Network2/Dynamics: Difference between revisions
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Baseline overheads: |
Baseline overheads: |
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Ethernet: 14+4 |
[http://en.wikipedia.org/wiki/Ethernet#Ethernet_frames Ethernet]: 14+4 |
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[http://en.wikipedia.org/wiki/IPv4#Packet_structure IPv4]: 20 + options |
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IPv6: 40 |
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[http://en.wikipedia.org/wiki/User_Datagram_Protocol#Packet_structure UDP]: 4 |
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ICMPv6: 4 |
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[http://en.wikipedia.org/wiki/IPv6_packet IPv6]: 40 |
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ICMP RA: 32 |
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[http://en.wikipedia.org/wiki/ICMPv6#Packet_format ICMPv6]: 4 |
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[http://tools.ietf.org/html/rfc4861#page-18 ICMPv6 RA]: 16 + prefix+{32} + mtu?{8} |
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[http://en.wikipedia.org/wiki/Transmission_Control_Protocol#TCP_segment_structure TCP]: 20 + options? |
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[http://en.wikipedia.org/wiki/Transport_Layer_Security#TLS_record_protocol TLS]: 5 + mac?{16,20,32} + pad?{4,8,16} |
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Revision as of 19:01, 29 August 2010
Prerequisite concepts: bandwidth, latency, jitter, availability, model, unicast, multicast, broadcast, network stack
First, some baseline analysis:
Suppose we have a wireless link with capacity C. Suppose we have N nodes. Suppose each node n wants to maintain f(n) connections. If f(n) = 1 then we could allocate up to C/N per connection. If f(n) = N then we could allocate up to C/N^2 per connection. Instructive values: C=30 Mbps, N=40, f(n)=N ==> 19 Kbps / conn. Conclusion: beware O(N^2) behavior.
Several important numbers that we need to predict and to measure include bandwidth and latency figures:
tx == transmit, rx == receive, btx == broadcast btx/tx/rx - ICMPv6+IPv6+phys - router discovery (RD) btx/rx - ICMPv6+IPv6+phys - duplicate address detection (DAD) tx/rx - ICMPv6+IPv6+phys - NS neighbor discovery (ND) tx/rx - UDP+IPv6+phys - DNS query tx/rx - JSON+SSH+TCP+IPv6+phys - DNS update where "phys" describes the equations' dependence on the "physical" layer's frame overhead and MTU notable "phys" layers: Ethernet -- ad-hoc wifi, infra wifi, 802.11s mesh, switch, hub TLS+UDP+IPv4 -- openvpn L2TP+IPsec+IPv4 -- raccoon, isakmpd, openswan, etc. UDP+IPv4 -- teredo
Baseline overheads:
Ethernet: 14+4 IPv4: 20 + options UDP: 4 IPv6: 40 ICMPv6: 4 ICMPv6 RA: 16 + prefix+{32} + mtu?{8} TCP: 20 + options? TLS: 5 + mac?{16,20,32} + pad?{4,8,16}