X-Git-Url: https://git.sommitrealweird.co.uk/quagga-debian.git/blobdiff_plain/191fe7a34582876de01d3e62c2a6587baf59a283..064d9c633233495319bcaa66335ea3d24c0bd7a1:/bgpd/IMPLEMENTATION.txt diff --git a/bgpd/IMPLEMENTATION.txt b/bgpd/IMPLEMENTATION.txt deleted file mode 100644 index fff360a..0000000 --- a/bgpd/IMPLEMENTATION.txt +++ /dev/null @@ -1,169 +0,0 @@ -$Id: IMPLEMENTATION.txt,v 1.2 2005/02/15 17:10:03 gdt Exp $ - -This file contains notes about the internals of the BGP -implementation. The initial impetus is understanding the memory usage -of Quagga'a BGP implementation. There may be some inaccuracies; it is -in the repository in the hopes that it will be significantly more -helpful than not. - -* FILES - -bgp_advertise.[hc]: - data structures: advertised prefixes, attributes - -bgp_aspath.[hc]: - struct aspath: - These are stored in a hash, apparently in wire format. - -bgp_attr.[hc]: - struct attr: contains all attributes - size(ILP32) 26 words/104 bytes (poor packing, v6/multicast is 10) - - bgp_attr_parse: origin, aspath, next hop probably most of interest - bgp_attr_origin: set flag bit - bgp_attr_aspath: put in refcounted hash table, so share pointer - bgp_attr_nexthop: store in attribute structure - -bgp_btoa.c: ? test program - -bgp_clist.[hc]: - data structures: community lists (including permit/deny state) - -bgp_community.[hc]: - data structures: community atttributes (multiple communities per struct) - -bgp_damp.[hc]: - per-route damping data, and damping control information - -bgp_debug.[hc]: - debugging support (vty config, dump of packets) - -bgp_dump.[hc]: - MRT-compatible dump format routines - -bgp_ecommunity.[hc]: - Extended communities attributes (multiple ecommmunities per struct) - -bgp_filter.[hc]: - AS path access list filtering - -bgp_fsm.[hc]: - Per-peer state machine for TCP connection, hold time, etc. - -bgp_main.c: - Daemon startup. - -bgp_mplsvpn.[hc]: - parsing of attribute structures for MPLS VPNs [need better description] - -bgp_network.[hc]: - Opening and binding of sockets, finding addresses for interfaces - -bgp_nexthop.[hc]: - data structures: Nexthop cache [not clear how used, if truly cache - in sense of memoization, or something else] - - importing EGP routes into IGP (thread created) - "scanning" (thread created) - bgp_scan: has useful clues to data structure complexity. Scanning - process iterates over database of received advertisements, and - builds 'cache' structure. - -bgp_open.[ch]: - Open messages, and capability negotiation - -bgp_packet.[hc] - sending and receiving of UPDATE/WITHDRAW - collision resolution for simultanteous opens - bgp_read: top-level read routine: reads whole packet (nonblocking) - and dispatches to per-message-type receive - - bgp_update_receive: - calls bgp_attr_parse - reads nrli into struct bgp_nrli update - - uninterning of aspath, community, ecommmunity, cluster, - transit which were interned in bgp_attr_parse - -bgp_regex.[ch]: - Glue to convert BGP regexps to standard (_ means many things). - -bgp_route.[hc]: - data structures: routes as received, static routes - Application of filters. Lots of route processing. - - bgp_nlri_parse: - sanity checks, then calls bgp_update with peer, prefix, attributes pointer - - bgp_update: bgp_update_main, then RS processing - - bgp_update_main: - find 'struct bgp_node *' for this afi/safi - look for route in table, then 'intern' attributes - ** interning is process of - looking for data in hash table, and putting there if missing, refcnt - using pointer to existing data - many validity checks - get new struct bgp_info (10 words/40 bytes) - call bgp_info_add with rn and bgp_info - call bgp_process - -bgp_routemap.c - implementation of route maps (match and set) - -bgp_snmp.c - SNMP glue. Not particularly interesting except to add variables or - debug SNMP. - -bgp_table.[hc] - data structures: struct bgp_table, struct bgp_node - allocation/lookup/utility operations - not a lot of protocol processin - -bgp_vty.[hc] - protocol-wide vty hooks - -bgp_zebra.[hc] - Processing interface events from zebra, redistribution of routes. - -bgpd.h - struct bgp_master: daemon main data structure - struct bgp: per-instance structure - struct peer_group - struct bgp_notify: (in-core representation of wire format?) - struct bgp_nexthop: (v4 and v6 addresses, *ifp) - struct bgp_rd: router distinguisher: 8 octects - struct bgp_filter: distribute, prefix, aslist, route_maps - struct peer: neighbor structure (very rich/complex) - struct bgp_nlri: reference to wire format - #define of protocol constants - attribute type codes - fsm states/events - timer values - -bgpd.c - instance/peer allocation - configuration - initialization/termination - -* DATA STRUCTURE SIZES - -Question: How much memory does quagga's bgpd use as a function of -state received from peers? - -It seems that a struct bgp_info is kept for each prefix. The "struct -attr *" is interned, and variables within that are interned. So, 40 -bytes are kept per received prefix, plus interned shared values. This -could be 36 if 'int suppress' where changed to a u_char and moved to -be with the other u_chars. Without MPLS, this could be 32 bytes. -Note that 8 bytes of this is linked list overhead, meaning that 24 -bytes are the raw per-prefix storage requirements. - -Also, a struct bgp_damp_info is apparently maintained per route; this -is fairly large (about 44 bytes). - -[TODO: the role of struct bgp_node.] - -* TIME COMPLEXITY - -It appears that received prefixes from each peer are stored in a -linked list.