lectures.alex.balgavy.eu

Lecture notes from university.
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      1 +++
      2 title = "Network: internet protocols"
      3 +++
      4 
      5 # Network: internet protocols
      6 **Internet protocols**
      7 IPv4
      8 
      9 - uses 32-bit addresses, in dotted decimal notation (e.g. 0x80D00297 == 128.208.2.151)
     10 - prefixes are written with lowest IP address in block and size of block
     11 - a prefix 37.60.0.0/16 means that first 16 bits are used by network
     12 - subnet mask — a string of 1s that has length of number after slash in the network portion of IP address (so 16 in /16), IP address AND subnet mask gives network prefix
     13 - header:
     14 
     15 ![screenshot.png](b7d058e98446748e74208485b13cd793.png)
     16 
     17 - Classless InterDomain Routing (CIDR) — combining multiple small prefixes into a larger prefix (route aggregation), with each router having the corresponding prefix information (like /22 or /20)
     18 - Network Address Translation (NAT)
     19     - house/company has a single external IP address and ports
     20     - devices have internal IP addresses
     21     - a Network Address Translation Box decides how to route within the home network
     22 
     23 ![screenshot.png](55be5c42fb10bf8e6dbb5bbd2648c51f.png)
     24 
     25 IPv6
     26 
     27 - many more addresses, simplified header (better bandwidth/latency), easier to add options, improved security support
     28 - uses 128-bit addresses, in hex notation (e.g. 8000::123:3567:89AB:CDEF)
     29 
     30 Internet Control Protocols
     31 
     32 - Internet Control Message Protocol (ICMP)
     33     - if there’s a fuckarino, routers send these messages to senders
     34     - used e.g. when dest is unreachable, time exceeded (used by traceroute), echo/echo reply (used by ping), router advert/solicitation
     35 - Address Resolution Protocol (ARP)
     36     - A outputs broadcast packet asking who owns an IP address, to every machine on the network
     37     - only the host with the IP address responds with Ethernet its address
     38 - Dynamic Host Configuration Protocol (DHCP)
     39     - every network has a DHCP server
     40     - on startup, a computer has a built-in link layer address in NIC, but no IP address
     41     - computer sends DHCP DISCOVER packet to server, which allocates a free IP address and sends back a DHCP OFFER packet
     42     - leasing — IP address assignment is for a fixed period of time, host has to ask for renewal just before it expires or lose the address
     43 - MultiProtocol Label Switching (MPLS)
     44     - adds a label in front of each packet, forwarding is based on the label instead of dest address
     45     - in between IP network protocol and PPP link protocol (it’s a “layer 2.5 protocol”)
     46     - MPLS headers are not part of layer packet or data link frame, so it’s independent — it can forward both IP and non-IP packets (hence “multiprotocol”)
     47 
     48 Interior Gateway Protocols
     49 
     50 - example — Open Shortest Path First (OSPF)
     51 - routing within a large independent network
     52 - a form of link state routing, uses a hierarchy called ‘areas’
     53 
     54 Exterior Gateway Protocol
     55 
     56 - example — Border Gateway Protocol (BGP)
     57 - routing between large independent networks
     58 - supports arbitrary policies from ISPs/companies/countries
     59 - a form of distance vector routing combined with a path vector protocol