Rate in Diagramm bestimmen
Steigung
Latency in Diagramm bestimmen (service curve)
x-verschiebung
Delay bound
horizontal (paralell zur sekunden achse)
Dir 24-8?
wenn ganzer prefix (/24) von einem Nächst hop abgebildet wird -> direkt in erster table reinschreiben (TBL24)
Falls nicht, index reinschreiben und alle 256 restlicehn /8 enumerieren
-> zweistufiger lookup mit index xor 8bit von addresse die wir anschauen wollen
How to define stuff in P4 (variables…)?
typedef bit<#bits> name
used for general things like ip4Addr_t, macAddr_t,…
header ethernet_t {
macAddr_t dstAddr;
macAddr_t, srcAddr;
bit<16> etherType;
}
Do we manually have to consider frame check sequence in P4?
no, checked and added automatically
What does struct define in P4?
unsorted collection of members…
i.e.
struct headers {
etherhet_t etherhet;
ipv4_t ipv4;
or
struct standard_metadata_t {
bit<9> ingress_port;
bit<32> packet length,…
Delay Bound
Backlog Bound
Steps Separate Flow Analysis?
compute Left Over Service Curve for each server tranversed by the flow
concatenate the left-over service curves
compute the bounds
How to calc left over service curve?
What means pay burst only once?
when concatenating servers
-> we choose the min of the rate
-> as throguh both only the minimum goes…
What are the R and T in a server?
R -> rate
T -> processing delay
Formula deterministic service curve vs. token bucket
token bucket
det. service curve
How to calc delay bound of server?
T + b/R
Rate in Diagramm bestimmen (service curve)
What is the OPT pseudo RR used in EDNS?
RR in additional section (max one allowed)
always related to messatge it is in
shall never be cached
TTL partly used for extend RCODE
RDATA contains key-value pairs
What tasks do routing perform?
route calculation
execution of routing protocols
maintenace of routing state
manitenance of forwarding table
What is the dest mac of arp?
broadcast (ff:ff:ff:ff:ff:ff)
What is the lookup time
How long is the frame checksum?
4 byte
Difference PDU and SDU?
Protocol Data Unit -> payload and header
Service Data Unit -> only payload
How does ZMAP know altough stateless?
info encode in request that is visible in response
-> target IP is encoded as TCP sequence number and the response used for validatoin
What is a lame delegation?
NS record points to NS without providing DNS or without authorative info on the zone
as consequence -> zone might become unreachable
What is OPT record in DNS?
used for EDNS -> most important part of this extension
contains
max UDP paylaod size
extended RCODE
extension information
When calculating the delay bound, do we use the output envelope?
no use the initial flow values
and use the concatenation of the left over service curves
How is arrivel curve of token bucket defined?
y_(r,b)(s) = r*s+b
How is rate latency service curve defined?
y_(r,b)(s) = r*[s-b]^+
where [x]^+ is max(0,x)
Difference token bucket arrival curve and rate latency service curve?
token bucket -> flow
rate latency service curve -> server
What can result in weird behavior by traceroute?
we have loadbalancer in between…
-> as we always go only one hop further, might be that packets return from different paths as loadbalancer forwarded differently…
How is BGP based load balancing also called?
anycast based
What does the TCB indicate in DNS?
contains all components of system you have to trust in general
-> in DNS -> all zones which could be included in resolution path
-> i.e. all zones which need to be trusted
How to plot service curve?
T x-axis displacement
R increase
Zuletzt geändertvor 2 Jahren
