection, filter/search criteria and many more.By using this GUI, any protocol field may be added to the summary view, filtering, and search functions, giving users greater freedom in monitoring the protocol fields that are important to them.In any of these choices, the configuration settings made can be saved to a file, imported from a configuration file, or the user can simply reset all of their settings to their original values by selecting the default option.

    Automated HDLC Testing using Client-Server

    • The usage of GL’s Windows Client/Server software provides users of T1/E1 analysis cards with the ability to operate their cards from a remote location, automate their operations, and connect to many sites. The Server software may do many tasks at the same time when requested to do so by the Client program. GL includes HDLC capture, playback, emulation, and analysis components that operate on a client-server architecture. WCS modules XX640 and XX641-File-based HDLC recording and playback, as well as remote recording and playback File-based HDLC Record/Playback (Hdlcfunc) is an optional program that provides HDLC traffic capture and replay. It also enables for the transmission and receipt of *.HDL frames files that are stored on both the server and the client computer. Features When receiving HDLC frames in HDL files on the server, the command syntax is displayed. When transmitting HDLC frames from an HDL file that is on the server, the command syntax is displayed. When receiving HDLC frames on the client, the command syntax is displayed. When transmitting the command syntax is displayed, the command is displayed.

    For further information on this application, please see the link below.Multi-channel HDLC emulation and analysis; file-based high throughput HDLC recording and playback are all features of the WCS module XX634.The HDLCTerr module emulates and analyzes multi-channel high-density liquid chromatography (HDLC).Additionally, it allows for the transmission of memory produced sequences of fixed or variable length HDLC frames, GL *.HDL Trace file frames, and a variety of bandwidth streams.The HDLCHpio module is responsible for HDLC recording and playback activities that are performed on files.It allows for the reception and transmission of HDLC streams with varying bandwidth (hyper channel, timeslot, and multiple sub-channel streams per timeslot).

    Please see this link for further information on these applications.

    Bridge and Monitor Connections

    • Monitor from a DSX-Patch Panel
    • Bridge Mode Connections for Monitoring T1/E1 Signals for RJ-45
    • Alternative Method for Bridge Mode Connections
    • RJ-45 Connections

    Resources:

    Please keep in mind that the XX in the Item No.refers to the hardware platform, which can be found at the bottom of the Buyer’s Guide, on which the program will be executing.As a result, depending on the hardware, XX can beETA or EEA (Octal/Quad Boards), PTA or PEA (tProbe Units), UTA or UEA (USB Units), HUT or HUE (Universal Cards), HDT or HDE (HD cards), and HDT or HDE (High Definition Cards).Return to the Index Page for Protocol Analysis

    Table Of Contents

    Detailed Description of High-Level Data Link Control Technology Objects from the HDLC Information Model (IMOs) HDLC Encapsulation Vendor-Specific Inventory and IMOs Service Alarms for HDLC Encapsulation

    High-Level Data Link Control

    The following sections of this chapter explain the amount of support that Cisco ANA offers for HDLC: Description of the technology Objects of the Information Model (IMOs) Inventory specific to each vendor, as well as IMOs service alarms

    Technology Description

    Please refer to Part 1: Cisco VNEs in this handbook for information on which devices are capable of supporting the various technologies.

    HDLC

    HDLC is a collection of data connection (Layer 2) protocols that are used to send synchronous data packets between nodes that are located close to one another.Data is arranged into addressable frames, which are then addressed.This format has been used for numerous multipoint-to-multipoint protocols, and it was the inspiration for the HDLC-like framing protocol specified in RFC 1662, which was later adopted.HDLC employs a zero-insertion/delete operation (bit stuffing) to guarantee that the bit pattern of the delimiter flag does not exist in the fields between the flags in the delimiter flag set.The HDLC frame is synchronous, and as a result, it is dependent on the physical layer (Layer 1) to clock and synchronize the transmission and receipt of frame transmission and reception.

    Information Model Objects (IMOs)

    Here’s a rundown of everything you should know about IMO: HDLC Encapsulation (IEncapsulation)

    HDLC Encapsulation

    The data link layer HDLC Encapsulation object is tied to an ATM/Frame Relay VC Multiplexer object via the Containing Termination Points attribute of the HDLC Encapsulation object.It is accessed primarily through a network layer object, such as the IP Interface, which is constrained by the Contained Connection Termination Points attribute of its Contained Connection Termination Points attribute.

