TCPIP procedures and application for the GTS Geoff

TCP/IP procedures and application for the GTS Geoff Molloy Communications and Computing Branch Bureau of Meteorology Australia

TCP/IP procedures and application for the GTS Agenda • • GTS Comms Evolution Network Topologies Overview of TCP/IP GTS IP Addressing Routing Data Transfer - TCP and FTP WMO standards – Sockets and FTP

TCP/IP procedures and application for the GTS Comms Evolution • Asynchronous to X. 25 to IP • X. 25 saw the introduction of error detection and correction. • The advantages of TCP/IP include cost, simplicity and the ability to use a range of high level (application) protocols. – http (web) Remote machine logins (telnet, rlogin, remsh) FTP (File Transfer Protocol) Smtp (e-mail) remote database access

TCP/IP procedures and application for the GTS Network Topology

TCP/IP procedures and application for the GTS IP Address format

TCP/IP procedures and application for the GTS. IP Address format (cont. ) 1 1 1 1 1 2 2 2 2 2 3 3 0 1 2 3 4 5 6 7 8 9 0 1 --+----------------------------- Class A |0| NET_ID | HOST_ID | |-+-+---------------+----------------| Class B |1|0| NET_ID | HOST_ID | |-+-+-+-------------+---------------| Class C |1|1|0| NET_ID | HOST_ID | |-+-+--------------------+--------| Class D |1|1|1|0| MULTICAST_ID | |-+-+----------------------------| Class E |1|1| EXPERIMENTAL_ID | --+-+---------------------------- FIGURE 5. IP Address Format.

TCP/IP procedures and application for the GTS IP Addresses • Must have public addresses for inter-agency communications. • Private addresses may be used within your organisation. • Network Address Translation (NAT) is used to convert between private and public addresses • WMO allocates public addresses for GTS: possible allocation for hosts, but cannot be used for Internet connection.

TCP/IP procedures and application for the GTS IP addresses (cont. ) • GTS Allocation: 193. 105. 177. 0 to 193. 105. 184. 0 • Private address allocations: – 10. 0 to 10. 255 – 172. 16. 0. 0 to 172. 16. 255 – 192. 168. 0. 0 to 192. 168. 255 • Subnet Mask: 2 ways to refer top this – 192. 168. 1. 1 255. 0 – 192. 168. 1. 1/24 • /24 = 11111111 0000

TCP/IP procedures and application for the GTS IP addresses (cont. ) • Get IP address from ISP • Possibly get IP address from WMO

TCP/IP procedures and application for the GTS Connection with NAT

TCP/IP procedures and application for the GTS How do you know which way to send ip packets – routing protocol

TCP/IP procedures and application for the GTS Routing • Two types of routing: Static and Dynamic • An internal routing protocol is used within your network. • The GTS uses BGP for routing (static routes can sometimes be used for stub networks) • ATTACHMENT II-15 Use of TCP/IP on the GTS give examples of setting up BGP Routing on a Cisco router – does not cover use of NAT.

TCP/IP procedures and application for the GTS Example of routing table gatekeeper-gw#sh ip route S 139. 163. 28. 254/32 [1/0] via 139. 163. 79. 1 B 202. 245. 39. 0/24 [20/0] via 193. 105. 178. 22, 2 d 23 h S 157. 128. 0. 0/16 [1/0] via 202. 12. 61. 9 B 203. 10. 243. 192/27 [20/1] via 203. 10. 243. 13, 05: 46: 25

TCP/IP procedures and application for the GTS BGP • Used by WMO on GTS • Uses a tcp connection on port 179 between to routers to send updates. • Each Network is given an Autonomous System (AS) number. • WMO have allocated AS numbers out of the private AS address range for the GTS

TCP/IP procedures and application for the GTS AS Numbers • Private range: 64512 through 65535 • MTN Centres and reserve: 64512 to 64639 • RA I: 64640 to 64767 • RA II: 64768 to 64895 • RA III: 64896 to 65023 • RA IV: 65024 to 65151 • RA V: 65152 to 65279 • RA VI: 65280 to 65407 • Antarctic and reserve: 65408 to 65535

TCP/IP procedures and application for the GTS Local BGP links • Allocate AS numbers for private links out of range: 65472 to 65535 • All GTS should not route this range.

