MEMO: see the reverse UK domain style; "UK.AC.RUTHERFORD.IBM-B" --------------------------------------------------------------- From: Paul Bryant Subject: So you like NSAPS? To: iptag@UK.AC.JNT PB660 IPTAG/92/23 SCIENCE AND ENGINEERING RESEARCH COUNCIL RUTHERFORD APPLETON LABORATORY CENTRAL COMPUTING DEPARTMENT NSAPs P Bryant May 19, 1992 -------------------------------------------------------------- 1 NSAPS This paper surveys how NSAPS are being/will be/may be used with a view to deciding on the use of NSAPS within the CLNS project. The survey is not exhaustive and in some cases the documents may be out of date. Comments are invited and a definitive scheme will follow. 2 Notes on the tables Field lengths suffixed by "x" are in octets otherwise they are decimal digits. Values are enclosed in "(" ")" and are in hexadecimal or decimal depending on the field length suffix. 3 Notes on the use of NSAPs in CLNS NSAPs are used for routing (ISO DP 10589). For this purpose the ID or identifier field is used for ES-IS (end system to router) routing and the preceding 2 octets (area field) is recommended to be left unallocat- ed and eventually used for optimising routing within a routing domain. The NSAP up to the area field is used for IS-IS routing. ISO DP 10589 requires binary encoding. The above two requirements mean that the UK JNT scheme for CONS cannot be used. First, it uses decimal encoding and secondly it does not re- quire the structure demanded by ISO DP 10589. In the case of Rutherford, where the NSAP address for CONS is highly structured and spread over the available NSAP space, there is no hope of utilising it for CNLS. ISO TR 9575 defines 3 levels of routing: * Area - a set of ESs and ISs - this is routed using the ID octets which may well be a MAC address. * Routing Domain - a set of areas connected with IS-IS connections but sharing the same intra-domain routing protocol. This could be a site or a country depending on organisational considerations. * Administrative domain - a set of Routing Domains under single manage- ment. This could be a set of sites or a set of countries. 4 US Gosip US Gosip defines the format below. +-----------+--------------------------------------+ |IDP | DSP | +----+------+----------------------------+----+----+ |AFI | IDI | HO-DSP | ID | SEL| +----+------+----+----+------+----+------+ | | | | |DFI | AA | Rsvd | RD | Area | | | +----+------+----+----+------+----+------+----+----+ | 1x | 2x | 1x | 3x| 2x | 2x| 2x | 6x| 1x| |(47)|(0005)|government wide us | |(47)|(0006)|delegated for DOD use only | +-----+-----+----+----+------+----+------+----+----+ IDP - Initial Domain Part DSP - Domain specific Part AFI - Authority and Format Identifier - defined by OSI IDI - Initial Domain Identifier - allocated by BSI HO - High Order DFI - DSP Format identifier - defined by GOSSIP AA - Administrative Authority - allocated by owner of the IDI Rsvd- Always useful in time of trouble RD - Routing Domain Identifier - allocated by owner of the AA Area- Area identifier - used to help routing ID - System Identifier - follows ISO DP 10589 SEL - NSAP Selector - follows ISO DP 10598 5 ISO 3848/Addendum 2 ISO 3848 defines the format below which is the basis for most schemes of interest. +--------------------------------------------+ |IDP | DSP | +-----------+-------------------+------+-----+ |AFI | IDI | HO-DSP | ID | SEL | +----+------+-------------------+------+-----+ |1x |2x | ? |1-8x | 1x | +----+------+-------------------+------+-----+ All elements in a Routing Domain have the same length ID. All elements in an area usually have the same area address (IDP+HO-DSP) and thus IS systems can easily identify destinations within the area which are routed on ID. If not in the area then the maximum number of digits from the IDP+HO-DSP are matched to route to another IS. (There is some doubt as to whether this statement is true and that a complete match is required). IDP+HO-DSP must be globally unique. 6 OSI NSAP Allocation in the Internet (RFC 1237) The Internet proposal follows US Gosip. +-----------+--------------------------------------+ |IDP | DSP | +----+------+----------------------------+----+----+ |AFI | IDI | HO-DSP | ID | SEL| +----+------+----+----+------+----+------+ | | | | |DFI | AA | Rsvd | RD | Area | | | +----+------+----+----+------+----+------+----+----+ | 1x | 2x | 1x | 3x| 2x | 2x| 2x | 6x| 1x| |(47)|(0005)|(80)| | | | | | | +-----+-----+----+----+------+----+------+----+----+ I have not found out the use of the Domain Format Identifier but suspect that it allows alternative encodings. 