    Table 24-1 HDLC Encapsulation (IEncapsulation)

    Attribute Name Attribute Description Scheme Polling Interval
    Virtual Connection Virtual connection Any Configuration
    Binding Information Binding information (User Name,.) Any Configuration
    Binding Status Binding status (Not Bound, Bound) Any Configuration
    IANA Type Internet Assigned Numbers Authority (IANA) type of the sublayer N/A N/A
    Containing Termination Points Underlying termination points (connection or physical) Any N/A
    Contained Connection Termination Points Bound connection termination points Any N/A

    Vendor-Specific Inventory and IMOs

    This technology does not have a vendor-specific inventory or IMOs at this time.

    Service Alarms

    In the case of this technology, there is no vendor-specific inventory or IMO.

    WAN Technologies – HDLC, PPP, Frame Relay and Ethernet

    • This technology does not have a vendor-specific inventory or IMOs.

    It is common for the technology you choose to be determined by your requirements as well as the services provided by your service provider. MPLS (Multi-Protocol Label Switching) is a typical alternative to the technologies listed above for transporting data over a service provider’s network.

    Leased Line WAN

    For businesses with several locations, we must employ a wide area network (WAN) to connect the LANs at each location.Broadband wide area networks (WANs), which are sometimes known as leased lines or circuits, are services supplied by telecommunications companies (telcos) to businesses (the client).The service provider provides the physical, layer 1 point-to-point connectivity between sites, and it is the responsibility of the devices at the edge of each site to ensure that data is sent between them in a suitable manner.Every client site will have ‘Customer Premises Equipment,’ which will normally consist of a router with a serial interface card and a Channel Service Unit / Data Service Unit (CSU/DSU) – these may be combined into a single physical device – as well as other network components.Data will be sent through the service provider’s network to another CPE belonging to the firm through a dedicated link to a telco ‘Point of Presence’ (PoP) established by the CPE.In the case of an IP packet with a destination address that is assigned to another host at a different site on the WAN, the packet will be routed through the local router before being sent elsewhere.

    The packet will be de-encapsulated by the router at the edge of a site’s LAN, which will read and remove the Ethernet header and trailer from the packet.For transmission across the wide area network, it will encapsulate each packet using one of the link-layer methods listed below.

    HDLC

    HDLC is a data connection layer protocol specified by the International Organization for Standardization (ISO) that is most often used for point-to-point links.HDLC is a protocol developed by the International Organization for Standardization (ISO) that is most commonly used for point-to-point links.An HDLC frame is similar to an Ethernet frame in that it contains the following information: An 8-bit flag that is used to indicate the start of a new frame.Even though HDLC is often only used for point-to-point communications with a single address, the address (8+ bits) indicates the destination address in the case of multi-hop links.In today’s world, control is only utilized in 8 or 16-bit formats.Informaton (variable) – the data that will be sent, which is typically in multiples of 8 bits.

    FCS (16 or 32 bits) — A frame check sequence that uses CRC (Cyclic Redundancy Check) to discover data issues in a frame.One major disadvantage of HDLC is that there is no field defined to indicate the layer three protocol that has been wrapped.This is a significant disadvantage.As a result, various more protocols that are based on HDLC have been developed.A proprietary Cisco implementation, for example, incorporates a 16-bit type field to distinguish between different types of data wrapped.

    Point-to-Point Protocol

    PPP is a non-proprietary protocol specified by the Internet Engineering Task Force (IETF) in RFC 1661 that may be used on point-to-point networks. PPP is a protocol that is comprised of three fundamental components:

    1. HDLC (RFC 1662), Ethernet (PPPoE), or ATM (PPPoA) are examples of encapsulation protocols.
    2. In order to create and preserve the configuration of the connection until its termination, a Link Control Protocol (LCP) must be used
    3. Network Control Protocols (NCP) are used to assist particular settings of the network layer. The PPP Internet Protocol Control Protocol (IPCP) is an example of a network protocol that supports IP
    4. for example,

    When customers utilize Digital Subscriber Lines (DSL) to connect to the internet, PPP is frequently employed.