TCP/IP procedures and application for the GTS Example of BGP routing gatekeeper-gw#sh ip bgp neigh 193. 105. 178. 22 route BGP table version is 205, local router ID is 134. 178. 31. 9 Status codes: s suppressed, d damped, h history, * valid, > best, i - internal Origin codes: i - IGP, e - EGP, ? - incomplete Network Next Hop Metric Loc. Prf Weight Path *> 140. 90. 88. 0/24 193. 105. 178. 22 0 64520 64513 i *> 202. 245. 36. 0 193. 105. 178. 22 0 64520 ? *> 202. 245. 39. 0 193. 105. 178. 22 0 64520 i *> 205. 156. 51. 96/27 193. 105. 178. 22 0 64520 64513 i Total number of prefixes 4 gatekeeper-gw#

TCP/IP procedures and application for the GTS BGP Conifiguration router bgp 64512 no synchronization network 134. 178. 0. 0 redistribute ospf 101 metric 20 match internal neighbor 193. 105. 178. 22 remote-as 64520 neighbor 193. 105. 178. 22 distribute-list 10 out neighbor 193. 105. 178. 22 filter-list 4 in neighbor 193. 105. 178. 22 filter-list 1 out ! ip as-path access-list 1 permit ^$ ip as-path access-list 4 permit ^64520$ ip as-path access-list 4 permit _64513$ ! access-list 10 permit 134. 178. 6. 0 0. 0. 0. 255 access-list 10 deny any

TCP/IP procedures and application for the GTS Useful cisco BGP commands • • Sh tcp Sh ip route Sh ip bgp neighbor 1. 1 advert

TCP/IP procedures and application for the GTS NAT • Static and Dynamic • Static needed for GTS so that hosts inside the network can be contacted and for security. • NAT addresses must appear in BGP routing table.

TCP/IP procedures and application for the GTS TCP overview • Connection oriented and reliable. • TCP uses a port number to define connections • Connection defined by source IP address/source port and destination IP address and destination port • Can have multiple connections to the same TCP port number

TCP/IP procedures and application for the GTS TCP Packet format

TCP/IP procedures and application for the GTS Common TCP ports • ftp-data 20/tcp # File Transfer Protocol (Data) • ftp 21/tcp # File Transfer Protocol (Control) • telnet 23/tcp # Virtual Terminal Protocol • smtp 25/tcp # Simple Mail Transfer Protocol • http 80/tcp # World Wide Web HTTP • pop 3 110/tcp # Post Office Protocol - V 3 • GTS ports >10000

TCP/IP procedures and application for the GTS UDP • Connectionless not reliable • Not used for GTS transfers • Examples: used for network management (SNMP), voice data

TCP/IP procedures and application for the GTS FTP • Uses 2 TCP connections: Control (port 21) and data (port 20) • Two modes: normal and passive. • Used for transferring files.

TCP/IP procedures and application for the GTS FTP Operation Normal Client host - connects to port 21 Client host “give me file on port 2345 Client/2345 host/20 –connects to port 2345 Passive Client host - connects to port 21 Client host “give me file on port 2345 Client host/2345 –connects to port 2345

TCP/IP procedures and application for the GTS FTP Commands get Retrieve a file put send a file binarysend or retrieve a file in raw binary format (no processing) cd Change directories on the remote system rename Rename a file on the remote system Hash display a ‘hash’ symbol which indicates how much data has been sent. Ls List the directory on the remote system.

TCP/IP procedures and application for the GTS FTP Example C: >ftp gorgon. ho. bom. gov. au Connected to gorgon. ho. bom. gov. au. 220 gorgon FTP server (Version 1. 7. 212. 5 Wed May 30 12: 19: 42 GMT 2001) ready. User (gorgon. ho. bom. gov. au: (none)): anonymous 331 Password required for anonymous. Password: 230 User gvm logged in. ftp> cd temp 250 CWD command successful. ftp> binary 200 Type set to I. ftp> put info. txt 200 PORT command successful. 150 Opening BINARY mode data connection for INFO. TXT. 226 Transfer complete. ftp: 833 bytes sent in 0. 01 Seconds 83. 30 Kbytes/sec. ftp> rename info. txt to final. txt 550 info. txt: No such file or directory. ftp> rename INFO. TXT final. txt 350 File exists, ready for destination name. 250 RNTO command successful. ftp> ls 200 PORT command successful. 150 Opening ASCII mode data connection for file list. test. zip final. txt 226 Transfer complete. ftp: 62 bytes received in 0. 00 Seconds 62000. 00 Kbytes/sec. ftp>

TCP/IP procedures and application for the GTS WMO Standards • FTP transfer • Socket Connections

TCP/IP procedures and application for the GTS WMO Socket Connections • WMO Use TCP ports > 10000 – Suggest that use ports > 30000 • Use separate sockets for ASCII and Binary data and separate sockets for transmit and receive. • Maintain socket connection • Old sockets should be closed when a new connection to the same port from the same host occurs – avoids problems with connection loss.