7 ANSI X3S3.3 The ANSI formal follows US Gosip apart from the IDP and IDI. +----+------+----------------------------------------+ |IDP | IDI | DSP | +----+------+-----+-----+------+----+------+----+----+ | | | DFI | ORG | Rsvd | RD | Area | ID | Sel| +----+------+-----+-----+------+----+------+----+----+ | 1x | 2x | 1x | 3x | 2x | 2x| 2x | 6x| 1x| |(39)|(840F)| | | | | | | | +----+------+-----+-----+------+----+------+----+----+ This is identical to US GOSSIP apart from IDP/IDI and the renaming of AA as ORG. I do not know what the significance of renaming AA (administra- tive Authority) as ORG (organisation) is. 8 ECMA TR/44, RFC 1195 These documents define the 9 low order octets of the DSP +--------+-----------+--------+ | SNID | SNADD | NSEL | +--------+-----------+--------+ | 2x | 6x | 1x | +--------+-----------+--------+ NSEL=Network Selector - indicates transport layer to select for a given TPDU and is used in OSI IS-IS routing protocol. Why "area" is renamed as SNID, ID as SNADD and SEL as NSEL is not known but NSAPS seem to be a topic where renaming of fields is a popular activity. 9 RARE WG4 recommendations RARE WG4 have defined the formal below. +---------+----------------------------+ |IDP | DSP | +----+----+--------------+-------------+ |AFI | IDI| CDP | CDSP| +----+----+------+-------+-------------+ | | | CFI | CDI | | +----+----+------+-------+-------------+ |1x | 3 |1 (1) | 3 | <=31| |(38)| | (2) | 5 | <=29| | | | (3) | 9 | <=25| | | | | | | |1x | 2x |1 (1) | 3 | <=12x| |(39)| | (2) | 5 | <=11x| | | | (3) | 7 | <=10x| +----+----+------+-------+-------------+ CDP - Country Domain Part CDSP- Country Domain Specific Part CFI - Country Format Identifier CDI - Country Domain identifier Note: it is unclear why the (39) DSP is limited to 14 rather than 17 octets. A second WG4 paper defines the DSP as being a pure addressing hierarchy and omits mention of the CI and CDI. Both papers were written in late 1990 before CLNS became a cult and may be out of date. This paper also mentions the use of ISO DP 10589 as being under develop- ment. 10 Norway CLNS project +-----------+---------------------------------------+ |IDP | DSP | +----+------+--------------+------------------------+ |AFI | IDI | CDP | CDSD | +----+------+------+-------+-------------+-----+----+ | | | CFI | CDI | |ID |NSEL| +----+------+------+-------+-------------+-----+----+ |1x | 2x |1 (1) | 3 | rest |6x |1x | |(39)|(578F)| (2) | 5 | | | | | | | (3) | 7 | | | | | | | (4) | 1 | | | | +----+------+------+-------+-------------+-----+----+ Norway follows WG4 with the addition of a CFI of 4 with CDI of 1. AFI is 39. The terminal 7 octets are 6 for a LAN address and 1 for a network selector NSEL which follows US GOSSIP. 11 Holland CLNS project +-----------+--------------------------------------+ |IDP | DSP | +----+------+-------------+------------------------+ |AFI | IDI | CDP | CDSD | +----+------+------+------+----+----+------+-------+ | | | CFI +CDI | SFI| SDI| ASDI| | +----+------+------+------+----+----+------+-------+ |1x | 3 | 4 | 1 | 4 | 1 | rest | |(38)|(528) | (1 100) | | | (0) | | |1x | 2x | | | | | | |(39)|(528F)| (1 100) | | | (0) | | +----+------+-------------+----+----+------+-------+ SFI -SURFnet format identifier allocated by SURFnet. SDI -SURFnet domain identifier (site) allocated by SURFnet. ASDI - Additional SURFnet domain identifier allocated by SURnet - re- served. If SFI=0 SDI maps an organisation to a number. If SFI=1 SDI is a number that maps onto a network (?). The "rest" is allocated locally. 12 UK CONS +----------+--------------------------------------------+ |IDP | DSP | +----+-----+--------------+----+---------+--------------+ |AFI | IDI | CFI | CDI | ID | SiteCode|SiteAllocation| +----+-----+------+-------+----+---------+--------------+ |1x | 3 |1 | 3 | 2 | 3-6 | rest | |(38)|(826)|(1) | (100) |(00)| | | +----+-----+------+-------+----+---------+--------------+ UK follows roughly WG4 with AFI of 38, CFI of 1 digit containing 1 and CDI of 3 digits containing 100. The CDSD contains 3 fields. First a 2 digit reserved for future use. Second is a variable length site code of between 3 and 6 digits. Third a variable length field allocated by the site. 13 Germany CLNS project +----+------+----------------------------------------------+ |IDP | IDI | DSP | +----+------+------+-----+-----+-----+----+------+----+----+ | | |DE-BT | FI1 | RI |Rsvd | RD | Area | ID | Sel| +----+------+------+-----+-----+-----+----+------+----+----+ | 1x | 2x | 2x | 1x | 1x | 2x | 2x| 2x | 6x| 1x| |(39)|(376F)|(3100)|(01) | | | | | | | +----+------+------+-----+-----+-----+----+------+----+----+ | | |DE_BT | FI1 | RI | RD |FI2 | | +----+------+------+-----+-----+-----+----+----------------+ | 1x | 2x | 2x | 1x | 1x | 2x | 