1. HOW NODE JOINS OR LEAVE IN PEER
TO PEER NETWORK
Presented by:
Chaitanya Pratap Singh
MCA(4th Semester)
South Asian University, new Delhi.

2. NODE JOIN (PEER JOIN)
 Joining peer sends a "join" request to the boot
peer, and gets a GUID back.
 Joining peer sends a "copy routing table" to the
boot peer.
 Joining peer finds the correct peers it should have
in its own routing table.

3. THE JOIN REQUEST
 The first peer to join the network apart from the boot
peer, will connect to the boot peer and send a "join"
message. The boot peer responds with a new GUID
to the joining peer.

4. THE COPY ROUTING TABLE REQUEST
 After getting a GUID, the joining peer requests to get
a copy of the boot peers routing table.

5. FINDING THE CORRECT PEERS FOR THE
ROUTING TABLE
 the joining peer uses this routing table to find the
peers it should really have in its routing table.

6. LEAVING NODE
 When a peer no longer wants to be part of a P2P
network, it will send a "leave" request to all peers in
its routing table

7. CONT…
 if A has B in its routing table, B does not necessarily
have A in its routing table.
 Thus, if A leaves a Chord network, it would have to
find the peers in the network that has A in its routing
table.
 In other words, find those peers which
have distance(X, A) closest to 20, 21, 22 etc. Once
those peers are found, the leaving peer (A) will
send a leave message to each of them.

8. CHORD STATE AND LOOKUP (1)
 Basic Chord: each m=6
node knows only 2 2m-1
N1
other nodes on the ring 0
 Successor N56 N8
 Predecessor (for ring K54
lookup(K54)
management) N51
 Lookup is achieved by
N14
forwarding requests N48
around the ring through
successor pointers
 Requires O(N) hops N42
N21
N38
8
N32

9. CHORD STATE AND LOOKUP (2) Finger table
N8+1N14
 Each node knows m m=6
N8+2N14
N8+4N14
other nodes on the ring 2m-1 N8+8N21
 Successors: finger i of n N1 N8+16
N32
0
points to node at n+2i (or N8+32
N42
successor) N56 lookup(K54) N8
 Predecessor (for ring K54 +1
management) N51 +2
 O(log N) state per node +4
 Lookup is achieved by N48 +16 +8 N14
following closest +32
preceding fingers, then
successor
N42
 O(log N) hops N21
N38
9
N32

10. JOINING THE RING
 Three step process:
 Initialize all fingers of new node
 Update fingers of existing nodes
 Transfer keys from successor to new node

11. JOINING THE RING — STEP 1
 Initialize the new node finger table
 Locate any node n in the ring
 Ask n to lookup the peers at j+20, j+21, j+22…
 Use results to populate finger table of j

12. JOINING THE RING — STEP 2
N8+1N14
N8+2N14
 Updating fingers of m=6 N8+4N14
existing nodes 2m-1 N8+8N21
N1 N8+16
N28
N32
0
 New node j calls 6 N8+32
N42
N56 N8
update function on
existing nodes that
N51 12
must point to j
 Nodes in the ranges N48 N14
+16 -16
[j-2i , pred(j)-2i+1]
 O(log N) nodes need
to be updated N42
N21
N38
N28 12
N32

13. JOINING THE RING — STEP 3
 Transfer key responsibility
 Connect to successor
 Copy keys from successor to new node
 Update successor pointer and remove keys
 Only keys in the range are transferred
N21 N21 N21 N21
N32 N32 N28 N32 N28 N32 N28
K24 K24 K24 K24 K30 K24
K30 K30 K30

14. NODE JOIN ALGORITHM

15. CONT…