Path: utzoo!mnetor!uunet!hpda!hplabs!ucbvax!A.ISI.EDU!Stevens From: Stevens@A.ISI.EDU (Jim Stevens) Newsgroups: comp.protocols.tcp-ip Subject: Much More Idle Chatter About Reference Models Message-ID: <12359521472.59.STEVENS@A.ISI.EDU> Date: 18 Dec 87 19:59:11 GMT Sender: daemon@ucbvax.BERKELEY.EDU Organization: Rockwell International Lines: 409 DISCUSSION OF LAYERED PROTOCOL MODEL Jim Stevens (Stevens@A.ISI.EDU) 18 December 1987 INTRODUCTION Recently CMC has distributed a nice multi-colored wall chart showing the DoD Internet Architecture and the protocols at each layer. I only list CMC as reference because their chart caused a flurry of e-mail messages on TCP-IP. Note that their chart is just the latest of many papers and reference-type-material to contain the same type of problems. Since many of you may not have seen the CMC chart, it is included for reference as Figure 1 at the end of this message. There are 2 problems with this chart: (1) Location of EGP, GGP, and HMP and (2) Incorrect Physical and Data Link protocols under some networks (especially radio networks). LOCATION OF NETWORK MANAGEMENT PROTOCOLS The location of EGP, GGP, and HMP have caused a flurry of e-mail messages on TCP-IP. These 3 protocols are network management protocols. There has been a lot of work in the last decade on protocol architectures which include network management that provide an answer to the question of the network management protocol location. Some of the efforts include ISO (reference ISO 7498 Part 4), CCITT (ISDN, see recommendation I.320), and AT&T (J.W. Timko, AT&T Technology, Vol 2, No 3). I intend to locate EGP, GGP, HMP, and ICMP within the ISDN protocol stack using the OSI management structure categories. All three of the above named efforts basically came up with the same architecture. These architectures just added a new dimension to the current the 7-layer OSI reference model. The 7-layer OSI model contains only 1 dimension, which I'll call the X dimension. The X dimension described the different services performed upon User data as it is sent from one host to another. The new architectures added a Y dimension which showed the different functions which must be performed at each layer. The three different functions that are performed are: 1. The (N)-layer performs some service upon user data and send the data onward. (This function is identical to that described in the original X dimension.) 2. The (N)-layer performs signaling between the different layers. (For packet switched networks this signaling is typically provided in the packet headers.) 3. The (N)-layer performs internal management decisions. Figure 2 shows the ISDN protocol stack and the 2 dimensions of their model. The user service function is the vertical stack of layers labeled with a U. The signaling function is the vertical stack of layers labeled with a C. The management function is the vertical stack of layers labeled with an M. The OSI management framework describes 3 management structure categories: 1. Systems Management System Management Application-Process (SMAP) System Management Application-Entity (SMAE) 2. (N)-layer management coordinates multiple instances of communications 3. (N)-layer operation coordinates single instance of communications The Systems Management is an application process which can use the entire protocol stack when communicating. The difference between a Systems Management application process and another user application process (such as Terminal Emulation) is that the Systems Management application has access to the control/management data within each of the protocol layers. EGP, GGP, and HMP are system management applications. The (N)-layer management/operation are processes within the (N)-layer. Thus these processes can only use the protocols which lie under them. ICMP is a Network-layer management process. INCORRECT PHYSICAL AND DATA LINK PROTOCOLS UNDER SOME NETWORKS The CMC chart has confused the Physical and Data Link protocols used within some networks and the Physical and Data Link protocols used to interface to these networks. This has been a common problem and has shown up in several different papers. Figure 3 shows a layered protocol chart which did not have this problem. Since I have worked on the DARPA Packet Radio Program and its follow on Survivable Adaptive Networks (SURAN) Program, I will use older