TCP/IP procedures and application for the GTS WMO Sockets Continued • Use CSN (channel sequence numbers) manditory – recommend 5 character CSN • Each message is preceded by a message length field of eight ASCII characters and a message type field of two ASCII characters. – BI for binary, AN for alphanumeric or FX for facsimile

TCP/IP procedures and application for the GTS Socket Data Format

TCP/IP procedures and application for the GTS Socket Programming • See ATTACHMENT II-15 Use of TCP/IP on the GTS

TCP/IP procedures and application for the GTS WMO FTP Procedures • Procedures for accumulating messages into files so as to minimise FTP overheads with short messages (applies only to existing message types); • file naming conventions for existing message types (existing AHL); • file renaming; • use of directories; • account names and passwords; • FTP sessions; • Local FTP requirements

TCP/IP procedures and application for the GTS Accumulating messages into files • Multiple messages in the one file • Messages should be accumulated in files thus: – length indicator, message 1 (8 characters); – format identifier (2 characters); – message 1; – length indicator, message 2 (8 characters); – format identifier (2 characters); – message 2; – and so on, until the last message;

TCP/IP procedures and application for the GTS FTP message format

TCP/IP procedures and application for the GTS File naming conventions • CCCCNNNN. ext where: – CCCC is the international four letter location identifier of the sending Centre, as defined in WMO publication No. 9, Volume C; – NNNN is a sequential number from 0 to 9999 generated by the sending Centre; – ext is – ‘ua’ for urgent alpha numeric information – ‘ub’ for urgent binary information – ‘a’ for normal alpha numeric information – ‘b’ for normal binary information – ‘f’ for facsimile information

TCP/IP procedures and application for the GTS File renaming • most centres detect the presence of a new file by scanning a directory. • To avoid problems with the receiving centre processing a file before it has completely arrived, all sending centres must be able to remotely rename the files they send • The file shall be sent with the extent ‘. tmp’ and then renamed • Recommended that a separate directory be used for each host system which is initiating FTP sessions to avoid the possibility of filename duplication

TCP/IP procedures and application for the GTS General FTP “Rules” • Anonymous FTP may be used, but not on servers accessible from the Internet • To Limit load, only one ftp session per centre per file type • receiving Centres to delete files after they have been processed • Do not use compression of files.

TCP/IP procedures and application for the GTS FTP suggestions • Use format identifier “ 00” – This allows the WMO request/repeat service to recover missing data. • Use filename of *. b to exchange alphanumeric or binary messages – CCCCNNNN. b - for alpha numeric and binary – CCCCNNNN. f - for facsimile (FAX T. 4) • Send one T 4 chart in each file • Send up to 100 messages in a file but do not delay sending a message for more than 60 seconds. • Read incoming files at least every minute.

TCP/IP procedures and application for the GTS Socket/FTP Comparison • Sockets: – Quick, low overhead – Requires programming – Request/Repeat system can be slow • FTP – More Delays – Standard clients (less programming) – Easy to see failures and repeat transmission.

TCP/IP procedures and application for the GTS Checklist for GTS link • Link requirements: – 1. Get link addresses and private AS numbers from WMO – 2. Agree whether to use BGP or not – 3. Establish connectivity between routers.

TCP/IP procedures and application for the GTS Checklist for GTS link cont. • Use only official IP addresses • Exchange details on host names. • Declare which IP addresses in your Centre are eligible to use the GTS. • Establish an IP connection with one or more Centres. • Configure dynamic routing with BGP (or static routing) • Obtain an autonomous-system number • Check the barrier between Internet and the GTS • Filter incoming and outgoing traffic in accordance with the requirements described above

TCP/IP procedures and application for the GTS Checklist for GTS link cont. • WMO socket requirements: – Define socket/port numbers to receive on – Agree on 3 or 5 digit sequence numbers • FTP requirements: – Exchange user-id and password of receive accounts – Exchange directory names – Agree on format identifier – preferably “ 00” (include WMO header/trailer) – Agree on filenames. Suggest: – Exchange information on maximum messages to be in a file and delays before sending a file and delays before reading a file (not essential but is useful information) – Agree on 3 or 5 digit sequence numbers

TCP/IP procedures and application for the GTS Email Standard • Proposed standard in documentation.

TCP/IP procedures and application for the GTS END