    Frame Relay

    Frame Relay, in contrast to HDLC and PPP, does not necessitate the use of a dedicated point-to-point link because it is a packet-switched technology.This eliminates the need for specific leased lines, which allows for more cost-effectiveness as a wide area network (WAN) technology.When compared to traditional communications systems, Frame Relay makes use of ″virtual circuits,″ which can be either Permanent Virtual Circuits (PVCs) or Switched Virtual Circuits (SVCs), instead of a real ″circuit″ (SVCs).In today’s world, PVCs are the most often utilized, with specialized mappings created by a service provider to connect the sites of each client.

    Carrier Ethernet

    Carrier Ethernet is an umbrella name for the deployment of wide area networks (WANs) utilizing Ethernet technology; it has also been referred to as Metro Ethernet.Customers can utilize Ethernet as a wide area network (WAN) between themselves and the service provider.Ethernet WAN services, at its most basic level, allow routers at the perimeter of a customer’s LAN to communicate with one another by sending frames between them using conventional Ethernet frames — the routers simply transmit frames to the MAC address of an interface on the destination router.Ethernet over MPLS (EoMPLS) is a technology that service providers may utilize to deliver this type of service to their customers.

    HDLC SDLC DATA OVER IP DATA NETWORKS

    IP Tube RS232 Technical Specifications
    LAN Network Interface: Two 10/100BaseT Full/Half Ethernet LAN Network Protocols Supported: IP, TCP, UDP, ICMP, Telnet, DHCP, DDNS, SSH RS232 Interfaces: 1-4 Sync/HDLC/Async, DCE/DTE RS232: 1 to 2 DB25M; DB60F connectorsupports 1 to 2 RS232s with DB25M adaptor cables DTR Controllable TransmissionCD Reception Indicator RS232 Interface Clocking: Synchronous: 75 to 256 Kilobits per seconds Asynchronous: 2.4/4.8/9.6/19.2/38.4 Kilobits per second RS232 Interface Control Signal Extension: Full On Emulation of DCE to DTE control signals: DTR; DSR; RST; CTS RS232 Over IP Protocol: TDM Over IPCircuit Extension Services Over IPHDLC Over IP WAN Network Protocols Supported: HDLC, SDLC, PPP, Frame Relay Regulatory: CESafety -IEC60950EMC – CFR 47 Part 15 Sub Part B:2002, EN55022:1994+A1&A2, EN55024, ICES-003 1997, CISPR 22 Level A Management: Secure Socket Shell – SSH Telnet support with Edit and Paste Template Files Console Port for Out of Band Management SNMP Public and Private MIB support with configured traps Quality of Service Support: IP Type of Service (TOS) CLI configurable IANA Registered UDP Port 3175 802.1p/q mac level prioritization TFTP Online Upgrade Capable (FLASH ROMs) IPTube is fully operational during upgrade Dimensions: Dimensions: 9″ (L) x 7.3” (W) x 1.50” (H) Environmental: 0° to 132° F (-10° to 50°C) operating temperature Up to 90% operating humidity (non-condensing) Optional Extended Temperature Range available Power: 12-30 VDC, 1.0A.Screw Locking Connector Universal Adapter 100/240 VAC 50/60 Hz Optional -48V 0.25 AmpHot Standby

    Overview

    • The Synchronous Data Link Control (SDLC) protocol is the earliest layer 2 protocol, having been developed by IBM in 1975 to handle traffic related to the Systems Network Architecture (SNA) (see later). SDLC is considered to be the precursor to HDLC.
    • The International Organization for Standardization (ISO) developed High-Level Data Link Control (HDLC) out of SDLC in 1979 (see later)
    • The Qualified Logical Link Control (QLLC) protocol was developed by IBM to enable SNA traffic over X.25
    • the Link Access Protocol Balanced (LAPB) protocol is one of the three layers that make up X.25 and was developed by the International Telecommunications Union (ITU-T) as a development of LAP, which itself was derived from HDLC.
    • However, unlike HDLC, LAPB is constrained to the use of the ABM transfer mode, which is point-to-point connections only (as discussed below).
    • LAPM provides HDLC services for V.42 modems
    • LAPD is used on the ISDN D channel to deliver packets
    • V.120 is used on ISDN Terminal Adapters to allow multiple users to communicate over a single link
    • and V.120 is used on the ISDN Terminal Adapters to allow multiple users to communicate over a single link.
    • Logical Link Control (LLC) is a protocol designed by the IEEE 802.2 and used to offer HDLC-style services over a local area network (see below).
    • Some of the operations of Frame Relay are similar to those of LAPD and V.120
    • PPP is a derivation of HDLC that encapsulates Protocol Data Units for transport across point-to-point lines
    • and TCP/IP is a derivation of TCP/IP.