1x | 10x | |(39)|(376F)|(3100)|(02) | | | | | +----+------+------+-----+-----+-----+----+------+----+----+ FI - Format Identifier RI - Regional Identifier RD - Routing Identifier Germany defines two formats The first follows ANSI X3S3.3 with the exception that the DFI and ORG fields are replaced with DE-BT of two octets containing 3100, FI1 of one octet of 01 and R1 of one octet which is a region code. Rsvd is 0. RD defines the site (presumably within the region. The second is for CONS where Rsvd, ID, Sel are replaced by a single field presumably allocated by the site. 14 DECNET Phase V NSAP used for transition. One assumes that after transition this format will become redundant. +-----------+--------------------------------+ |IDP | | +----+------+--------------------------------+ |AFI | IDI | DSP | +----+------+----------------------+----+----+ | | | Loc Area | ID | Sel| +----+------+----------------------+----+----+ | 1x | 4x | 2x | 6x| 1x| |(47)|(0020)|(0013) area 19 | DA |(20)| +----+------+----------------------+----+----+ NSAP for DECNET Phase V after transition (proposal from Dave Kelsey). DA = DECNET phase IV address = AA000400nnnn nnnn = area*1024+node number SEL = 20 hex DECNET transport and session control = 21 OSI transport +-----------+------------------------------------+ |IDP | | +----+------+------------------------------------+ |AFI | IDI | DSP | +----+------+------------------+-----------------+ | | |Pre-DSP | CDSP | +----+------+---+-----+----------------+---+-----+ | | |CFI|CDI | |LocArea|ID | Sel | +----+------+---------+--------+-------+---+-----+ | 1x | 2x | 1 |3 | 0-6x | 2x | 6x| 1x | |(39)|(826F)|(1)|(107)| | | |(21) | +----+-----+----+-----+--------+-------+---+-----+ The CDSP is converted between CFI - Country Format Identifier CDI - Country Domain Identifier ID is recommended to be the ethernet address In this scheme each site or ISO CLNS routing domain is defined by up to 6 octets. This should probably be a site code and could follow the current JNT CONS scheme although codes with odd numbers of digits would have to be padded to an even number. Alternatively all codes could be 3 octets - but see discussion below. 15 NORDUNET Follows US GOSSIP and Internet draft OSI NSAP address format. +-----------+------------------------------------------------+ |IDP | | +----+------+------------------------------------------------+ |AFI | IDI | DSP | +----+------+----+---------+------+---------+----+------+----+ | | |DFI | AA |Revd |RD |Area|System|NSEL| +----+------+----+---------+------+---------+----+------+----+ | 1x | 4x | 1x | 3x | 2x | 2x | 2x| 6x | 1x | |(47)|(0023)|(00)| (00000n)|(0000)| | | | | |NORDUnet backbone (000001)| | (0001) |(01)|MacAdd| | |DK (UNI-C) (000002)| | | |IPAddr| | |FI (FUNET) (000003)| | | |or | | |IS (SURIS) (000004)| | site | |some- | | |NO (UNINETT) (000005)| | | |thing | | |SE (SUNET) (000006)| | | |else | | |NORDUnet DECnet transition| | | | | | | (000007)| | (0001) |DA |MacAdd|SEL | +--------------------------+------+---------+----+------+----+ 16 Switzerland (SWITCH/WG2/DP-91-1)) Switzerland uses the ISO DCC scheme +----------+----------------------------+ |IDP | DSP | +----+-----+--------------+-------------+ |AFI | IDI | CHDP | CHDSP| +----+-----+------+-------+-------------+ | | | CHFI |CHDI | | +----+-----+------+-------+-------------+ |1x | 3 |2 (11)| 2 | <=31| Large organisations |(38)|(756)|2 (21)| 4 | <=29| Intermediate | | |2 (31)| 8 | <=25| Small | | | | | | |1x | 2x |1x(11)| 1x | <=15x| Large organisations |(39)|(756)|1x(21)| 2x | <=14x| Intermediate | | |1x(31)| 4x | <=12x| Small | | |1x(80)| 3x | <=13x| US Gosip DSP users +----+-----+------+-------+-------------+ CHDI - Swiss Domain Identifier CHFI - Swiss Format Identifier The format is compatible with the use of the 9 low order octets with ECMA 117. Switch expect to use CHFI = 11 and CHDI = 11 17 Practical considerations DEC recommend that the ID field is the MAC address of the ES. Their routers provide a means for an ES indicating its MAC address to the IS thus requiring no table maintenance for ESs. Indications are that ISs from other suppliers may not include this facility. A network can be split into a set of "routing domain confederations" within a routing domain. The significance is that the structure within such a confederation is private to the confederation. This reduces the size of the tables needed within the ISs and reduces routing information traffic. In the case of Europe you could consider a department being a confederation within a site, a site being a confederation within a country and a country being a confederation within European. It would appear that there is