27 February 2014

Crash on Course: Convergence

The following movie-hack flew across the screen in the first chapter of my short story, Origins, and it wasn't appropriate to bore yáll with it there, so I'm boring yáll with it here. Here's what happens when fact and fiction combine. I think it's scribomania, as I used-to fill up napkins and eventually notebooks, the occasional pedestrian sketch, I now write twice a year for a few days that resemble more of the mania and less of the scribe, and the rest of the year I post the chapters after fucking with them a few minutes around morning emails, a word here, a dream there. I wasn't lying when I wrote that I've preemptively written twenty chapters in advance. Sure, I'll post the occasional poem from my phone, waiting in a cafe or takeout lobby, and the tech, which has become more study and notes than papers, ...I'm doing it again, right now, adding this [expletive deleted] intro. It's quite fun, new positions recently have become available. Contention....

[IGRP] [iBGP-AS (Router-cloud computing) - eBGP]
Connection oriented, call setup, established network, virtual circuit, call first, path unknown
Global vs Decentralized; distance vector <_> link state
IGRP CISCO, EGP BGP as intra, inter
OSPF Link State, Hierarchical        secure, unlimited, authenticated
RIP distance vector, Global - 15 hops, periodic updates
Forward source routing. Performance
IntraAS: can focus on performance
InterAS: policy may dominate over performance policy
IntraAS: single admin, so no policy decisions needed, scale, hierarchical routing saves table sizes
InterAS: admin wants control over how its traffic is routed & who routs thru its netw

SRC 1234(5678) -- 8=1 -- multicast has route info, source deleting route, not destination, has the sending-address info. Source Routing vs Transparent Bridge ...is like, Greater Overhead vs Optimal Path (STA)     (see next <>) Link aggregation, logically combines connections reduces bandwidth in traffice, but is limited directionally with load balancing. PAgP <> LACP: Set the desireable (1)/auto (2), same facing, (auto, active (1), passive (2))

PAgP Desireable Auto/Auto
LACP Active Passive/Manual
VLAN secure and flexible, trunk with VLAN TAGS
VLAN routing destination, IP doesn't change, but the mac addy does (header, VLAN tags)
IP address destination MAC of next hop;
ARP (routers), sometimes pings fail while initializing ARP;
WLAN, (AP) attenuation, receiving signal strength (PCP/PCF)
(Whereas, Pico/Scatter nets are Bluetooth nomenclatures.)
IPv4 32bits/4bytes [see: IPv4 addressing]
IPX 10 bytes = 4MAC+6ADDY (from mac of sender)
Area, ID, SCL               IPv6 128bits/16bytes [see: IPv6 addressing]
ARP: MAC address
RARP: Network Layer (4) IP address/ some limitations

Intra domain; policy, scale, performance
InternalGP: RIP, IGRP, OSPF    <<<>>>    External Gateway Protocol: BGP
Hierarchical impractical because cannot store all destinations in routing table Autonomous Systems with different intra-AS, gateways/border router. Intra AS <> Inter AS >> The interwebs = b/w autonomous systems. The intra = w/in autonomous systems

Gateways; propogate/share tables intra, intra AS learn optimal network gateways/locations by choosing least cost. RIP (routing information protocol): distance vector, local, 15 hops,
UDP periodic advertisement, up to 25 subnets w/ distance, convergence, table propagation, and population, every 30seconds. OSPF link-state global, advertises link changes, flooding, 'hello, database description (DBD), link state request (LSR), link state update (reply) (LSU), link state acknowledgement (LSACK)' {public, shares neighbor nodes info with netw every 10 seconds, supports VLSM & CIDR, authenticated and unlimited hop count.

Hierarchy within domain local, no broadcasting only hello messages, area border routers of
boundary routers stemming from network backbone, knows local topologies, summarized
distances; area border routers become default gateways for internal routers.
BGP: subnet reachability propagation. eBGP: for border routers, allowed if BGP on all routers.

BGP peers exchange routing infor, in order to disseminate infor for eventual forwarding: route chosen by manual or autonomous factors. MSGS: OPEN, UPDATE, KEEPALIVE, NOTIFICATION

A Sin (2π F * T + 0)
Amplitute SINE (2pi Frequency * Time + Delay(-+))

Inverse distributive exponential conversion. Parallel vs Serial: Byzantine Robustness: LANs, Link Layer, shared medium: MAC IEEE 802: connection, connectionless, acknowledged connectionless: Random Vs Deterministic. 

Carrier Sense Multiple Access CSMA: Choose One
Collision Detection CSMA CD --(*Used when wired)
Collision Avoidance CSMA CA --(*Used when wireless)

Topology: Discovery Vs Routing: Hidden vs Exposed

Layer 2 Addressing, MAC address, used for unicast, multicast, and broadcast addressing being the key the bits to-the-left in a MAC address indicate they type of transmission (casting) XX (the second even is a unicast, the second odd a multicast) 

POST< boot, profile, topologies, single-point of failure, hub vs switch, hub is/has one collision domain, switch has many b/c of store and forward, hub at default is a repeater/broadcaster, switch turns each Ethernet port into a gateway.