    Synchronous Data Link Control (SDLC)

    • SDLC was invented by IBM before HDLC, despite the fact that it is a subset of HDLC. SDLC was the first link layer protocol to be based on synchronous, bit-oriented operation. When synchronous serially transmitted bits are sent across a data link, the SDLC is used to manage them. Data lines can be full/half-duplex, switched or unswitched, single-point, multipoint, or even looping. SDLC is intended for the transmission of SNA communications. In the SDLC, a link station is a logical connection that connects two nodes that are physically adjacent. On an SDLC line, only one Primary Link Station is permitted at a time. A device can be configured as either a Primary or a Secondary link station, depending on its function. A device set as a Primary link station is capable of communicating with both PU 2.0 nodes and PU 2.1 nodes (APPN), as well as controlling the secondary devices in the network. It is possible to configure a device as a secondary link station, in which case it acts as a PU 2.0 device and can communicate with Front End Processors (FEP). However, it can only communicate with a primary device when the primary device permits it to do so, which means that the primary device sets up and tears down connections and controls the secondary devices. If the device is configured to allow negotiated link stations, XID frames can be sent between the stations to determine which station is the secondary and which station is the primary station. A primary station is in charge of issuing orders, controlling the connection, and initiating error-recovery procedures. A device configured as a secondary station has the ability to communicate with a FEP, coexist with other secondary devices over an SDLC link, and function as a secondary PU 2.0 device, among other functions. SDLC supports line speeds of up to 64Kb/s, for example, the V.24 (RS-232) protocol at 19.2Kb/s, the V.35 protocol (up to 64Kb/s), and the X.21 protocol. The frame format for SDLC, which is nearly identical to HDLC, is depicted in the diagram below. Flag – Starts and stops the error checking operation with the hexadecimal value 0x7E, which is equivalent to the binary value 01111110.
    • Address – This is merely the secondary address because all communication is carried out through a single primary device alone. The address might be for a single person, a group of people, or a broadcast address.
    • Control – this indicates the role of the frame and can be one of the following types of controls: This section comprises the Send Sequence Number, which is the number of the next frame to be transmitted, as well as the Receive Sequence Number, which is the number of the next frame to be received, as well as any other information that may be required. In addition, there is a Poll Final Bit (P/F), which is responsible for error checking.
    • Monitoring (S) – this can report on the current situation, request and stop transmitting data, and acknowledge I frames.
    • Unnumbered (U) – This has no sequence numbers (thus the name ″unnumbered″), and can be used to set up secondary processes. It may also have an Information field in some instances.
    • Data – this can include Path Information Unit (PIU) or Exchange Identification (XID) information.
    • This check is performed on both the transmitting and receiving of the frame
    • it is also known as the Frame Check Sequence (FCS).

    This element serves as the address field for the station being polled, and it serves as the address field for the station sending in a response. As such, this field essentially serves as the address of the secondary station. This is the control field.

    High-Level Data Link Control (HDLC)