advantage in a confederation equating with a single IDP HO-DSP combination although there will be many exceptions - for example to take account of DECNET phase IV. A corollary is that a "site code" will be needed for the backbone. The code 0000 is suggested. Apologies to those familiar with JIPS who may find such a comment obvious. Extending this concept a "site code" will be needed (or rather exists) for the European backbone. This code has been donated/loaned from the NORUNET 47 series and GB will need to obtain such a site code for its international IS. The code in use in the CLNS WG4 pilot is: 47.0023.0000.0001.0000.0001.0001.xxxx.xxxx.xxxx.00 Practical experience with JIPS and the above considerations indicate that the CLNS project should follow the JIPS structure with a site being a confederation with a single connection to a backbone confederation of completely interconnected ISs. There should be an international IS form- ing part of an international confederation which may or may not be completely interconnected depending on topological considerations. 18 Comment The options for NSAPs for the CLNS project are limited. The use of an AFI of 47 is essential if the DECNET community is to be accommodated. The use of the AFI should be on an interim basis pending the completion of the transition from DECNET phase IV to phase V. A very rough estimate is that it will be needed for two years. On the longer term an AFI of 47 or 39 could be used. 39 has advantages as it follows the philosophy of NSAPs being structured on a country basis. The use of 47 would involve the application for an address space on the lines adopted by NORDUnet. On a world wide basis this would merely lead to an alternative set of country codes. The reason for NORDUnet's decision is to follow RFC1237 which in turn follows US Gosip. However Country Code (DCC) subdomain will be common in the international Inter- net." and goes on to refer to the ANSI X3 proposal. It is an interesting argument as to whether 47 or 39 should be used and on balance I prefer 39. The choice will only be apparent in retrospect when we see if products depend on which is chosen. There is no option but to follow ISO DP 10598 in structuring the NSAP into essentially two parts - AFI+IDI+HO-DSP for IS-IS routing and ID for ES-IS routing. Routers are unlikely to work with any other scheme. The SEL field does not take part in routing. An "area" would seem to relate best to a site although there seems no good reason why a site should not be composed of a number of areas - it probably depends on local circumstances. The "routing domain" and "administrative domain" could relate to GB although it could be argued that the world wide academic networks (or just European networks) could be an administrative domain. In principle the structure of the ID field is a local matter except that its length has to be uniform within the routing domain. The popular choice for the length of ID (1<=ID<=8) is 6 octets since it is antici- pated that this will contain the MAC address of the end system. This goes counter to the view that an NSAP should be independent of the underlying protocols - but ISO DP 10598 already undermines this philoso- phy by overtly using the structure of the NSAP for routing. To go against this may be to put the UK in a unique and lonely position. We have the situation where the best choice depends on the availability of products. Thus it is recommended that the ID should be 6 octets and a weak recommendation that it contain the MAC address. It is understood that JNT has obtained an allocation for the binary DCC scheme (39 region) which is 1107 hex (2 octets). Thus we cannot follow UK Gosip and are left with 2 octets for the site (or AA field) rather than 3. The current site JNT codes defined in "UK Academic Community OSI Requirements Note 6" could be used which, apart from 4 or so codes, are 4 or less digits which may be padded to 2 octets. Following US GOSSIP the next 2 octets are reserved and the RD field of 1 octet could be used for subdividing a site into several routing domains. This leads to the structure illustrated below. +-----------+-------------------------------------------+ |IDP | | +----+------+-------------------------------------------+ |AFI | IDI | DSP | +----+------+-------------------------+-----------------+ | | |Pre-DSP | CDSP | +----+------+---+-----+----+------+---+----+-------+----+ | | |CFI|CDI |site|Rsvd |RD |Area|ID |Sel | +----+------+---------+----+------+---+----+-------+----+ | 1x | 2x | 1 |3 | 2x| 2x |2x | 2x | 6x | 1x | |(39)|(826F)|(1)|(107)| |(0000)| | |MAC add|(21)| +----+-----+----+-----+----+------+---+----+-------+----+