Trust by Workflow in Autonomic Communication - Computer Network Security - page 139

where media flows arriving at n inputs are transformed by Φ to m outputs. The inter-
pretation of model (2) to represent, for instance forwarding is straightforward — Φ is
then forwarding information base that defines in-node processing path from input i to
output j . A number of different media datagrams processing types, that are termed —
generic functions ( g l ) found in most advanced Internet routers is around ten [11]; they
are receiving and transmitting, forwarding, SSL processing, IPv4/IPv6 interoperabil-
ity, header compression, classification, metering, scheduling, shaping, etc. — rela-
tively small number of g l makes workflow exchange feasible.
In-node processing of a particular datagram instantiates and chains as required
these generic functions per micro flow. Note, the micro flow awareness is no longer a
scalability concern, new router designs are emerging that take advantage of flow
awareness, e.g. a truly autonomic cross-protect router by J. Roberts [12].
A workflow W k is a chain of generic functionalities for a single micro flow; each
workflow is a sequence of functions from (2) for the k -th micro flow as shown in (3),
where a dot sign is sequential order within a k -th workflow, square brackets are for
repetition. Workflow's sequence starts with the receiving of a datagram at the i -th
physical interface, continues with processing by function F ij that defines the next

,

function F jp , and so on until the datagram leaves the node's protocol stack.

,

(3)

F k ij F k jp W k = • [ ] , ,

,

In-node datagram processing as modelled by Φ is an in-node hammock — directed
acyclic graph interconnecting physical interfaces; matrix Φ being asymmetric and
triangular. Figure 1 shows an example (adopted from [13]) of a datagram processing
hammock composed of five generic functions: g 1 — receiving of a datagram from a
link; g 2 — optional datagram header decompression, g 3 — forwarding with optional
interoperability processing between IPv4 and IPv6, g 4 — optional header compres-
sion, g 5 — queuing and transmission to a link.

v4 Fwd
F 1,3

V4 HDec
F 1,1

v4 HCom
F 3,5

Receive
F 1

v6-v4 Transmit

F 7

v4-v6
F 3,4

F 4,3

g 31

Input
Interface

V6 HDec
F 1,2

v6 HCom
F 4,6

Output
Interface

v6 Fwd
F 1,4

g 2

g 1

g 3

g 4

g 5

Fig. 1. In-node datagram processing hammock

A number of workflows can be instantiated from a hammock in Fig1. For example,
expression (4) outlines a workflow of a router that receives IPv4 datagrams from a
wireless link, decompresses their headers, converts to IPv6 and sends over to wireless
link with new headers compressed.