    • HDLC is a protocol that is currently regarded as a sort of umbrella protocol under which many different Wide Area protocols may be found. HDLC was designed by the International Telecommunications Union (ITU-T) in 1979, and there are three types of stations described under HDLC: a primary station that entirely controls all data link activities, issuing instructions from secondary stations, and has the capability of holding separate sessions with various stations
    • b secondary stations that receive commands from primary stations
    • Secondary Station – This station can only respond to one primary station at a time.
    • Secondary stations can only communicate with one another through a Primary station.
    • Combined Station – This station has the ability to send and receive orders and answers from another station
    • and
    • It is possible to configure a channel so that it is usable by a station in one of three ways: Balancing – this arrangement allows one primary station to communicate with a number of secondary stations through half-duplex, full-duplex, switched, unswitched, point-to-point, or multipoint pathways
    • unbalanced
    • The term ″symmetrical″ refers to when two stations with primary and secondary portions are connected via a point-to-point connection and instructions and answers are multiplexed over a single physical channel.
    • When two combined stations communicate through a point-to-point link, which can be either full-duplex or half-duplex, or switched or unswitched, they are considered balanced.
    • A station can be in one of three modes when it is sending data: Normal Response Mode (NRM) is a mode of operation in which the secondary station must first obtain permission from the primary station before transmitting data. Asynchronous Response Mode (ARM) is mostly utilized on multi-point lines, and it allows the secondary station to send data without first obtaining permission from the primary station to do so. Asynchronous Balanced Mode (ABM) is a transmission mode that is rarely utilized since it allows one station to commence transmission without the other station’s authorization. This is the most typical method of operation for point-to-point connections.
    • The HDLC frame format is illustrated in the following diagram: The HDLC frame begins and concludes the error checking procedure with the hexadecimal value 0x7E, which corresponds to the binary value 01111110. HDLC frame types are classified into three categories as indicated by the control field: Information Data communication between stations is accomplished through the usage of frames. The frame sequence numbers are stored in the send sequence, also known as next send N(S), and the receive sequence, also known as next receive N(R). It is referred to as Poll when the primary station is seeking a response from a secondary station and Final when the secondary station is signaling the end of transmission or indicating a response from the primary station.
    • Supervisory Frames are used to acknowledge frames, request retransmissions, or request that transmission be halted temporarily.
    • The supervisory code identifies the sort of supervisory frame that is being transmitted.
    • Unnumbered frames are used for the initialization or termination of a network link.
    • The Unnumbered bits serve to identify the sort of Unnumbered frame that is being utilized.

    Logical Link Control (LLC)

    LLC is a subset of High-Level Data Link Control (HDLC), and it makes use of the Asynchronous Balanced Mode (ABM) subclass of HDLC in order to function properly.It is located between the MAC layer and the layer 3 protocols in the Data Link layer, and it is an essential element of the IEEE 802.2 specification.It is also used in many other applications.There are three types of LLCs: limited liability companies, limited partnerships, and limited liability partnerships.

    1. Limited Liability Company (LLC) Class 1 – Connectionless (CL), this service transmits and receives Link Service Data Units (LSDU) without the requirement for acknowledgement. It facilitates communication between points, as well as across groups, and is well suited for use with higher-level protocols that handle all of the sequencing, addressing, routing, and recovery tasks for you. IPX, TCP/IP, Vines, XNS, AppleTalk, and other protocols are examples of this. LLC1 consumes fewer network resources than LLC2 or LLC3 since it is not required to implement the data-integrity protections that are included in the following two approaches. The layer 3 protocols are in charge of data flow and integrity, and they are also in charge of security. LLC1 operates Type 1 operations, which means that Protocol Data Units (PDUs) are exchanged without connections, and there is no sequencing, acknowledgment, or error-checking of PDUs
    2. LLC Class 2 – Connection-Oriented (CO), which is a connection-oriented service that provides a point-to-point link between Link Service Access Points
    3. LLC Class 3 – Connection-Oriented (CO), which is a connection-oriented service that provides a connection-oriented link between Link (LSAP). Despite the fact that LLC2 reacts to the higher layer protocol in terms of opening and shutting connections, LLC2 is in charge of flow management, frame sequencing, and error recovery. When a connection must be created, LLC2 can perform Type 1 or Type 2 activities. In these cases, the LLC sublayer is responsible for the establishment of the connection, acknowledgment, sequencing, and error checking. LLC2 is generally required in environments that run protocols such as NetBIOS and SNA
    4. LLC Class 3 – Acknowledged-Connectionless (AC), which is a ‘connectionless-acknowledged’ implementation that is rarely used
    5. LLC Class 4 – Acknowledged-Connectionless (AC), which is a ‘connectionless-acknowledged’ implementation that is rarely used
    6. LLC Class 5 – Acknowledged-Connectionless (AC), which is

    The LLC PDU’s organizational structure is depicted in the diagram below. This is located at the beginning of the data portion of the Ethernet frame (see the IPX/SPX specification for further information). The LLC command PDUs are listed in the following table:

    Operation Command Response Format Control Field Hex. Value
    Type 1 (CL) Unnumbered Information (UI)   Unnumbered (U) 03
      Exchange Identification (XI) Exchange Identification (XI) Unnumbered (U) AF, BF
      Test (TEST) Test (TEST) Unnumbered (U) E, F3
    Type 2 (CO) Information (I) Information (I) Information (I) 00 00 to FE FF
      Receiver Ready (RR) Receiver Ready (RR) Supervisory (S) 01 00 to 01 FF
      Receiver Not Ready (RNR) Receiver Not Ready (RNR) Supervisory (S) 05 00 to 05 FF
      Reject (REJ) Reject (REJ) Supervisory (S) 09 00 to 09 FF
      Set Asynchronous Balance Mode Extended (SABME) Unnumbered Acknowledgement (UA) Unnumbered (U) 6F, 7F (SABME) and 63, 73 (UA)
      Disconnect (DISC) Disconnected Mode (DM) Unnumbered (U) 43, 53 (DISC) and 0F, 1F (DM)
        Frame Reject (FRMR) Unnumbered (U) 87, 97
    Type 3 (AC) Ack Connectionless, seq 0 (AC0) Ack Connectionless, seq 0 (AC0) Unnumbered (U) 67, F7
      Ack Connectionless, seq 0 (AC1) Ack Connectionless, seq 0 (AC1) Unnumbered (U) E7, F7

    The LLC SAP’s role is to filter through the incoming MAC frames and direct them to the appropriate application or higher layer protocol to which they are assigned.NetBIOS makes use of the SAP address of F0, IP makes use of 06, DLSw makes use of 04, and Network Management makes use of F4.The Null SAP, address 00, does not identify any SAP to any protocol since it is not associated with any protocol.The following is a more comprehensive list:

    SAP Protocol
    00 Null SAP
    04 SNA
    05 SNA
    06 TCP
    08 SNA
    0C SNA
    42 Spanning Tree
    7F ISO 802.2
    80 XNS
    AA SNAP
    E0 IPX
    F0 NetBIOS
    F8 RPL
    FC RPL
    FE OSI
    FF Global SAP
    • The Control field specifies the sequence of events and/or the instructions and answers. There are three different kinds: In Type 2 operations, the Information Transfer (I) PDU is responsible for performing a numbered information transfer.
    • In Type 2 operations, the Supervisory (S) PDU is responsible for acknowledgment, retransmission requests, and suspension of I PDUs
    • in Type 1 operations, the Unnumbered (U) PDU is responsible for some control functions and unsequenced information transfer
    • and in Type 2 operations, the Supervisory (S) PDU is responsible for acknowledgment, retransmission requests, and suspension of I PDUs.

    A specific case of Subnetwork Access Protocol (SNAP) exists in which the DSAP and SSAP are both set to AA and the Control field is set to 03.This is referred to as SNAP-AA.Then, immediately after the control field, three bytes are set aside for the Organizational Unique Identifier (OUI), followed by two bytes for the Protocol Identifier (PID) (see the IPX/SPX article for more information on this).However, unlike the SAP, which is often used for IEEE 802.x compliant protocols, the SNAP protocol is intended to allow non-IEEE compliance protocols to become pseudo-compliant without the need for extensive re-writing of code in the network driver.This implies that the frame is an Ethernet frame rather than an 802.3 frame from a particular vendor, as indicated by the OUI of 00-00-00.This is particularly handy when the frame spans many media types.

    When it exits the tunnel, it will be reconstructed as an Ethernet frame rather than anything else.

    What is HDLC and what is its role in networking?

    HDLC (High-level Data Link Control) is a collection of protocols or rules that are used to send data between network nodes or between network locations (sometimes called nodes).The International Organization for Standardization (ISO) developed the HDLC data link layer protocol, which is more specifically a bit-oriented, synchronous data link layer protocol (ISO).HDLC is defined under the ISO/IEC 13239:2002 standard.The International Electrotechnical Commission (ECI) is an international electrical and electronic standards body that frequently collaborates with the International Organization for Standardization (ISO).

    How does HDLC work?

    • During HDLC, data is arranged into a logical unit (referred to as a frame), which is then delivered across the network to a destination that validates that it arrived successfully. The HDLC protocol also regulates the rate at which data is sent, known as the flow rate. HDLC is one of the most widely used internet protocols (IP) in what is known as Layer 2 of the industry communication reference model, which is known as Open Systems Interconnection (OSI) (OSI). Layer 1 is the detailed physical level that generates and receives electronic signals
    • Layer 3 is the higher level that has knowledge of the network, including access to router tables that indicate where to forward or send data
    • and Layer 4 is the highest level that has knowledge of the network and has access to router tables that indicate where to forward or send data.