fielded Improved Packet Radio (IPR generation Packet Radios) as an example to explain how the confusion arises. Normally, the 7 protocol layers are implemented in a single box. The protocol drivers are then contained within either the OS kernel or applications residing above the OS. This is not true however in Packet Radio, where the 7 protocol layers are implemented in 3 different boxes interconnected via a BBN 1822 line. Figure 4 shows how the DOD protocols stack is implemented in 3 boxes interconnected together with BBN 1822. The Hosts interface to the Packet Radio Network via a Host Interface Unit (HIU). The actual interface between the HIU and the Hosts is a defined host access protocol running on top of BBN 1822. The hosts implements the Session and higher layer protocols such as FTP and mail. The HIU interface to the actual Packet Radios (PRs) using a defined device access protocol running on top of BBN 1822. The HIUs implement the Internet and Transport protocols such as IP and TCP. The PRs communicate to each other using the PR Channel Access Protocol (CAP) at the network and upper data link layers, CSMA at the lower data link layer, and spread spectrum at the physical layer. The PRs thus implement the Network, Link, and Physical layers. There is often confusion between the host or device interface to Packet Radio and the actual protocols used within Packet Radio. That is why the CMC chart shows BBN 1822 as the Packet Radio Network Physical protocol instead of spread spectrum. It is fairly easy to catch this type of error for radio networks, since the radio network physical layer must be some sort of RF transmission scheme such as Spread Spectrum (SS) or Amplitude Modulation (AM). ------------------------------------------------------------------------------ Figure 1 Layered Protocol Model Taken from CMC chart, Fall 1987 DOD MODEL +-------+ +------+ +-------+ +--------------------------+ +-------+ Appli- | File | | Mail | | Term- | | User Programs | | Name | cation | Trans-| | Text | | inal | | | | Server| | fer | | RFC | | Emul- | | | | | | Server| | 822 | | ation | | | | | +-------+ +------+ +-------+ +--------------------------+ +-------+ ^ ^ ^ ^ ^ ^ ^ . . . . . . . . . . . . . . v v v v v v v +-------+ +------+ +-------+ +-----------+ +------+ +-----+ +-------+ Util- | FTP | | SMTP | |Telnet | | NETBIOS | | TFTP | | NFS | | NSP | ity | MIL | | MIL- | | MIL- | | RFC | | | | | | | | STD | | STD | | STD | | 1001/ | | | | | | RFC | | 1780 | | 1781 | | 1782 | | 1002 | | | | | | 882 | +-------+ +------+ +-------+ +-----------+ +------+ +-----+ +-------+ ^ ^ ^ ^ ^ ^ ^ ^ . . . . . . . . .............................. ............................ . . v v +-----+ +-----+ +-----+ +------------------+ +-------+ Trans- | EGP | | GGP | | HMP | | TCP | | UDP | port | | | | | | | MIL-STD 1778 | | RFC | | | | | | | | | | 768 | +-----+ +-----+ +-----+ +------------------+ +-------+ ^ ^ ^ ^ ^ . . . . . . . . . . .................................................... . v Inter- +------------------------------------+----------------+ net- | Internet Protocol (IP) | ICMP | work | MIL-STD 1777 | RFC 792 | +------------------------------------+----------------+ ^ . . .............................................. . . . . . . . . . . v v v v v +-----+ +-------+ +---------+ +------------+ +--------------+ Net- | Pkt | | BBN | | Pkt | | CCITT X.25 | | Ethernet ARP | Work |Radio| | 1822 | |Satellite| |Packet Layer| | RFC 826 | +-----+ +-------+ +---------+ +------------+ +--------------+ ^ ^ ^ ^ ^ ^ . . . . . . . . . . . . ....... ......... ....... . . . . . . . . . . . . . . v v v v v . +------+ +-----+ +-----+ +-----+ +--------------+ +-------+ Data . | BBN | | BBN | |LAPB | |LAPB | |IP / Ethernet | | IEEE | Link . | HDH | | VDH | | BSC | |HDLC | | RFC 894 | | 802.2 . | | | | | | | | +--------------+ +-------+ . | | | | | | | | ^ ^ . | | | | | | | | . . . | | | | | | | | . ....................... . | | | | | | | | . . . . . . | | | | | | | | v v v v v . | | | | | | | | +------+ +-----+ +-----+ +----+ . +------+ +-----+ +-----+ +-----+ | | | | | | | | . ^ ^ ^ ^ | | | | | | | | . . . . . | | | | | | | | . .......................... | | | | | | | | . . . . . | | | | | | | | v v v v v | | | | | | | | +----+ +-----+ +-----+ +------+ +------+ | | | | | | | | Phys- |BBN | |CCITT| | EIA | | EIA | |MilStd| | IEEE | |IEEE | |IEEE | |FDDI| ical |1822| |V.35 | |RS449| |RS232C| | 188C | |802.3 | |802.4| |802.5| | | +----+ +-----+ +-----+ +------+ +------+ +------+ +-----+ +-----+ +----+ ------------------------------------------------------------------------------ FIGURE 2. ISDN Protocol Stack Taken from CCITT I.320 Control User Data System Management ________ ________ ________ | \ \ | \ \ | \ \ | \ \ | \ \ | \ \ \ \ ______\ \ \ ______\ \ \ ______\ \ | | \ | | o \ | | \|______| \|______| o \|______| @ @ o o @ @ @ o o @ @ oooooo@ooooooooo o @ @ o @ o @ @ o @ ooooooooooo @ ______@____ _o_____@_ o @ | \ @ \o @ \o @@@@@@@@@ | \ C o \ @ o \ @ | \ ________\@ o \ @ | \ |\ @ \ o M @\ | \ | \ U o\ @ \ | \ | \ _________\_________\ | \ |\ | | | | \ | \ | 7 - Appl | | | \ | \|__________| | | \ |\ | | | | \ | \ | 6 - Pres | | | \ | \|__________| | | \ |\ | | | | \ | \ | 5 - Sess | | | \ | \|__________| | | \ |\ | | | | \ | \ | 4 - Tran | | | \ | \|__________| | | \ |\ | | | | \ | \ | 3 - Netw | | ______________| \ | \|__________| | . \ |\ | | | . \ | \ | 2 - Link | | . . \ | \|__________| | . . \ | | | . . \ | 1 - Phys | | . . _______________\|__________|_________| . Physical Media | . ___________________________| ------------------------------------------------------------------------------ Figure 3. Layered DOD Reference Model Chart Taken from "Tactical Information Exchange (TIE) Framework Development (For the 1990s Time Frame" October 1981 +-----+ +----------+ +------------+ Application | MTP | |Multimedia| | Conference | | | |Message | | | +-----+ +----------+ +------------+ ^ ^ ^ ^ . . . . . . . . . . . . +------+ +---+ . . +----+ +------+ . . Utility |TELNET| |FTP| . . |TFTP| |Name | . . | | | | . . | | |Server| . . +------+ +---+ . . +----+ +------+ . . ^ ^ . . ^ ^ . . . . . . . . . . . . . . . . . . ................. ....... . . . . . . . . . . v v v . +------------------+ +---------+ +-----+ +--------+ . Transport | TCP | | UDP | | GGP | | NVP II | . +------------------+ +---------+ +-----+ +--------+ . ^ ^ ^ ^ . . . . . . . . . . . ................................ ......... . . . . v v +-----------------------------------------------+ - - - - - - - - - Internet | Internet Protocol | Stream Protocols ! +-----------------------------------------------+ - - - - - - - - - ^ . . ...................................................... . . . . . . . . . . . . v v v v v v +----------+ +------+ +------+ +-----+ +-----+ +------+ Network | ARPANET | |SATNET| |CCITT | |PRNET| |JTIDS| | DIN | | HOST/IMP | | | | X.25 | | | | | |2 SIP | +----------+ +------+ +------+ +-----+ +-----+ +------+ ^ ^ ^ ^ ^ ^ . . . . . . . . . . . . .............. ......... . . . . . . . . . . . . . . . . . . . . . . v v . v v v v v v +----+ +----+ . +-----+ +----+ +-----+ +-----+ +-----+ +------+ Link |HDH | |VDH | . | VDH | |HDH | |HDLC | |CSMA | |TDMA | |ADCCP | |HDLC| |RTP | . | RTP | |HDLC| | | | | | | | | +----+ +----+ . +-----+ +----+ +-----+ +-----+ +-----+ +------+ ^ ^ . ^ ^ ^ ^ ^ ^ . . . . . . . . . . . . . . . . . . v v v v v v v v v +---+ +-----+ +----+ +-----+ +----+ +-----+ +-----+ +-----+ +------+ Physical |M/W| |Modem| |BBN | |Modem| |M/W | |X.21 | | SS | |SS/FH| | M/W | | | | | |1822| | | | | | | | | | | | | +---+ +-----+ +----+ +-----+ +----+ +-----+ +-----+ +-----+ +------+ Key: ADCCP Advanced Data Communications Control Procedures DIN 2 SIP AUTODIN II Segment Interface Protocol FH Frequency Hop HDH HDLC Distant host JTIDS Joint Tactical Information Distribution System MTP Mail-Transport Protocol M/W Modem / Wire NVP II Network Voice Protocol PRNET Packet Radio Network RTP Real Time Protocol SATNET (Experimental) Satellite Network SS Spread Spectrum TDMA (Synchronous) Time Division Multiple Access VDH Very Distant Host ---------------------------------------------------------------------------- Figure 4 Host Interface to Packet Radio +---------------+ | | Host Application |FTP, Mail, etc.| | | Utility | | +---------------+ ^ . BBN 1822 and defined host access protocol . v +---------------+ | | Host Transport | TCP | Interface | | Unit | | Internetwork | IP | | | +---------------+ ^ . BBN 1822 and defined device access protocol . v +---------------+ | | Packet Network | Channel | Radio | Access | | Protocol | | | | | Link | CSMA | | | | | Physical | Spread | | Spectrum | | | +---------------+ ---------------------------------------------------------------------------- -------