    When a frame is sent, programming in Layer 3 generates a frame that typically contains the network addresses of the source and destination networks. HDLC (Layer 2) wraps the Layer 3 frames and adds data link control information to a new, bigger frame, which is referred to as an HDLC frame.

    How is HDLC used in IT networks?

    Synchronous data link control (SDLC) protocol, which is widely utilized by IBM’s huge customer base in mainframe computer settings.HDLC is based on IBM’s synchronous data link control (SDLC) protocol.Normal Response Mode is the term used to describe the HDLC protocol that is essentially SDLC.The networking industry has utilized HDLC to develop various additional standards that are still in use today, including frame relay protocols such as the ISDN protocol stack known as Link Access Procedure Balanced (LAPB) (LAPB).The framing mechanism, which employs the Point-to-Point Protocol (PPP) over synchronous lines to connect numerous servers to a WAN (wide area network) internet link, as well as Cisco HDLC framing techniques, which add protocol fields to the HDLC header, are all based on this protocol specification.As part of what is known as a multidrop or multipoint network, a primary station – often at the mainframe computer – delivers data to secondary stations that may be local or may be located at remote sites via dedicated leased lines in what is known as a normal response mode.

    (This is not the type of network that we are used to thinking about; it is a nonpublic closed network.) A half-duplex communication system is typically used in this configuration.) Variations of HDLC are also used in public networks that employ the X.25 communications protocol, as well as frame relay, which is a protocol that is used in both public and private wide area networks (WANs).When using the X.25 version of HDLC, a data frame will include a packet of information.A X.25 network is one in which data packets are transported to their destinations following paths determined by network circumstances as observed by routers and reassembled in the proper order at the end destination.When using duplex connections, the X.25 version of HDLC employs peer-to-peer communication, with both ends being able to begin conversation.Link Access Procedure, Balanced is the name given to this mode of HDLC (LAPB).

    The HDLC versions and their respective users are summarized in the following table.

    How do HDLC frames work?

    The high-density data link control (HDLC) protocol is based on IBM’s synchronous data link control (SDLC) protocol, which is widely utilized in mainframe computing settings by IBM’s huge client base.This mode of operation is known as Normal Response Mode in high-density long-wavelength communication (HDLC).It was from HDLC that various additional standards, such as frame relay protocols and the ISDN protocol stack known as Link Access Procedure Balanced (LAPB), were derived in the networking industry (LAPB).The framing mechanism, which employs the Point-to-Point Protocol (PPP) over synchronous lines to connect numerous servers to a WAN (wide area network) internet link, as well as Cisco HDLC framing techniques, which add protocol fields to the HDLC header, are all based on this protocol specification.As part of what is known as a multidrop or multipoint network, a primary station – often at the mainframe computer – delivers data to secondary stations that may be local or may be located at remote sites through dedicated leased lines in what is known as a normal response mode.The network in question is not the type of network that we are used to seeing; it is a nonpublic closed network.

    Communication is often half-duplex in this configuration.) HDLC variants are also used in public networks that employ the X.25 communications protocol, as well as frame relay, which is a protocol that is used in both public and private wide area networks (WANs).An individual packet is included within a data frame when using HDLC in the X25 format.A X.25 network is one in which data packets are transported to their destinations following paths determined by network circumstances as observed by routers and reassembled in the proper order at the ultimate destination.) When using duplex connections, the X.25 version of HDLC employs peer-to-peer communication, with both ends being capable of initiating conversation.The Link Access Procedure, Balanced mode of HDLC is the name given to this mode (LAPB).The HDLC variants and who employs them are summarized in the following table:

    HDLC frame types

    • There are three different types of HDLC frame structures that are regularly utilized. The names of them are as follows: Information frames (I-frames) are data packets that transport user data from the computer network layer while also transmitting error control information with the data. In addition, I-frames have control fields that are used to construct data functions.
    • The supervisory frames (S-frames), which are broadcast anytime it becomes unable to ″piggyback″ on transmitted data, are used to relay error and flow control information. In order to avoid this, S-frames do not contain any information fields.
    • Unnumbered frames (U-frames), which are used for a variety of additional functions, including link management, are also present. Information fields are present in some of them, but they are absent in others.

    Thi

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